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MODIFICATION OF BIORHYTHMIC ACTIVITY
FIELD OF THE INVENTION
The present invention relates to systems and methods for modification of
biorhythmic activity.
S BACKGROUND OF THE INVENTION
Various techniques and systems have been proposed for modification of
biorhythmic activity. The following patents are believed to represent the
state of the
prior art: U.S. Patent 5,267,942 to Saperston, entitled Method For Influencing
Physiological Processes Through Physiologically Interactive Simuli. U.S.
Patent
5,076,281 to Gavish, the present inventor, entitled Device and Method for
Effecting
Rhythmic Body Activity. Further relevant prior art appears in the References
Cited
listings _ of the aforesaid patents and in the Background sections thereof.
U.S. Patent
5,423,328 also to Gavish describes a monitoring device which is particularly
suitable
for use in the present invention.
SUMMARY OF THE INVENTION
The present invention seeks to provide an improvement to the systems
and techniques of the prior art.
There is thus provided in accordance with a preferred embodiment of the
present invention a system for modifying naturally occurring biorhythmic
activity
including a monitor for analyzing biorhythmic activity of a user, a
biorhythmic activity
modifier for providing to the user a stimulus input which is operative to
change at least
one aspect of the biorhythmic activity of the user, and a driver operative to
control the
operation of the biorhythmic activity modifier, so as to change at least one
non-
frequency characteristic of the input to the user, in response to changes in
the
biorhythmic activity of the user during operation of the modifier.
Preferably, the driver is operative to change at least one non-frequency
characteristic of the input to the user in response to at least one
corresponding change
in a non-frequency characteristic of the biorhythmic activity of the user
during
operation of the modifier.
In accordance with a preferred embodiment of the present invention the
non-frequency characteristic of the input to the user forms part of a
recurrent pattern.
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Preferably, the driver is also responsive to selectable operator commands for
governing the manner in which the non-frequency characteristic of the input to
the user is
changed.
In accordance with a preferred embodiment of the present invention the non-
6
frequency characteristic includes the relationship of at least two components
of a generally
recurrent pattern.
Preferably the selectable operator commands are operative to select at least
one
of a plurality of relationships between at least two characteristics of a
generally recurrent
pattern of the input to the user which are modified.
In accordance with a preferred embodiment of the present invention the
modifier is also responsive to the time relationship between a generally
recurrent pattern in the
biorhythmic activity of the user and a generally recurrent pattern in the
input to the user.
Preferably, the driver is operative in an at least partially predetermined
manner.
In accordance with a preferred embodiment of the present invention the system
'i5 also comprises a shift detector receiving inputs from the monitor and the
modifier and
providing a shim correction output to the modifier.
Preferably, the shift detector also receives an input from the driver and is
responsive thereto for providing the shift correction output to the modifier.
In accordance with a preferred embodiment of the present invention the input
from the driver includes operator command determined instructions.
Preferably, the shift correction output is provided in response to the time
relationship between the onsets of biorhythmic activity signals and stimulus
inputs to the user.
In accordance with a preferred embodiment of the present invention the shift
correction output is provided by delaying the onset of stimulus inputs to the
user.
Preferably the shift correction output is provided by moving up the onset of
stimulus inputs to the user.
In accordance with a preferred embodiment of the present invention the at
least
one non-frequency characteristic of the biorhythmic activity of the user forms
part of a
recurrent pattern. ,
The stimulus input may be an audio input, a visual input, a tactile input or a
combination of them.
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Preferably, the monitor is operative to analyze respiration information.
There is additionally provided in accordance with a preferred embodiment of.
the present invention a method for modifying naturally occurring biorhythmic
activity including
analysing biorhythmic activity of a user, providing to the user a stimulus
input which is
operative to change at least one aspect of the biorhythmic activity of the
user; and changing at
least one non-frequency characteristic of the input to the user, in response
to changes in the
biorhythmic activity of the user during operation of the modifier.
It is appreciated that the various stimulus inputs may be provided to a user
individually or simultaneously in multiple forms. Thus for example, an audio
stimulus may be
combined with a visual and/or tactile stimulus, or two or more audio, visual
or tactile stimuli
may be provided simultaneously alone or together with other types of stimuli.
For example, the
audio stimulus may be provided in stereo form and the visual stimulus may be
provided in
stereo form in order to provide the user with three-dimensional perception of
the stimulus.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be understood and appreciated more fully from the
following detailed description, taken in conjunction with the drawings in
which:
Fig. 1 is a simplified block diagram illustration of a system for modification
of
biorhythmic activity constructed and operative in accordance with a preferred
embodiment of
the present invention;
Fig. 2 is a flowchart illustrating operation of a monitor employed in the
system
of Fig. 1;
Fig. 3 is a flowchart illustrating operation of a driver employed in the
system of
Fig. 1;
Fig. 4 is a flowchart illustrating operation of a biorhythmic activity
modifier
employed in the system of Fig. 1;
Fig. 5 is a flowchart illustrating operation of a shift detector employed in
the
system of Fig. l;
Fig. 6 is an annotated illustration of a typical monitored biorhythmic
activity
signal which is subject to analysis in accordance with the present invention;
Fig. 7 is an illustration of modification of a typical monitored biorhythmic
activity signal in accordance with the present invention which illustration
ignores time shifts
and the correction thereof;
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Fig. 8 is an illustration of shift correcting modification of a typical
monitored
biorhythmic activity signal in accordance with the present invention;
Figs. 9A, 9B & 9C are block diagrams illustrating the three alternative
embodiments of the structure of a pattern generator employed in an audio
stimulus generating
version of the system ofFig. 1 whose operation is illustrated generally in
Fig. 4; ,
Figs. l0A and IOB are block diagrams illustrating two alternative embodiments
of the structure of a pattern generator employed in a visual stimulus
generating version of the
system of Fig. 1 whose operation is illustrated generally in Fig. 4;
Fig. 11A and 11B are block diagrams illustrating two alternative embodiments
of a pattern generator employed in a pressure stimulus generating version of
the system of Fig.
1 whose operation is illustrated generally in Fig. 4;
Figs. I2A and 12B are block diagrams illustrating two alternative embodiments
of a pattern generator employed in a electrical stimulus generating version of
the system of Fig.
1 whose operation is illustrated generally in Fig. 4;
Fig. 13 is a block diagram illustrating an embodiment of a pattern generator
employed in a thermal stimulus generating version in the system of Fig. 1
whose operation is
illustrated generally in Fig. 4;
Fig. I4 is an illustration of a typical respiration signal and modification of
the
respiration signal through .the use of an audio stimulus in accordance with a
preferred
embodiment of the present invention;
Fig. I S is a simplified illustration of a biorhythmic activity monitoring
device
and biorhythmic activity sensor, constructed and operative in accordance with
a preferred
embodiment of the present invention;
Fig. 16A is a simplified sectional illustration of a portion of the
biorhythmic
activity sensor of Fig. I5, taken along lines XVI - XVI in Fig. 15, and
including a force
transducer which responds to compressive stress;
Fig. I6B is a simplified sectional illustration of a portion of the
biorhythmic
activity sensor of Fig. I5, taken along lines XVI - XVI in Fig. 15, and
including a force
transducer which responds to stretching; ,
Figs. 17A, 17B and i 7C are simplified illustrations of a portion of the
biorhythmic activity monitoring device of Figs. I5, 16A and 16B, showing a
stretchable belt
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disposed in a belt protector, constructed and operative in accordance with a
preferred
embodiment of the present invention;
Fig. 18 is a simplified sectional illustration of a portion of a biorhythmic
activity
sensor, constructed and operative in accordance with another preferred
embodiment of the
5 present invention; and
Fig. 19 is a simplified sectional illustration of a portion of a biorhythmic
activity
sensor, constructed and operative in accordance with yet another preferred
embodiment of the
present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Reference is now made to Fig. 1, which is a simplified block diagram
illustration
of a system for modification of biorhythmic activity constructed and operative
in accordance
with a preferred embodiment of the present invention.
The system of Fig. 1 preferably comprises a monitor IO for analyzing
biorhythmic activity of a user. Monitor IO receives electrical signals
representing biorhythmic
activity of an individual, here designated BAS, from a biorhythmic activity
sensor I2. A
greferred biorhythmic activity sensor is that described and claimed in U.S.
Patent 5,423,328 to
the present inventor, it being appreciated that any other suitable sensor may
be employed
alternatively or additionally. The connection to sensor 12 may be wired or
wireless.
The operation of monitor 10 is principally to provide output indications
2o representing one or more pattern components of the sensed biorhythmic
activity of the user.
Preferably, the output indications include parameter indications PAR which are
of a
quantitative nature and a MONTRG trigger indication which represents the
timing of the
biorhythmic pattern components. The monitor 10 also preferably provides an
error indication
ERR when it does not receive acceptable electrical signals representing
biorhsrthmic activity of
26 the user and thus cannot provide suitable parameter and trigger
indications.
A biorhythmic activity modifier 14 receives the parameter indications from
monitor 10 and is operative for providing to the user a stimulus input which
is operative to
change at least one aspect of the biorhythmic activity of the user. A driver
16 preferably but
not necessarily also receives the parameter and error indications PAR and ERR
from the
30 monitor and is operative by an operator, who may be different from the
user, to control the
operation of the biorhythmic activity modifier 14 by providing a set of
operational command
inputs, collectively referred to as MOPC, so as to cause at least one non-
frequency pattern
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component of the input to the user to be related to at least one non-frequency
pattern
component of the existing biorhythmic activity of the user which is sensed by
sensor 12.
In accordance with a preferred embodiment of the invention, the driver 16 is
responsive to operator commands, which may come from the user.
In accordance with one preferred embodiment of the invention, the modifier 14
may also be responsive to an output from a shift detector 18. Shift detector
18 preferably
receives the MONTRG trigger indication from the monitor 10 as well as an
MODTRG trigger
indication from modifier 14 indicating the timing of the input to the user.
The shift detector 18
is operative to measure the timing relationship between the two trigger
indications MONTRG
and MODTRG and to provide a timing shift indication SFT to the biorhythmic
activity
modifier 14 causing it to reduce the time separation between successive MONTRG
and
MODTRG trigger indications. The shift detector 18 receives an operational
command input
SOPC from driver 16 which governs the criteria according to which the shift
detector 18
provides the timing shift indication SFT to the biorhythmic activity modifier
14.
The MOPC inputs supplied by driver 16 to biorhythmic activity modifier 14
govern the criteria according to which the modifier 14 responds to the PAR and
SFT
indications received thereby.
Reference is now made to Fig. 2, which is a flowchart illustrating operation
of a
monitor employed in the system of Fig. 1. The BAS signals received from
biorhythmic activity
sensor 12 are subjected to pattern and trend analysis. The pattern analysis
preferably includes
pattern identification which constitutes identification of recurrent features
in the signals, such
as rising and falling parts of the signals and expresses these features in
parameters which are
associated with identifiable components of the physiological activity
monitored by sensor 12.
The trend analysis constitutes identification of changes in one or more
parameters in the
recurrent features, such as a decrease in amplitude over multiple signal
patterns.
A description of prior art pattern and trend analysis is provided in U.S.
Patent
5,076,281 of the present inventor. The pattern and trend analysis employed in
the present
invention goes beyond that described in U.S. Patent 5,076,281 as will now be
described with
additional reference to Fig. 6.
Fig. 6 illustrates a typical respiration signal as sensed by a belt-type
respiration
sensor as described in U.S. Patent 5,423,328. The BAS signals and their
changes thereof with
respect to time changes, are operated upon by a subroutine which provides a
search for special
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points. In general these special points are located where the BAS signal or
the first and second
time derivatives thereof reach minima, maxima and zero. Typical special points
in the signal
shown in Fig. 6 are a, at which the first time derivative has a maximum
following a local
minimum; and b, at which the BAS signal reaches a maximum, the first time
derivative is at
a
zero and the second time derivative is negative.
In accordance with a preferred embodiment of the present invention, most or
aII
of the special points are detected in real time. The remainder of the BAS
signal may be
analyzed in real time or stored for near-real time analysis.
Following determination of the locations of the special points, a time
9 0 relationship analysis is performed to determine whether the time
separation between special
points exceeds predetermined limits. The time relationship analysis is
preferably carried out on
predetermined special points. The special points subject to the time
relationship analysis may or
may not be mutually adjacent. If the limits are exceeded an output is provided
which initiates
error handling procedures.
~ 5 If the limit is not exceeded, it is necessary to determine if the special
point is an
onset point. If this point is determined to be an onset point, the onset of a
signal pattern has
been detected. Although it is appreciated that the onset may be arbitrarily
determined,
depending on the nature of the signal, any one of the special points which
appears
distinctiveness in the signal environment may be selected. In the present
description, a is
20 referred to as indicating onset of a signal pattern.
Once the signal onset is determined, the MONTRG signal output of the monitor
(Fig. 1) is provided to shift detector 18 (Fig. I). Information relating to
the special points,
including their location relative to the onset of the pattern and other
special points, are stored.
The stored special points are then used to calculate raw parameters which are
25 eventually employed to provide the PAR outputs of the monitor 10 (Fig. I}.
Examples of raw
parameters in a BAS pattern having one rising part and one falling part
include the following
(Fig. 6):
P 1 (n) Pattern duration - the time between successive pattern onsets, which
is
the sum ofP2(n} + P3(n) defined hereinbelow, n indicating the number of the
pattern;
3o P2(n) Pattern rise time - the time separation between point a and the
following
point b, n indicating the number of the pattern;
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P3(n) Pattern fall time - the time separation between point b and the
following
point a, n indicating the number of the pattern;
P4(n) Pattern maximum amplitude - the signal amplitude at point b measured
with reference to previous point a. It is appreciated that additional
parameters may include
relationships between the above-mentioned parameters as well as any other
suitable .
parameters.
As illustrated in Fig. 2, at every stage of the operation, the different
parameters, for example the raw parameters, may be displayed to the operator
as operator
indications, thereby allowing the operator to control all steps of the
operation.
The raw parameters are also examined for acceptability to see whether they fit
within predetermined limits. If not, an output is provided which initiates
error handling
procedures, which may provide to the operator an error output indication ERR.
If the parameters fit within the predetermined limits, trend parameters are
then
calculated. Trend parameters indicate the changes in each of the raw
parameters and their
mutual relationships over time in a series of acceptable patterns. Examples of
trend parameters
include changes in the absolute or relative value of a parameter between
successive patterns.
The trend parameters are then examined for acceptability to see whether they
fit
within predetermined limits. If not, an output is provided which initiates
error handling
procedures, which may provide an error output indication at an operator
interface. Error
indications are typically provided in the case of irregularity in the raw
parameters or sudden
sharp changes therein.
So long as the raw and trend parameters fit within the predetermined limits
and
are thus acceptable they are subject to moving averaging over a predetermined
number of
patterns. These moving averages are supplied to the modifier 14 and driver 16
as the PAR
inputs (Fig. I).
Indications of the raw and trend parameters which fall within the
predetermined
limits of acceptability and error indications ERR and the moving averages of
those parameters
may also be supplied to the operator.
Reference is now made to Fig. 3, which is a flowchart illustrating operation
of a
driver, such as driver 16, employed in the system of Fig. 1. The driver is
responsive to operator
commands to provide a plurality of functionalities which will now be
described:
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Shift correction strategy - This determines the manner in which shift
correction
is effected. Shift correction relates to the time difference between the onset
of each pattern in
the BAS signal which is monitored and the onset of each corresponding pattern
in the stimulus
a
output provided by modifier 14 (Fig. 1). The mechanism of shift correction
will be described
hereinbelow in greater detail with reference to Fig. 8.
It is noted that when an ERR output is present, indicating an irregular BAS
signal, shift correction is normally not carned out. Typical matters dealt
with by the shift
correction strategy are the time relationship or the number of elapsed
patterns between
successive corrections and the magnitude of shifts that are effected.
I p Error handling strategy - This determines the manner in which an output
indication of error is provided to the operator, e.g. in a visual, audio,
tactile or other suitable
manner.
Driving strategy - This determines which parameters are to be modified, to
what degree and in what manner.
15 Stimulus strategy - This determines the general and specific type or types
of
stimulus that are employed. For example, when audio stimuli are employed, the
nature of a
sound pattern and even the identity of a musical composition and its internal
structure, as well
as its instrumentation, spectral distribution and amplitude may be selected.
As another
example, when visual stimuli are employed, the shape, color, dynamics,
intensity and
20 complexity of the visual stimulus may be selected.
The stimulus strategy may also include determination of any of the foregoing
features based directly or indirectly on the characteristics of the monitored
BAS signal in real
time or near real time, responsive to the ERR and PAR signal outputs of the
monitor 10 (Fig.
1 ).
25 One or more types of stimulus and the balance between them may also be
selected. An independently controlled pattern generating metronome stimulus
may also be
selected by the operator.
The driver 16 provides modifier operational commands (~iOPC), embodying
. all of the above strategy selections, to the modifier 14.
3~ Reference is now made to Fig. 4, which is a flowchart illustrating
operation of
the modifier 14 employed in the system of Fig. 1. The modifier 14 receives PAR
signals from
the monitor 10. In the absence of such signals, pseudo-PAR signals are
generated. In the
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preferred embodiment of the present invention, the pseudo-PAR signals are
identical to the last
received PAR signals.
The PAR signals and the pseudo-PAR signals, to the extent that each are
present, are modified to produce modified-PAR (MPAR) signals in accordance
with criteria
5 represented by the MOPC inputs received from the driver 16, in accordance
with the strategies
selected by the operator and in accordance with the SFT input from shift
detector 18. The
MPAR signals are employed to generate patterns of stimulus inputs to a user.
Simultaneously with generation of the patterns of stimulus inputs to a user,
the
modifier 14 provides a MODTRG trigger output to shift detector 18, which
indicates the onset
10 of each pattern of the stimulus inputs to the user.
Reference is now made to Fig. 5 which illustrates operation of the shift
detector
18 of the apparatus of Fig. 1. The shift detector 18 receives both the MODTRG
signal from
the modifier 14, giving the onset of the stimulus output patterns and the
MONTRG output
from the monitor 10, giving the onset of the monitored BAS signal. The shift
detector 18
determines the time interval between the pattern onsets represented by these
two inputs, which
may arrive at the shift detector I S in different order and provides an output
indication SFT
indicating whether the stimulus output onsets trail the BAS signal onsets and
if so, by how
much.
If the stimulus output onsets trail the BAS signal onsets by more than a
predetermined time, as indicated by the SFT output indication, the shift
detector enables the
SFT input to the modifier 14, which input is also determined by the SOPC input
received from
the driver 16 in accordance with the selected shift correction strategy. The
SFT input causes
the modifeer 16 to shift the onsets of the stimulus output patterns so as to
minimize the amount
by which the stimulus output onsets trail the BAS signal onsets. It is
appreciated that
depending on the amount by which the stimulus output onsets trail the BAS
signal onsets and
the stability of the BAS signal, the entire required correction may not be
made immediately.
Reference is now made Fig. 7, which is an illustration of modification of a
typical monitored biorhythmic activity signal in accordance with the present
invention. For the -
purposes of clarity and simplicity of explanation, the illustration of Fig. 7
and the explanation
thereof which follows ignores time shifts and the correction thereof, which
are explained
hereinbelow with reference to Fig. 8.
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Fig. 7 includes an illustration of a typical BAS signal 100 which is received
by
monitor 10 (Fig. 1). In the present example, the BAS signal may represent a
respiration signal
produced by a sensor of the type described in U.S. Patent 5,423,328, it being
appreciated that
alternatively, depending on the type of sensor employed, the BAS signal may be
any suitable
signal representative of biorhythmic activity of interest.
The BAS signal 100 may be seen to be composed of two parts, an inspiration
part 102, which is the rising part of the signal, and an expiration part 104,
which is the falling
part of the signal. The durations of the inspiration part 102 and expiration
part 104 are
indicated by respective shaded and unshaded portions 106 and 107. The
relationship between
the inspiration part 102 and the expiration part 104 and the parameters P2 and
P3 are
indicated, P2 representing the inspiration part, whose duration is indicated
by reference
numeral I06 and P3 representing the expiration part, whose duration is
indicated by reference
numeral 107.
For some applications, as inducing relaxation, it is desired to increase P3.
This
is preferably accomplished without a corresponding increase in P2, thereby
increasing the ratio
of P3 to P2. In some other applications, as in fitness, a decrease of P2 may
be preferable. In
practice, where an audio stimulus is provided to the user, a first audio
sound, represented by
a waveform I08, such as a trumpet sound, represents the desired inspiration
part and a second
audio sound, represented by a waveform 109, such as a flute sound, represents
the desired
expiration part. The sound intensity is represented by the amplitude of
waveforms 108 and
109.
With each successive pattern, the duration of the flute sound increases
relative
to the duration of the trumpet sound, thus causing the user to gradually
increase the duration
of the expiration part of his respiration both in the absolute and relative to
the duration of the
inspiration part of his respiration.
In Fig. 7, the duration of that part of the audio stimulus input to the user
which
is identified by the user with inspiration is identified as Q2, while the
duration of that part of
' the stimulus input to the user which is identified by the user with
expiration is identified as Q3.
Q2 is identified by shaded portion 110, while Q3 is identified by unshaded
portion 112. It is
seen that the ratio of Q3 to Q2 increases gradually with each successive
pattern.
In the preferred embodiment illustrated in Fig. 7, Q2 of the audio stimulus,
which indicates the duration 110, is intended to overlay the inspiration
portion 102 of the BAS.
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Q2 is equal to <P2>, which is the moving average of P2, and corresponds to a
preferred
strategy, supplied by the MOPC, of not changing the duration 106 of the
inspiration portion
102 of the user. On the other hand, Q3 of the audio stimulus, which indicates
the duration 112,
is selected to be longer than the expiration portion 104 of the user. Q3 is
longer than <P3>, the
moving average of the expiration duration 107 of the user, by about 0.5 to 1
second.
It is appreciated that as distinguished from the prior art, which merely
changes
the parameter P1, which is the duration of the entire pattern, the present
invention changes the
relative durations of portions of the pattern. While this may have the effect
of changing the
duration of the entire pattern and thus changing the frequency of the
biorhythmic signal, the
- present invention is nevertheless concerned principally with changing the
both the absolute and
relative durations of portions of the pattern independently of changes in the
frequency of the
biorhythmic signal. Alternatively or additionally, the present invention also
provides changes in
other non-frequency parameters, such as the relative amplitudes of various
parts of a pattern,
which may include two or more parts.
16 As noted above, Fig. 7 does not deal with time shifts or the correction
thereof.
In accordance with a preferred embodiment of the invention, and as
distinguished from the
prior art, the present invention corrects for time shifts, which otherwise
would render the
modifications described in Fig. 7 largely useless.
It is appreciated by the present inventor, in contrast to the teaching of the
prior
art, that in order for entraining to occur, the stirnuIi must be coextensive
in time with the
biorhythmic signal parts that they are intended to stimulate. In order to
enhance the user-
perceived synchronization between the stimuli and the corresponding
biorhythmic signal parts,
time shift correction is required.
The present inventor has realized that the temporal nature of the entrainment
phenomenon requires that modifications to the stimulus applied to the user
occur in the time
domain rather than in the frequency domain. Modifications in the time and
frequency domains
are not equivalent to each other or mutually reciprocal when generally
recurrent, but not
identical, patterns are concerned.
This can be demonstrated by calculating the breathing rate indicated by a
sequence of breaths of duration Ti = 4, 4.8, 6, 3.2 and 2 seconds.
In the time domain, the respiration rate is expressed in units of breaths per
minute by 60l<Ti>, where <Ti> is the average breath duration which equals:
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(4 + 4. 8 + 6 + 3.2 + 2) / 5 seconds = 4 seconds.
Thus the respiration rate is given as I S breaths ger minute.
In the frequency domain, the respiration rate is equal to the average of the
individual respiration rates, expressed as <60/Ti>, and here equals:
(6014 + 60/4.8 + 6016 + 60/3.2 + 60/2)/5 = 17.25 breaths per minute.
It is seen that the results of the two calculations differ by i 5% in this
case.
In general <1/Ti> is not equal to 1/<Ti> because shorter durations dominate in
<1/Ti>, while longer durations dominate in 1/<Ti>.
Time shifts between the biorhythmic signals and the stimulus input occur for
the
following reasons:
1. Variation in the periodicity of the biorhythmic signals from pattern to
pattern
is well established but cannot be predicted in advance for each individual
pattern. Furthermore,
the periodicity of the biorhythmic signals is affected by the stimuli during
application of the
stimulus input. Thus, the stimulus input cannot be timed in advance such that
the onset of each
part thereof corresponds precisely to the onset of each individual pattern of
the biorhythmic
signal.
2. The timing of the stimuli in the stimulus inputs is based on averages of
past
timing of monitored biorhythmic signals due to physiological reasons. The user
requires a
relatively regular and predictable stimulus in order for successful
entrainment to take place.
These conditions are generally not fulfilled in the prior art.
Reference is now made to Fig. 8 which is an illustration of shift correcting
modification of a typical monitored biorhythmic activity signal in accordance
with the present
invention.
Fig. 8 includes an illustration of a typical BAS signal 200 which is received
by
monitor IO (Fig. 1 ) and may be identical to the BAS signal 100 illustrated in
Fig. 7. Fig. 8 also
includes an illustration of a typical audio stimulus 210 comprising two sound
stimulus inputs
208 and 209 to the user, which may be identical to stimulus inputs 108 and I09
respectively,
shown in Fig. 7. For the reasons seen above, following one or more patterns.
the onsets of the
BAS signal 200 and the stimulus input 208 may not coincide, as indicated at
reference numeral
222, where the onset of the stimulus input lags behind the onset of the BAS
signal by a time
duration S 1.
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In order to compensate for this lag, the present invention causes the onset of
a
following stimulus input pattern, indicated by reference numeral 223 to be
delayed by an .
amount D I which may be equal to S I or be a suitably weighted amount
dependent on S 1, so as
to reduce or eliminate the amount of lag, as seen at reference numeral 225.
The delay D I in
onset is seen to be achieved preferably by extending the expiration
influencing part of the
stimulus signal, here indicated by reference numeral 226. Alternatively, the
delay in onset may
be effected by increasing the duration of the inspiration influencing part or
both parts.
More generally it is appreciated that the manner in which the onset correction
mandated by the SFT output (Fig. I) is effected is determined by the MOPC
output to modifier
I4 (Fig. I).
Similarly, following one or more patterns, the onsets of the BAS signal 200
and
the stimulus input 210 may not coincide, as indicated at reference numeral
232, where the
onset of the stimulus input leads the onset of the BAS signal by a time
duration S2.
In order to compensate for this lead, the present invention causes the onset
of a
following stimulus input pattern, indicated by reference numeral 233 to be
moved backward by
an amount D2 which may be equal to S2 or be a suitably weighted amount
dependent on S2,
so as to reduce or eliminate the amount of lead, as indicated at reference
numeral 235. The
early onset is preferably achieved by decreasing the duration of the
expiration influencing part
of the stimulus signal or alternatively decreasing the duration of the
inspiration influencing part
2a or both parts..
It is appreciated that due to the various factors affecting the timing of the
BAS
signal at successive patterns, the BAS signal pattern onsets may Lead or lag
the stimulus input
pattern onsets in a random or pseudorandom manner. The purpose of this feature
of the
present invention is to limit, insofar as possible, the time extent of such
lead or lag, thereby to
enhance the physiological effectiveness of the resulting entrainment.
Reference is now made to Figs. 9A, 9B & 9C, which are block diagrams
illustrating the three alternative embodiments of the structure of a pattern
generator employed
in an audio stimulus generating version of the system of Fig. I whose
operation is illustrated
generally in Fig. 4.
Referring specifically to Fig. 9A, it is seen that the pattern generator is an
audio
pattern generator including a sequencer 300 which receives the MPAR output
(Fig. 4). The
sequencer 300 interfaces with a pattern codes storage device 302 which stores
predetermined
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pattern codes which are employed to operate a sound synthesizer 304 in
accordance with the
timing and strategy established by the MPAR input. The sequences 300 also
provides the
MODTRG output to shift detector 18 (Fig. 1).
The output of the sound synthesizer 304 is supplied via a digital to analog
5 converter 306 and an amplifier 308 to audio output devices, such as speakers
310, which
provide the stimulus input to the user {Fig. 1).
Refernng now specifically to Fig. 9B, it is seen that the pattern generator is
an
audio pattern generator including a sequences 320 which receives the MPAR
output (Fig. 4).
The sequences 320 interfaces with a pattern storage device 322 which stores
predetermined
10 sound patterns, which are preferably randomly accessible digitally recorded
sound segments
and are outputted via the sequences 320 in accordance with the timing and
strategy established
by the MPAR input. The sequences 320 also provides the MODTRG output to shift
detector
18 {Fig. 1).
The output of the pattern storage device 322 is supplied via a digital to
analog
15 converter 326 and an amplifier 328 to audio output devices, such as
speakers 330, which
provide the stimulus input to the user (Fig. 1 ).
Refernng specifically to Fig. 9C, it is seen that the pattern generator is an
audio
pattern generator including a timing controller 350 which receives the MPAR
output (Fig. 4).
The timing controller 350 provides ON/OFF and select commands to a sound
generator 352 in
accordance with the timing and strategy established by the MPAR input. The
timing controller
350 also provides the MODTRG output to shift detector I8 (Fig. I).
The output of the sound generator 352 is supplied via an amplifier 358 to
audio
output devices, such as speakers 360, which provide the stimulus input to the
user (Fig. 1).
Reference is now made to Figs. lOA and lOB, which are block diagrams
illustrating two alternative embodiments of the structure of a pattern
generator employed in a
visual stimulus generating version of the system of Fig. 1.
Referring specifically to Fig. 10A, it is seen that the pattern generator is a
visual
pattern generator including a sequences 370 which receives the MPAR output
{Fig. 4). The
sequences 370 interfaces with a pattern codes storage device 372 which stores
predetermined
pattern codes which are employed to operate a video generator 374 in
accordance with the
timing and strategy established by the MPAR input. The sequences 370 also
provides the
MODTRG output to shift detector 18 (Fig. I ).
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16
The output of the video generator 374 is supplied to a video display 376,
which
provides the stimulus input to the user (Fig. 1).
Referring specifically to Fig. I OB, it is seen that the pattern generator is
a visual
pattern generator including a timing controller 380 which receives the MPAR
input (Fig. 4).
Timing controller 380 provides ON/OFF and select commands to a visual pattern
generator
3 82 in accordance with the timing and strategy established by the MPAR input.
The timing
controller 380 also provides the MODTRG output to shift detector 18 (Fig. 1).
The output of the visual pattern generator 382 is supplied to a display 384,
preferably an LCD display, which provides the stimulus input to the user (Fig.
1 ).
1o Reference is now made to Fig. 11A and 11B, which are block diagrams
illustrating two alternative embodiments of a pattern generator employed in a
pressure stimulus
generating version ofthe system ofFig. 1.
Referring specifically to Fig. IlA, it is seen that the pattern generator is a
pressure pattern generator including a sequencer 390 which receives the MPAR
output (Fig.
15 4). The sequencer 390 interfaces with a pressure pattern codes storage
device 392 which stores
predetermined pressure pattern codes which are employed to operate a
controlled pressure
generator 394 in accordance with the timing and strategy established by the
MPAR input. The
sequences 390 also provides the MODTRG output to shift detector I8 (Fig. 1).
The output of the controlled pressure generator 394 is supplied to a pressure
20 application device 396, which provides the stimulus input to the user (Fig.
I).
Referring specifically to Fig. 11B, it is seen that the pattern generator is a
pressure pattern generator including a timing controller 400 which receives
the MPAR output
(Fig. 4). Timing controller 400 provides ON/OFF and select commands to a
controlled
pressure generator 402 in accordance with the timing and strategy established
by the MPAR
25 input. The timing controller 400 also provides the MODTRG output to shift
detector I8 (Fag.
I).
The output of the pressure pattern generator 402 is supplied to a pressure
application device 404, preferably a cuff or other tactile output device,
which provides the
stimulus input to the user (Fig. 1 ). ,
30 ' Reference is now made to Figs. 12A and 12B, which are block diagrams
illustrating two alternative embodiments of a pattern generator employed in a
electrical
stimulus generating version of the system of Fig. I .
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17
Referring specifically to Fig. 12A, it is seen that the pattern generator is
an
electrical pattern generator including a sequences 410 which,receives the MPAR
output (Fig.
4). The sequences 410 interfaces with an electric pattern codes storage device
412 which
stores predetermined electrical pattern codes which are employed to operate a
current pattern
generator 414 in accordance with the tinting and strategy established by the
MPAR output.
The sequences 410 also provides the MODTRG output to shift detector 18 (Fig. 1
).
The output of the current pattern generator 414 is supplied to an electric
impulse application device, such as electrodes 416, which provide the stimulus
input to the
user (Fig. 1 ).
Referring specifically to Fig. 12B, it is seen that the pattern generator is
an
electrical pattern generator including a timing controller 420 which receives
the MPAR input
(Fig. 4). Timing controller 420 provides ON/OFF and select commands to a
current pattern
generator 422 in accordance with the timing and strategy established by the
MPAR input. The
timing controller 420 also provides the MODTRG output to shift detector 18
(Fig. 1 ).
The output of the electrical pattern generator 422 is supplied to an electric
impulse application device, such as electrodes 426, which provide the stimulus
input to the
user (Fig. 1).
Reference is now made to Fig. 13, which is a block diagram illustrating an
embodiment of a pattern generator employed in a thermal stimulus generating
version in the
system of Fig. 1. It is seen that the pattern generator is a thermal pattern
generator including a
timing controller 430 which receives the MPAR input (Fig. 4). Timing
controller 430 provides
ONIOFF and select commands to a thermal pattern generator 432 in accordance
with the
timing and strategy established by the MPAR input. The timing controller 430
also provides
the MODTRG output to shii3 detector 18 (Fig. 1 ).
The output of the thermal pattern generator 432 is supplied to an thermal
application device 434, such as a heating pad, which provide the stimulus
input to the user
(Fig. 1 ).
Reference is now made to Fig. 14 which is an illustration of a typical
respiration
signal and modification of the respiration signal through the use of an audio
stimulus in
accordance with a preferred embodiment of the present invention.
The respiration signal, indicated by reference numeral 500, is similar to that
shown in Fig. 6 but includes additional features which are subject to the
above-described
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18
analysis of special points. The modification of the respiration signal by
using an audio stimulus
shown in Fig. 14 may be similar to that of Fig. 7, but employs more complex
relationships
between PAR signals, which represent the moving averages of the raw parameters
of the
analyzed biorhythmic activity signal BAS, and the MPAR signals, which
represent the modified
parameters which control the audio stimulus input to the user.
Typical special points which characterize an nth recurrent pattern in the BAS
signal 500 include the following:
a - the location where the first time derivative has a maximum following a
local
minimum;
b - the location at which the BAS signal reaches a maximum, the first time
derivative is equal to zero and the second time derivative is negative;
c - the location at which the first time derivative crosses the value of a
predetermined fraction, e.g. 0.2 of the value of the first time derivative at
point a;
d - the location at which the amplitude of the BAS signal crosses the value of
a predetermined fraction, e.g. 0.7 of the signal amplitude at point b,
calculated with reference
to point a.
Throughout the present specification and claims, point a, is taken to
represent
the onset of the BAS signal.
The special points a - d for each pattern n are stored and the following raw
parameters are calculated therefrom:
P 1 (n) Pattern duration - the duration of pattern n, which is the sum of
P2(n)
and P3(n) defined hereinbelow;
P2(n) Pattern rise time - the time separation between point a and the
following
point b, n indicating the number of the pattern;
P3(n) Pattern fall time - the time separation between point b and following
point a, n indicating the number of the pattern;
P4a(n) Inspiration amplitude - the signal amplitude at point b measured with
reference to previous point a; -
P4b(n) Expiration amplitude - the signal amplitude at point b measured with
reference to following point a;
PS{n) Pattern rest time - the time separation between point a of pattern n+1
and a point 507 obtained by crossing a line connecting points b and d in
pattern n and a
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19
horizontal line passing through point a of pattern n+1. P5(n) is calculated in
practice based
inter alia on parameters P4a(n) and P4b(n}.
P6(n) Breath holding time - the time separation between points c and b.
Referring to the above special points it may be appreciated that the BAS
pattern 500 is
composed of four parts, an inspiration part 502, which is the rising part of
the BAS signal and
corresponds to active inspiratory efforts of a user, a breath holding part
504, which is the
relatively flat part of the signal and corresponds to the inflated state of
the user's lungs of the
user, which is controlled voluntarily by the user in Yoga exercises; an
expiration part 506,
which is part of the falling part of the BAS signal and corresponds to the
recoil of the user's
chest back to its relaxed state; and a rest part 508, which is the rest of the
falling part and
represents a static effortless state of the respiratory cycle known as "post
expiration". The rest
part 508 is known to be sensitive to mental stress or relaxation of the user.
The durations of the various parts of the BAS pattern are represented
graphically by differently shaded parts of the diagram and are indicated by
reference numerals
as follows
Inspiration part - 510
Breath holding part - 511
Expiration part - 512
Rest part - 513
The lower part of Fig. I4 includes an example of a three-part audio stimulus,
which constitutes the input to the user and is produced by the audio pattern
generator shown
in Fig. 9A, which is controlled by the modified parameters MPAR in response to
modified
operator commands MOPC supplied by driver 16 (Fig. 1) in response to operator
selection.
In this example, the selected driving strategy is to induce elongation of the
duration 51 I of the breath holding part 504 and elongation of the falling
part which includes
durations 512 and 513 of the expiration part 506 and the rest part 508
respectively of the BAS
signal of the user. The selected driving strategy also calls for increasing
the ratio between the
duration S I3 of the rest part 508 to the duration 5 I2 of the expiration part
506. At the same
- time, the attention of the user to the music is preferably maintained by
adding non-recurrent
components to the audio stimulus. Randomness can be applied to both the
structure of the
music and the duration of specific parts of the music. Altogether, the
structure of the audio
stimulus is designed to increase the entrainment efficiency, while at the same
time entertaining
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the user. It is to be appreciated that for the sake of conciseness and
clarity, the features of shift
correction, described hereinabove with reference to Fig. 8, are not here
described with
reference to Fig. 14, although they are employed in practice.
In accordance with a preferred embodiment of the present invention an audio
5 stimulus pattern is provided including an inspiration part whose duration is
indicated by
reference numeral 515, a breath holding part, whose duration is indicated by
reference numeral
516 and a falling part, whose duration is indicated by reference numeral 5I7.
The audio stimulus pattern is shown in the illustrated example of Fig. 14 as
including five outputs 520, 522, 524, 526 and 528, each may be corresponding
to a different
10 musical instrument. Each output appears along a separate track and is
designated as follows:
The height of the output indication along each track indicates the pitch
thereof, while the
thickness of the output indication indicates its intensity.
Output 520 is seen to comprise two successive tones 530 and 532, having equal
duration, tone 530 having a pitch and an intensity lower than that of tone
532. The overall
i5 duration 515 of tones 530 and 532 is designated as MPAR Q4 and is equal to
the moving
average of raw parameter P2 minus the moving average of raw parameter P6, here
designated
~P2> - <P6>, which is equal to the current average inspiration duration of the
user.
Output 522 is seen to comprise a single recurring tone 534 having a duration
515 designated as MPAR Q4 and a plurality of non-recurring tones 536,
collectively having a
20 duration 516, corresponding in time mainly to the breath holding part 504
of the BAS signal.
The overall duration of output 522 is designated as MPAR Q2 and is typically
equal to 1.05 -
1.1 times the moving average of raw parameter P2, here designated <P2>, and is
5% to 10%
longer than the current average inspiration duration of the user.
Output 524 is seen to comprise a single recurring tone 538 having a variable
duration 517 designated as MPAR Q3, corresponding in time mainly to the
falling part 506 &
508 of the BAS signal. Duration S 17 (MPAR Q3) is preferably equal to the
moving average
of raw parameter P3 plus one-half a second plus a random time factor R, where
R is between -
0.25 seconds and +0.25 seconds, here designated <P3> + 0.5 + R. The intensity
of output 524
is designated as MPAR Q5 and is proportional to the ratio of the average rest
time to the ,
average expiration time in the BAS signal. This ratio is expressed as
<P3>/(<P3> - <P5>).
Output 526 is seen to comprise a plurality 540 of tones separated from each
other in pitch by equal pitch separations, designated as MPAR Q6. These pitch
separations are
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21
proportional to the reciprocal of the moving average of the pattern duration,
expressed by
1/<P I>.
The duration of the individual ones of the plurality 540 of tones are selected
to
be about one second. The overall duration of the plurality 540 of tones is
designated by MPAR
Q3, referred to above.
Output 528 is seen to comprise a generally non-recurring series of tones of
varying number and duration, whose intensity designated as MPAR Q7, which is
proportional
to the moving average amplitude of raw parameter P4a, expressed by <P4a>.
Output 528 is
provided only when MPAR QI, which equals the sum of Q2 and Q3, is equal to the
moving
average of the pattern duration, i.e. <P I>, is greater than a given value,
typically 6 seconds.
In general, alI or some of the series of tones, designated as outputs 520,
522,
525 and 528, which are presented as discrete tones, may be replaced by
continuous or partially
continuous pitch variations.
Reference is now made to Figs. 15, 16A and 16B which illustrate a biorhythmic
activity monitoring device 600, constructed and operative in accordance with a
preferred
embodiment of the present invention. Biorhythmic activity monitoring device
600 may be
employed with monitor I O of the system of Fig. I disclosed hereinabove.
Stress detecting device 600 preferably includes a biorhythmic activity sensor
602 slidably disposed on a belt 604 worn by a user. Belt 604 is preferably
elastic and/or
stretchable along at least a portion of its length. Output signals of sensor
602 may be
preferably transferred to monitoring apparatus (not shown) either by wired or
wireless
communication. Alternatively, device 600 may be provided with a display 606
for displaying
information obtained from the output of sensor 602 by appropriate processing.
As seen best in Fig. I6A, sensor 602 preferably comprises a deformable
structure 6i0 having a U-shaped structure and constructed of an elastic
material so as. to
permit angular deformation between a pair of legs 612 and 614 of the U-shaped
structure. A
force transducer 6I6 is preferably fixedly attached to an inner surface of leg
612, such as by
bonding thereto, and is mechanically linked via an elastic body member 618 to
an inner surface
- of leg 614.
Alternatively, as seen in Fig. I6B, force transducer 616 together with elastic
body member 618, which respond to compressive stress only, may be replaced by
a force
transducer 617 which responds to stretching and may be located in any part of
deformable
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22
structure 610 that deforms under forces exerted by belt 604 thereupon. Force
transducer 6I6
or 617 may be responsive to an electrical property, such as resistance,
capacitance or
inductance, in which case two electric leads 620 and 622 may be attached
thereto for
transmitting electrical output thereof. It is appreciated that deformable
stzucture 610 may be
fabricated in a variety of other shapes, as long as a deformation of the
structure 610 may be _
transferred to transducer 616.
Deformable structure 6I0 of sensor 602 presses against a user's body or
clothing by stretchable belt 604. Displacement of belt 604 in a direction
generally perpendicular
to its length is preferably limited by a cover 624 or any other suitable
device, such as a flange
(not shown) on deformabIe structure 610. An upper surface of leg 614 is
preferably smooth
and cover 624 is configured so as not to touch belt 604 and to permit sensor
602 to slide along
belt 604.
Circumferential changes of a user's body, such as at the chest or abdomen,
cause corresponding length changes in elastic belt 604 which can be monitored
by sensor 602.
These length changes cause tension changes in belt 604 which cause deformation
of
deformabie structure 610, since belt 604 abuts thereagainst. Transducer 616
then outputs a
signal in correspondence with a deformation of deformable structure 610. The
structure of
sensor 602 eliminates force components in belt 604 not associated with the
circumferential
changes. This feature makes sensor 602 relatively insensitive to body
movements not
associated with breathing.
The sensor disclosed in U.S. Patent 5,423,328 is also capable of monitoring
breathing of a user, as described therein. However, the sensor of U.S. Patent
5,423,328 suffers
from two problems which the present invention solves, as described
hereinbelow.
The first problem is that the force acting on the base of the '328 sensor
depends
on the angle between the elastic belt and the top of the sensor base. This
means that the '328
sensor is sensitive to the particular position of the sensor on the user's
body. For example, the
'328 sensor will give a different output depending upon whether it is mounted
on the abdomen
or on the breast of a woman, which differ in curvature. The '328 sensor does
not function if
mounted over a concave surface, such as between a woman's breasts or folds of
abdomen in
fat persons, and also does not function when a user is lying on the sensor
base, so the sensor is
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23
"buried". This is because the sensor base of the '328 sensor is not supported,
and no force is
transferred in these cases to the transducer.
The second problem is that the '328 sensor is sensitive to "belt trapping". If
a
user Leans against a surface in such a way that the belt is sandwiched between
the user's body
' S and the supporting surface, e.g., while sleeping or leaning back against a
chair, the belt
becomes trapped with the result that changes in the chest or abdomen
circumference at this
region do not induce corresponding variations in the belt length.
The present invention solves the first problem of angle dependence by
providing
a pair of smooth cylindrical guides 630 on an extension of leg 6I2 of
deformable structure 610,
1 o through which elastic belt 604 is guided. As a result, tensions in belt
604 are transferred to leg
6I4 of deformable structure 610 at a constant angle, irrespective of the angle
at which elastic
belt 604 reaches deformable structure 6I0. In addition, the support of leg 612
by a body
surface does not play any role in the function of device 600.
Reference is now made additionally to Figs. 17A, 17B and 17C. The present
15 invention solves the second problem of "belt trapping" by providing a belt
protector 640 that
creates a low-friction guide for elastic belt 604 which runs therethrough.
Because of the low
coefficient of friction between belt 604 and belt protector 640, belt 604 is
free to expand along
its length without being "trapped" against or "pinched" between internal parts
of belt protector
640.
20 Belt protector 640 is preferably flexible, at least along a portion of its
length.
Belt protector 640 may be constructed from one or more parts, each of which
may be elastic or
flexible. Belt protector 640 may have a variety of forms. Fig. 17A illustrates
a generally
rectangular cross section. Fig. 17B illustrates a generally circular cross
section, and Fig. I7C
illustrates a generally spiral form. Preferably, one portion of belt protector
640 may be attached
25 to another portion thereof, so as to facilitate wrapping of belt protector
640 around a user. For
example, at least a portion of an outer surface of belt protector 640 may be
constructed of
VELCRO brand multiple hook fastener so as to self stick to another portion of
the outer
surface. Alternatively, especially for the circular cross section
configuration shown in Fig. 17B,
belt protector 640 may include a silicone rubber tube which may be caused to
adhere to
30 another portion of belt protector 640.
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24
It is noted that device 600 may be provided with guides 630 but without belt
protector 640, or vice versa, without guides 630 but with belt protector 640,
depending on the
particular requirements and implementation of device 600. Guides 630 may be
suitable adapted
to the configuration of beat protector 640. For example, in the case of a
circular cross sectional
belt 604 and belt protector 640, guides 630 may include a hole or grooves for
guiding
therethrough belt 604.
The structure of sensor 602 enables calibrating sensor output with respect to
magnitude of breathing movements. It is essential for signal calibration of
sensor 602 that
circumferential changes associated with breathing movements of a user should
be translated
70 into proportional changes in the length of belt 604, independently of the
chest/abdomen
diameter. This may be accomplished simply by wrapping belt 604 completely
around the user's
body, as shown in Fig. 15. It is appreciated that monitoring circumferential
changes, as
disclosed, is not restricted to breathing movements. For example, uterus
contractions produce
circumferential changes at the belly height in pregnant women. Quantification
of such
contractions, without exerting significant pressure, is a feature with signif
cant commercial
importance.
The following discussion will show that this arrangement meets the above
mentioned requirement.
Let L be the length of the stretchable part of belt 604, which subtends an
angle
~ (360° per turn), when it is wrapped around. The relation L = k~, is
preserved for a constant
k, if the belt sticks to the body, k being a geometrical proportionality
constant. Thus, the same
relation holds for circumferential changes, i.e. OL=k ~c~. Thus dLIL= ~~/~, as
required.
In the embodiments of Figs. 15, 16A and 16B, belt protector 640 is preferably
attached to sensor 602. Reference is now made to Fig. 18 which illustrates a
portion of a
biorhythmic activity sensor 650, constructed and operative in accordance with
another
preferred embodiment of the present invention. In this embodiment, deformable
structure 610
is encapsulated by belt protector 640, and cover 624 may be eliminated if
desired. Deformable
structure 610 is preferably fixedly attached to one side of belt protector
640. One of the .
smooth cylindrical guides 630 may be eliminated, and instead, belt 604 is
preferably fixed to a
post 651.
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Reference is now made to Fig. 19 which illustrates a portion of a biorhythmic
activity sensor 660, constructed and operative in accordance with yet another
preferred
embodiment of the present invention.
Biorhythmic activity sensor 660 preferably includes a belt 662 which is
disposed
_ 5 in a belt protector 664, which are preferably substantially identical to
belt 604 and belt
protector 640, respectively, described hereinabove. One end 666 of belt 662 is
preferably fixed
to an inner surface of belt protector 664, and an opposite end 668 of belt 662
is preferably
attached to a force transducer 670. Force transducer 670 responds to
stretching forces acting
thereupon, and may be electrical, in which case, it is supplied with two
electrical leads 672 and
10 674. This embodiment thus eliminates the need for a deformable structure
and belt guides of
the embodiments of Figs. I 5 - 18.
It is appreciated that various features of the invention which are, for
clarity,
described in the contexts of separate embodiments may also be provided in
combination in a
single embodiment. Conversely, various features of the invention which are,
for brevity,
15 described in the context of a single embodiment may also be provided
separately or in any
suitable subcombination.
It will be appreciated by persons skilled in the art that the present
invention is
not limited by what has been particularly shown and described hereinabove.
Rather the scope
of the present invention is defined only by the claims which follow:
