[chbot] Determining delay between two similar signals

[Eliot Blennerhassett]

On 5/07/20 5:27 pm, Robin Gilks wrote:
> Me again!
> 
> I'm still getting nowhere with my project that will use ultrasonic
> transducers to measure wind speed.
> 
> I understand that I need to run a cross correlation between the original
> transmitted signal and the delayed received one in order to work out the
> delay and hence (with a fixed distance between transducers) the speed of
> the wind.

Late to the party here...

Code here in mtdm.h and mtdm.cc does multi tone delay measurement.

https://salsa.debian.org/multimedia-team/zita-alsa-pcmi/-/tree/master/apps

Sadly it contains zero comments. I can see it uses a mix of 13
sinewaves. I'd have to think harder to say how it works, or find the
authors original explanation if it exists.

Origin of the code is here http://kokkinizita.linuxaudio.org/linuxaudio/

where it claims sub-sample accuracy

"jack-delay: This is a small command line JACK app you can use to
measure the latency of your sound card. It uses a phase measurements on
a set of tones to measure the delay from the output to the input.
Accuracy is about 1/1000 of a sample.