Hello, and thank you for using this service.
Sorry to hear you are having trouble. Will see what I can do to help.
Modern headsets generally do not produce "sidetone" as it degrades audio quality. Also, most people prefer not to hear sidetone, as the voice can generally be heard through the headset, unless that headset blocks sound and/or the person has hearing impairment.
So, how it works on most devices and computers now, is that "sidetone" or any other audio mixing is done by the application driving the headphones and microphone.
What app are you using where you need or want sidetone?
With a Mac, it would seem your options out there are very limited for sidetone. While there is a plugin for skype to produce sidetone, it's only available for Windows.
I have found this app that you can try that may work.
You can also search for other options, but the "rule" is going to be in my initial answer to your question. For the most part, your headset isn't going to produce sidetone, unless you buy a very special headset that advertises that it will, or someone has figured out a hack to make it produce sidetone. However, the problem with hacks is that they may just introduce feedback.
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