Sound pressure monitor in artificial mouth - has capacitor microphone coupled to digital comparator

摘要

A wobbulator (W) generates in known manner a sound frequency of, for example, 200-4, 500 Hz. The frequency varies from the upper to the lower value every 0.5 seconds. The sound frequency passes by way of a programmable amplifier (P) and a mouth amplifier (V1) to a loudspeaker (L) and an artificial mouth. From the mouth the sound passes to a microphone whose frequency response is to be tested. Simulataneously, it passes to a condenser microphone (M) to measure sound pressure. The microphone output passes via an amplifier (V2) to a device (E) which rectifies the audio signal and evaluates its maximum value, which it converts to digital form and passes it to a comparator (D) where it is compared with a reference value from a memory (R). A correction signal i is derived in a control circuit (B) and this is passed to the programmable amplifier.