VoIP services often provide a better quality voice transmission than expected, and could even be better than calls from a regular fixed line.
Some VoIP services offer an enhanced audio quality not available on PSTN lines.
VoIP services could be subject to more quality variations than PSTN calls due to congestion elsewhere on the internet.
VoIP and broadband
Calls made over a broadband connection are subject to performance issues related to the connection.
VoIP performance can be affected by:
downloading large files while a VoIP call is in progress
where the connection meets the public internet
the amount of other internet traffic
Check with VoIP providers about the quality of their service.
Faulty headphones or microphones can affect the audio quality of VoIP.