This is rather a typical question. People uploading their favorite songs as music on hold and when they call in with their phones they don’t get the quality they expected.
The short answer is:
Public Telephone Network is not capable of transmitting high definition audio. It doesn’t matter that you uploaded a perfect sound file and your iPhone can play it nicely, the quality is limited by the telephone network. Try to call in VoIP with our Desktop or Mobile application and you’ll get a much better quality (yet, it will not be the same quality that you might get if you play the same song on your computer)
Little bit more technical answer:
Telephone Network operates mostly on G.711 codec. Which has 8kHz sampling, 8 bits per sample, mono. The music file that you typically upload is equivalent of 44.1kHz sampling, 16 bits per sample, stereo. It carries 20x more data than G.711! No wonder you can hear the difference.
Our VoIP client uses equivalent of 16kHz sampling with 16bit per sample, mono. So it sounds much better than a telephone, but yet not the same as original file.
44.1kHz sample:
G.711 sample:
What to do:
- Do not upload music with a lot of low frequency sounds or high frequency sounds.
- Use sound editor to adjust the music you like to the low quality of telephone network (try to convert it to 16Khz to preview the quality, try to reduce the volume of the music before the upload to avoid trembling sound on some old phones)
good free audio editor https://www.audacityteam.org/download/