Speech processor with background suppression

1 speech processor with 1 8 1 background suppression 2 BF494 +12V 0 R14 12 6 11 R20 C19 >A4 1 R12 C15 *see 0. 86458 1006 C18 II 10n R19 R10 C13 R11 C14 104 I560n Cl 10n 4706 T1 CS O I 820n I 165 R9 ** metal film On *see text ES1 ES2 9(S3 o 50k ES4 5 A1,A2= IC 1=TL082 A3, A4=1C 2=TL082 D1...D3= 1N4148 ES1... ES4 = IC 3= 40668 C17 770. 16V A speech processor is commonly used in public-address installations and in utility transmitters. It augments the average value of the speech signal, so that in spite of a high level of background noise or, in the case of a radio transmission, a lot of inter- ference, speech recognition remains possible. In many cases it is, how- ever, undesirable that this back- ground noise or interference is enhanced together with the wanted signal. A possible remedy, as out- Tn lined here, is to provide an adjustable threshold at which the speech pro- cessor becomes active. With reference to the diagram, the signal from the microphone is amplified in Ti (a low-...