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33

For example, if the frequency difference is small, a beat frequency vibrato effect is obtained. If tuned an octave higher than the marimba bar, the result is harmonious.--DWM

5,140,637

43.75.Rs DEVICE AND METHOD FOR REMOVING VOCAL SIGNALS

Timothy McCarthy, North Valley Stream, NY 18 August 1992 (Class 381/1); originally filed 1 December 1989

"Some users of stereophonic sound reproduction equipment find it desirable to delete the vocal component of prerecorded music so that only the instrumental component can be heard. This allows a user to sing and be accompanied by the instrumental music without interference from the prerecorded vocal." If one assumes that the singer's voice in the original recording was recorded equally in both of the stereophonic channels, and

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RE. PRODUCEI•• • .27 21 AMPLIFIER a/-22 34

this is often the case, one way to eliminate the voice is to connect the circuit between the reproducer and the amplifier as shown. Then the new singer can connect the new microphone as shown at 40 to add the new vocal to the left channel. Of course this will also cancel out anything else recorded in both channels. When switch 25 is in the alternate position, the original recording is reproduced.--DWM

5,005,204

43.85.Jq DIGITAL SOUND SYNTHESIZER AND METHOD

Michael A. Deaett, assignor to Raytheon Company 2 April 1991 {Class 381/51); filed 18 June 1985

This patent purports to describe how a linear prediction synthesizer could serve as a general purpose sound synthesizer. In fact, the intended application is to synthesize transient, underwater sounds. The method differs from typical uses of LPC for speech synthesis in that there is no periodic excitation signal. Excitation is provided entirely by a random number sequence. The patent text clarifies that, "it is assumed that an autoregressive model will provide an adequate description of the transient signal."•DLR

5,170,435

43.88.Ja WAVEGUIDE ELECTROACOUSTICAL

TRANSDUCING

Michael D. Rosen and Hal Greenberger, assignors to Bose Corporation

8 December 1992 (Class 381/86); filed 2 March 1992

Bose's previously patented "acoustic cannon" can be folded and contoured to make an efficient low-frequency transducer for use in a vehicle. Driving signals to the subwoofer and to the higher frequency

5,198,604

43.75.Tv RESONANT EFFECT APPARATUS FOR ELECTRONIC MUSICAL INSTRUMENT

Iwao Higashi and Yasuyuki Umeyama, assignors to Yamaha Corporation

30 March 1993 (Class 84/626); filed in Japan 12 September 1990

This digital electronic musical instrument has a number of musical tone signal forming circuits that differ in their resonance frequency char- acteristics. These circuits can be used to respond to the depressed key of an electronic piano, for example, so that the tones from different resonant "strings" are distributed within a multichannel sound system to effect "spatial broadness in a musical tone." To provide for sympathetic string vibration circuits, other than the one or more assigned to a given note, the outputs of the other resonant circuits are weighted to reflect the distance between the sounded and resonance "strings." To a retired piano re- searcher (the reviewer) this seems to be a difficult way to make a piano sound.--DWM

loudspeakers are contoured in a clever way that minimizes excessive cone excursions in both systems.--GLA

5,170,436

43.88.Ja ACOUSTIC SPEAKER SYSTEM

Daryl G. Powell, assignor to Allan L. Powell, Chattanooga, TN 8 December 1992 {Class 381/90); filed 24 January 1991

A vented, tower-shaped, loudspeaker enclosure has slotted internal baffles that only partially obstruct its cross section. These probably serve a useful function by damping organ-pipe resonances. However, the patent states: "The baffles have a plurality of reed fingers which are excited at predetermined frequencies to resonant thereby resulting in a controlled resonance developed by the air within the cabinet to provide a bass re- sponse more transient than that of conventional speaker systems..."-- GLA

1754 J. Acoust. Soc. Am., Vol. 94, No. 3, Pt. 1, Sept. 1993 Review of Acoustical Patents 1754

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