PCM audio amplitude values?

Question

I am starting out with audio recording using my Android smartphone.

I successfully saved voice recordings to a PCM file. When I parse the data and print out the sign

Answer 1

Lots of good answers here, but they don't directly address your questions in an easy to read way.

What exactly are the units for the amplitude values? The values are signed 16-bit, so they must range from -32K to +32K. But what do these values represent? Decibels?

The values have no unit. They simply represent a number that has come out of an analog-to-digital converter. The numbers from the A/D converter are a function of the microphone and pre-amplifier characteristics.

If I use 8-bit values, then the values must range from -128 to +128. How would that get mapped to the volume/"loudness" of the 16-bit values? Would you just use a 16-to-1 quantisation mapping?

I don't understand this question. If you are recording 8-bit audio, your values will be 8-bits. Are you converting 8-bit audio to 16-bit?

Why are there negative values? I would think that complete silence would result in values of 0

The diaphragm on a microphone vibrates in both directions and as a result creates positive and negative voltages. A value of 0 is silence as it indicates that the diaphragm is not moving. See how microphones work

For more details on how sound is represented digitally, see here.