# Microphone self noise

Discussion in 'The Projects Forum' started by mhe, Mar 2, 2012.

1. ### mhe Thread Starter New Member

Aug 10, 2011
10
0
Hi

I have a microphone with sensitivity performance of 40dB at 1kHz.
The signal to noise ratio is 60dB

I have found that 60dB signal to noise ratio correspond to 94-60 = 34dB selfnoise.

Can someone tell me how much self noise I should expect in VOLT based on these two parameters, if I measure in an silent environment.

Datasheet for the microphone.

Thanks...

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2. ### mhe Thread Starter New Member

Aug 10, 2011
10
0
Hi again

At 94dB = 1Pa the microphone produces 10mV and hence 10mV/Pa

Since the self-noise at 34dB correspond to 0.001Pa, the microphone produces 10microVolt noise when placed in a silent environment.

3. ### mhe Thread Starter New Member

Aug 10, 2011
10
0
Hi

I am trying to calculate the noise contribution from a microphone.

In the datasheet the following information are reported.
Sensitivity : -40dB at 1kHz.
S/N Ratio : 60dB.

-- My Calculation ----
NoiseFloor = 94dB - 60dB = 34[dB]
Sensitivity = 10^(-40/20) = 10[mV/Pa] or 10[mV/N/m^2]

NoiseFloor in Pa = 10^(NoiseFloor/20) Po = 10^(34/20)*2*10^-5 = 0.001 [Pa];
NoiseFloor in mVolt = Sensitivity * NoiseFloor = 10*0.001 = 0.01 [mV]

*Po: In pure silence there is a constant pressure-atmospheric pressure Po.

Is this calculation correct ?

Thanks