Frequency translation by high-frequency spectral envelope warping in hearing assistance devices
AssigneeStarkey Laboratories, Inc.
InventorKelly Fitz
Life of this patent
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Abstract
Disclosed herein, among other things, is a system for frequency translation by high-frequency spectral envelope warping in hearing assistance devices. The present subject matter relates to improved speech intelligibility in a hearing assistance device using frequency translation by high-frequency spectral envelope warping. The system described herein implements an algorithm for performing frequency translation in an audio signal processing device for the purpose of improving perceived sound quality and speech intelligibility in an audio signal when presented using a system having reduced bandwidth relative to the original signal, or when presented to a hearing-impaired listener sensitive to only a reduced range of acoustic frequencies.
Claims21
A method for processing an audio signal received by a hearing assistance device, comprising:
- filtering the audio signal to generate a high frequency filtered signal, the filtering performed at a splitting frequency;
- transposing at least a portion of an audio spectrum of the filtered signal to a lower frequency range by a transposition process to produce a transposed audio signal;
- and
- summing the transposed audio signal with the audio signal to generate an output signal, wherein the transposition process includes:
- estimating an all-pole spectral envelope of the filtered signal from a plurality of line spectral frequencies;
- using a digital signal processor, applying a warping function to the all-pole spectral envelope of the filtered signal to translate the poles above a specified knee frequency to lower frequencies, thereby producing a warped spectral envelope;
- and
- exciting the warped spectral envelope with an excitation signal to synthesize the transposed audio signal.
A method for processing an audio signal received by a hearing assistance device, comprising:
- filtering the audio signal to generate a high frequency filtered signal, the filtering performed at a splitting frequency;
- transposing at least a portion of an audio spectrum of the filtered signal to a lower frequency range by a transposition process to produce a transposed audio signal;
- and
- summing the transposed audio signal with the audio signal to generate an output signal, wherein the transposition process includes:
- estimating an all-pole spectral envelope of the filtered signal from a plurality of line spectral frequencies;
- using a digital signal processor, applying a warping function to the all-pole spectral envelope of the filtered signal to translate the poles above a specified knee frequency to lower frequencies, thereby producing a warped spectral envelope;
- and
- exciting the warped spectral envelope with an excitation signal to synthesize the transposed audio signal,
- wherein magnitudes and angles of poles in the spectral envelope are estimated from the line spectral frequencies, and coefficients of a spectral envelope filter are computed from the estimated magnitudes and angles, and
- wherein the excitation signal is a prediction error signal, produced by filtering the high-pass signal with an inverse of the estimated all-pole spectral envelope.
Dependencies are inferred from the claim text.