Sound just has an amplitude at every sample, but this is too low level to be very useful. Instead you would probably make a net process the same kind of featur

Sound just has an amplitude at every sample, but this is too low level to be very useful. Instead you would probably make a net process the same kind of features a human has, which is a list of frequencies at each sample, each with an amplitude. (In humans we have oscillating hairs that perform an analog frequency extraction, while with computers you'd use a fourier transform to do it mathematically.)