We found this circuit in a 1986 documentation. It uses only LEDs, batteries, resistors and the power supply which can consist of 4 batteries or a 9V battery. The basic circuit uses two-color LEDs.
STMicroelectronics MP23AB02B MEMS Audio Sensor is a compact, low-power microphone built with a...
This circuit was found in the National component manual which is not currently simple to obtain....
This circuit is from the 80's and can be implemented with modern equivalent components. R1 is 2M5,...