GB949576A - Noise meter - Google Patents

Abstract

949,576. Noisemeters; voltage measurements. MINE SAFETY APPLIANCES CO. Nov. 3,1960, No. 37824/60. Heading G1U. [Also in Division G4] A noisemeter comprises an integrating circuit 5 which includes a detector circuit 32, a storage condenser 46, a potential source 36 connected between the transistor base and one side of the storage condenser and a single pole, double throw, switch 37 whose switch arm 40 is connected to the other side of the condenser and is cyclically driven by a rotary drive 43 into alternate connection with the switch contacts 38, 39; so that repeatedly the condenser is first charged through the transistor output and then has its potential applied across a meter 6. A further driving arrangement 51 operates in timed relationship with the drive 43 to operate a condenser discharge switch 44 so that the condenser is discharged after each time period of its connection across the meter 6. The detector circuit 32 may incorporate a transistor 33 and the switch driving arrangements may be rotary driven cams. As described the complete noisemeter circuit includes a microphone 1, a linear feedback amplifier 2 of conventional design, a logarithmic attenuator 3 and a further linear amplifier 4. After being processed by these stages the noise signal is passed to the integrating stages of the invention, and the record obtained will be logarithmically related to the original noise input. This if of advantage since the ear is logarithmically responsive to sound energy. The charge and metering periods of the storage condenser are made sufficiently long for the meter record to be observed visually.