how can I calculated average Sound intensity (dB)?

I am studying underwater footage of fish for the summer, recorded on go-pros, and am interested in the average sound intensity (in decibles) for each minute of each video (each video is 8 minutes total). The files are currently in mp4s. I have another program that will show me an audio visualization of a waveform in (decibels), and I will read a instantaneous sound intensity at any point, but I can’t find a way to get an average of these points for over period of time without writing down the decibels by hand for every instant and then averaging them all in excel, or playing the videos outloud for an app on my phone which records average sound intensity (but it is finicky and introduces a lot of error, so I’m trying to find another way). It doesn’t seem like that difficult of a task, all I want is the average “relative loudness” for each minute in each video, but I’ve been scratching my head as how to get these data. (I am using a windows 7)

Is there a feature in Audacity that would allow me to do this? Or can I somehow convert a sound file into some other format that displays the amplitude/sound intensity at each instant, so I can copy and paste them into excel or R to get an average?

I appreciate any help! Thank you!

What are you trying to accomplish?

You can’t get the acoustic SPL level from a recording… That’s only possible if you made a calibration with an SPL meter at the time of the recording. Then, you could calibrate the digital dB levels to the acoustic dB levels. (Then, it’s a simple subtraction… If 80dB SPL recorded to -10dBFS (digital) then -20dBFS is 70dB SPL, etc.)

There are ways of finding the digital level.

If you select a portion of the audio and run the Amplify effect, it will default to whatever gain (or attenuation) needed for 0dB peaks. So for example, if Amplify defaults to +6dB your current peaks are -6dB, etc. (You can optionally cancel the effect after noting the dB level.)

The optional [u]ACX Check Plug-in[/u] will give you the peak, RMS (a kind of average), and [u]A-weighted RMS[/u] RMS levels. (SPL meters normally use A-weighting,)

This isn’t exactly what it was designed for, but the “Contrast” tool will give you the “RMS” average for whatever audio you have selected (see: