Have set-up a IVR service on my home asterisk set-up so that people ringing our home phone number can choose who to leave a message for (i.e select 1 for my VM extension, etc).
For the link in title and the reference to Audacity was the best solution (sweep wasn't playing nicely with pulseaudio and I was a bit over figuring out why, and sox conversion from basic Sound Recorder files wasn't working as obviously as examples suggested it might). I have played a bit with Audacity as a multi-track recorder for guitar session fooling and was pleased to find all paths seemed to suggest it was the answer.
I was trying to be too clever and set all the options myself - then found this link and presto - one last trick however was to leave it sample format at 32-bit float, mono and 8000Hz rate as mentioned (if you set the project rate to 8000 Hz I found I needed to change it to playback) .. then export as 'WAV (Microsoft) singed 16 bit PCM' sorted.
