Measuring Electro Acoustic characteristics

[shreesan]

Hello. I am working on Electrical output of a microphone. So far I can acquire my analog signal using DAq Assistant NI USB 6009 and view my waveform graph but the plot is in time vs amplitude(V) unit. I want to plot it in frequency vs decibels unit. Also the amplitude of the acquired electrical output of a microphone is in 0.000xx range for audible signal. I don't get clear understanding why the range is very low. I am grateful if anyone can help me to get a clear knowledge of these. Thank you.

[Lysandros]

The microphone will probably output a signal in the millivolt range, because it is a passive device, with probably no built-in amplification.

If your USB device is configured to read a signal in the +-10V range, then resolution will be very low. Configure your device to a lower input range, while also checking that your acquired voltage doesn't exceeds the range.

Keep in mind, that your DAQ's input impedance is relatively low (like 150kOhm), which may cause the the microphone to start draining current, which will limit the voltage that your A/D converter sees. Consult the output impedance of your mic' as well.

[Ryan3]

The DAQ Assistant Express VI can be found on the Functions palette by going to Express » Input. Place the DAQ Assistant on the block diagram by dragging and dropping it from the Functions palette. The Assistant should automatically launch when you drop the VI on the diagram.

[dsb@NI]

Are you still working on this? Lysandros offered some practical advice to consider when acquiring from passive acoustic sensors. If you still need help converting acquired voltages to sound pressure level, try the Sound Level Meter (DAQmx) example VI installed with the Sound and Vibration Toolkit which has a free evaluation. You may also want to consider using the DSA Soft Front Panel to acquire, perform FFT, visualize SPL (dB) versus frequency, and log waveform data to file.

[Ryan3]

@mysacstate myochsner 

Thanks for the input. I could modify at the last moment.

[Parthiban_SM]

I am trying to acquire the signal from the microphone and display the sound level in dB(A). I wrote some basic LV code and compared the output with reference noise meter. above 40 dB there is no issues but not able to measure below 40 dB. our anechoic room ambient noise is 30 dB but the output still in 41 dB. I suspect the code and tried the same thing in the Sound level meter(DAQmx) example VI but I got the same result. Microphone has the capability to measure below 40dB. I am missing something, please support me to short out this issue    

DAQ Device:

1. NI cDAQ-9189

2. NI 9230

Microphone: MI 1271 ONOSOKKI

Preamplifier: MI 3170 ONOSOKKI

https://www.onosokki.co.jp/English/hp_e/products/keisoku/s_v/mi1281.html#spe 

Attachment: Channel configuration image

Also help me to locate the icon marked in the attached Image.(Magnitude to dB)

[Henrik_Volkers]

Had a look at the powerspectrum?

[dsb@NI]

This older post may help explain why you cannot read SPL below 41 dB SPL through the 9230.

[Parthiban_SM]

Thanks for the reply. It is highly helpful. The way you explained in the older post was awesome.

[Parthiban_SM]

@Henrik_Volkers

Thanks for your valuable time and reply. I tried power spectrum too