Miniature portable noise dosimeter - comprises microphone, variable frequency oscillator, mixer and filter having quadratic transfer function around resonance

摘要

The portable noise dosimeter comprises a microphone, a variable frequency oscillator, a mixer and an electronic filter with a transfer function varying quadratically either side of the resonance frequency. The measuring circuit is coupled to a counter for recording the amount of noise within a given interval, e.g. one day. Pref. the measuring circuit comprises a CMOS transistor circuit. An optical indicator may also be coupled to the measuring circuit for signalling when the authorised level of noise is above the permissible level. The noise dosimeter is lightweight and compact in order that it may easily be carried around. The appts. has a low power consumption to provide a long operating time from a small supply battery.