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US 6,993,480 B1Granted
Voice intelligibility enhancement system
AssigneeSRS Labs, Inc.
InventorArnold I. Klayman
Life of this patent
Estimating the term…
Abstract
Intelligibility of a human voice projected by a loudspeaker in an environment of high ambient noise is enhanced by processing a voice signal in accordance with the frequency response characteristics of the human hearing system. Intelligibility of the human voice is derived largely from the pattern of frequency distribution of voice sounds, such as formants, as perceived by the human hearing system. Intelligibility of speech in a voice signal is enhanced by filtering and expanding the voice signal with a transfer function that approximates an inverse of equal loudness contours for tones in a frontal sound field for humans of average hearing acuity.
Claims62
A system for enhancing intelligibility of a voice signal that is degraded by factors that reduce intelligibility of the voice signal, said system comprising:
- an input configured to receive a voice signal that includes human spoken words;
- an aural filter operatively coupled to said input, said aural filter configured to filter said voice signal to produce a filter output signal wherein low frequencies below speech frequencies and high frequencies above speech frequencies are attenuated with respect to speech frequencies;
- a speech expander operatively coupled to said aural filter to produce an expanded signal, said speech expander configured to amplify said filter output signal according to an amplifier gain, wherein said amplifier gain is a function of an envelope amplitude of said filter output signal;
- and
- a combiner configured to combine at least a portion of said expanded signal and at least a portion of said voice signal to produce an enhanced signal representing said spoken words;
- wherein, when the voice signal is operating a high volume levels, the system emphasizes middle speech frequencies over low and high frequencies;
- and
- wherein, when the voice signal is operating at low volume levels, the system provides more low and high frequency components of the voice signal than when the voice signal is operating a high volume levels;
- such that the system provides a transfer function which approximates an inverse of the transfer function of human hearing.
6 more elements
A communication device for sending voice information to a communication receiver, where the voice information may become contaminated by noise that reduces the intelligibility of the voice information, said communication device comprising:
- a sender configured to send a voice signal comprising words spoken by a person over a communication channel;
- and
- a voice enhancer operably connected to said sender, said voice enhancer comprising:
- an aural filter operatively coupled to a voice signal in said sender, said aural filter configured to filter said voice signal to produce a filter output signal wherein low frequencies below speech frequencies and high frequencies above speech frequencies are attenuated with respect to speech frequencies;
- a speech expander operatively coupled to said aural filter to produce an expanded voice signal, said speech expander configured to amplify said filter output signal according to an amplifier gain, wherein said amplifier gain is a function of an envelope amplitude of said filter output signal;
- and
- a combiner configured to combine at least a portion of said expanded voice signal and at least a portion of said voice signal to produce an enhanced voice signal;
- wherein said voice enhancer is configured to provide a transfer function that approximates an inverse of loudness contours for human hearing;
- wherein said speech expander comprises a gain controlled amplifier;
- and
- wherein the amplifier gain increases according to an attack time constant when said envelope amplitude has a positive slope and said amplifier gain decreases according to a decay time constant when said envelope amplitude has a negative slope.
8 more elements
A communication device configured to receive voice information from a communication sender, comprising:
- a communication receiver configured to receive voice information comprising words spoken by a person from a communication channel;
- and
- a voice enhancer operably connected to said communication receiver, said voice enhancer comprising:
- an aural filter configured to filter an input signal to produce a filtered signal;
- an expander comprising an amplifier configured to amplify said filtered signal to produce an amplified signal, wherein a gain of said amplifier is a function of an amplitude envelope of said filtered signal;
- and
- a combiner configured to combine at least a portion of said amplified signal and at least a portion of said input signal to produce an output signal;
- wherein said voice enhancer enhances formants of the voice information to increase intelligibility of the voice information;
- and
- wherein said voice enhancer provides a transfer function that approximates a complement of Fletcher-Munson curves for tones in a frontal sound field for humans.
7 more elements
An apparatus, comprising:
- an aural filter configured to filter an input signal comprising words spoken by a person to produce a filtered signal;
- an expander comprising an amplifier configured to amplify said filtered signal to produce an amplified signal, wherein a gain of said amplifier depends in part on an envelope of said filtered signal;
- and
- a combiner configured to combine at least a portion of said amplified signal and at least a portion of said input signal to produce an output signal;
- wherein said apparatus is configured to provide a transfer function that emphasizes middle speech frequencies over low and high frequencies at high volume levels and is flatter at low volume levels.
2 more elements
A method for enhancing intelligibility of voice information, comprising the steps of:
- filtering at least a portion of a first signal that includes human voice sounds to produce a filtered signal having an amplitude envelope;
- expanding at least a portion of said filtered signal using an amplifier having a variable gain to produce an enhanced signal;
- detecting the amplitude envelope to produce a gain control signal to control the gain of the amplifier;
- and
- combining at least a portion of said first signal with said enhanced signal to produce an improved signal;
- wherein the method emphasizes middle speech frequencies over low and high frequencies at high volume levels and is flatter at low volume levels, such that the method provides a transfer function which approximates an inverse of loudness contours for human hearing.
3 more elements
An apparatus for enhancing intelligibility of voice information, said apparatus comprising:
- aural filter means for filtering an input signal to produce a filtered signal, said input signal containing human voice information;
- gain controlled amplifier means for amplifying the filtered signal to produce an expanded signal;
- gain control means for controlling a gain of the gain controlled amplifier as a function of an envelope amplitude of the filtered signal;
- attack time means for increasing the gain for an attack time when a slope of the envelope amplitude is positive;
- decay time means for decreasing the gain for a decay time when the slope of the envelope amplitude is negative;
- and
- combiner means for combining at least a portion of said expanded signal with at least a portion of said input signal;
- wherein said apparatus is configured to provide a transfer function that emphasizes middle speech frequencies over low and high frequencies at high volume levels and is flatter at low volume levels, such that said transfer function approximates an inverse of loudness contours for human hearing of tones in a sound field.
5 more elements
An apparatus, comprising:
- an input configured to receive an input signal comprising words spoken by a person;
- and
- a dynamic filter configured to filter said input signal to produce an enhanced signal with modified voice components, said dynamic filter configured to provide a transfer function that depends at least in part on an envelope of the input signal, wherein said transfer function emphasizes middle speech frequencies over low and high frequencies at high volume levels and is flatter at low volume levels.
A method of improving the intelligibility of voice sounds contained within a signal source when the signal source is reproduced through a loudspeaker, said method comprising the following steps:
- detecting an envelope of a signal source comprising words spoken by a person to produce a control signal;
- filtering the signal source according to a frequency response related to human hearing characteristics to produce a filtered signal;
- modifying the frequency response used to filter said signal source wherein the amount of modification is a function of the control signal;
- and
- combining the signal source with the filtered signal to produce an output signal having enhanced voice sounds;
- wherein, when the first signal is operating a high volume levels, the method emphasizes middle speech frequencies over low and high frequencies;
- and
- wherein, when the first signal is operating at low volume levels, the method provides more low and high frequency components of the first signal than when the first signal is operating a high volume levels;
- such that the method provides a transfer function which approximates an inverse of loudness contours for human hearing.
6 more elements
A method of emphasizing human speech sounds contained within a signal source to produce an output signal comprises the following steps:
- bandpass filtering said signal source to produce a filtered signal wherein said filtered signal includes speech frequencies and attenuates frequencies below and above speech frequencies;
- analyzing at least a portion of said filtered signal to produce a control signal wherein said control signal represents a slope of an amplitude envelope of said filtered signal;
- amplifying said filtered signal during a first amplification period to provide an enhancement signal wherein the level of amplification of said filtered signal is increased when the slope is positive;
- amplifying said filtered signal during a second amplification period to provide an enhancement signal wherein the level of amplification of said filtered signal is decreased when the slope is negative;
- and
- combining said enhancement signal with said signal source to produce an output signal;
- wherein said method provides a transfer function that emphasizes middle speech frequencies over low and high frequencies at high volume levels and is flatter at low volume levels, such that said transfer function approximates an inverse of loudness contours for human hearing of tones in a sound field.
4 more elements
A voice enhancement device for enhancing intelligibility of a voice signal comprising:
- a filter configured to receive a voice input signal, the filter configured to attenuate low frequencies below speech frequencies and high frequencies above speech frequencies with respect to speech frequencies to produce a filtered signal;
- an envelope detector configured to receive at least a portion of the filtered signal, the envelope detector configured to detect an envelope amplitude of the filtered signal to produce an envelope signal, wherein the envelope signal approximates the envelope amplitude of the filtered signal;
- an amplifier configured to receive the filtered signal, the amplifier having a gain control input for controlling a gain of the amplifier, the amplifier configured to amplify the filtered signal according to the gain to produce an amplified signal;
- an attack/decay buffer comprising an attack time constant and a decay time constant configured to receive the envelope signal and to produce a gain control signal to control the gain of the amplifier, wherein the attack/decay buffer provides the gain control signal to the gain control input to increase the gain of the amplifier at a rate given by the attack time constant when the envelope signal has a positive slope and to decrease the gain of the amplifier at a rate given by the decay time constant when the envelope signal has a negative slope;
- and
- a combiner configured to add at least a portion of the voice input signal with the amplified signal to produce an enhanced voice signal;
- wherein said device is configured to provide a transfer function that approximates an inverse of loudness contours for human hearing of tones in a sound field.
4 more elements
Dependencies are inferred from the claim text.