Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM FOR AN METHOD OF AUDIO SIGNAL PROCESSING FOR
PRESENTATION IN A HIGH-NOISE ENVIRONMENT
FIELD OF THE INVENTION
Some embodiments of the present invention relate to novel systems, method,
and circuits that may be useful for achieving quality sound presentation in
high-noise
environments. Specifically, the present invention provides systems, methods,
and circuits
for processing audio signals.
BACKGROUND OF THE INVENTION
Achieving quality sound presentation in high-noise environments, such as
moving
vehicles, remains particularly challenging. For example, the bass response of
a system in
such an environment is generally inadequate. While the bass response may be
boosted with
an equalizer to compensate for this inadequacy, this approach typically causes
a muffled
treble response, thus diminishing the sound quality. In addition to a muffled
treble, bass
boosting may undesirably increase the dynamic range of the sound presentation.
In a noisy
environment, there is very little audio range between the volume floor set by
the noise
(typically around 80 dB in moving vehicles) and the volume ceiling set by the
physiology of
the ear (typically around 110 dB). Increasing the dynamic range of sound
presented in a
noisy environment may be aesthetically undesirable because the sound level may
approach
the ear's physiological volume ceiling, resulting in an unpleasant, annoying,
or even painful
response. Accordingly, a new approach is needed for quality audio presentation
in a high-
noise environment.
- Typical consumer sound transducers, such as commercial speakers, are
acoustically
efficient between approximately 600 and 1,000 cycles. To compensate for the
inefficient
performance of such transducers outside this range, systems often employ a
variety of special
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speakers and amplifiers that can be quite expensive. A system that compensates
for this
inefficient performance without the introduction of extra and often expensive
hardware
would be beneficial.
Today, the dynamic range of sound in motion pictures is created and mixed in
an
environment the size of a movie theater. Quality playback of motion picture
audio in a small
environment, such as a home entertainment area or an automobile, is difficult
at best. In a
small environment, audio standing waves often develop, producing an annoying
acoustical
signal at the frequency of the standing wave. Compensation for such specific
standing waves
in a given small environment would produce a higher quality audio
presentation.
Finally, in contrast to the careful attention given to movie sounds and music,
the audio
in electronic video games are often mixed haphazardly. This haphazard mixing
often does
not present full, balanced audio to the listener. Enhancing the audio signal
frequency wide
across the full dynamic range will present higher quality audio.
SUMMARY OF THE INVENTION
Some embodiments of the present invention relate to novel systems, methods,
and
circuits that may be useful for
achieving quality sound presentation in high-noise environments. In one
aspect, the present
invention provides systems for processing an audio signal. In one embodiment,
the system
may comprise a primary equalizer that produces an equalized audio signal by
adjusting the
amplitude of the low frequency portions of the audio signal corresponding to
audible bass
sounds and adjusting in the opposite direction the amplitude of the high
frequency portions of
the audio signal corresponding to audible treble sounds, wherein the adjusting
and the
adjusting in the opposite direction intersect between a crossover range of
frequencies
producing a substantially negligible gain in the crossover range; a compressor
that produces a
compressed audio signal by compressing the dynamic range of the audio signal;
and a mirror
equalizer that produces a substantially opposite effect as the primary
equalizer.
In another embodiment, the system may comprise a primary equalizer that
produces
an equalized audio signal by decreasing the amplitude of the low frequency
portions of the
audio signal corresponding to audible bass sounds and increasing the amplitude
of the high
frequency portions of the audio signal corresponding to audible treble sounds,
wherein the
decreasing and the increasing intersect between a frequency range producing a
substantially
negligible gain in the range; a compressor that produces a compressed audio
signal by
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compressing the dynamic range of the audio signal; and a mirror equalizer that
produces a
substantially opposite effect as the primary equalizer.
In an alternative embodiment, the system may comprise a primary equalizer that
produces an equalized audio signal by adjusting the amplitude of the low
frequency portions
of the audio signal corresponding to audible bass sounds and adjusting in the
opposite
direction the amplitude of the high frequency portions of the audio signal
corresponding to
audible treble sounds, wherein the adjusting and the adjusting in the opposite
direction
intersect between a frequency range producing a substantially negligible gain
in the range; a
compressor that produces a compressed audio signal by compressing the dynamic
range of
the audio signal; a mirror equalizer that produces a substantially opposite
effect as the
primary equalizer; and a final equalizer that adjusts the amplitude of the
signal at frequencies
predetermined to be related to sound presentation anomalies associated with
the anticipated
listening environment.
In yet another embodiment, the system may comprise a primary equalizer that
produces an equalized audio signal by decreasing the amplitude of the low
frequency portions
of the audio signal corresponding to audible bass sounds and increasing the
amplitude of the
high frequency portions of the audio signal corresponding to audible treble
sounds, wherein
the decreasing and the increasing intersect between a frequency range
producing a
substantially negligible gain in the range; a compressor that produces a
compressed audio
signal by compressing the dynamic range of the audio signal; a mirror
equalizer that produces
a substantially opposite effect as the primary equalizer; and a final
equalizer that adjusts the
amplitude of the signal at frequencies predetermined to be related to sound
presentation
anomalies associated with the anticipated listening environment.
- -
The system of the present invention may, in some embodiments, further comprise
a
speaker system responsive to the output signal of the mirror equalizer.
In one embodiment, the crossover range may be approximately 600 Hz to
approximately 1,000 Hz. In another embodiment, the primary equalizer and the
mirror
equalizer may adjust amplitude according to a substantially linear function of
frequency.
In one embodiment, the compressor may compress the audio signal by attenuating
the
30 high amplitude portions of the audio signal. Alternatively, the
compressor may compress the
audio signal by amplifying the low amplitude portions of the audio signal. In
a specific
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embodiment, the compressor may compress the dynamic range of the audio signal
to less
than about 10 dB.
In another embodiment, the primary equalizer may use at least one filter to
adjust the
amplitude of the high frequency portions of the audio signal and the mirror
equalizer may use
at least one filter to produce a substantially opposite effect on the high
frequency portions of
the audio signal as the primary equalizer; wherein the filters may have a
substantially equal
and opposite effect on the audio signal.
Alternatively, the primary equalizer may use at least one filter to adjust the
amplitude
of the low frequency portions of the audio signal and the mirror equalizer may
use at least
to one filter to produce a substantially opposite effect on the low
frequency portions of the audio
signal as the primary equalizer; wherein the filters may have an equal and
opposite effect on
the audio signal.
In one embodiment, the primary equalizer may decrease the amplitude of the low
frequency portions of the signal by about 10 dB at 100 Hz. In another
embodiment, the
primary equalizer may increase the amplitude of the high frequency portions of
the signal by
about 8 dB at 8 kHz.
The primary equalizer may increase the amplitude of the low frequency portions
of
the signal by about 10 dB at 100 Hz. Alternatively, the primary equalizer may
decrease the
amplitude of the high frequency portions of the signal by about 8 dB at 8 kHz.
In yet another embodiment, the mirror equalizer may increase the amplitude of
the
low frequency portions of the signal by about 10 dB at 100 Hz. In a further
embodiment, the
mirror equalizer may decrease the amplitude of the high frequency portions of
the signal by
about 8 dB at 8 kHz.
In a further embodiment, the mirror equalizer may decrease the amplitude of
the low
frequency portions of the signal by about 10 dB at 100 Hz. Alternatively, the
mirror
equalizer may increase the amplitude of the high frequency portions of the
signal by about 8
dB at 8 kHz.
In another aspect, the present invention provides methods for processing an
audio
signal. In one embodiment, the method may comprise primary equalizing the
audio signal by
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adjusting the amplitude of the low frequency portions of the audio signal
corresponding to
audible bass sounds and adjusting in the opposite direction the amplitude of
the high
frequency portions of the audio signal corresponding to audible treble sounds,
wherein the
adjusting and the adjusting in the opposite direction intersect between a
frequency range
producing a substantially negligible gain in the range; compressing the
dynamic range of the
audio signal; and mirror equalizing the audio signal in a substantially
opposite way as the
primary equalizing.
In another embodiment, the method may comprise primary equalizing the audio
signal
by adjusting the amplitude of the low frequency portions of the audio signal
corresponding to
audible bass sounds and adjusting in the opposite direction the amplitude of
the high
frequency portions of the audio signal corresponding to audible treble sounds,
wherein the
adjusting and the adjusting in the opposite direction intersect between a
frequency range
producing a substantially negligible gain in the range; compressing the
dynamic range of the
audio signal; mirror equalizing the audio signal in a substantially opposite
way as the primary
equalizing; and adjusting the amplitude of the signal at frequencies
predetermined to be
related to sound presentation anomalies associated with the anticipated
listening environment.
In another aspect, the present invention provides circuits for processing an
audio
signal. In one embodiment, the circuit may comprise a primary equalizer that
produces an
equalized audio signal by adjusting the amplitude of the low frequency
portions of the audio
signal corresponding to audible bass sounds and adjusting in the opposite
direction the
amplitude of the high frequency portions of the audio signal corresponding to
audible treble
sounds, wherein the adjusting and the adjusting in the opposite direction
intersect between a
frequency range producing a substantially negligible gain in the range; a
compressor that
produces a compressed audio signal by compressing the dynamic range of the
audio signal;
and a mirror equalizer that produces a substantially opposite effect as the
primary equalizer.
In an alternative embodiment, the circuit may comprise a primary equalizer
that
produces an equalized audio signal by adjusting the amplitude of the low
frequency portions
of the audio signal corresponding to audible bass sounds and adjusting in the
opposite
direction the amplitude of the high frequency portions of the audio signal
corresponding to
audible treble sounds, wherein the adjusting and the adjusting in the opposite
direction
intersect between a frequency range producing a substantially negligible gain
in the range; a
compressor that produces a compressed audio signal by compressing the dynamic
range of
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the audio signal; a mirror equalizer that produces a substantially opposite
effect as the primary
equalizer; and a final equalizer that adjusts the amplitude of the signal at
frequencies
predetermined to be related to sound presentation anomalies associated with
the anticipated
listening environment.
According to another embodiment of the present invention, there is provided a
system for processing an audio signal comprising: a primary equalizer that
produces an
equalized audio signal by adjusting the amplitude of the low frequency
portions of said audio
signal corresponding to audible bass sounds and adjusting in the opposite
direction the
amplitude of the high frequency portions of said audio signal corresponding to
audible treble
sounds, wherein said adjusting and said adjusting in the opposite direction
intersect between a
crossover range of frequencies producing a substantially negligible gain in
said crossover
range; a compressor that produces a compressed audio signal by compressing the
dynamic
range of said audio signal; and a mirror equalizer that produces a
substantially opposite effect
as said primary equalizer, wherein said audio signal is used as both a source
and control for
the compressor, and wherein said compressor compresses said audio signal by
attenuating the
high amplitude portions of said audio signal and amplifying the low amplitude
portions of
said audio signal.
According to another embodiment of the present invention, there is provided a
system for processing an audio signal comprising: a primary equalizer that
produces an
equalized audio signal by decreasing the amplitude of the low frequency
portions of said
audio signal corresponding to audible bass sounds and increasing the amplitude
of the high
frequency portions of said audio signal corresponding to audible treble
sounds, wherein said
decreasing and said increasing intersect between a frequency range producing a
substantially
negligible gain in said range; and a compressor that produces a compressed
audio signal by
compressing the dynamic range of said audio signal; and a mirror equalizer
that produces a
substantially opposite effect as said primary equalizer, wherein said audio
signal is used as
both a source and control for the compressor, and wherein said compressor
compresses said
audio signal by attenuating the high amplitude portions of said audio signal
and amplifying
the low amplitude portions of said audio signal.
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According to still another embodiment of the present invention, there is
provided a system for processing an audio signal comprising: a primary
equalizer that
produces an equalized audio signal by adjusting the amplitude of the low
frequency portions
of said audio signal corresponding to audible bass sounds and adjusting in the
opposite
direction the amplitude of the high frequency portions of said audio signal
corresponding to
audible treble sounds, wherein said adjusting and said adjusting in the
opposite direction
intersect between a frequency range producing a substantially negligible gain
in said range; a
compressor that produces a compressed audio signal by compressing the dynamic
range of
said audio signal; a mirror equalizer that produces a substantially opposite
effect as said
primary equalizer; and a final equalizer that adjusts the amplitude of said
signal at frequencies
predetermined to be related to sound presentation anomalies associated with
the anticipated
listening environment, wherein said audio signal is used as both a source and
control for the
compressor, and wherein said compressor compresses said audio signal by
attenuating the
high amplitude portions of said audio signal and amplifying the low amplitude
portions of
said audio signal.
According to yet another embodiment of the present invention, there is
provided a system for processing an audio signal comprising: a primary
equalizer that
produces an equalized audio signal by decreasing the amplitude of the low
frequency portions
of said audio signal corresponding to audible bass sounds and increasing the
amplitude of the
high frequency portions of said audio signal corresponding to audible treble
sounds, wherein
said decreasing and said increasing intersect between a frequency range
producing a
substantially negligible gain in said range; and a compressor that produces a
compressed
audio signal by compressing the dynamic range of said audio signal; a mirror
equalizer that
produces a substantially opposite effect as said primary equalizer; and a
final equalizer that
adjusts the amplitude of said signal at frequencies predetermined to be
related to sound
presentation anomalies associated with the anticipated listening environment,
wherein said
audio signal is used as both a source and control for the compressor, and
wherein said
compressor compresses said audio signal by attenuating the high amplitude
portions of said
audio signal and amplifying the low amplitude portions of said audio signal.
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According to a further embodiment of the present invention, there is provided
a
method for processing an audio signal comprising the steps of: primary
equalizing said audio
signal by adjusting the amplitude of the low frequency portions of said audio
signal
corresponding to audible bass sounds and adjusting in the opposite direction
the amplitude of
the high frequency portions of said audio signal corresponding to audible
treble sounds,
wherein said adjusting and said adjusting in the opposite direction intersect
between a
frequency range producing a substantially negligible gain in said range;
compressing the
dynamic range of said audio signal; and mirror equalizing said audio signal in
a substantially
opposite way as said primary equalizing, wherein said compressing of said
audio signal
attenuates the high amplitude portions of said audio signal and amplifies the
low amplitude
portions of said audio signal.
According to yet a further embodiment of the present invention, there is
provided a method for processing an audio signal comprising the steps of:
primary equalizing
said audio signal by adjusting the amplitude of the low frequency portions of
said audio signal
corresponding to audible bass sounds and adjusting in the opposite direction
the amplitude of
the high frequency portions of said audio signal corresponding to audible
treble sounds,
wherein said adjusting and said adjusting in the opposite direction intersect
between a
frequency range producing a substantially negligible gain in said range;
compressing the
dynamic range of said audio signal; mirror equalizing said audio signal in a
substantially
opposite way as said primary equalizing; and adjusting the amplitude of said
signal at
frequencies predetermined to be related to sound presentation anomalies
associated with the
anticipated listening environment, wherein said compressing of said audio
signal attenuates
the high amplitude portions of said audio signal and amplifies the low
amplitude portions of
said audio signal.
According to still a further aspect of the present invention, there is
provided a
circuit for processing an audio signal comprising: a primary equalizer that
produces an
equalized audio signal by adjusting the amplitude of the low frequency
portions of said audio
signal corresponding to audible bass sounds and adjusting in the opposite
direction the
amplitude of the high frequency portions of said audio signal corresponding to
audible treble
sounds, wherein said adjusting and said adjusting in the opposite direction
intersect between a
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frequency range producing a substantially negligible gain in said range; a
compressor that
produces a compressed audio signal by compressing the dynamic range of said
audio signal;
and a mirror equalizer that produces a substantially opposite effect as said
primary equalizer,
wherein said audio signal is used as both a source and control for the
compressor, and wherein
said compressor compresses said audio signal by attenuating the high amplitude
portions of
said audio signal and amplifying the low amplitude portions of said audio
signal.
According to another embodiment of the present invention, there is provided a
circuit for processing an audio signal comprising: a primary equalizer that
produces an
equalized audio signal by adjusting the amplitude of the low frequency
portions of said audio
signal corresponding to audible bass sounds and adjusting in the opposite
direction the
amplitude of the high frequency portions of said audio signal corresponding to
audible treble
sounds, wherein said adjusting and said adjusting in the opposite direction
intersect between a
frequency range producing a substantially negligible gain in said range; a
compressor that
produces a compressed audio signal by compressing the dynamic range of said
audio signal; a
mirror equalizer that produces a substantially opposite effect as said primary
equalizer; and a
final equalizer that adjusts the amplitude of said signal at frequencies
predetermined to be
related to sound presentation anomalies associated with the anticipated
listening environment,
wherein said audio signal is used as both a source and control for the
compressor, and wherein
said compressor compresses said audio signal by attenuating the high amplitude
portions of
said audio signal and amplifying the low amplitude portions of said audio
signal.
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In a different aspect, there is provided methods for hard-programming
adjustments into at least one multi-band equalizer that compensates for
anomalies associated
with an anticipated listening environment. In one embodiment, the method may
comprise
presenting a test audio signal into the anticipated listening environment;
detecting audio
presentation anomalies associated with the anticipated listening environment
from responses
from the test audio signal; determining the frequency associated with the
anomalies of the
audio signal; adjusting the amplitude at the frequency to compensate for the
anomalies in the
multi-band equalizer; and hard-programming the adjustment at the frequency
into at least one
multi-band equalizer.
In an alternative embodiment, the method may comprise presenting a test audio
signal
into the anticipated listening environment, wherein the test audio signal is
selected from the
group consisting of broadband noise and frequency sweeps; detecting audio
presentation
anomalies associated with the anticipated listening environment from responses
from the test
audio signal, wherein the anomalies are detected with a device selected from
the group
consisting of a fast Fourier analyzer and a computer frequency analyzer;
determining the
frequency associated with the anomalies of the audio signal by analyzing the
results of from
the detecting device; adjusting the amplitude at the frequency with the multi-
band equalizer
to compensate for the anomalies; and hard-programming the adjustment at the
frequency into
the multi-band equalizer.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. I is a schematic view of and example system in which the equalizer,
compressor,
and mirror equalizer are coupled together.
FIG. 2 is a schematic view of the equalizer, compressor, and mirror equalizer
coupled
together, where the equalizers amplify and attenuate opposite to those of FIG.
I.
FIG. 3 is .a detailed schematic of one example of one embodiment of the
present
invention.
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FIG. 4 is a schematic view of an equalizer, compressor, and mirror equalizer
coupled
with a speaker.
FIG. 5 is a schematic view of an equalizer, compressor, mirror equalizer and a
multi-
band equalizer sequentially coupled together.
FIG. 6 is a schematic view of an equalizer, compressor, mirror equalizer and
an
amplifier sequentially coupled together.
FIG. 7 is a schematic view of the process of detecting anomalies, determining
the
frequency where the anomaly occurs, and then adjusting amplitude at that
frequency.
FIG. 8 is a schematic view of an equalizer, compressor, mirror equalizer, and
final
equalizer coupled together.
FIG. 9 is a schematic view of an equalizer, compressor, mirror equalizer,
final
equalizer, amplifier, a multi-band equalizer, and a speaker coupled together.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
It is to be understood that the present invention is not limited to the
particular
methodology, compounds, materials, manufacturing techniques, uses, and
applications,
described herein, as these may vary. It is also to be understood that the
terminology used
herein is used for the purpose of describing particular embodiments only, and
is not intended
to limit the scope of the present invention. It must be noted that as used
herein and in the
appended claims, the singular forms "a," "an," and "the" include the plural
reference unless
the context clearly dictates otherwise. Thus, for example, a reference to "an
element" is a
reference to one or more elements and includes equivalents thereof known to
those skilled in
the art. Similarly, for another example, a reference to "a step" or "a means"
is a reference to
one or more steps or means and may include sub-steps and subservient means.
All
conjunctions used are to be understood in the most inclusive sense possible.
Thus, the word
"or" should be understood as having the definition of a logical "or" rather
than that of a
logical "exclusive or" unless the context clearly necessitates otherwise.
Language that may
be construed to express approximation should be so understood unless the
context clearly
dictates otherwise.
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Unless defined otherwise, all technical and scientific terms used herein have
the same
meanings as commonly understood by one of ordinary skill in the art to which
this invention
belongs. Preferred methods, techniques, devices, and materials are described,
although any
methods, techniques, devices, or materials similar or equivalent to those
described herein
may be used in the practice or testing of the present invention. Structures
described herein
are to be understood also to refer to functional equivalents of such
structures. All references
cited herein are incorporated by reference herein in their entirety.
The system, methods, and circuitry described herein are designed to
accommodate the
conversion of audio signals with a broad dynamic range to a narrow dynamic
range without
distorting or altering the original work and to compensate for environmental
factors. This
system is particularly suited for playing music, movies, or video games in
high-noise
environments such as an automobile, airplane, boat, club, theatre, amusement
park, shopping
center, etc. Furthermore, the system, methods, and circuitry of the present
invention seek to
improve sound presentation by processing an audio signal outside the
efficiency range of
both the human ear and audio transducers which is between approximately 600 Hz
and
approximately 1,000 Hz. By processing audio outside this range, a fuller and
broader
presentation may be obtained.
Referring to the figures, FIG. 1 is a schematic view of one embodiment of the
present
invention. The system comprises a primary equalizer 20, a compressor 30, and a
mirror
equalizer 40. A graphical representation of the functionality of each
individual component is
shown within the drawing of each. An audio input signal 10 is inputted into
the primary
equalizer 20 and an enhanced audio output signal 50 is produced from the
mirror equalizer
40. The primary equalizer 20 in this embodiment receives an audio input signal
10,
attenuates the amplitude of the portion of the signal corresponding to the
bass spectrum of
sound, and amplifies the amplitude of the signal corresponding to the treble
spectrum of
sound. For example, the low audible bass portion (around 100 Hz) may be
decreased by
about 10 dB, the high audible treble portion (around 8 kHz) may be increased
by about 8 dB,
and the portions in between are adjusted as a linear function of frequency. A
variety of
suitable equalizers are known in the art. One such analog equalizer is shown
in block 11
of FIG. 3.
At some frequency between this high frequency amplification and low frequency
attenuation the effects of the amplification and attenuation intersect at the
crossover point. At
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this crossover point, the effect of these two processes on the audio signal
exactly cancel each
other out and produce a net gain of zero. Centered around this crossover point
is a range of
frequencies where these two processes substantially negate their effect on the
audio signal.
In one embodiment of the present invention, this range is between
approximately 600 Hz and
approximately 1,000 Hz. In this embodiment, the crossover range is specially
designed to be
within the efficiency range of standard sound transducers and the human ear.
Other
embodiments may shift this crossover point as necessitated by the specific
application.
Referring again to FIG. 1, the primary equalizer 20 feeds the compressor 30.
The
compressor amplifies and attenuates the signal inversely proportional to the
amplitude of the
signal. That is, low amplitudes are provided high amplification (or low
attenuation) while
high amplitudes are provided high compression (or low amplification). This
results in a
lower dynamic range of the signal. The dynamic range of the signal, for
example, may be
lowered to as little as 10 dB or less. Furthermore, in another embodiment of
the present
invention, the compressor may attenuate the high amplitudes of an audio signal
more than
low amplitudes. In another embodiment the compressor may amplify low
amplitudes of an
audio signal more than high amplitudes. A variety of suitable compressors are
known in the
art. One embodiment of a compressor is shown in block 12 of FIG. 3.
Returning again to FIG. 1, after compression, the audio signal is fed into the
mirror
equalizer 40. This mirror equalizer 40 provides the opposite functionality as
the primary
equalizer 20. Here, in this specific embodiment, the mirror equalizer
increases the amplitude
of the portion of the signal corresponding to the bass spectrum of sound and
decreases the
amplitude of the signal corresponding to the treble spectrum of sound. This
mirror equalizer
40 also has a crossover point that is substantially the same crossover point
as the primary
equalizer 20. For example, the low audible bass portion (around 100 Hz) may be
increased
by about 10 dB, the high audible treble portion (around 8 kHz) may be
decreased by about
8dB, and the portions in between are adjusted linearly as a function of
frequency. The
primary equalizer 10 and mirror equalizer 30 are ideally chosen to be
complementary so that
they have equal and opposite affects. One embodiment of a mirror equalizer is
shown in
block 13 of FIG. 3.
After primary equalization, compression, and mirror equalization, the
processed audio
signal may be applied directly to a speaker system, through a multi-band
equalizer to a
speaker system, or through an amplifier to a speaker system. Because the bass
portion may
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be reduced before compression and enhanced after compression, the sound
presented to the
speakers has a spectrum rich in bass tones and free of the muffling effects
encountered with
conventional compression. Also, this embodiment produces a rich sound even
from a small
speaker system, for example, those having magnets less than 10 oz.
Furthermore, because the
dynamic range has been reduced by compression, the sound may be presented
within a
limited volume range. For example, this system may comfortably present quality
sound in a
high-noise environment with an 80 dB noise floor and a 110 dB sound threshold.
FIG. 2 shows another embodiment of the present invention. This embodiment is
similar to that embodiment shown in FIG. 1. In this embodiment, the primary
equalizer 20
receives an audio input signal 10, amplifies the amplitude of the portion of
the signal
corresponding to the bass spectrum of sound, and attenuates the amplitude of
the signal
corresponding to the treble spectrum of sound. The embodiment of FIG. 2
amplifies the
signal where the embodiment of FIG. 1 attenuates. Likewise, the embodiment of
FIG. 2
attenuates the signal where the embodiment of FIG. I amplifies. The mirror
equalizer in
FIG. 4 also has the opposite functionality of the mirror equalizer in FIG. 1.
FIG. 3 is a diagram of one specific embodiment of the present invention. This
embodiment shows implemented with analog components. The equalizer is shown in
block
11, the compressor in block 12, the mirror equalizer in block 13, an optional
power supply is
shown in block 20, and a 10 channel equalizer in block 21. All of the
components shown are
standard, commercially available components. Each individual module may be
implemented
with another reasonable substitute known in the art.
FIG. 4 represents another embodiment of the present invention. FIG. 4 shows
the
embodiment of FIG. I coupled with a speaker system 60.
FIG. 5 represents another embodiment of the present invention. In this
embodiment a
multi-phase equalizer 100 is coupled with a mirror equalizer 40 before the
audio signal is
output 50. In a further embodiment of the invention such a signal outputs from
the multi-
band equalizer 100 to a speaker system that is not shown in the drawings.
FIG. 6 represents another embodiment of the present invention. In this
embodiment
an amplifier 110 is coupled to the mirror equalizer 40 prior to output 50. In
a further
embodiment of the invention such a signal outputs from the amplifier 110 to a
speaker system
that is not shown in the drawing.
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FIG. 7 represents another embodiment of the present invention. In FIG. 7, an
audio
presentation response 15 is introduced and anomalies in the audio presentation
are detected
by process 70. A graphical representation of such a signal with an audio
anomaly is shown
within the drawing of process 70. Note the extraordinarily large amplitude of
the audio
presentation at one frequency 71. Some signals may present multiple or no
anomalies. For
example, a particular listening environment may produce such anomalous audio
responses
such as those from standing waves. For example, such standing waves often
occur in small
listening environments such as an automobile. The length of an automobile, for
example, is
around 400 cycles long. In such an environment, some standing waves are set up
at this
frequency and some below. Standing waves present an amplified signal at their
frequency
which may present an annoying acoustic signal. FIG. 7, for simplicity, shows
only one
anomaly. Thus, the process 70 detects an anomalous presentation in a signal,
such as a
portion of a signal at a given frequency amplified due to a standing wave.
Next, process 80
determines the frequency at which such an anomalous audio presentation occurs
81. In the
drawing, 81 points to the point on the graph where the frequency at which the
anomalous
audio presentation occurs. Once the frequency at which an anomalous
presentation occurs is
determined, the amplitude of the signal at this frequency is then decreased as
shown in 90.
Note in the functional representation within the drawing 90 the anomalously
high amplitude
is reduced, which compensates for anomalies in the audio presentation.
Automobiles of the
same size, shape, and of the same characteristics, such as cars of the same
model, may
present the same anomalies. The frequency and amount of adjustment performed,
in a further
embodiment, may be preset in an equalizer to reduce anomalous responses for
future
presentation in the listening environment. For example, the frequency and
adjustment
amount of anomalous responses in a model of an automobile may be preset in an
equalizer
that is implemented with the cars audio system to compensate for these
acoustical anomalies.
FIG. 8 shows the embodiment of the invention shown in FIG. 1 with a final
equalizer
70 that adjusts the amplitude of the audio signal at frequencies predetermined
to be related to
sound presentation anomalies associated with the anticipated listening
environment.
FIG. 9 illustrates the embodiment of FIG. 8 with an amplifier 110 for audio
amplification, a multi-band equalizer 100, for further fine-tuning, and a
speaker system 60 for
sound presentation.
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The embodiments of the present invention are premised on the assumption that
most
audio transducers are efficient between about 600 Hz and about 1,000 Hz.
Furthermore, the
human ear is very efficient within this range. Because of these efficiencies,
the present
invention may do most of its audio processing outside of this range to improve
the overall
quality of the sound presentation.
One embodiment of the present invention provides for a system for processing
an
audio signal with a primary equalizer, compressor, and mirror equalizer. The
primary
equalizer produces an equalized audio signal by adjusting the amplitude of the
low frequency
portions of an audio signal corresponding to audible bass sounds and adjusting
in the opposite
direction the amplitude of the high frequency portions of an audio signal
corresponding to
audible treble sounds. These adjustments occur in a substantially linear
function of
frequency. The above mentioned adjusting of the low frequency portions of the
signal and
the adjusting in the opposite direction of the high frequency portion of the
signal intersect
between a frequency range that produces a substantially negligible gain within
this range.
is The point where these adjustments intersect is the crossover point and
produces a gain of
zero. The range around this point is the crossover range. For example, this
crossover point
may occur between about 600 Hz and about 1,000 Hz. An embodiment may further
comprise
a compressor that produces a compressed audio signal by compressing the
dynamic range of
the audio signal by attenuating high amplitude signals, amplifying low
amplitude signals, or
by doing a combination of both. The compressor may compress the dynamic range
of the
audio signal to less than about 10 db. Finally, a mirror equalizer produces a
substantially
opposite effect on the audio signal as the primary equalizer. This mirror
equalizer has
substantially the same crossover point and range as the primary equalizer.
At the crossover point, the effects on the audio signal of the two
adjustments, in both
the primary and mirror equalizers, exactly cancel each other out and produce a
net gain of
zero. Centered around this crossover point is the crossover range of
frequencies where these
two adjustments substantially negate their effect on the audio signal. This
crossover range, in
one embodiment of the present invention, is between approximately 600 Hz and
approximately 1,000 Hz. In this embodiment, the crossover range may be
specially designed
to be within the efficiency range of standard sound transducers and the human
ear. Other
embodiments may shift this crossover point as necessitated by the specific
application.
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In one specific embodiment of the system, the primary equalizer boosts the
high
frequency portions of an audio signal and attenuates the low frequency
portions of an audio
signal. The mirror equalizer does the opposite; it attenuates the high
frequency portions of an
audio signal and boosts the low frequency portions of an audio signal. In each
equalizer, at
the same frequency between the high frequency boosting and low frequency
attenuating and
boosting, the effects of the boosting and attenuation intersect at the
crossover point.
In another specific embodiment of the system, the primary equalizer attenuates
the
high frequency portions of an audio signal and boosts the low frequency
portions of an audio
signal. The mirror equalizer does the opposite; it boosts the high frequency
portions of an
to audio signal and attenuates the low frequency portions of an audio
signal.
In yet another specific embodiment of the system, the primary equalizer and
mirror
equalizer use at least one filter. The equalizers may, for example, use a high-
band and a low-
band filter. The filter that operates on the high frequency portion of an
audio signal in the
primary equalizer produces an equal and opposite effect on the audio signal as
the filter in the
mirror equalizer. That is, for example, if the high frequency filter in the
primary equalizer
boosts the signal 8 db at 8 kHz, then the high frequency filter in the mirror
equalizer
attenuates the signal 8 db at 8 kHz. For example, if the high frequency filter
in the primary
equalizer attenuates the signal 8 db at 8 kHz then the high frequency filter
in the mirror
equalizer boosts the signal 8 db at 8 kHz. For example, if the low frequency
filter in the
primary equalizer boosts the signal 10 db at 100 Hz, then the low frequency
filter in the
mirror equalizer attenuates the signal 10 db at 100 Hz. Finally, for example,
if the low
frequency filter in the primary equalizer attenuates the signal 10 db at 100
Hz, then the low
frequency filter in the mirror equalizer boosts the signal 10 db at 100 Hz. In
between these
frequencies the filters boost and attenuate at a substantially linear function
of frequency.
Another embodiment of the system includes a final equalizer which, after
mirror
equalization, may adjust the amplitude of the audio signal at frequencies
predetermined to be
related to sound presentation anomalies associated with the anticipated
listening environment.
These frequencies have been previously detected to be associated with
acoustical anomalies
such as standing waves, and accented and absorbed frequencies. The frequency
and
magnitude of adjustment performed may be preset in this final equalizer to
reduce any
anomalous responses. Thus, audio signals played through this final equalizer
in
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environments in which the final equalizer was prepared may present music
absent anomalies
associated with the listening environment.
Another embodiment of the system may present an audio signal after primary
equalization, compression, and mirror equalization to an amplifier. The system
may also
present an audio signal to a multi-band equalizer for fine-tuning. The system
may also
present an audio signal to a speaker. These three components may be
implemented, in any
combination with or without each other.
Another embodiment of the present invention is a method for processing an
audio
signal with a primary equalizing step, a compression step, and a mirror
equalizing step. The
primary equalizing step produces an equalized audio signal by adjusting the
amplitude of the
low frequency portions of an audio signal corresponding to audible bass sounds
and adjusting
in the opposite direction the amplitude of the high frequency portions of an
audio signal
corresponding to audible treble sounds. These adjustments occur in a
substantially linear
function of frequency. With this method, the above-mentioned adjusting of the
low
frequency portions of the signal and the adjusting in the opposite direction
of the high
frequency portion of the signal intersect between a crossover range that
produce a
substantially negligible gain within this crossover range. For example, one
method may have
a crossover range may occur between approximately 600 Hz and approximately
1,000 Hz.
This method further comprises a compressing step that produces a compressed
audio signal
by compressing the dynamic range of the audio signal by attenuating high
amplitude signals,
amplifying low amplitude signals or by doing a combination of both. The
compressing step
in this method of one embodiment of the present invention may compress the
dynamic range
of the audio signal to less than about 10 db. The final step of this method is
a mirror
equalizing step that produces a substantially opposite effect as the primary
equalizing step.
This mirror equalizing step has substantially the same crossover range as the
primary
equalizing step.
In one specific embodiment of the present invention, the primary equalizing
step
boosts the high frequency portions of an audio signal and attenuates the low
frequency
portions of an audio signal. The mirror equalizing steps does the opposite; it
attenuates the
high frequency portions of an audio signal and boosts the low frequency
portions of an audio
signal. In each equalizing step, at some frequency between the high frequency
boosting and
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low frequency attenuating the effects of the boosting and attenuating
intersect at the
crossover point and produce a net gain of zero.
In another specific embodiment of the present invention, the primary
equalizing step
attenuates the high frequency portions of an audio signal and boosts the low
frequency
portions of an audio signal. The mirror equalizing step does the opposite; it
boosts the high
frequency portions of an audio signal and attenuates the low frequency
portions of an audio
signal. This embodiment also has a crossover point and a crossover range that
may be chosen
according to the specific application.
Another embodiment of the present invention includes a final equalizing step
which,
after the mirror equalizing step, adjusts the amplitude of the audio signal at
frequencies
predetermined to be related to sound presentation anomalies associated with
the anticipated
listening environment. These frequencies have been previously detected to be
associated
with acoustical anomalies. The frequency and magnitude of the adjustment may
be preset in
this step to reduce any anomalous responses. Thus, audio signals played
through this final
equalizing step, in environments in which the final equalizing step was
prepared, may present
music without anomalies.
The methods of the present invention may be performed by any number of
processors.
It may be performed by a computer, computer software, electrical circuit, an
electrical chip
programmed to perform these steps, or any other means to perform the method
described.
In one method of the present invention, the primary equalizing and mirror
equalizing
steps may use at least one filter. The filters that operate in the high
frequency portion of the
signal in the primary and mirror equalizing steps produce an equal and
opposite effect.
That is, for example, if the high frequency filter in the primary equalizing
step boosts the
signal 8 db at 8 kHz then the high frequency filter in the mirror equalizing
step attenuates the
signal 8 db at 8 kHz. For example, if the high frequency filter in the primary
equalizing step
attenuates the signal 8 db at 8 kHz then the high frequency filter in the
mirror equalizing step
boosts the signal 8 db at 8 kHz. For example, if the low frequency filter in
the primary
equalizing step boosts the signal 10 db at 100 Hz then the low frequency
filter in the mirror
equalizing step attenuates the signal 10 db at 100 Hz. Finally, for example,
if the low
frequency filter in the primary equalizing step attenuates the signal 10 db at
100 Hz then the
low frequency filter in the mirror equalizing step boosts the signal 10 db at
100 Hz. In
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between these frequencies, the filters boost and attenuate at substantially
linear functions
of frequency.
Another embodiment of the present invention provides for a circuit for
processing an
audio signal comprising a primary equalizer, compressor, and mirror equalizer.
The primary
equalizer produces an equalized audio signal by adjusting the amplitude of the
low frequency
portions of an audio signal corresponding to audible bass sounds and adjusting
in the opposite
direction the amplitude of the high frequency portions of an audio signal
corresponding to
audible treble sounds. These adjustments occur in a substantially linear
function of
frequency. In this circuit, the above mentioned adjusting of the low frequency
portions of an
to audio signal and the adjusting in the opposite direction of the high
frequency portion of an
audio signal intersect between a frequency range that produces a substantially
negligible gain
within this range. The circuit may further comprise a compressor that produces
a compressed
audio signal by compressing the dynamic range of the audio signal by
attenuating high
amplitude signals, amplifying low amplitude signals or by doing a combination
of both. The
compressor in this circuit may, for example, compress the dynamic range of the
audio signal
to less than about 10 db. Finally, the circuit of this embodiment includes a
mirror equalizer
that produces a substantially opposite effect as the primary equalizer and has
substantially the
same crossover range as the primary equalizer.
The primary and mirror equalizers, in this circuit have a matched crossover
point and
a matched crossover range. At this crossover point the effect of these two
adjustments on the
audio signal exactly cancel each other out and produce a net gain of zero.
Centered around
this crossover point is the crossover range. This crossover range, in one
embodiment of the
present invention, is between approximately 600 Hz and approximately 1,000 Hz.
In this
embodiment, the crossover range is specially designed to be within the
efficiency range of
.25 standard sound transducers and the human ear. Other embodiments may
shift this crossover
point as necessitated by the specific application.
In one specific embodiment of the present invention, the primary equalizer
boosts the
high frequency portions of an audio signal and attenuates the low frequency
portions of an
audio signal. The mirror equalizer does the opposite; it attenuates the high
frequency
portions of an audio signal and boosts the low frequency portions of an audio
signal. In each
equalizer, at some frequency between the high frequency boosting and low
frequency
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attenuating and boosting the affects of the boosting and attenuation intersect
at the crossover
point.
In another specific embodiment of the present invention, the primary equalizer
attenuates the high frequency portions of an audio signal and boosts the low
frequency
portions of an audio signal. The mirror equalizer does the opposite; it boosts
the high
frequency portions of an audio signal and attenuates the low frequency
portions of an audio
signal. In each equalizer, at some frequency between the high frequency
boosting or
attenuating and low frequency attenuating or boosting the two processes
intersect at the
crossover point.
The circuit of the present invention may include a final equalizer which,
after mirror
equalization, adjusts the amplitude of the audio signal at frequencies
predetermined to be
related to sound presentation anomalies associated with the anticipated
listening environment.
These frequencies have been previously detected to be associated with
acoustical anomalies
and hard programmed into this circuit. The frequency and amount of adjustment
performed
may be preset in this final equalizer to reduce any anomalous responses. Thus,
audio signals
played through this final equalizer may present music absent anomalies
associated with the
listening environment in environments in which the final equalizer was
prepared.
The circuit of this embodiment of the present invention may be implemented in
a
digital circuit, an analog circuit, or any combination of both. Any part of
this circuit,
equalizers or compressors, may individually be digital or analog, and may be
coupled
together. Those working in the art know various compressor and equalizer
circuitry that may
be implemented to produce the claimed results.
In the circuit of the present invention, the primary equalizer and mirror
equalizer may
use at least one filter. The filter that operates on the high frequency
portion of the signal in
the primary and mirror equalizers produce an equal and opposite effect. That
is, for example,
if the high frequency filter in the primary equalizer boosts the signal 8 db
at 8 kHz then the
high frequency filter in the mirror equalizer attenuates the signal 8 db at 8
kHz. For example,
if the high frequency filter in the primary equalizer attenuates the signal 8
db at 8 kHz then
the high frequency filter in the mirror equalizer boosts the signal 8 db at 8
kHz. For example,
if the low frequency filter in the primary equalizer boosts the signal 10 db
at 100 Hz then the
low frequency filter in the mirror equalizer attenuates the signal 10 db at
100 Hz. Finally, for
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example, if the low frequency filter in the primary equalizer attenuates the
signal 10 db
at 100 Hz, then the low frequency filter in the mirror equalizer boosts the
signal 10 db
at 100 Hz. In between these frequencies the filters boost and attenuate at
substantially linear
functions of frequency.
In another embodiment of the present invention this circuit may present an
audio
signal after primary equalization, compression, and mirror equalization to an
amplifier. The
circuit may also present an audio signal to a multi-phase equalizer for fine-
tuning. The
system may also present an audio signal to a speaker. These three components
may be
implemented in any combination, with or without each other.
A further embodiment of the present invention is the method of hard-
programming
adjustments into a multi-band equalizer that compensates for anomalies
associated with the
anticipated listening environment. This method includes a number of steps. The
first step is
presenting a test audio signal into an anticipated listening environment. This
test audio signal
may be broadband noise, frequency sweeps, or any other test signal known in
the art. The
test audio signal may be music that is well known and exhibits an understood
response. The
next step in the method is detecting audio presentation anomalies associated
with the
anticipated listening environment from responses from the test audio signal.
This step may
be performed with a fast Fourier analyzer, a computer frequency analyzer, or
any other
system that analyzes the amplitude response of an audio signal over a broad
range of
frequencies. By analyzing the response returned by the listening environment,
one may
determine the frequencies where standing waves occur in the environment,
frequencies that
are accented by the environment, frequencies that are absorbed by the
environment, or any
other type of anomalous response due to the presentation environment. Once the
frequencies
of the anomaly and the magnitude of the anomaly are known, a multi-band
equalizer may be
adjusted to compensate for these anomalies. Finally, the magnitude of these
adjustments at
these set frequencies may be hard-programmed into a multi-band equalizer or a
set of multi-
band equalizers. Hard-programming sets the values so they are unchangeable by
a future
user. These values may be stored in some storage device or physically set.
Thus, by using
this multi-band equalizer in a system used in the anticipated listening
environment or a
reasonably similar environment, one may present music free from environmental
anomalies.
For example, one specific embodiment of the present invention comprises
developing
a multi-band equalizer that is hard-programmed with adjustments that
compensate for
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anomalies associated with one model of automobile. Each car of the same model
likely
presents very similar listening anomalies due to their similar size, shape,
structural make-up,
speaker placement, speaker quality, and speaker size. While inside one model
of the car, a
user may implement the method of this embodiment by playing a test signal
through the cars
sound system. While this test signal is playing a computer with frequency
response software
and hardware, such as a fast Fourier analyzing software, may detect anomalous
responses by
the environment to the test signal. The system may detect standing waves that
occur do to the
small size of the car, it may detect frequencies that are accented or absorbed
by the material
in the car, or it may detect diffraction affects from the shape of the car.
Once these anomalies
are detected, the frequency and magnitude of the anomalies are noted and
adjustments of the
proper magnitude are made in a multi-band equalizer at those frequencies. This
method may
be repeated until environment related anomalies are reasonably adjusted for.
The magnitude
of the adjustments at each frequency is noted along with the frequency. These
values are
then hard programmed into equalizers and implemented in an audio system of
cars of the
same model. By following this method each car may ultimately have an audio
system that
presents anomalous free sound.
It is to be understood that the above described embodiments are illustrative
of only a
few of the many possible specific embodiments which can represent applications
of the
principles of the invention. Numerous and various other possibilities for use
of the present
invention will be obvious to those skilled in the art without departing from
the
scope of the claims.
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