4034-B VOICE AND 1A.20 FACE ANALYSER MICROPHONES , 1970's

On the left is a Sound analyser with a tubular stem attached to a standard 4021 microphone see Item A0561, this was used in the STL for testing sound in finite spaces such in the ear canal of an artificial head, by this means the sound response could be measured from telephone transducers such as phone receivers. Equipment such as the Bruel & Kjaer Microphone Amplifier and Beat Frequency oscillator would be used together with this item, see Items A1882B & A1884.
The second item is also a standard 4021 microphone marked A1.520 with a bracket mounted above the diaphragm, which looks temporary, the distance of this bracket, could be changed for different distances to monitor the response from the human voice. This item may have been used as measurement instrument for monitoring telephone receivers. Both objects came from STL (Standard Communication Laboratories).

Donated by John Barnes

A1864