How to calculate the sound pressure (Pa) of an audio signal ?

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Antonio Spera 2021-1-14

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回答： jibrahim 2024-2-22

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Hi, I need your help. I have an audio signal y that I obtained using the function:

[y,fs] = audioread("audio.wav");

and I wanted to understand how it is possible to calculate the sound pressure (Pa) of this audio. I need Pa of the audio to calculate the sound pressure level (SPL). Thanks for your help.

Antonio.

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Md Saiful Islam 2022-4-7

编辑：Md Saiful Islam 2022-4-7

@Mathieu NOE

You are absolutely right. The calibration factor is non-linear. It needs a calibration over a range of dB level. I followed your suggestion. However, I have a calibrator only for 94 dB and 114 dB. For both cases, I found the measured sound level from the wav file as 73 dB and 92.3 dB which means I need to add a gain of 20 dB, i.e., calibration factor around 12.1. How can I be so sure about the measurement below 50dB or any other values except 94 and 114 dB?

Mathieu NOE 2022-4-8

hello

I don't find that there is a lot of non linearity in your calibration

94 dB / 114 dB at the calibrator gives you a reading of 73 / 92.3 dB so the 20 dB increase at the calibrator translates into a 19.3 dB delta at the "recorder" side which I personnaly find not too bad (0.7 dB non linearity is in many acoustic measurements a non event).

If you have the possibility to compare your microphone to a high quality "lab" certified mic then you should be fine.

otherwise you can use a good loudspeaker and simply start with a 94 dB tone, then go down in signal input amplitude to check the linearity at lower levels.

all the best

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jibrahim 2024-2-22

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Here are relevant functions available with Audio Toolbox that are related to measuring loudness of an audio signal:

calibrateMicrophone: Calibration factor for microphone
acousticLoudness: Perceived loudness of acoustic signal using the Zwicker Method (ISO 532-1:2017(E)) or the Moore-Glasberg Method (ISO 532-2:2017(E))
loudnessMeter: Standard-compliant loudness measurements. Calculates the momentary loudness, short-term loudness, integrated loudness, loudness range (LRA), and true-peak value of an audio signal.
integratedLoudness: Measure integrated loudness and loudness range
splMeterhttps://www.mathworks.com/help/audio/ref/splmeter-system-object.html#d126e65252: Measure sound pressure level of audio signal