IVR volume raise & lower?

For some reason my IVR’s volume appears to fade in & out. It does not appear to be choppy, but more so come & go in volume. I am using 8000mhz mono wav files. I do not feel that it is a bandwidth issue, because I am hearing the IVR from outside the office over a analog interface in the server. The server is a Intel® Pentium® D CPU 3.00GHz with a gig of ram. Here is top…

top - 15:58:47 up 75 days, 18:27, 1 user, load average: 0.00, 0.00, 0.00 Tasks: 70 total, 1 running, 69 sleeping, 0 stopped, 0 zombie Cpu(s): 0.0%us, 0.0%sy, 0.0%ni, 99.3%id, 0.7%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 1026956k total, 342028k used, 684928k free, 135044k buffers Swap: 2096440k total, 6260k used, 2090180k free, 88116k cached
The box is not even being touched. Would I be better using a different sound format?

It is always better to use file formats acorrding to codec formats. For example: if you’re using gsm codec, have .gsm file, using alaw, have .al files etc.

Did you test the voice by connecting inside office? What devices and connections you use?

Thanks for the tip. As for the quality of the equipment, they are on a managed switch with an isolated VLAN for the phones. Call quality is great. However, the ivr’s volume does appear to fade internally & externally.