Just had to upload voice prompts to an Alcatel OmniPCX.

The process:
Record the message using the "Sound Recorder" on Windows 7 (which saves to WMA format and it's got a high sample rate and it got 2 channels etc)
Upload to a Ubuntu 10.10 Linux box and use ffmpeg to convert to the correct format as follows

# wrapped for readability remove `\' and put it all on one line to run
ffmpeg -i Message20101208.wma  \
-ac 1 -ar 8000 \
convertedMessage20101208.wav

Upload the converted file to the OmniPCX PABX

The format that get's downloaded from the OmniPCX and converted to PC format is noted below so I made the file I wanted to upload the same.

OmniPCX Voice Prompt Compatible Format
Bit Rate: 128kbps
Audio Sample Size: 16bit
Audio Sample Rate: 8KHz
Channels: 1(mono)
Audio Format: PCM

Of course you could use a Windows app to achieve the same thing (something like OSS Audacity).