Note: Descriptions are shown in the official language in which they were submitted.
CA 02248019 1998-09-02
Process and device for the transmission of sound.
The invention concerns a process for the transmission of sound by meansof at least one sound transmission means, which emits sound signals
perceivable by a person.
Such processes serve, for instance, in the transfer of music picked up by a
microphone or recorded on a recording medium. In this connection, the
sound transmission means is a loudspeaker or also a head phone which
emits sound signals in such a manner that they are coupled to human
hearing via the eardrum. Via loudspeakers which are placed in rooms or in
headphones, the eardrum is vibrated by such acoustic signals which are, in
turn, processed by the internal hearing organ of the individual. In specific,
such incoming signals enter the hearing passage and make contact with
the eardrum which is set into vibrating motion which is carried over to the
hammer, anvil and stirrup bones of the middle ear resulting in further
processing by the cochlea.
Problematic to this well-known auditory process are acoustic signals which
have a frequency somewhat under 700 Hertz (Hz). As human hearing is
CA 02248019 1998-09-02
particularly sensitive to frequencies in the range between 700 and 6,000
Hz, a sound in this range need only have a moderate intensity to be
perceived. In contrast to this, considerably higher volume is needed in
order that frequencies lower than 700 Hz are perceived. This characteristic
of human hearing proves itself to be a particular disadvantage regarding
the transmission of music, as in such a case lower frequencies (i.e., under
700 Hz) are strongly suppressed.
As a result of such suppression the acoustic signals used to perform
rhythm are extremely pushed into the background so that, as a result,
transmitted music is less lively. In order to counteract this condition
various processes are known which can make possible an effective
increase of the sound pressure of low-frequency audio signals.
One known procedure, for example, involves the general increase in
volume of transmitted audio waves of music. Hereby, lower frequency
signals are, in comparison to mid- and higher-range signals, louder, as the
suppression curve becomes flatter with increasing sound pressure.
Detrimental in this process, however, is the fact that mid- and high-range
audio signals manifest a higher wave pressure and concomitantly a
considerably higher volume that, in extreme cases, is so high that the pain
threshold of a person is reached or exceeded. This leads to an
overburdening of the eardrum which, in the long run, can lead to hearing
damage .
In another well-known procedure lower frequencies, as contrasted to mid-
and/or higher-frequency audio signals, are especially amplified. This has
the advantage that in the mid- and higher-frequency ranges, the pain
~ CA 02248019 1998-09-02
threshold is not reached. A disadvantage here, however, is that such a
procedure, to be successful, requires complex amplifiers having a variable
amplification capacity (an amplification factor of about 1 to 10 million )
which are exceptionally complex and, accordingly, costly and which,
additionally, require a considerable energy demand. Furthermore, such
systems require complex sound transmission means, for example large
loudspeakers, which due to their complexity and large size can be
transported only with considerable effort.
EP 0 553 525 A1 discloses a device for the transmission of sound where
sound transmission means are arranged in the abdominal or in the dorsal
region of a person. Especially when the means are located in the abdominal
region, but also when they are located in the dorsal region, a relatively
high degree of dampening of the sound occurs already over short
distances, the skin, tissue and other parts of the body underlying the
sound transmission means having extremely good dampening
characteristics .
US 4 641 345 describes a device for the transmission of sound where the
sound transmission means is arranged at the back of a vehicle seat. The
transmission of sound to the body is dampened considerably is this case as
well. The dampening effect is produced in this case not only by the skin,
tissue and other parts of the body, but in addition also by the dampening
characteristics of the driver's seat.
Accordingly, the object of the invention is to improve a process of audio
signal transmission of the described category so that along with mid- and
higher-frequency audio waves, low-frequency audio waves can also be
transmitted economically and, technically speaking, easily and,
CA 02248019 1998-09-02
consequently, with extreme efficiency and, above all, without dampening
losses.
In a process for transmission of sound as described at the outset, the
stated object is achieved according to the invention by the fact that for
transmitting low-frequency sound signals, in particular, the sound
transmission means is positioned in the chest region, in the vicinity of the
breastbone, of the person so that a direct transmission path is obtained
from the sound transmission means via the Eustachian tube to the bones
of the middle ear of the person.
The transmission especially of low-frequency audio waves by sound
transmission means positioned in the vicinity of the breastbone of a person
via the Eustachian tube to the bones of the middle ear provides on the one
hand the particular advantage that the eardrum and, thus, the dampening
effect of the eardrum are bypassed. Accordingly, there is no need for
compensation of the dampening effect, for example by variable audio
amplification of the like, in order to achieve transmission of low-frequency
audio signals in a way properly adapted to human hearing.
On the other hand, it is an advantage that by arranging the sound
transmission means in the vicinity of the breastbone the vibrations are
transmitted to the entire chest cavity, the breastbone being connected with
the ribs and, via the latter, with the pleura. The chest cavity in its turn setsthe air in the lobes of the lung into vibration. From there, the vibrations
propagate via the pharyngeal tube to the Eustachian tube and from there to
the bones of the middle ear. It is the advantage of this arrangement that
the entire chest cavity is used as a resonator forming sort of a band pass
filter similar to the well-known subwoofer. One thereby obtains a
CA 02248019 1998-09-02
particularly advantageous transmission, especially of low-frequency audio
signals, while bypassing the eardrum.
The process can be realized with simple technical means and requires only
a relatively low amount of energy. It can, accordingly, also be effected in a
mobile device.
In order to transmit the entire frequency spectrum of audio waves
previously mentioned, an especially profitable embodiment of the process
provides that the audio signals are additionally transmitted via another
sound transmission means, for example a loudspeaker of a headphone,
which would make possible the coupling of acoustic signals to the eardrum
of the person.
In such a manner mid- and/or higher-frequency waves, in particular, could
be transmitted in a conventional manner to the eardrum while at the same
time, independent to this, lower-frequency waves will be additionally
transmitted in an especially effective way via sound transmission means
which for example could be placed in the area of the breastbone of a
person.
The sound transmission means could be a loudspeaker or a resonator or
the like, all known as such.
The stated object is also achieved according to the invention by a device
for the transmission of sound with at least one sound transmission means,
in which the at least one sound transmission means is positioned in the
chest region of a person in the vicinity of the breastbone, so that a direct
-
CA 02248019 1998-09-02
sound transmission path from the sound transmission means via the
Eustachian tube to the bones of the middle ear of the person is obtained.
In particular, regarding the selection of audio signals that are transmitted
via sound transmission means placed in this way in the vicinity of the
breastbone of a person, it is particularly advantageous that the at least one
sound transmission means is preceded by at least one distribution device
for the distribution of the sound signals.
Principally speaking, the most varied configurations of distribution devices
could be used; advantageously the at least one distribution device includes
at least one frequency filter device.
With regard to the frequency filter means, the most varied configurations
are conceivable; advantageously the frequency filter is a low pass which,
technically speaking, would be easy to realize.
Also possible, however, would be that the frequency filter device involve a
frequency switch and a low pass, as well as a high pass - whereby mid-
and high-frequency waves passing through the high pass would be
transmitted via a further transmission means which emits sound coupled to
the eardrum of the person.
Sound transfer devices which could be considered here involve the most
varied implementations. Technically simple implementations would be
loudspeakers and/or resonators.
Further details and advantages of the invention are explained in greater
detail in the following description with reference to the drawings.
- CA 02248019 1998-09-02
In the drawings are shown:
Fig. 1: a schematic flowchart of the inventive process for transmission of
sound;
Fig. 2: an inventive device for transmission of sound.
The invention concerning the transmission of sound is best described on
the basis of fig. 1. As can be seen in fig. 1, sound signals are conveyed
from a sound source (40) to a distribution means (50). In principle, a
multiplicity of apparatuses could be considered respective to the use as
distribution means (50). For example a frequency filter means or a
frequency switch which, further, could for example be realized via a low
pass (20) and a high pass (30). Higher-frequency sound signals would
thereby be transferred via the eardrum (60) to the inner ear (80) whereas
lower-frequency sound signals would be transmitted over the breastbone
(70) to the inner ear (80). The transfer is effected for instance via
loudspeakers (27), (37) whereby the subsequently switched loudspeakers
(27) coupled with the low pass is positioned in the vicinity of the
breastbone (70), while the loudspeaker linked to the high pass (37) is
exemplarily presented in the form of a headphone. It goes without saying
that the lower-frequency sound signals can be additionally transmitted via
the loudspeaker (37).
An example of such a setup for the transmission of sound, which is given
in figure 2, includes a sound pickup or transmission device (10), for
example a tape recorder or a microphone with an activated amplifier,
which transmits signals over a signal line (11) to the frequency filter means
in the form a low-pass (20) and high-pass (30).
CA 02248019 1998-09-02
Only lower-frequency sound signals pass through the low-pass (20), where
the low-pass (20) is so constructed that only sound signals lower than 700
Hz can pass through it, while at the same time mid- and higher-frequency
sound signals above 700 Hz of the sound signals are filtered out of the
low-pass (20).
Contrastingly, only mid- and/or higher-frequency sound signals above 700
Hz pass through the high-pass (30) while sound signals under 700 Hz are
filtered out of the sound signals of the high-pass (30).
Regarding the low-pass (20) as well as the high-pass (39), appropriately
engineered amplifiers (25), (35) can be subsequently activated respective
to their assigned frequency ranges - such frequencies of which are, in turn,
transmitted by the amplifiers to the loudspeakers (27), (37).
As mentioned above, the loudspeaker (27) is arranged in the vicinity of the
breastbone (70) of a person so that a direct sound transmission path from
the loudspeaker (27) over the chest cavity, to the Eustachian tubes, and
then to the bones of the middle ear results. The chest cavity of the person
functions, hereby, as an additional resonating body similar to that used for
the transmission of low-frequency sound signals in audiotechnics -- a
subwoofer.
The loudspeaker (37) can, for example, be the familiar loudspeaker, or as
has already been mentioned above, a headphone or anything similar which
can make possible the coupling of sound via the eardrum of a person (69).
CA 02248019 1998-09-02
Via this is technical apparatus, mid- and higher-frequency sound signals are
transmitted in an already well-known manner by utilization of the eardrum
of a person (69) while lower-frequency sound signals are essentially
transferred over the chest cavity and the Eustachian tubes to the bones of
the middle ear of a person (80). As a result, one achieves a particularly
realistic transmission of sound, in particular that of music.
Such a technical apparatus can be realized on the basis of simple technical
means. Such a system is light, compact and portable and is, accordingly,
useable everywhere, anytime. Particularly so in the case of portable
devices similar to cassette recorders or CD-players. Further, such a system
requires very little energy and can be even driven by battery, whereby,
such a system would be independent of external energy sources. Finally,
such a system, on the basis of the preceding argumentation, is also
particularly economical to manufacture and is, accordingly, also a good
value for the customer.
