Hearing aid with amplitude compression achieved by clipping a modulated signal
AssigneeNational Research Development Corporation
InventorsRichard Langton Gregory, Ian Alexander Low
Life of this patent
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Abstract
A hearing aid is arranged to restrict the dynamic range of the audio input signal to be compatible with the range which is characteristic of the hearing defect of the user. By means of phase-shift modulation for example, the input signal is converted to a single sideband at HF which is then peak-clipped to a predetermined value. The effective degree of clipping is determined by the AGC level of an input amplifier which is controlled by the user. The clipped signal is restored to the audio band for reproduction at a preset level.
Claims10
A hearing aid comprising:
- means responsive to sound waves to produce an electrical input signal in the audio-frequency band;
- means for transposing said input signal to a high-frequency band to produce a transposed signal;
- limiting means for limiting the peak amplitude of said transposed signal to a predetermined value to produce a peak-limited signal;
- means for restoring said peak-limited signal to the audio-frequency band to produce a restored signal;
- and means for audio reproduction of said restored signal.
A hearing aid comprising:
- means responsive to sound waves to produce an electrical input signal in the audio-frequency band;
- means for producing a carrier signal in the high-frequency band;
- means for mixing said input signal and said carrier signal to derive a sideband of said carrier signal;
- limiting means for limiting the peak amplitude of said sideband to a predetermined value;
- means for mixing said carrier signal and said peak-limited sideband to derive an output signal in the audio-frequency band, said output signal representing said input signal in peak-limiting form;
- and means for audio reproduction of the said output signal.
Dependencies are inferred from the claim text.