What is MATLAB for Android Device microphone input data unit?

Dear community,

I've recently seen the newly introduced "Microphone Sensor" input for MATLAB mobile. When I enable the microphone of my smartphone in MATLAB, I see that the "Level dB" value almost always has a "negative" sign. What is the "level" here? Is it "Sound Pressure Level" or something else? If it is the "Sound Pressure Level", what is the reference pressure level for dB calculation?

I undrestand that the output of the Microphone sensor may differ from device to device and I believe there may be a calibration constant in mV/mPa (or sth. like that). May be we can do that conversion via Post-processing.

I wonder if there is a built-in or a programmatic method to get SPL signal from the microphone.

Best regards.

Answer 1

[Adit Kirtani]

Hi Halil,

For your first question, the level bar indicates sound being received by the microphone. You can read into it at this documentation page:

https://www.mathworks.com/help/matlabmobile/ug/acquire-audio-data-from-a-mobile-device-microphone.html

We can definitely, amplify our audio signal as required, here is a handy MATLAB Community Post:

https://www.mathworks.com/matlabcentral/answers/315781-how-do-i-amplify-my-sound-using-soundsc

For your final question, I would suggest the splMeter class. Here is it’s documentation page:

https://www.mathworks.com/help/audio/ref/splmeter-system-object.html

I hope this helps,

Adit Kirtani.