Go Down

### Topic: How to convert sound sensor output reading to decibel value? (Read 7245 times)previous topic - next topic

#### Giridharan97

##### Mar 10, 2018, 05:06 pm
Hi,

My project is about measurement of sound with microphone sensor using arduino. The microphone sensor detected the sound and I got the reading from the serial monitor in the arduino. But I didn't know how to convert that reading form the serial monitor into decibel.

So kindly provide me with your possible answer so that my project will be fulfilled.

If there is any expression which convert the reading into decibel value, kindly mention below

#### PieterP

#1
##### Mar 10, 2018, 06:23 pmLast Edit: Mar 10, 2018, 06:24 pm by PieterP
The open-circuit voltage of the microphone doesn't tell you anything about the sound intensity if it's not calibrated.

If you just want to convert it to a logarithmic scale, the power in dBm is defined as 10 log10(P / 1 mW).
For voltages, this is defined as the power dissipated by the voltage into a 600Ω resistor. Remember that P = VI = V² / R.

In other words: dBm = 10 log10(10/6) + 20 log10(V).

If you don't even care about the voltage, just the scale, you can just use: dB = 20 log10(ADC_value).

Pieter

#### slipstick

#2
##### Mar 10, 2018, 06:47 pm
But if you want the value in dB(A), i.e. normal SOUND intensity decibels, then you'll need to calibrate your microphone against a known decibel meter and sound source. A free smartphone app might do for the sound meter if you're not too bothered about high accuracy.

Steve

#### PieterP

#3
##### Mar 10, 2018, 07:05 pmLast Edit: Mar 10, 2018, 07:06 pm by PieterP
dB(A) implies A-weighting of the input signal to account for the relative loudness perceived by the human ear. AFAIK, this is not possible on an Arduino.

You probably mean dB(SPL) which is the sound pressure level.

#### Giridharan97

#4
##### Mar 13, 2018, 05:58 am
Thanks. Is there any expression is available to obtain the decibel value

#### Grumpy_Mike

#5
##### Mar 13, 2018, 08:05 amLast Edit: Mar 13, 2018, 08:06 am by Grumpy_Mike
Is there any expression is available to obtain the decibel value

Otherwise no.

#### DVDdoug

#6
##### Mar 13, 2018, 04:04 pmLast Edit: Mar 13, 2018, 04:07 pm by DVDdoug
Quote
Thanks. Is there any expression is available to obtain the decibel value
We can't give you an exact formula/expression because your microphone & preamp are uncalibrated.

But, I'll give you a made-up example -