Arduino Audio Sound Level Meter
Introduction: Arduino Audio Sound Level Meter
This is add-on of the audio amplifier project result which is introduced in other instructable. (https://www.instructables.com/PC-Speaker-Amplifier/)
Usually many types of sound level meters are directly connected with input (or rarely output) signal lines of amplifier.
But personally I’m thinking any electrical connections with amplifier circuit may surely degrade music playback quality by inserting some noises or causing any interference with audio signals.
Therefore, I’m prefer to use totally isolated sound level measuring method such as monitoring current fluctuation according to the changed intensity of audio signal.
To prove the idea, I made prototype device to detect current changes and turn the measurement result into visual effect.
I connected current measuring sensor (ACS712 hall effect current meter) to power supply line and interfacing it with LED indicator circuit.
Firstly this method seems very plausible before to actually measure current fluctuation according to the audio output differences from speaker.
But the result was disappointing as DC current change is a little bit small and current measurement usually lagging behind the dynamic audio signal fluctuations.
Therefore, visual indication which is following DC current change is very dull and unimpressive.
Due to the reason, I selected the Adafruit sound/noise measuring break-out board as alternative solution.
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This is sound level meter using Arduino Nano and Adafruit Electret Capsule Microphone break-out which including MAX4466 amplifier IC chip.
As this breakout board and LED indicator circuit using totally separated power supply from the amplifier, personally wanted total isolation with audio signal can be possible.
The microphone breakout is receiving any sounds (or noises) at surrounding and amplifying it enough to produce voltage to be fed to Arduino.
Therefore, according to the sound level changes, output voltage quickly following and dynamically driving 8 LEDs indicator circuit.
Let’s look more detail on the circuit made.
Step 1: Sound Level Meter Schematics
Overall circuit is consists with three major components such as Arduino Nano, Adafruit MAX4466 break-out board and 74HC595 Shift register IC.
The operation of sound level meter is as follows.
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- Adafruit break-out board installed with ceramic microphone which detecting audio signal
- Detected very small audio signal (uV ~ mV) by microphone is amplified by MAX4466 IC and amplification ratio can be adjust by small VR attached to the break-out board
- Amplified audio signal voltage fed to the analogue input port A1 of Aduino nano (You can use any of analog port available)
- Received input voltage by Arduino is in range of (0.3 ~ 0.5V) and it’s my VR setting of Adafruit break-out board (When you setting the VR differently, output voltage range will be different from mine)
- According to the received present voltage level, sketch C-program driving 74HC595 to drive 8 LEDs up to certain level (Detail will be shown later when explaining sketch C-program)
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When LEDs are driven directly without 74HC595, total 8 digital ports of Arduino should be used.
But only 3 control lines are necessary when shift register is used and that’s why 74HC595 is included to this circuit.
I will not explain shift register IC’s operational details as web contents are quite abundant in Internet.
You can see similar project example using 74HC595 in other instructable. (https://www.instructables.com/Disk-Usage-and-File-Download-Indicator/)
Step 2: Wiring Drawing
Wiring diagram is much simple as only single 74HC595 IC is connected with 8 LEDs.
Three (3) control lines (Data, Latch, Clock) are connected between 74HC595 and Arduino Nano.
Usually current limiting resistor (220ohm ~ 330ohm) is required between 74HC595 output pin and LED anode terminal.
Although my circuit is working without current limiting resistors, please use resistor still as the standard wiring method requires it.
Step 3: Parts
As the circuit is simple, used components are not many.
Adafruit MAX4466 board is not shown in the picture above as it attached and fixed on the front side.
The following break-out boards and electronic parts are used. 1003