QuickDAQ for measuring sound level

[Rschell]

My office has recently acquired a DT9837, and a license for QuickDAQ, to set up a sound room and measure the sound created by a prototype. Along with the DT9837 we have three 130f20 microphones from PCB Piezotronics. Currently I can connect them to the daq but I was wondering if there was a way to get QuickDAQ to display the measurements for the sound in dB.

I'm also not sure if I have the right EU set. Currently I have it set for Pa because the manual for the microphones gives the sensitivity as 45 mv/Pa 

[JRys]

Hello,

QuickDAQ does not have the ability to convert an mV signal from a microphone directly to dB. 

I have a few notes about this and from what I picked up here and there this is how you get to dB.

First, determine sound pressure using the following formula.

Once you have sound pressure, use the following to get decibels:

Where P = pressure in pascals
Po = reference pascals (constant = 0.00002 Pa)

Let’s say the average value from the microphone is 10mV. 

I’m going to use the Sensitivity value of 450mV/Pa (PCB.com p/n 378A04).

P = 0.010 / 0.450 = 0.022

dB = 20 Log( 0.022 / 0.00002) = 60.82dB

if you play with the numbers, 45dB is about 4mV. 

I'm not a sound engineer so you should double-check this with the people at www.pcb.com.
 

Best regards,

John