Patent GB-600336-A (GB)
Title: Improved electrical means for indicating sound pitch or voice inflection
Inventor: HORVITCH GERARD MICHAEL
IPC: G10L25/90
Filed: 1945-09-07
Abstract: 600,336. Frequency measurements. HORVITCH, G. M. Sept. 7, 1945, No. 23100. [Class 37] [Also in Group XV] A pitch or inflection indicator, particularly for speech training of deaf and dumb persons, comprises means for converting sound or voice vibrations into electronic signals of corresponding frequency with a series of filters each passing a signal of predetermined frequency, and a series of devices each operative by a signal of predetermined frequency and each adapted to vibrate or depress a particular key or reed to indicate the signal. The indicator comprises a master amplifier and distribution network 1, the input to which is fed through an amplifier 2, coupling transformer 3, and amplifier 4 to a transformer 5 having two outputs 6, 7. The output 6 feeds a sound intensity indicator 8 and a slow speed wave form analyser 9. Eight identical reed circuits 10 corresponding to the notes of an octave are provided, one being shown in detail enclosed in chain-dotted lines. Each reed circuit comprises an amplifier 11, a frequency selector and amplifier 12, a volume expanded amplifier 13 having a low frequency voltage to actuate the reed, and first and second harmonic selectors and reed actuators 14, 15. The selector valve 16 selects a single note in the filters 17, the first harmonic of that note in the filters 18, and the second harmonic in the filters 19. These three notes are rectified in the rectifier 20 and control the amplification of the amplifier 21, which emits a frequency capable of best being conveyed by the reed 22. The valve 20 also feeds amplifiers 23, 24 so that the filters 25 resonate to the first harmonic of the note generated and the filters 26 to the second harmonic. Rectifiers 27, 28 feed relays 29, 30 which depress the first harmonic reed 36 or the second harmonic reed 38. In order to enable frequencies to be generated by depressing the reeds, a generator 40 is provided for each of the reeds 22. Condensers 41, 42 change the frequency to the first or second harmonic when the first or second harmonic reeds 36, 38 are depressed. The indicator is controlled by means of a six-pole nine-point ganged master switch 46 connected to a class line 60 and a microphone line 61. An automatic switch'selector control 59 is coupled to the master switch 46 and feeds an automatic selector line 65 so that on operation of the master switch on one pitch indicator (e.g. the teacher's) the master switches on all the other indicators in the circuit take up appropriate positions. Microphones 63, 64 are connected to the master switch 46 as shown. By setting the master switch to different positions the teacher may instruct a class with or without using his own set, a pupil may examine his own speech or generate notes on his reeds and examine their characteristics, the teacher may generate notes on his reeds and the class examine their characteristics, or the teacher may instruct through amplifier only without using his reeds. The pupils place four fingers of each hand on the eight reeds covering the notes of the basic octave, the two thumbs being placed on the harmonic reeds, vibration of the reeds being transmitted to the fingers. The first and second harmonics are indicated by the separate thumbs, and the third harmonic may be indicated by simultaneous vibration of both reeds touching the thumbs. Harmonics may alternatively be indicated by lamps.