Sound measurement in arduino - error when decreasing the sample window
A quick google indicates that the maximum sample rate on an arduino is around 9.6 kHz. So you're going to get 2 or 3 sample per measurement. Realistically you need several ms to get a meaningful range, the idea of calculating a peak to peak range on a handful of samples just doesn't make sense.

I'm not sure why you don't get a number out when you use micros() but even if it did give a number it wouldn't have a lot of meaning.

Either you need to use something that can sample far faster or you need to re-evaluate what you are trying to do and see if there is a better way to achieve your requirements.