io

46

length dimensions (arrows F and G) but the excitation is now applied in the circumferential direction. The resulting shear deformation of the piezocer- amic pieces produces torsional movement of the end disks as indicated by curled arrows J and K. The assembly is encapsulated within a protective layer of soft polymer that can support shear wave propagation and that, in turn, within an outer epoxy shell that is geometrically shaped to permit easy penetration of the whole assembly into the sediment. Variants of this design are discussed, such as using entire tubes of shear coupled piezoceramic instead of the several pieces 40, or making the end disks themselves from shear coupled pieces of piezoceramic.--WT

5,357,486

43.38.Fx ACOUSTIC TRANSDUCER

R. E. Pearce, assignor to Innovative Transducers, Incorporated 18 October 1994 (Class 367/159); filed 2 December 1992

Multiple laye/s of PVDF film are wrapped on the outer cylindrical surface of a hollow tube of relatively flexible material such as polyurethane or neoprene. This is surrounded by another hollow concentric cylinder of a rigid material such as aluminum or stainless steel. The clearance between the two cylinders is sufficient to create a hermetically sealed annular cavity that contains the PVDF film. This cavity is filled with air or dry nitrogen to some desired ambient pressure. In response to an incident pressure wave, the flexible inner tube deforms thereby stretching the PVDF film and generating an output voltage. Conversely, application of an excitation voltage results in deformation of the flexible tube and hence radiated sound.--WT

5,384,856

43.38.Ja ACOUSTIC SYSTEM

Noboru Kyouno et aL, assignors to Mitsubishi Denki Kabushiki Kaisha

24 January 1995 (Class 381/103); filed in Japan 21 January 1991

In two-way and three-way loudspeaker systems the summed output of analog frequency dividing filters is typically nonminimum phase. By using digital, linear phase FIR filters it is possible to make the channels combine properly, and to compensate for loudspeaker amplitude and delay character- istics in the same process. The patent document describes a method and circuitry for doing this more or less automatically. The text is clearly written and informative.--GLA

5,268,965

43.38. Kb USER SELECTABLE NOISE CANCELING

FOR PORTABLE MICROPHONES

Merhdad Badie and William R. Williams, assignors to Motorola, Incorporated

7 December 1993 (Class 381/91); originally filed 11 November 1991

A sound transducer 502 is mounted within a housing 510 defining the microphone. Sound ports 304 and 308 on opposite sides of the microphone are coupled to two sides of the sound transducer. When mounted on the

510

3O2

5/2

clothing of the user, sound to one of the sound ports is reduced because of the mounting clip 310. Removal from clothing allows access to this port and hence noise canceling action.--MDB

5,288,955

43.38.Kb WIND NOISE AND VIBRATION NOISE REDUCING MICROPHONE

Bruce W. Staple et aL, assignors to Motorola, Incorporated 22 February 1994 (Class 181/158); originally filed 5 June 1992

With communication between a bicycle racer and his support crew in mind, this microphone and housing have a rounded front portion and a flat rear portion. The microphone capsule faces out of the rear flat portion or face. The mounting means includes a rubber pad between the microphone housing and a pedestal for mounting, e.g., on the handlebar directly in front of the rider.--MDB

5,388,159

43.38.Lc EQUALIZING CIRCUIT FOR REPRODUCED SIGNALS

Haruo Sakata, assignor to Clarion Company 7 February 1995 (Class 358/166); filed in Japan 20 December 1991

This is a sort of reconstruction algorithm that extends the upper- frequency range of reproduced audio or video signals beyond the bandwidth actually received. The trick, obviously, is to do this in a way that is per- ceived as enhancement rather than distortion. The patent document is clearly written and includes a great many helpful illustrations.--GLA

5,388,162

43.38.Ja SOUND INNOVATION SPEAKER SYSTEM

Tong-Hoon Sohn, Seoul, Republic of Korea 7 February 1995 (Class 381/160); filed in Rep. of Korea 9 July

1991

Two loudspeakers in boxes are arranged to face each other, so that sound is radiated through the four-sided cavity between them. This arrange- ment has been patented previously. In this patent the novel feature appears to be, "... sound wave absorbing material perforated with cone-shaped holes extending radially (outward)."--GLA

5,394,474

43.38. Lc ECHO ATTACHING CIRCUIT AND AUDIO

DEVICE USING THE SAME

Jun Hirai and Kaoru Izawa, assignors to Rohm Company 28 February 1995 (Class 381/63); filed in Japan 15 December 1992

Does your Karaoke system introduce noise when you add artificial reverberation? Help is at hand. A compandor scheme is combined with tic-controlled level adjustment to minimize noise pickup as well as internal noise generation.--GLA

1259 J. Acoust. Soc. Am., Vol. 98, No. 3, September 1995 Reviews of Acoustical Patents 1259

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