If  some of your participants experience audio issues you should look to these ways to improve the quality of their experience.

Despite the fact that they may have great internet connections if the "last mile" to their computer has become congested or if they are on a wireless connection, bandwidth issues can still come into play. The fact that only some clients on a call had issues  but others did not speaks to a localized issue - such as network congestion or momentary weakness causing audio drops.

Here are our general tips regarding sound quality:

If users are experiencing what sounds like scrambled audio or robotic voices, there is a data bandwidth issue happening.  Depending on everyone’s Internet connection to the conference and who actually is listening, there will be different audio experiences heard. 

Any users on wireless Internet will also hear scrambled or robotic audio due to interference and a small amount of bandwidth capable of being shared.  If someone is presenting, we highly recommend they present from a hard line connected to the respective PC.

To save on audio bandwidth, try asking presenters to place their microphones on “push-to-talk” which is an option offered to users once they are invited to speak.  Using push-to-talk turns the data transmission on and off saving everyone bandwidth when audio is not transmitting.

I hope one of these solutions helps with your users' audio quality issue.