Signal processing circuit and method for increasing speech intelligibility
First Claim
1. A method of processing an audio signal in a hearing aid for increasing speech intelligibility to a human comprising the steps of:
- receiving an audio signal;
differentially amplifying a first frequency range that substantially comprises first speech formant frequencies and a second frequency range that substantially comprises second formant frequencies of said audio signal;
mixing an injected inaudible signal tone with said audio signal;
sensing a level of presence of the signal tone; and
automatically controlling gain amplification of only the second frequency range based on the sensed level of the injected signal tone, wherein regenerative oscillation of the audio signal is substantially prevented.
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Abstract
A signal processing circuit and method for increasing speech intelligibility. The invention comprises a receiving circuit for receiving an audio signal detectable by a human. A gain amplifying circuit provides gain amplification of the audio signal. A shaping filter modifies the audio signal to be in phase with a second audio signal present at the receiving circuit and which is detected by the human unprocessed by the signal processing circuit. The shaping filter further differentially amplifies first and second speech formant frequencies to restore a normal loudness relationship between them. A feedback circuit controls the gain amplification in the gain amplifying circuit for enabling the signal processing circuit to substantially prevent regenerative oscillation of the amplified audio signal. Additionally, a signal tone may be injected into the signal processing circuit for automatically controlling the gain amplifying circuit.
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Citations
24 Claims
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1. A method of processing an audio signal in a hearing aid for increasing speech intelligibility to a human comprising the steps of:
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receiving an audio signal;
differentially amplifying a first frequency range that substantially comprises first speech formant frequencies and a second frequency range that substantially comprises second formant frequencies of said audio signal;
mixing an injected inaudible signal tone with said audio signal;
sensing a level of presence of the signal tone; and
automatically controlling gain amplification of only the second frequency range based on the sensed level of the injected signal tone, wherein regenerative oscillation of the audio signal is substantially prevented. - View Dependent Claims (2, 3, 4)
amplifying substantially only second speech formant frequencies of said audio signal to normalize a loudness relationship between said second speech formant frequencies and first speech formant frequencies.
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3. The method of claim 1 further including modifying said audio signal wherein said modified audio signal is in phase with a second audio signal present at the receiving circuit and which is detectable by the human and unprocessed by the signal processing circuit.
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4. The method of claim 1 wherein the step of automatically controlling comprises:
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sensing an amplified audio signal; and
processing said amplified audio signal to provide a negative feedback only to the second frequency range for substantially preventing regenerative oscillation of said amplified audio signal.
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5. A method of processing an audio signal in a hearing aid for increasing speech intelligibility to a human comprising the steps of:
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receiving an audio signal;
passing the audio signal through a signal processing circuit having an output, and outputting a modified audio signal from the output;
phase aligning the modified audio signal with an unpassed audio signal present at the output;
amplifying frequencies of said audio signal differentially wherein a second frequency range comprising second speech formant frequencies of said audio signal has an amplified gain greater than a gain amplification of a first frequency range comprising first speech formant frequencies, regardless of a presence of noise in the first and second frequency ranges; and
controlling said amplified gain based on an inaudible signal tone, wherein the signal processing circuit substantially prevents regenerative oscillation of said amplified audio signal. - View Dependent Claims (6, 7, 8, 9, 10)
amplifying only said second frequency range of said audio signal to normalize a loudness relationship between said second speech formant frequencies and first speech formant frequencies.
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7. The method of claim 5, wherein the step of phase aligning comprises:
providing first and second filters for phase aligning first and second speech formant frequencies with the unpassed audio signal present at the output.
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8. The method of claim 7 further including a step of mixing a signal tone with said audio signal and wherein said step of controlling comprises sensing a level of presence of the signal tone and automatically controlling said gain amplification based on the sensed level of the signal tone.
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9. The method of claim 5 wherein the step of controlling comprises:
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sensing an amplified audio signal; and
processing said amplified audio signal to provide a negative feedback for substantially preventing regenerative oscillation of said amplified audio signal.
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10. The method of claim 9, further including the steps of:
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mixing a signal tone with said audio signal;
sensing a level of presence of the signal tone; and
controlling automatically said gain amplification based on the sensed level of the signal tone.
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11. A hearing aid signal processing circuit for increasing speech intelligibility to a human, said human having at least one eardrum, comprising:
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a receiving circuit for receiving an audio signal;
a gain amplifying circuit for differentially amplifying a first frequency range comprising first speech formant frequencies and a second frequency range comprising second speech formant frequencies of said audio signal as a function of the difference in decibels for restoring a sound pressure level of said second frequency range to a normal level dependent on said human and a frequency of said audio signal; and
a feedback circuit for controlling gain amplification of only one of the frequency ranges based on a sensed level of an inaudible continuous signal tone, wherein the signal processing circuit substantially prevents regenerative oscillation of the audio signal. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification