If you use MP3 file in the IVR,and meet the problem on voice quality or voice volume,you can transfer to wav with wavepad.exe tools.
you can download wavepad from google.
Audio file is normally used in IVR, and music on hold/transfer. ZYCOO CooVox IP PBX support audio file with wav, gsm
Please follow this guide to convert your audio file to the supported format on CooVox IP PBX.
Step 1: Please download the wavepad.exe tool;
Step 2: Open the wavepad tool, then open your audio file and enable the wav format, please take the following diagram as reference;
Step 3: Save the audio file as wav, click【File】【Save File As】：
Besides of wav. format, other formats can be converted by the tool with the same way.