U.S. patent application number 11/845815 was filed with the patent office on 2008-08-07 for audio reproduction method and apparatus with auto volume control function.
This patent application is currently assigned to Samsung Electronics Co., Ltd.. Invention is credited to Chi-ho Jung.
Application Number | 20080187149 11/845815 |
Document ID | / |
Family ID | 39674222 |
Filed Date | 2008-08-07 |
United States Patent
Application |
20080187149 |
Kind Code |
A1 |
Jung; Chi-ho |
August 7, 2008 |
AUDIO REPRODUCTION METHOD AND APPARATUS WITH AUTO VOLUME CONTROL
FUNCTION
Abstract
An audio reproduction method and apparatus, in which an audio
volume is automatically controlled based on audio energy and human
auditory characteristics. The audio reproduction method includes
splitting a reproduction audio signal into audio signals
corresponding to a plurality of frequency bands, extracting audio
energy for each of the frequency bands, and comparing the audio
energy for each of the frequency bands with a predetermined
threshold and controlling the volume of the audio signal
corresponding to each of the frequency bands.
Inventors: |
Jung; Chi-ho; (Seoul,
KR) |
Correspondence
Address: |
STANZIONE & KIM, LLP
919 18TH STREET, N.W., SUITE 440
WASHINGTON
DC
20006
US
|
Assignee: |
Samsung Electronics Co.,
Ltd.
Suwon-si
KR
|
Family ID: |
39674222 |
Appl. No.: |
11/845815 |
Filed: |
August 28, 2007 |
Current U.S.
Class: |
381/72 |
Current CPC
Class: |
H04R 3/04 20130101; H03G
5/165 20130101; H03G 9/025 20130101 |
Class at
Publication: |
381/72 |
International
Class: |
A61F 11/06 20060101
A61F011/06 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 1, 2007 |
KR |
2007-10677 |
Claims
1. An audio reproduction method comprising: splitting a
reproduction audio signal into audio signals corresponding to a
plurality of frequency bands; extracting audio energy for each of
the frequency bands; and comparing the audio energy for each of the
frequency bands with a predetermined threshold to control a volume
of an input audio signal corresponding to each of the frequency
bands.
2. The audio reproduction method of claim 1, wherein the threshold
comprises preset auditory characteristic data.
3. The audio reproduction method of claim 1, wherein the extraction
of the audio energy comprises: counting a reproduction time of each
audio signal having a higher level than a second predetermined
threshold for a predetermined period of time and storing the
counted reproduction time; extracting an audio volume value for
each of the frequency bands; and calculating the audio energy based
on the stored reproduction time and the extracted audio volume
value.
4. The audio reproduction method of claim 1, wherein the
controlling of the volume of the audio signal comprises: comparing
the audio energy for each of the frequency bands with the
predetermined threshold; generating a volume control signal every
time the audio energy exceeds the predetermined threshold; and
controlling the volume of the audio signal corresponding to each of
the frequency bands according to the volume control signal.
5. The audio reproduction method of claim 1, further comprising:
generating a predetermined alarm signal for a corresponding
frequency band if the audio energy for the frequency band exceeds
the predetermined threshold.
6. An audio reproduction apparatus comprising: a band splitting
unit to split a reproduction audio signal into audio signals
corresponding to a plurality of frequency bands; an audio
monitoring unit to accumulate reproduced audio energy for each of
the frequency bands, comparing the audio energy for each of the
frequency bands with a predetermined threshold, and to generate
volume control information; and a volume control unit to control a
volume of an input audio signal corresponding to each of the
frequency bands according to the volume control information
generated by the audio monitoring unit.
7. The audio reproduction apparatus of claim 6, wherein the audio
monitoring unit comprises: a reproduction time counting unit to
count the reproduction time of an audio signal having a higher
level than a predetermined threshold for a predetermined period of
time; a volume counting unit to extract an audio volume value for
each of the frequency bands; an audio energy calculation unit to
calculate the audio energy for each of the frequency bands based on
the stored reproduction time and the extracted audio volume value;
a threshold storage unit to store auditory thresholds for the
frequency bands based on human auditory characteristics; and a
volume control processing unit to compare the audio energy for each
of the frequency bands, calculated by the audio energy calculation
unit, with the threshold for each of the frequency bands, stored in
the threshold storage unit, and generating an alarm signal of a
particular pattern and generating a volume control signal
indicating an excessive amount of the audio energy from the
threshold if the audio energy exceeds the threshold.
8. The audio reproduction apparatus of claim 7, wherein the volume
control unit comprises: a second band splitting unit to split the
input audio signal into second audio signals corresponding to the
plurality of frequency bands; and a sub volume control unit to
control the volume of each of the second audio signals split by the
band splitting unit according to the volume control signal for each
of the frequency bands.
9. An audio volume control method comprising: presetting a volume
step and a volume control value for each frequency band based on
human auditory characteristics; splitting an audio signal into
audio signals corresponding to a plurality of frequency bands;
determining the volume control value preset for each frequency band
according to an input volume value; controlling the audio volume
for each of the frequency bands split according to the volume
control value determined for each of the frequency bands; and
synthesizing the split audio signals corresponding to the frequency
bands.
10. The audio volume control method of claim 9, wherein the
controlling of the audio volume for each of the frequency bands
split according to the volume control value comprises comparing the
volume control value determined for each frequency band with a gain
value of an audio signal corresponding to the frequency band,
outputting a gain value corresponding to the comparison result, and
applying a gain value obtained based on the output gain value and a
previous gain value to an input audio signal, to generate an output
audio signal.
11. An audio volume control apparatus comprising: a storage unit to
store a volume control value for each frequency band corresponding
to a volume step based on human auditory characteristics; a band
splitting unit to split an audio signal into audio signals
corresponding to a plurality of frequency bands; a volume
processing unit to determine the volume control value for each
frequency band, stored in the storage unit, according to an input
volume value; a sub volume control unit to control the volume of
each of the split audio signals according to the volume control
value determined for each of the frequency bands by the volume
processing unit; and a band synthesis unit to synthesize the split
audio signals corresponding to the frequency bands whose volumes
are controlled by the sub volume control unit.
12. The audio volume control apparatus of claim 11, wherein the
band splitter may include band pass filters or quadrature mirror
filters (QMFs).
13. The audio volume control apparatus of claim 11, wherein the
volume control unit comprises: a level measurement unit to measure
a gain value of the audio signals corresponding to each of the
frequency bands; a level comparison unit to compare the volume
control value determined for a frequency band with a gain value of
an audio signal corresponding to the frequency band and outputting
a gain value corresponding to the comparison result; a gain
calculation unit to calculate a gain value to be applied to an
input audio signal corresponding to the frequency band based on the
output gain value and a previous gain value; a multiplier to
multiply the input audio signal corresponding to the frequency band
by the gain value calculated by the gain calculation unit, to
generate an output audio signal.
14. An audio volume control apparatus to reproduce a reproduction
audio signal from an input audio signal, comprising: a volume
control unit to control a plurality of frequency bands of the input
audio signal according to corresponding ones of characteristics of
the respective frequency bands of the reproduction audio
signal.
15. The audio volume control apparatus of claim 14, wherein the
characteristics of the respective frequency bands comprise at least
one of an audio reproduction time counted according to each sample
value of the frequency bands and a threshold, and audio volume
value generated according to each volume value of the frequency
bands and a user input volume value.
16. The audio volume control apparatus of claim 14, wherein the
volume control unit reproduces the reproduction audio signal from a
previous input audio signal.
17. The audio volume control apparatus of claim 14, wherein the
volume control unit controls a volume of each of the plurality of
frequency bands of the input audio signal according to a user input
volume control signal and a corresponding one of characteristics of
the respective frequency bands of the reproduction audio
signal.
18. The audio volume control apparatus of claim 17, wherein the
user input volume control signal comprises a signal to control an
overall volume of the reproduction audio signal.
19. The audio volume control apparatus of claim 17, wherein the
user input volume control signal comprises a signal to control a
volume of each of the plurality of frequency bands of the
reproduction audio signal.
20. The audio volume control apparatus of claim 17, wherein the
user input volume control signal is compared to each of the
corresponding one of characteristics of the respective frequency
bands of the reproduction audio signal to generate a volume control
signal to control each volume of the frequency bands of the input
audio signal.
21. The audio volume control apparatus of claim 14, wherein the
characteristics of the respective frequency bands of the
reproduction audio signal comprise a reproduction time of each of
frequency bands of the reproduction audio signal with respect to a
reference.
22. The audio volume control apparatus of claim 21, wherein the
reproduction time comprises the number of times counted when a
level of each of the frequency bands of the reproduction audio
signal is greater than a reference, for a predetermined period of
time.
23. The audio volume control apparatus of claim 14, wherein the
characteristics of the respective frequency bands of the
reproduction audio signal comprise an audio energy of each of the
frequency bands of the reproduction audio signal with respect to a
reference.
24. The audio volume control apparatus of claim 14, wherein the
characteristics of the respective frequency bands of the
reproduction audio signal comprise a reproduction time and an audio
energy of each of the frequency bands of the reproduction audio
signal with respect to a reference
25. The audio volume control apparatus of claim 14, further
comprising: a band splitting unit to split the production audio
signal into the plurality of frequency bands and to split the input
audio signal into the plurality of frequency bands.
26. The audio volume control apparatus of claim 14, wherein the
volume control unit comprises sub-volume control units to
correspond to the respective frequency bands.
27. The audio volume control apparatus of claim 26, wherein each of
the sub-volume control units measures a gain value of each of the
frequency bands of the input audio signal, and compares the gain
value of each of the frequency bands of the input audio signal with
a corresponding volume control value to calculate a final gain
value to be applied to the input audio signal
28. The audio volume control apparatus of claim 26, wherein each of
the sub-volume control units comprises: a level measurement unit to
measure a gain value of each of the frequency bands of the input
audio signal; a level comparison unit to compare the gain value of
each of the frequency bands of the input audio signal with a
corresponding volume control value to generate a comparison result;
and a level calculation unit to calculate a final gain value
according to the comparison result, so that the final gain value is
applied to the input audio signal.
29. The audio volume control apparatus of claim 26, wherein the
volume control unit controls a plurality of frequency bands of the
input audio signal according to an equal loudness curve and the
characteristics of the respective frequency bands of the
reproduction audio signal.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of Korean Patent
Application No. 10-2007-0010677, filed on Feb. 1, 2007, in the
Korean Intellectual Property Office, the disclosure of which is
incorporated herein in its entirety by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present general inventive concept relates to an audio
reproduction apparatus and method, and more particularly, to an
audio reproduction apparatus and method, in which an audio volume
can be automatically controlled based on audio energy and human
auditory characteristics.
[0004] 2. Description of the Related Art
[0005] Research on noise-induced hearing loss shows that hearing
may be damaged by long-period exposure to noise of a higher level
than a predetermined level. For this reason, various international
industrial accident-related organizations establish noise exposure
control regulations and use them as industrial accident-related
standards.
[0006] As the number of users of portable devices and earphones (or
headphones) increases, a more number of users complain of serious
levels of hearing damage.
[0007] In this context, audio volume control apparatuses for
protecting hearing have been developed.
[0008] U.S. 2003/0002688 A1, published on Jan. 2, 2003 and entitled
"Volume Regulating and Monitoring System," discloses a conventional
technique related to a conventional audio volume control
apparatus.
[0009] In the conventional audio volume control apparatus, an input
audio signal is converted into an electric signal, the electric
signal is compared with a threshold, an alarm signal is generated
every time the electric signal exceeds the threshold, and then the
adjusted audio signal is output.
[0010] According to research on noise-induced hearing loss, it is
known that hearing loss is proportional to the total energy of
noise, i.e., (audio volume.times.time). In other words, according
to noise exposure standards, hearing loss is induced by exposure to
85 dB noise for 8 hours, 88 dB noise for 4 hours, 91 dB noise for 2
hours, and 97 dB noise for 30 minutes.
[0011] According to the conventional technique related to the
volume control apparatus, a threshold for preventing hearing loss
is set by referring to only audio volume.
[0012] As a result, even if the audio signal is adjusted to below
the threshold, hearing loss may also be induced by long-time
exposure to the audio signal.
[0013] Moreover, the conventional volume control apparatus does not
consider a fact that the sensitivity of ears varies with audio
frequency components. Since the human ears are generally
insensitive to low-frequency sound, they may feel
intermediate/high-frequency sound louder when they concentrate on
low-frequency sound.
SUMMARY OF THE INVENTION
[0014] The present general inventive concept provides an audio
reproduction apparatus and method, in which an audio volume is
automatically controlled based on audio energy and human auditory
characteristics.
[0015] The present general inventive concept also provides an audio
volume control apparatus and method to automatically control an
audio volume based on human auditory characteristics.
[0016] Additional aspects and utilities of the present general
inventive concept will be set forth in part in the description
which follows and, in part, will be obvious from the description,
or may be learned by practice of the general inventive concept.
[0017] The foregoing and/or other aspects and utilities of the
present general inventive concept may be achieved by providing an
audio reproduction method including splitting a reproduction audio
signal into audio signals corresponding to a plurality of frequency
bands, extracting audio energy for each of the frequency bands, and
comparing the audio energy for each of the frequency bands with a
predetermined threshold and controlling a volume of an output audio
signal corresponding to each of the frequency bands.
[0018] The foregoing and/or other aspects and utilities of the
present general inventive concept may also be achieved by providing
an audio reproduction apparatus including a band splitting unit to
split a reproduction audio signal into audio signals corresponding
to a plurality of frequency bands, an audio monitoring unit to
accumulate reproduced audio energy for each of the frequency bands,
to compare the accumulated audio energy for each of the frequency
bands with a predetermined threshold, and to generate volume
control information, and a volume control unit to control a volume
of an input audio signal corresponding to each of the frequency
bands according to the volume control information generated by the
audio monitoring unit.
[0019] The foregoing and/or other aspects and utilities of the
present general inventive concept may also be achieved by providing
an audio volume control method including presetting a volume step
and a volume control value for each frequency band based on human
auditory characteristics, splitting an audio signal into audio
signals corresponding to a plurality of frequency bands,
determining the volume control value preset for each frequency band
according to an input volume value, controlling the volume of each
of the split audio signals according to the volume control value
determined for each of the frequency bands, and synthesizing the
split audio signals corresponding to the frequency bands.
[0020] The foregoing and/or other aspects and utilities of the
present general inventive concept may also be achieved by providing
an audio volume control apparatus including a storage unit to store
a volume control value for each frequency band corresponding to a
volume step based on human auditory characteristics, a band
splitting unit to split an input audio signal into audio signals
corresponding to a plurality of frequency bands, a volume
processing unit to determine a volume control value for each
frequency band, stored in the storage unit, according to an input
volume value, a sub volume control unit to control a volume of each
of the split audio signals according to the volume control value
determined for each of the frequency bands by the volume processing
unit, and a band synthesis unit to synthesize the split audio
signals corresponding to the frequency bands whose volumes are
controlled by the sub volume control unit.
[0021] The foregoing and/or other aspects and utilities of the
present general inventive concept may also be achieved by providing
an audio volume control apparatus to reproduce a reproduction audio
signal from an input audio signal, the audio volume control
apparatus including a volume control unit to control a plurality of
frequency bands of the input audio signal according to
corresponding ones of characteristics of the respective frequency
bands of the reproduction audio signal.
[0022] The characteristics of the respective frequency bands may
include at least one of an audio reproduction time counted
according to each sample value of the frequency bands and a
threshold, and audio volume value generated according to each
volume value of the frequency bands and a user input volume
value.
[0023] The volume control unit may reproduce the reproduction audio
signal from a previous input audio signal.
[0024] The volume control unit may control a volume of each of the
plurality of frequency bands of the input audio signal according to
a user input volume control signal and a corresponding one of
characteristics of the respective frequency bands of the
reproduction audio signal.
[0025] The user input volume control signal may include a signal to
control an overall volume of the reproduction audio signal.
[0026] The user input volume control signal may include a signal to
control a volume of each of the plurality of frequency bands of the
reproduction audio signal.
[0027] The user input volume control signal may be compared to each
of the corresponding one of characteristics of the respective
frequency bands of the reproduction audio signal to generate a
volume control signal to control each volume of the frequency bands
of the input audio signal.
[0028] The characteristics of the respective frequency bands of the
reproduction audio signal may include a reproduction time of each
of frequency bands of the reproduction audio signal with respect to
a reference.
[0029] The reproduction time may include the number of times
counted when a level of each of the frequency bands of the
reproduction audio signal is greater than a reference, for a
predetermined period of time.
[0030] The characteristics of the respective frequency bands of the
reproduction audio signal may include an audio energy of each of
the frequency bands of the reproduction audio signal with respect
to a reference.
[0031] The characteristics of the respective frequency bands of the
reproduction audio signal may include a reproduction time and an
audio energy of each of the frequency bands of the reproduction
audio signal with respect to a reference
[0032] The audio volume control apparatus may further include a
band splitting unit to split the production audio signal into the
plurality of frequency bands and to split the input audio signal
into the plurality of frequency bands.
[0033] The volume control unit may include sub-volume control units
to correspond to the respective frequency bands.
[0034] Each of the sub-volume control units may measure a gain
value of each of the frequency bands of the input audio signal, and
compares the gain value of each of the frequency bands of the input
audio signal with a corresponding volume control value to calculate
a final gain value to be applied to the input audio signal
[0035] Each of the sub-volume control units may comprise a level
measurement unit to measure a gain value of each of the frequency
bands of the input audio signal, a level comparison unit to compare
the gain value of each of the frequency bands of the input audio
signal with a corresponding volume control value to generate a
comparison result, and a level calculation unit to calculate a
final gain value according to the comparison result, so that the
final gain value is applied to the input audio signal.
[0036] The volume control unit may control a plurality of frequency
bands of the input audio signal according to an equal loudness
curve and the characteristics of the respective frequency bands of
the reproduction audio signal.
[0037] The foregoing and/or other aspects and utilities of the
present general inventive concept may also be achieved by providing
an audio volume control apparatus, including a volume control unit
to reproduce a reproduction audio signal from an input audio signal
and to control a plurality of frequency bands of a second input
audio signal according to a reference volume signal and
corresponding ones of characteristics of the respective frequency
bands of the reproduction audio signal.
[0038] The foregoing and/or other aspects and utilities of the
present general inventive concept may also be achieved by providing
a computer-readable medium containing computer-readable codes as a
program to execute a method of an audio volume control apparatus,
the method including reproducing a reproduction audio signal from
an input audio signal, and controlling a plurality of frequency
bands of a second input audio signal according to a reference
volume signal and corresponding ones of characteristics of the
respective frequency bands of the reproduction audio signal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] These and/or other aspects and utilities of the present
general inventive concept will become apparent and more readily
appreciated from the following description of the embodiments,
taken in conjunction with the accompanying drawings of which:
[0040] FIG. 1 is a block diagram of an audio reproduction apparatus
according to a first exemplary embodiment of the present
invention;
[0041] FIG. 2 is a detailed block diagram of an audio monitoring
unit illustrated in FIG. 1;
[0042] FIG. 3 is a detailed block diagram of a volume control unit
illustrated in FIG. 1;
[0043] FIG. 4 is a block diagram of an audio reproduction apparatus
according to a second exemplary embodiment of the present
invention;
[0044] FIG. 5 is a block diagram of an example of a frequency band
splitting unit illustrated in FIG. 4;
[0045] FIG. 6 is a block diagram of another example of a frequency
band splitting unit illustrated in FIG. 4;
[0046] FIG. 7 is a graph of an equal loudness curve showing human
auditory characteristics;
[0047] FIG. 8 illustrates an example of a database for storing
volume values determined for different frequency bands by a volume
processing unit illustrated in FIG. 4;
[0048] FIG. 9 is a block diagram of an example of a sub dynamic
range control unit of a sub-volume control unit illustrated in FIG.
4; and
[0049] FIG. 10 is a block diagram of a frequency band synthesis
unit illustrated in FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0050] Reference will now be made in detail to the embodiments of
the present general inventive concept, examples of which are
illustrated in the accompanying drawings, wherein like reference
numerals refer to the like elements throughout. The embodiments are
described below in order to explain the present general inventive
concept by referring to the figures.
[0051] FIG. 1 is a block diagram of an audio reproduction apparatus
according to a first exemplary embodiment of the present
invention.
[0052] Referring to FIG. 1, the audio reproduction apparatus
includes a frequency band splitting unit 110, an audio monitoring
unit 120, and a volume control unit 130.
[0053] The frequency band splitting unit 110 splits a reproduction
(or output) audio signal into audio signals corresponding to a
plurality of frequency bands using a Frequency band pass filter or
a quadrature mirror filter (QMF).
[0054] The audio monitoring unit 120 calculates the energy of an
audio signal corresponding to each of the frequency bands based on
a user input volume value and audio reproduction information
corresponding to a predetermined period of time, compares the
calculated energy with a predetermined threshold, and generates
volume control information for a corresponding frequency band if
the energy for the frequency band exceeds the threshold. At this
time, the volume control information includes a volume control
value and an alarm signal of a predetermined pattern.
[0055] The volume control unit 130 divides an input audio signal
into audio signals corresponding to a plurality of frequency bands
using a Frequency bandpass filter or a QMF and controls amplitude
of the audio signal corresponding to each of the frequency bands
differently according to a volume control value generated by the
audio monitoring unit 120.
[0056] FIG. 2 is a detailed block diagram of the audio monitoring
unit 120 of FIG. 1.
[0057] Referring to FIG. 2, a reproduction time counting unit 210
counts an audio reproduction time during which an audio sample
value of the reproduced audio signal exceeds a minimum threshold
value for a predetermined period of time and stores the counted
audio reproduction time as a count value. The reproduction time
counting unit 210 may count the audio reproduction time with
respect to the entire reproduction frequency band.
[0058] The volume counting unit 220 calculates the average of
reproduced audio samples for each of the frequency bands at
predetermined time intervals and extracts the calculated average as
an audio volume value for the frequency band.
[0059] In another exemplary embodiment of the present invention,
the volume counting unit 220 compares a user input volume value
with a reproduced audio volume value for each of the frequency
bands and extracts an audio volume value (or loudness) for the
frequency band.
[0060] The audio energy calculation unit 230 calculates audio
energy for each of the frequency bands based on the counted audio
reproduction time stored in the reproduction time counting unit 210
and/or the extracted audio volume value extracted by the volume
counting unit 220. For example, audio energy E can be expressed by
an integral equation as follows:
E=.intg.(T.times.V)dt (1)
where T indicates an audio reproduction time and V indicates an
audio volume value.
[0061] The auditory threshold storage unit 240 stores a threshold
value for each of the frequency bands in order to prevent hearing
damage based on human auditory characteristics. Generally, the
human auditory characteristics can be expressed as an equal
loudness curve as illustrated in FIG. 7.
[0062] The volume control processing unit 250 compares the
threshold for each of the frequency bands, which is stored in the
auditory threshold storage unit 240, with the audio energy for each
of the frequency bands, which is calculated by the audio energy
calculation unit 230, and generates volume control information, for
example, an alarm signal of a particular pattern and a volume
control signal indicating an excessive amount of the audio energy
if the audio energy exceeds the threshold.
[0063] The alarm signal generation unit 260 generates an audio
signal of the particular pattern every time it receives the alarm
signal of the particular pattern from the volume control processing
unit 250.
[0064] FIG. 3 is a detailed block diagram of the volume control
unit 130 of FIG. 1.
[0065] A frequency band splitting unit 310 splits the input audio
signal into audio signals corresponding to a plurality of frequency
bands using the frequency band pass filter and the QMF. A sub
volume control unit 320 controls the volume of the audio signal
split by the frequency band splitting unit 310 according to the
volume control signal generated by the audio monitoring unit 120.
For example, when the frequency band splitting unit 310 generates
an audio signal corresponding to a first sub-frequency band, an
audio signal corresponding to a second sub-frequency band, . . . ,
and an audio signal corresponding to an n.sup.th sub-frequency
band, and the audio monitoring unit 120 generates a first volume
control signal for the first sub-frequency band, a second volume
control signal for the second sub-frequency band, . . . , and an
n.sup.th volume control signal for the n.sup.th sub-frequency band.
A first sub volume control unit 322 then increases or reduces an
audio volume value for the first sub-frequency band according to
the first volume control signal and the user input volume value, a
second sub volume control unit 324 increases or reduces an audio
volume value for the second sub-frequency band according to the
second volume control signal and the user input volume value, and
an n.sup.th sub volume control unit 326 increases or reduces an
audio volume value for the n.sup.th sub-frequency band according to
the n.sup.th volume control signal and the user input volume value.
Thus, it is possible that when a user increases an audio volume,
the volume of a low-frequency sound is maintained as is and the
volume of an intermediate/high-frequency sound is increased. In
addition, the volume of a frequency band in which much energy is
accumulated is gradually reduced.
[0066] Adders 370 and 380 synthesize the audio signals for the
frequency bands whose volumes are controlled by the sub volume
control unit 320, thereby reconstructing the original audio
signal.
[0067] FIG. 4 is a block diagram of an audio reproduction apparatus
according to a second exemplary embodiment of the present
invention.
[0068] Referring to FIG. 4, the audio reproduction apparatus
includes a frequency band splitting unit 410, an equal loudness
curve data storage unit 430, a volume processing unit 420, a sub
volume control unit 440, and a frequency band synthesis unit 450.
The sub volume control unit 440 includes a first sub dynamic range
control unit 442, a second sub dynamic range control unit 444, . .
. , and an n.sup.th sub dynamic range control unit 446.
[0069] The frequency band splitting unit 410 splits an input audio
signal into audio signals corresponding to one or more frequency
bands using a frequency band pass filter or a QMF.
[0070] The equal loudness curve data storage unit 430 stores an
audio volume control value for each frequency band according to a
volume step by referring to an equal loudness curve. The audio
volume control value is information about an audio volume value
that has to be maintained for each frequency band.
[0071] The volume processing unit 420 reads the audio volume
control value corresponding to a user input volume step from the
equal loudness curve data storage unit 430.
[0072] The sub volume control unit 440 performs a dynamic range
control on a volume of the audio signal corresponding to each
frequency band split by the frequency band splitting unit 410
according to the audio volume control value for each frequency band
that is read by the volume processing unit 420. In other words, the
first sub dynamic range control unit 442 controls the volume of an
audio signal corresponding to a first sub frequency band according
to a volume control value for the first sub frequency band read by
the volume processing unit 420. The second sub dynamic range
control unit 444 controls the volume of an audio signal
corresponding to a second sub frequency band according to a volume
control value for the second sub frequency band read by the volume
processing unit 420. The n.sup.th sub dynamic range control unit
446 controls the volume of an audio signal corresponding to an
n.sup.th sub frequency band according to a volume control value for
the n.sup.th sub frequency band read by the volume processing unit
420.
[0073] The frequency band synthesis unit 450 synthesizes the audio
signals corresponding to the frequency bands whose volumes are
controlled by the sub volume control unit 440 using an inverse QMF
synthesis technique.
[0074] FIG. 5 is a block diagram of an example of the frequency
band splitting unit 410 of FIG. 4.
[0075] Referring to FIGS. 4 and 5, the frequency band splitting
unit 410 splits an audio signal into audio signals corresponding to
a plurality of desired frequency bands using a plurality of
frequency band pass filters, i.e., a first frequency band pass
filter through an n.sup.th frequency band pass filter. The
frequency band pass filters may be 2.sup.nd-order or 4.sup.th-order
infinite impulse response (IIR) filters.
[0076] FIG. 6 is a block diagram of another example of the
frequency band splitting unit 410 of FIG. 4.
[0077] Referring to FIGS. 4 and 6, the frequency band splitting
unit 410 splits an audio signal into audio signals corresponding to
a plurality of desired sub frequency bands using QMFs. In FIG. 6,
H1, H2, . . . , HN indicate complex gain values for the sub
frequency bands. The split audio signals are down-sampled through
first through n.sup.th down-sampling processes.
[0078] FIG. 7 is a graph of an equal loudness curve showing the
human auditory characteristics.
[0079] Physically measured sound pressure (or sound intensity) is
not equal to volume that is actually perceived by the human
auditory system. The human ears have irregular response property
with respect to audible frequency sound. For example, the
sensitivity of the human ears to sound of 1-5 kHz is very high,
whereas the sensitivity of human ears to sound below or over 1-5
kHz is very low.
[0080] A graph showing the human auditory characteristics is called
an equal loudness curve.
[0081] FIG. 8 illustrates an example of the equal loudness curve
data storage unit 430 of FIG. 4.
[0082] Referring to FIGS. 4 through 8, the equal loudness curve
data storage unit 430 stores volume control values g11, g12, . . .
, gNM for frequency band 1, frequency band 2, . . . , frequency
band M according to volume step 1, volume step 2, . . . , volume
step N. The volume control values g11, g12, . . . , gNM are
information about volume values that have to be maintained for
frequency band 1, frequency band 2, . . . , frequency band M,
respectively, and are determined with reference to the equal
loudness curve. For example, for the volume step 2 of 40 dB, volume
control values of 100 Hz (frequency band 1), 200 Hz (frequency band
2), and 300 Hz (frequency band 3) are determined as 52 dB, 40 dB,
and 38 dB with reference to the equal loudness curve illustrated in
FIG. 7. Thus, the equal loudness curve data storage unit 430 stores
a total of N.times.M volume control values when N volume steps and
M frequency bands are determined. In another exemplary embodiment
of the present invention, the volume control values g11, g12, . . .
gNM may be updated according to audio energy accumulated for the
frequency band 1, frequency band 2, . . . , frequency band M.
[0083] FIG. 9 is a block diagram of an example of the sub dynamic
range control unit 440 of FIG. 4.
[0084] Referring to FIGS. 4 and 9, a level measurement unit 910
measures the gain value for each of the frequency bands split by
the frequency band splitting unit 410.
[0085] A level comparison unit 920 compares the volume control
value for each frequency band read by the volume processing unit
420 with the gain value for the frequency band measured by the
level measurement unit 910, so that a gain value g(n) is output
according to the comparison result. For example, a gain value of an
input audio signal X(n) is compared with a volume control value.
When the gain value is less than the volume control value, the gain
value is increased by the volume control value. When the gain value
is greater than the volume control value, the gain value is reduced
by the volume control value.
[0086] A gain calculation unit 930 calculates the gain value g(n)
to be applied to the input audio signal X(n) using the gain value
determined by the level comparison unit 920 and a previous gain
value.
[0087] A delay unit 940 delays the input audio signal X(n) until
the gain value g(n) to be applied to the input audio signal X(n) is
calculated.
[0088] A multiplier 950 multiplies the input audio signal X(n) by
the gain value g(n) calculated by the gain calculation unit 930,
thereby generating an output audio signal Y(n).
[0089] FIG. 10 is a block diagram of the frequency band synthesis
unit 450 of FIG. 4.
[0090] Referring to FIGS. 4 and 10, the audio signals corresponding
to the frequency bands are up-sampled by a first up-sampling
process, a second up-sampling process, . . . , an n.sup.th
up-sampling process. The up-sampled audio signals are compensated
by corresponding ones of gain values G1, G2, . . . , GN. The gain
values G1, G2, . . . GN are complex gain values of QMFs. Finally,
the audio signals corresponding to the frequency bands are
synthesized by adders 1010 and 1020, thereby being reconstructed to
a broad band signal having frequency components like the input
audio signal.
[0091] As described above, according to the present general
inventive concept, a signal having components as shown in the equal
loudness curve is the loudest sound that can be perceived by the
human ears. Thus, an audio volume can be adjusted for each
frequency band based on a user input volume value and the equal
loudness curve. Moreover, an alarm signal can be generated for each
frequency band when audio energy approximates a threshold. At the
same time, unnecessary audio energy reproduction is prevented,
thereby preventing hearing damage. Therefore, by automatically
controlling the audio volume using audio energy accumulated for
each frequency band, safe and reliable hearing protection can be
achieved. Furthermore, by controlling the audio volume for each
frequency band according to the equal loudness curve, an optimized
equalizer can be implemented.
[0092] The present invention can also be embodied as computer
readable code on a computer readable medium. The computer-readable
medium may include a computer-readable recording medium and a
computer-readable transmission medium. The computer readable
recording medium is any data storage device that can store data
which can be thereafter read by a computer system. Examples of the
computer readable recording medium include read-only memory (ROM),
random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks,
optical data storage devices, and carrier waves. The computer
readable transmission medium can also be distributed over network
coupled computer systems, for example, a wired or wireless network
or the Internet, so that the computer readable code is stored and
executed in a distributed fashion.
[0093] Although a few embodiments of the present general inventive
concept have been shown and described, it will be appreciated by
those skilled in the art that changes may be made in these
embodiments without departing from the principles and spirit of the
general inventive concept, the scope of which is defined in the
appended claims and their equivalents.
* * * * *