How can I change the ring tone on my Polycom VoIP phones?

Polycom VoIP phones can use standard .WAV files as ring tones. Choose your .WAV file of choice and make sure it's in the correct format:

Check if it's in the right format:

# file rington.wav
ringtone.wav: RIFF (little-endian) data, WAVE audio, ITU G.711 mu-law, mono 8000 Hz

If not, you can convert it with sox:

# sox mywave.wav -r 8000 -U -c1 mywave.wav resample -ql

Place the .WAV file in the FTP folder your Polycom phones retrieve their SIP information from. If you edit sip.cfg you'll find a line as shown below. You can edit that line and put your own .WAV files in there.

...
<sampled_audio saf.1="SoundPointIPWelcome.wav" saf.2="" saf.3="" saf.4="" saf.5="" saf.6="" saf.7="" saf.8="" saf.9="" saf.10="" saf.11="" saf.12="" saf.13="" saf.14="" saf.15="" saf.16="" saf.17="" saf.18="" saf.19="" saf.20="" saf.21="" saf.22="" saf.23="" saf.24=""/>
...

Now, on your Polycom phone (I'm using a IP 430 SIP, yours might differ a bit if you're using another model), navigate the menus like this:

[Menu]
[3] (Settings)
[1] (Basic)
[3] (Ring Type)

Scroll to the bottom of the list to see your custom ring tones.