Yes I know... True, that is another issue. Yeahhh and that too. But I do this just for fun! It is not meant to be an A.P. replacement or something, just an hobby project. Though, it might actually become quiet usable :)
So, basically this is nothing else than a teensy audioshield feeding its own input with its output. That is the hardware part. The rest is software, on the teensy and the PC.
The teensy 3.2 generates a sinewave of some adjustable frequency and this is sent to the output of the audioshield. With an external loop this is then is fed back into the input of the shield which is then read by the teensy and being analyzed. The idea is to put some equipment under test into the loop.
The software is still a mess. Publishing anyway. Remember it is work in progress ;)