Isophotometric sonometer for acoustic energy - has series of parallel filters set to successive octaves

摘要

The psophometric sonometer determines immediately by means of separate values an acoustic energy balanced in accordance with the spectral sensitivity curve of a normal ear. It combines an aperiodic pre-amplifier/or known gain supplied by a calibrated microphone, and a psophometric filter shaping the frequency of an output signal from the pre-amplifier in accordance with the sensitivity curve. Measurement of the shaped signal level is by aperiodic amplifiers of set gain in cascade, each supplying a set of level detectors with response thresholds stepped at regular intervals within the gain. Each detector works in conjunction with a separate indicator having two states representing its response.