US 7,031,474 B1Granted

Acoustic correction apparatus

AssigneeSRS Labs, Inc.

InventorsThomas C. K. Yuen, Alan D. Kraemer, Richard Oliver

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Abstract

An acoustic correction apparatus processes a pair of left and right input signals to compensate for spatial distortion as a function of frequency when said input signals are reproduced through loudspeakers in a sound system. The sound-energy of the left and right input signals is separated and corrected in a first low-frequency range and a second high-frequency range. The resultant signals are recombined to create image-corrected audio signals having a desired sound-pressure response when reproduced by the loudspeakers in the sound system. The desired sound-pressure response creates an apparent sound image location with respect to a listener. The image-corrected signals can also be spatially-enhanced to broaden the apparent sound image and improve the low frequency characteristics of the sound when played on small loudspeakers.

Claims35

Dependent claims

An audio correction system for enhancing spatial and frequency response characteristics of sound reproduced by two or more loudspeakers, said audio correction system comprising:

an image correction module configured to correct a perceived vertical image of sound when said sound is reproduced by a plurality of loudspeakers, said image correction module altering said sound as a first function of frequency over a first frequency range and altering said sound as a second function over a second frequency range, wherein said first function of frequency is independent of said second function of frequency;
a bass enhancement module configured to enhance a bass response of said sound when said sound is reproduced by said plurality of loudspeakers, said bass enhancement module modulates the amplitude of a higher-frequency signal with a lower-frequency signal to produce a signal envelope where said higher-frequency signal is modulated by said lower-frequency signal, wherein said base enhancement module comprises:
a first band pass filter that filters said sound at a first frequency;
at least a second band filter that filters said sound at a second frequency, wherein said second frequency is different than said first frequency;
a third band pass filter that filters said sound at a third frequency, wherein said third frequency is different than said first and second frequencies;
a combiner that combines the output of said first, second and third band-pass filters to generate a combined filtered signal;
a compressor that reduces the gain of the at least a portion of the high amplitudes in the combined filtered signal;
and
a base punch circuit that increases the gain of at least a portion of the low amplitudes in the combined filtered signal;
and
an image enhancement module configured to spectrally shape difference information associated with said sound to enhance a horizontal image of sound when said sound is reproduced by said plurality of loudspeakers.

8 more elements

A sound enhancement system comprising:

a first sound enhancement module configured to correct a perceived height of an apparent sound stage produced by a plurality of loudspeakers;
a second sound enhancement module configured to modulate a midbass signal with a low-frequency signal by multiplying the amplitude of said midbass signal with said low-frequency signal to produce a signal envelope, wherein said second sound enhancement module comprises:
a first band pass filter that filters said apparent sound stage at a first frequency;
at least a second band filter that filters said apparent sound stage at a second frequency, wherein said second frequency is different than said first frequency;
a third band pass filter that filters said apparent sound stage at a third frequency, wherein said third frequency is different than said first and second frequencies;
a combiner that combines the output of said first, second and third band-pass filters to generate a combined filtered signal;
a compressor that reduces the gain of the at least a portion of the high amplitudes in the combined filtered signal;
and
a base punch circuit that increases the gain of at least a portion of the low amplitudes in the combined filtered signal;
and
a third sound enhancement module configured to correct a perceived width of said apparent sound stage produced by said loudspeakers.

8 more elements

A method for enhancing audio sounds to improve a perceived sound stage and to improve perceived bass components of said sound, comprising the acts of:

height-correcting a sound signal to improve a perceived height of an apparent sound stage produced by a plurality of loudspeakers;
bass-enhancing the sound signal, said sound signal comprising a low-frequency audio signal and a higher frequency audio signal, said low-frequency audio signal missing from the apparent sound stage, said bass-enhancing comprising multiplying the amplitude of the higher-frequency audio signal by the low-frequency audio signal to produce a signal envelope where said higher-frequency signal is modulated by said lower-frequency signal, wherein bass-enhancing comprises:
filtering said sound signal at a first frequency to produce a first filtered signal;
filtering said sound signal at a second frequency to produce a second filtered signal, wherein said second frequency is different than said first frequency;
filtering said sound signal at a third frequency to produce a third filtered signal, wherein said third frequency is different than said first and second frequencies;
combining the first, second and third filtered signals to generate a combined filtered signal;
reducing the gain of the at least a portion of the high amplitudes in the combined filtered signal;
and
increasing the gain of at least a portion of the low amplitudes in the combined filtered signal;
and
width-enhancing the sound signal to improve a perceived width of the apparent sound stage produced by said loudspeakers.

8 more elements

Dependencies are inferred from the claim text.