I realized today that the problem with my headset with in-line microphone is that it only works with devices like my cell phone that only have one jack. My BrailleNote Touch Plus has two separate jacks for a headset and a microphone. I don't have a microphone.
I may try the Bluetooth headset again. What I meant to say about that is the sound quality isn't as sharp as that of the device's built-in mic, but it might be better than fluctuating volume. Thanks for all your help.