Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR APPLYING A USER
SELE(~ .~ FREQUENCY RESPONSE PATTERN TO AUDIO
SIGNALS PROVIDED TO A CELLULAR TELEPHONE SPEAKER
BACKGROUND OF THE INVENTION
I. Field of the Invention
The invention generally relates to cellular telephones and other
10 mobile telephones and in particular to the audio output of a cellular
telephone.
II. Description of the Related Art
In designing cellular telephones and other mobile telephones,
engineers typically attempt to provide a flat fre~uency response pattern for
audio signals provided to the speal~er of the cellular telephone to thereby
ensure that the voice of the other party to a telephone call is reproduced as
accurately as possible. The bandwidth of audio signals transmitted within
20 cellular systems is fairly narrow and the best fre~uency response pattem thatcan typically be achieved is one that is relatively flat within the fairly narrow
bandwidth. An example of such a frequency response pattern (represented
in arbitrary units) is illustrated in FIG. 1. As can be seen, the frequency
response 2 is relatively flat within a central range of frequer.cies 4.
Such a flat frequency response pattern is best for many usage
situations but may not be desirable for others. ~or example, a user may
operate the cellular telephone is a noisy environment wherein the sound
spectrum of the noise is skewed toward higher or lower frequencies.
Examples include manufacturing environments wherein noise may be
30 either primarily high pitched or primarily low pitched. A cellular telephone
providing a fairly flat frequency response to output voice signals may not be
ideal for such situations. In other situations, as a result of signal
trarl-cmicsion prob}ems, the received voice signal of the other party may be
skewed in frequency. Indeed, the hearing range of the user may, itself, be
35 skewed either toward higher or lower frequencies such that a flat cellular
telephone output frequency response may not be ideal regardless of the
presence of noise or transmission problems.
For such situations and for such users, it would be desirable to allow
the user to modify the freguency response pattern of the output audio
40 signals to yield a signal that is more easily heard. For example, if the noise
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spectrum of the environment in which the cellular telephone is operated is
skewed toward higher frequencies or if the received signal, as a result of
transmission problems lacks sufficient higher frequencies, it would be
desirable to allow the user to increase the output level of the cellular
5 telephone speaker for the higher frequencies to thereby allow the user to
hear the other party more clearly. Likewise, for a user who may not hear as
well at higher frequencies than at lower frequencies, it would also be
desirable to allow the user to increase the sound levels for the higher
frequencies. Even in the absence of significant noise or transmission
10 problems and even for users having normal hearing, it is still desirable to
allow the user to ad~ust the frequency response, even if only to achieve a
perceived listening improvement.
However, typical cellular telephones and other mobile telephones do
not provide the user with the capability of adjusting the fre~uency response
15 pattem. Accordingly, there is a need to remedy that deficiency, and it is to
that end that the invention is primarily drawn.
SUMMARY OF THE INVENTION
In accordance with the invention, a cellular telephone or other
mobile telephone having an audio speaker or other audio transducer is
provided with a means for receiving audio signals and a means for filtering
the audio signals to alter a frequency response pattern thereof. The means
for filtering operates in response to user control to al~ow the user to adjust
the frequency response pattern as desired. In th~s manner, the user may
adjust the frequency response to compensate for local noise or transmission
problems or for hearing abnormalities to thereby allow the user to hear the
other party to a telephone call more clearly. At minimum, the user may
gain at least a perceived listening improvement.
In an exemplary embodiment, the means filtering the audio signals
operates to filter the audio signals provided to the speaker in accordance
with one of a predetermined set of frequency ~e~ se patterns. In one
specific embodiment, the cellular telephone includes a means for storing
selected sets of audio frequency filter parameters and the user selects one of
35 the sets of filter parameters by pressing a corresponding button on a front
control panel of the cellular telephone. In another embodiment, the
cellular telephone includes an equalizer scroll bar allowing a larger number
of sets of filter parameters to be conveniently accP~se~.
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The invention is particularly well suited for use in cellular
telephones employing digital signal processing (DSP) units which digitally
process audio signals, for example, to decode received vocoder packets.
Within such cellular telephones, the DSP is merely reconfigured or
reprogrammed to filter the audio signals subsequent to vocoder decoding. A
wide variety of other implementations are also possible.
BRIEF DESCRIPTION OF THE DRAWINGS
The features, objects, and advantages of the present invention will
become more apparent from the detailed description set forth below when
taken in conjunction with the drawings in which like reference characters
identify correspondingly throughout and wherein:
1~ FIG. 1 is a graph of a typical fre~uency response pattern for a cellular
telephone configured in accordance with the prior art;
FIG. 2 is a bloclc diagram of a cellular telephone configured, in
accordance with a first exemplary embodiment of the invention, with a set
of frequency response selection buttons allowing a user to select one of a set
of predetermined fre~uency response patterns;
FIGS. 3A - 3D are graphs illustrating exemplary frequency response
patterns employed by the cellular telephone of FIG. 2;
FIG. 4 is a bloc}c diagram of pertinent internal components of the
cellular telephone of FIG. 2;
FIG. S is a block diagram of a cellular telephone configured, in
accordance with a second exemplary embodiment of the in~ention, with a
single frequency response selection scroll bar allowing the user to scroll
through a set of predeterrnined frequency response patterns.
DETAILED DESCRIPTION OF THE PREFERRED
EMBODIMENTS
With reference to the remaining figures, exemplary embodiments of
the invention will now be described. The exemplary embodiments will
35 primarily be described with reference to block diagrams illustrating
apparatus elements. It shouid be appreciated that not all components
necess~ry for a complete implementation of a practical system are illustrated
or described in detail. Rather, only those components necessary for a
thorough understanding of the in~rention are illustrated and described.
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FIG. 2 illustrates the external components of a cellular telephone 10
having a front control panel 11 including a keypad 12, a PHONE button 14, a
SEND button 16, a display 18 and a set of equalizer buttons generally denoted
20. In a preferred embodiment, a single button is used to scroll throu~h the
5 equalization options. Cellular telephone 10 also includes a microphone 22,
a speaker 24, and an antenna 26. In use, a user presses PHONE button 14 to
activate cellular telephone 10, enters a telephone number to be dialed using
keypad t2, then presses SEND button 16 to transmit the telephone number
to a local cellular ~ase station (not shown) to thereby initiate a telephone call
10 to a remote user. Once the telephone call is connected, the user speaks
through microphone 22 and hears the voice of the other party to the
telephone call through speaker 24.
During the telephone call (or at any other time) the user may press
one of the equalizer buttons 20. Equalizer buttons 20 control internal
15 components (to be described in greater detail below) for adjusting the
frequency response of audio signals output throu~h speaker 24, perhaps to
allow the other party to be more easily heard. Four such eql-~li7er buttons
20 are shown in FIG. 2. The four buttons provide frequency response
patterns having, respectively, enhanced high and low frequencies, enhanced
20 high frequencies only, enhanced low frequencies only, and reduced high
and low frequencies. Graphs illustrating the four frequency response
patterns (in arbitrary units) are provided in FIGS. 3A - 3D. In other
embodiments more or fewer equalizer buttons 20 are provided, or
alternative fre~uency response patterns are provided, or both. In general,
25 ~ny desired frequency response pattern can be pre-programmed by the
manufacturer. In an embodiment to be described below, the front panel of
the cellular telephone includes an eqll~li7Pr scroll bar allowing the user to
scroll through a greater number of frequency response patterns than can be
accommodated with separate equalization buttons 20 each controlling only a
30 single corresponding frequency response pattern.
If the user presses one of buttons 20, the frequency response pattem
colle~l.onding to the pressed button is applied to audio signals provided to
speaker 24, i.e. the audio signals are filtered in accordance with the selectet
frequency response pattern. Thereafter, the voice of the other party to the
35 call (and all other sounds to be output through the speaker) are adjusted in
accordance with the selected frequency response. Thus, for example, the
user may select frequency response 27 of FIG. 3A which de-emphasizes
center frequencies 28. If the user has trou~le hearing higher frequencies, he
or she may select frequency response 29 of FIG. 3B which enhances higher
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frequencies 30. As another example, if the user is in an environment
having significant low frequency noise, the user may select fre~uency
response pattern 31 of FIG. 3C to thereby increase low frequencies 32 to
compensate for the noise. As a last example, the user may select frequency
-5 response pattem 33 of FIG. 3D to de-emphasize both high frequencies 34 and
low frequencies 35.
~To select another frequency response pattern, the user merely presses
the corresponding button 20 of the desired pattern. The previously pressed
button is automatically returned to is normal position. To return to a
10 default state wherein a relatively flat frequency response (or a default
frequency response pattem) is provided, the user merely re-presses the
currently de-pressed button. In an alternative embodiment, the buttons
employed for selecting frequency response patterns serve other uses as well.
In such an embodiment, a MODE button (not shown) is provided to allow
15 selection of the operational mode of the buttons. In that embodiment, the
buttons operate to adjust the frequency response only while placed in the
appropriate mode.
Although not shown in FIG. 2, indicia may be provided on cellular
telephone front control panel 11 adjacent to buttons 20 identifying the
20 fre~uency response pattern associated with each button. Altematively, or in
addition, suitable identifying graphics or text may be presented on the
display. In particular, the shape of the corresponding frequency response
pattern may be displayed graphically within display 24. Such a graphical
display is particular~y desirable for embodiments wherein the buttons serve
25 multiple purposes thereby allowing the currently selected functions of the
buttons to be properly identified.
The manner by which the fre~uency response patterns are applied to
the audio signals will now be described with reference to FIG. 4 which
illustrates pertinent internal components of cellular telephone 10. More
30 specifically, FIG. 4 illustrates that cellular telephone 10 inclutes a control
unit 40, a DSP 42, a receiver/transmitter unit 44, a digital-to-analog (D~A)
converter 46 and an analog-to-.li~it~l (A/D) converter 48. DSP 42 further
includes a vocoder encoder 50, a vocoder decoder 52, an equalization fil~er 54
and a filter table 56. Front control panel 11, microphone 22, speaker 24 and
35 antenna 26 are also shown symbolically in FIG. 4.
In use, as user of cellular telephone 10 speaks into microphone 22, his
or her voice is routed by control unit 40 into the DSP 42 for processing
therein. Vocoder encoder 50 of DSP 42 converts the voice signals into
vocoder packets. The packets are encoded, by units not separately shown,
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using a cellular transmission protocol such as Code Division Multiple
Access (CDMA). The encoded signals are routed to receiver/transmitter 44
for transmission via antenna 26 to the local base station (not shown) and
forwarded therefrom to a remote telephone (also not shown). Voice signals,
5 in the form of encoded vocoder data packets, are received by DSP 42 either
directly from receive/transmitter unit 44 or from the additional CDMA
processing units not separately shown. The vocoder packets are decoded by
vocoder decoder 52 of DSP 42 into a digital speech signal. The digital speech
signal is routed through equalization filter 54 which, if controlled to do so,
10 filters the speech signal in accordance with a selected set of filtering
p~rameters read from filter table 56. The digital filtered signal is converted to
an analog signal by D/A converter 46 then provided to speaker 24. All of the
forgoing operations are performed under the control of control unit 40.
If the user pressed one of the equalization buttons 20 of the front
15 control panel 11, control unit 40 receives the user selection and controls DSP
42 to adjust the fre~uency response accordingly via equalization filter 54.
More specifically, DSP 42 reads predetermined digital filter parameters
corresponding to the selected frequency response pattern from filter table 42,
then equalization filter 54 filters the signal using the selected filter
~0 parameters in accordance with otherwise conventional techniques. Filter
table 42 may be a ROM, RAM or similar storage device having the filter
coefficients stored therein for the four frequency response patterns of FIGS.
3A - 3D. If the user does not select a specific frequency response pattern,
then e~ualization filter 54 either does not filter the digital signal or it
25 employs a default set of filter parameters read from filter table 56.
As noted, the resulting filtered digital speech signal is converted to an
analog signal by D/A converter 46 for output to speaker 24. The user thereby
hears the voice of the other party (or whatever other sounds are received by
the telephone) subject to the selected frequency response pattern. The user
30 may change the frequency response pattern any number of times during a
single telephone call as needed or desired.
The filtering is applied only to the received signals. Hence, the voice
of the user is not filtered for the other party, althou~h such a feature could
be provided in alternative embodiments. Additional conventional filters
35 may be provided within the DSP, or in conjunction therewith, for
performing conventional filtering operations such as noise reduction or
smoothing.
Thus FIGS. 2 - 4 illustrate a first embodiment wherein separate
buttons 20 are provided for each of a predetermined set of f~ecluency
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response patterns. In a second embodiment illustrated in FIG. 5, a single
scroll bar 120 is provided for selecting the frequency response. The
arrangement of FIG. 5 is similar to that of FIG. 2 and like components are
identified with like refere,lce numerals incremented by 100. Only pertinent
5 differences will be described in detail. Briefly, FIG. 5 illustrates a ce}lular
telephone 110 having a front control panel 111 including a keypad 112, a
PHONE button 114, a SEND button 116, a display 118 and single scroll bar
120. Cellular telephone 110 also includes a microphone 122, a speaker 124,
and an antenna 126.
Scroll bar 120 allows the user to scroll through a set of predetermined
frequency response patterns. As with the embodiment of FIG. Z, the patterns
are pre-stored as filter parameters in a filter table accessible by an
equalization filter (neither shown in FIG. 5). A graphic is presented within
display 120 (under control of an internal control unit also not shown)
15 illustrating the currently selected frequency response pattern.
By providing scroll bar 120, rather than individual buttons, any
number of different predetermined frequency response patterns may be
provided. The user simply scrolls through the patterns until finding one
that provides the greatest clarity or is otherwise most desirable.
20 Deactivation of the frequency pattern adjustment is achieved by scrolling
until reaching the end of the predetermined patterns, after which either no
filtering or default filtering is again employed.
What has been described are exemplary embodiments of a cellular
telephone configured to allow a user to select a frequency response pattern
25 for applying to audio signals output through the speaker of telephone. in
general, any desired frequency response pattern may be provided by the
manufacturer merely by pre-programming the filter table with appropriate
values. As noted, the filter parameters may be set to yield fre~uency
response patterns substantially as shown in FIGS. 3A - 3D. In other cases,
30 appropriate filter parameters may be determined empirically by testing
actual users with a variety of frequency response patterns to determine
which are most useful or desired. As can be appreciated, a wide range of
possible techniques for determining the appropriate filter parameters for
storage in the filter table may be employed consistent with the general
principles of the invention. Furthermore, a filter table is not necess~ry.
Rather, any suitable means for filtering may be employed. For example, the
audio signals subsequent to conversion to analog signals may be routed
through electronic circuitry configured to directly vary the electrical
characlelislics of the audio signals.
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The previous description of the preferred embodiments is provided
to enable any person skilled in the art to malce or use the present invention.
The various modifications to these embodiments will be readily apparent to
those skilled in the art, and the generic principles defined herein may be
5 applied to other embodiments without the use of the inventive faculty.
Thus, the present invention is not intended to be limited to the
embodiments shown herein but is to be accorded the widest scope consistent
with the principles and novel features disclosed herein.
10 WE CLAIM:
