This sound meter or sonometer was found in a Popular Electronics from the 80's. The circuit can be easily implemented today, and the microphone is made of electret or ceramic.
We found this adapter in a 1970s American documentation on instrumentation. It is suitable for analog...
This circuit was obtained from an Electronic Design from 1964. Transistors admit modern...
This charger is from an old publication of 1975. The PNP transistor can be the BC558 and the NPN...