Using AudioWorklet convert volume meter value into decibel

First, thanks for your sharing, I would like to know how to convert volume into decibel by using AudioWorklet. In your AudioWorklet volume meter example, I can get volume value. This link is the example I found https://github.com/GoogleChromeLabs/web-audio-samples/commit/7c109d7d21c24bfa031f843877837e36ea0028cb .

// volume need to * 100 to make sure value between 1 to 10
this._volume = Math.max(rms, this._volume * SMOOTHING_FACTOR) * 100;
 
// I would like to know is this the correct way to convert volume to decibel? 
// My example is 16bits so I divided by 32767
const dB = 10 * Math.log10(this._volume / 32767);  

[rvadhavk]

I just curious, is this the correct way to get real or close dB value? Or it’s just ratio.

This isn’t my area of expertise, so I could be wrong, but to get the “real” loudness in dB instead of just computing a ratio of current power to max power, I believe you need some reference measurement to know the relationship between the RMS of the actual sound pressure in pascals and the RMS of the unitless PCM data: https://en.wikipedia.org/wiki/Decibel#Acoustics. So unless you can ask your users to play some sort of calibration sound at a known fixed distance from the microphone or you know exactly what microphone they’re using and what the gain is and everything, you can’t know the absolute loudness.

[Mayvis]

This won’t be very reliable. For example with autoGainControl you already can influence this value. The output on MacOs Safari and MacOs Chrome is really different.

I like the approach in this example (I started also with the volume-meter example) better and I assume it’s even less resource intensive.

I prefer to use AudioWorklet instead of using autoGainControl😅. Because I also have to manipulate float32 to int16…etc. I worked on an AI company and build ASR associated project. I know the reliability that you mention. Thank you.