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Sound Level Meter

This is a sound level meter circuit consisting of an electret condenser Mic, pre-amplifier circuit using NE5534/TL071 and LM3915 bar/dot display driver chip.
According to the sound pressure captured by Mic, this device shows sound levels with LEDs.
As the LM3915 requires predefined input voltage levels for correct operation, a pre-amplifier circuit is utilized for amplifying the weak Mic input signal.
For dynamically displaying sound pressure levels with 10 LEDs, the LM3915 bar/dot display driver chip should be configured to support a certain input voltage range such as 60mV ~ 1.25V.
I bought about 10EA of these chips quite a long time ago (Maybe more than 10 years ago!).
Supposedly I had planned to make a battery capacity level meter or audio sound level meter with these chips.
But I forgot the chips are available in my inventory and they are gathering dust for quite a long time.
Now let’s make some useful gadgets with this old but good analog IC chip!”

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