How can I decipher an M4A file?

I have my Swift app that records audio in chunks of multiple files, each M4A file is approx 1 minute long. I would like to go through those files and detect silence, or the lowest level.

While I am able to read the file into a buffer, my problem is deciphering it. Even with Google, all it comes up with is "audio players" instead of sites that describe the header and the data.

Where can I find what to look for? Or even if I should be reading it into a WAV file? But even then I cannot seem to find a tool, or a site, that tells me how to decipher what I am reading.

Obviously it exists, since Siri knows when you've stopped speaking. Just trying to find the key.

How can I decipher an M4A file?
 
 
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