4,913,260

43.50. Ki GAS SILENCING SYSTEM WITH

CONTROLLING SOUND ATTENUATION

Blaise M. Fallon, assignor to Tenneco, Incorporated 3 April 1990 (Class 181/254}; filed 11 January 1988

An exhaust silencing system provides actively controlled sound at- tcnuation by use of a bypass allowing some gas to flow around at least part of the muffler. A bypass control valve regulates the division of gas flow, in response to a pressure signal adjusted by the driver. The patent describes the circuits and instruments for visually indicating the amount of bypass flow and the sound level of the exhaust leaving the systcm.--CHA

4,947,432

43.66.Ts PROGRAMMABLE HEARING AID

Jan T6pholm, assignor to T6pholm & Westermann ApS 7 August 1990 (Class 381/68.2}; filed in Germany 3 February 1986

The patent describes a programmable hearing aid with an amplifier and transmission section having characteristics that can bc controlled by signals from a separate control unit. Signals from the latter arc sent by a wireless transmitter to a receiver in the hearing aid where they arc dcmodu- latcd. The control unit contains a memory for certain of the parameters which determine the transmission characteristics of the hearing aid amplift-

10 33 3•. 35 36

31.,,.j r 1 I

37 38 39 11

,I

er. A keypad on the control unit recalls desired parameters from its memory via a digital control unit. These then modulate the transmitter. A control unit in the receiver is activated by the demodulated wireless signals, and establishes the desired amplifier transmission characteristics. The separate control unit with the keypad is relatively small, but large enough to be easily operated by the fingers.--SFL

SIGNAL P•OCESSING

CIRCUITRY RECEIVER MICROPHONE 20 22 24 26

// •20A 22A 26A j .

-44

ments as desired. The circuit also employs a multiplexer to selectively direct digital pulses to individual storing means. Typically, up to four parameters of the amplifier may be controlled. Each control unit contains a ring counter and an EEPROM. Circuit patterns for digitally controlled resistors on a chip are shown, along with other circuit details.--SFL

4,949,580

43.66.Yw AUDIO ANALYSIS SYSTEM

John F. Graham, Thousand Oaks, CA and Donald N. McLaughlin, Chatsworth, CA

21 August 1990 {Class 73/646}; filed 31 May 1989

In a manner reminiscent of the method described by Botsford 2 dec- ades ago for evaluating hearing damage risk, this sound spectrum analyzer displays sound-pressure level in kilohertz bands 0.5-1, 1-1.4, 1.4-1.8, 1.8- 2.25, 2.25-2.8, 2.8-3.6, and 3.6-15. More specifically, sound pressure level is displayed as plus or minus deviation from the average level in all bands. An overlay is provided to indicate deafness risk. For example, for the band 1.8-2.25 kHz, a level of 55 dB is labeled SPL peak comfort threshold; a level of 85 dB is labeled SPL peak maximus; a level of 95 dB is labeled SPL peak damage risk. It is not obvious in what time interval sound-pressure level is to be averaged nor the rule of averaging, nor the number of years in the noise for a stated deafness risk. The 40 claims deal with circuit details. Reference

is twice made to "a 130-dB omnidirectional microphone."--RWY

4,947,433

43.66.•s CIRCUIT FOR USE IN PROGRAMMABLE HEARING AIDS

Anton M. Gebert, assignor to Siemens Hearing Instruments, Incorpo- rated

7 August 1990 (Class 381/68); filed 29 March 1989

The patent describes a hearing aid with signal processing circuitry in the amplifier. A number of variable electrical clements arc provided to change the electrical characteristics of the amplifier, such as its gain, fre- quency response or AGC action. Ring counters, having a plurality of states selected by applying digital pulses, arc employed to vary the electrical clc-

4,791,671

43.72.Ar SYSTEM FOR ANALYZING HUMAN SPEECH

Leonardus F. Willems, assignor to U.S. Philips Corporation 13 December 1988 (Class 381/49); filed in The Netherlands 22 Febru-

ary 1984

This speech pitch analyzer simultaneously performs two distinct types of analysis, and selects the best quality results of each to determine the final value. In a frequency domain approach, the spectral maxima arc extracted from a fairly narrow-band spectrum as harmonics, having frequency sepa- rations that arc then measured. In a time domain approach, periodicity is extracted from an autocorrelation. These results arc combined and weight- ed statistically to determine the fundamental frequency valuc.--DLR

1487 J. Acoust. Soc. Am. 89(3), March 1991; 0001-4966/91/031487-01 $00.80; ¸ 1991 Acoust. Soc. Am.; Patent Reviews 1487

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