lined with acoustical material and is arranged so that the air from the vacuum cleaner discharge is kept separate from the motor cool- ing air.-J'BG

4•80,587

43.50.Gf NOISE-SUPPRESSING JET ENGINE NOZZLES AND METHOD

Waman v. Bhat, assignor to The Boeing Company 28 July 1981 (Class 181/213); fred 8 May 1979

This patent describes a series of deflectors which can be located in the discharge nozzle of a jet engine to reduce the noise radiated by the engine. This is accomplished by arranging the deflectors asymmetrically in the nozzle. By providing deflectors at the upper portion of the discharge nozzle, jet noise received below the engine is reduced and the fan exhaust flow is discharged below the primary flow to further reduce the noise.-JBG

4,107,460

43.70.Sc APPARATUS FOR RECOGNIZING WORDS

FROM AMONG CONTINUOUS SPEECH

Gene Grunza and Marvin B. Herschef, assignors to Threshold Technology, Incorporated

15 August 1978 (Class 179/1SD); filed 6 December 1976

The word detector described in this patent operates on sets of binary features collected by processing the outputs of a filter bank. It is an improvement on an earlier U.S. patent 3,943,295, and is said to offer superior •bility to detect spoken words by using certain "phonetic class features" and by detecting sequences of these class features. Nineteen filter channel outputs are first combined into these higher level phonetic class features based on spectral ampli- tude and rate of change measures. Time normalization is accom- plished by collapsing adjacent data frames whenever they are suf- ficiently similar. Temporal sequences of these higher level features are compared on a frame-by-frame basis with other previously stored (trained) sequences in order to recognize a word from the trained vocabulary. An improved method of search assures that new incoming data will be checked against the initial portions of all po- tential candidates, even while another candidate is already being processed.-DLR

3,967,066

43.70.Lw SECRET TELEPHONY

Robert C. Mathes, assignor to Bell Telephone Laboratories, Incorporated

29 June 1976 (Class 179/1.5R); filed 24 September 1941

This is one of several patents on crypto-telephony based on vo- coder technology which were applied for before World War II and were only recently issued after aleclassification of such matters. This patent describes a switching arrangement whereby a key con- sisting of a recorded series of sounds having random frequency and amplitude changes is combined with the speech signal to be en- coded. Each of these two signals is analyzed with an 11-channel fil- ter bank and the corresponding filter outputs are added. A further encoding is performed by transmitting only the modulus of the sum of the outputs of each pair of filters with respect to a given refer- ence level. This latter technique, named "re-entrant masking," conceals the signal levels corresponding to maximum and minimum output in a filter band.-DLR

3,985,958

43.70.Lw SECRET TELEPHONY

Homer W. Dudley, assignor to Bell Telephone Laboratories, Incorporated

12 October 1976 (Class 179/1.$R); filed 18 December 1941

This is one of several patents on crypto-telephony based on vo- coder technology which were applied for before World War II, and were only recently issued after aleclassification of such matters. This patent describes a multiple-anode vacuum tube commutator arrangement which sequentially selects the outputs of the filters in a 10-channel filter bank. A second identical filter bank in the

transmitter is simultaneously fed a recording of a key encoding sig- nal consisting of randomly varying frequencies and amplitudes. The outputs of corresponding filters from each of the two banks are added and their sum transmitted. At the receiver a like recording is played on a synchronized turntable, then analyzed by another like filter bank, and this time corresponding frequency band signals are differenced, reproducing the original speech signal.-DLR

4 A36,435

43.75.Tv KEYING SYSTEM IN AN ELECTRONIC

MUSICAL INSTRUMENT

Minoru Kakita and Tsuneo Kosugi, assignors to Victor Company of Japan

2 December 1980 (Class 84/1.22); filed in Japan 16 May 1977

This is a keying system for an electronic musical instrument of the harmonic synthesis type. Typically such instruments borrow a limited number (e.g., 8 or 9) approximate harmonics from the near- est members of the equally tempered scale, in order to reduce the required number of tone generators and electronic switches. In this instrument the instantaneous amplitude control of the tone signal output from each oscillator comes from the addition of an envelope control voltage (for the time function) to the summation of the har- monic level control voltages (for the spectrum function) correspond- ing to the various usages of that oscillator (as an approximate har- monic) for the notes being played at that time. The purpose is to reduce the number of electronic gating circuits required. In dis- cussing the relative merits of harmonic synthesis and formant organ types, the patent gives the erroneous impression that sawtooth and pulse waves used in formant organs contain only odd harmonic components.-DWM

4,244,264

43.75.Tv SYSTEM FOR REGISTERING AND

SELECTING STOPS IN A MUSICAL INSTRUMENT

Dominique Fellot, assignor to Thomson-CSF 13 January 1981 (Class 84/345); filed in France 23

February 1977

This patent describes a digital capture combination action for pipe organ (or an equivalent electronic organ using stop knobs) in which the goals are to increase the number of combinations which can be permanently stored, to reduce the energy requirements for switching stops, to increase switching reliability, and to decrease switching noise. The fixst purpose is fulfilled by allowing "the com- bination to be recorded on an economical and easily transportable carrier such as a magnetic medium (flexible disks, for example)." The energy requirements are reduced by so designing the digital storage and readout that the control unit emits "positioning com-

1626 J. Acoust. Soc. Am. 71(6), June 1982; 0001-4966/82/061626-02500.80; ¸ 1982 Acoust. Soc. Am.; Patent Reviews 1626

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