5,195,141

43.38. Lc DIGITAL AUDIO EQUALIZER

reason a loudspeaker sounds different when used with power amplifiers having low versus high damping factors is that the frequency response of the system changes.--GLA

Seong-Cheol Jang, assignor to Samsung Electronics Company 16 March 1993 (Class 381/103); filed in Korea 9 August 1990

The bulk of the patent is devoted to a computer program that sets the coefficients of several recursive digital filters so that their combined re- sponse will match a desired curve entered by the user. The stated reason for using a digital equalizer and its accompanying A-to-D to D-to-A converters is, "...so that its characteristics are considerably improved compared to the analog audio equalizer, and the user may arbitrarily change the characteris- tics." It appears that the general methodology and circuit flow could just as well be applied to active analog filter sections, but this would presumably degrade performance.--GLA

5,255,325

43.38. Lc SIGNAL PROCESSING CIRCUIT IN AN

AUDIO DEVICE

Shunsuke Ishimitsu, Hisashi Kihara, and Shuichi Mori, assignors to Pioneer Electronic Corporation

19 October 1993 (Class 381/107); filed in Japan 9 October 1991

This is an audio gain control circuit that might be incorporated into a compressor, expander, or limiter. Such devices often employ dynamic ad- justment of attack and release time constants. The inventors propose instead

10

COMPRESSOR 1 INPUT SIGNAL

I TIME CONSTANT SETTING l SECTION

F3 IJTIME CONSTANT /

INPUT L iI I-L TA6tE SIGNA I IJ TIME CONSTANT l

c*! LEVEL / oETECrlNG I / SECTION J

L__LJTIME CONSTANT I

-•TABLE •41n

I TIME C( SELECT]

SECTI! ß

I-•tVARIABLE GAIN q CONTROL _OUTPUT /SECTIO) "•SIGNAL •STANT I

•ROL

I

to select one of several settings from a time constant table in response to signal level. According to the patent, "As a result, the output signal of the signal processing circuit has less distortion and sounds more natural."-- GLA

5,263,091

43.38. Lc INTELLIGENT AUTOMATIC THRESHOLD CIRCUIT

James K. Waller, Jr., Lake Orion, MI 16 November 1993 (Class 381/94); filed 10 March 1992

The circuit is intended to automatically and reliably determine the level of background noise in an audio signal, and thereby to set the threshold level for single-ended noise reduction or other signal processing. The patent is clearly written and provides useful general information about noise reduc- tion circuits and strategies.--GLA

5,268,527

43.38. Lc AUDIO POWER AMPLIFIER WITH

REACTANCE SIMULATION

James K. Waller, Jr., Lake Orion, MI 7 December 1993 (Class 84/736); filed 25 November 1991

This is a solid-state guitar amplifier that includes an equalizer circuit to simulate the sound of a vacuum-tube guitar amplifier. The inventor is appar- ently one of the half-dozen people in this country who understand that the

5,191,615

43.38.Md INTERRELATIONAL AUDIO KINETIC

ENTERTAINMENT SYSTEM

Michael B. A!dava and Hazen L. Maclntyre, assignors to The Drummer Corporation

2 March 1993 (Class 381/3); filed 17 January 1990

It would be fun, and possibly instructive, if you could pick out a melody on your synthesizer keyboard and watch a mechanical toy cavort in response to the music. The patent describes a method for encoding and transmitting kinetic information along with stereo audio signals via low- power FM.--GLA

5,264,850

43.38.Md HAND-HELD SOUND DIGITIZER SYSTEM

Ramin Khorran, assignor to Arkay Technologies, Inc. 23 November 1993 (Class 341/155); filed 12 November 1991

The housing of a hand-held microphone also incorporates an A/D con- verter and signal control circuitry. The device connects directly to a parallel printer port of any IBM PC or compatible computer. a complementary soft- ware program stores digitized audio into memory. Since no auxiliary board is required, the system can also be used with a laptop computer.--GLA

5,271,021

43.38.Nc DIGITAL OPTICAL SOUND SYSTEM

E!wyn R. Berlekamp and Lloyd R. Welch, assignors to Cyclotomics, Incorporated

14 December 1993 (Class 371/37.1); filed 13 December 1991

This patent and its companion 5,271,022 provide a good background in the perils and pitfalls of putting digital soundtracks on film. A sophisti- cated method is described for estimating bit locations and then correcting errors during the playback process.--GLA

5,277,184

43.38.Si MRI SOUND SYSTEM TRANSDUCER AND

HEADSET

Russell C. Messana, Petaluma, CA 11 January 1994 (Class 128/653.5); filed 30 September 1992

The patent shows a device that provides communication to a patient undergoing an MRI test. All parts are nonmagnetic so as not be affected by the intense magnetic field of the MRI equipment. A piezoelectric loud- speaker in a nonmagnetic enclosure delivers sound to a pair of flexible plastic tubes that lead to "earphones" that are made from sound deadening material and that are provided with a closed cavity to which sound is deliv- ered pneumatically via the plastic tubes.--SFL

5,216,718

43.38.Vk METHOD AND APPARATUS FOR PROCESSING AUDIO SIGNALS

Mitsoyoshi Fukuda, assignor to Sanyo Electric Company 1 June 1993 (Class 381/18); filed in Japan 26 April 1990

The patent document describes a DSP implementation of steering logic for playback of Dolby-encoded stereo. Anyone involved in programming DSP chips, or anyone interested in digital audio processing, will find the patent informative.--GLA

616 J. Acoust. Soc. Am., Vol. 96, No. 1, July 1994 Reviews of Acoustical Patents 616

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