Electrical audio signal processing systems and devices – Sound effects – Reverberators
Patent
1986-03-12
1988-12-20
Ng, Jin F.
Electrical audio signal processing systems and devices
Sound effects
Reverberators
381 68, 381 682, 381104, H04R 2500, H04R 304, H03G 320, H03G 1104
Patent
active
047929774
ABSTRACT:
A hearing aid that is compact and efficient and that provides a high degree of control over its frequency response and also over its output level versus input level characteristic. The frequency response control includes an adjustable four pole high pass filter and an adjustable four pole low pass filter, to define the pass band, and an adjustable slope filter, to define the slope within the pass band. The control over the output level versus input level characteristic includes an input AGC system with well defined, independent control of compression threshold and compression ratio, an adjustable peak clipper, and a selectable output AGC system that tracks the peak clipper setting. The hearing aid incorporates a number of novel circuits including a state variable filter with adjustable corner frequency, a filter that can be continuously adjusted from a single pole low pass characteristic to a single pole high pass characteristic, a circuit to provide a range of reference voltages to accurately set the range of control currents used to control the corner frequencies of the state variable filters, a compansion system surrounding the filter network to effectively increase its limited dynamic range, a differential voltage threshold detector, a differential voltage controlled current source with an exponential relationship of output current to differential input voltage, an adjustable clipping circuit, a voltage clamp to prevent voltage excursions from going substantially below a substrate voltage, and bias compensation circuit to supply the input bias current of a transistor.
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Authors: F. Callias, F. Salchli, D. Girard, M. Perrin & Ph. Aubert Title: A Set of 4 IC's In CMOS Technology for a Programmable Hearing Aid; published in the IEEE 1988 Custom Integrated Circuits Conference, May, 1988.
Solid State Microtechnology for Music data sheet, entitled "Dual Linear-Antilog Voltage Controlled Amplifier" by Solid State Micro Technology for Music, Inc. (1 page).
Article entitled "Coming To Terms With Hearing Aid Technology" by Preben Brunved, published in the Hearing Journal, Jun., 1985 (5 pages).
LTI data sheet, entitled "Dual Continuous Analog High Pass Filter" by LTI, bearing designation 500-73-1 (4 pages).
Anderson James R.
Brander Richard
Beltone Electronics Corporation
Byrd Danita R.
Ng Jin F.
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