Just a couple of days ago I received an email asking about side-tone. Marshall Wilgard asks;
“A VoIP expert has written that he would never buy an IP phone that did
not have “sidetone” in the handset because he would want to hear a
little of his own voice when he talked. The Grandstream phones I use
do “not” have sidetone. Do you believe that sidetone is important? And
if so, which brands of IP phones have sidetone?”
As you note, sidetone is the mixing of a little of the users voice into the earpiece such that they can hear themselves as they speak. I believe that sidetone is critically important to comfortable user experience with a phone.
It’s very unnatural to not hear yourself, or hear yourself from another acoustic perspective, as you engage in conversation. Without sidetone you sound like you are very far away even though the other party sounds very near. It’s an inversion of acoustic perspective that can be discomforting.