My question is this: what does the y-axis represent? What is MATLAB actually plotting here? Thanks!
What you are observing is the digital representation of the voltage, which in fact represents the acoustic pressure. Workflow would be something like:
- Vibrating larynx is producing
Acoustic Pressure [Pa]
- Variations of that pressure are converted by the microphone into
- Voltage is being sampled and quantized by the ADC (Analog to Digital Converter) and represented as series of numbers.
Now knowing your microphone's sensitivity
[mV/Pa] you can relate the voltage and acoustic pressure. Additionally if ADC's parameters are known (or measured) then you can directly relate sample values to Pascals.