Yes the interviewer usually is able to hear me. If it is a virtual interview though, do it in a quiet room if possible. Unfortunately, I don’t know any references for the low tone technique as I learnt it from my own experience when I realised I didn’t stutter or block when I whispered because there is less tension in your mouth when you whisper. Integrating this into the low tone technique, I slow my speech down and lower it to a volume that is not too quiet but is a little less quieter than the average persons volume when speaking. Have you ever had had a university professor who speaks with a tone that you would describe as calming, slow, low volume but still audible enough that the students can understand the professors words? If so, this is how I speak when I use the technique. If you haven’t had a professor that speaks like that, I’ll see if I can find a YouTube video of someone similar.