Time delay of audio signal

Question

Here is the scenario:

I'm generated a signal which is: 200ms @ 2kHz 1000ms of zeros 200ms @ 2kHz

and i want to calculate the time delay between them, not between the two synthetic audio part. but by playing the signal on a speaker and recording it using a microphone (adds noise)

Fs = 44100

i tried: 1. cross correlation 2. calculation the diff between two maximas of RMS window at the size of 8820 samples. (we get the maxima when the window is on the sound part.

the distance between the speaker and the mic is around 30cm. i cant get a steady result. why?

Answer 1

If you want to do this accurately and consistently then one method I have used in the past is to loop back one channel (e.g. the left channel) from the output to the input and then use the other (i.e. right) channel for the timing test. You can then cross correlate between the left (loopback) and right (actual audio) channels. This eliminates many potential sources of error (buffer delays, hardware latency, software issues, etc), since the left and right channels will always be "in sync" and you should be able to make measurements accurate to +/- 1 sample period (+/- 12 µs at 44.1 kHz).