I am an audio and acoustics professional in that I design audio systems and recording studios etc. for a living. That said, both of our sulcatas respond immediately to visual cues of course. My wife and I have noticed that we absolutely CAN wake them up using the intercoms and cameras in the house with our voice and if I'm talking to her on the phone and she's near the big one, he begins looking around for me. I can take video as evidence. Also, he absolutely hated any high pitched motor, string trimmer, vacuum, Dremel, drill, etc. and one time the security alarm went off and he started thrashing his head left and right trying to escape it. They most definitely CAN hear. If you think they can't hear test your smoke detectors in the same room.
For those of you where physics is not your strong suit, sound moves through air and when it hits a solid the wave creates resonance in that solid. That is why there is a sound transmission coefficient rating in all construction materials. This is why those railings in museums with audio work when you rest your elbows on the rail and your fingers in your ear. The transducer on the rail creates a wave that becomes mechanically connected to your ear when you plug your ear with your finger.
Now... the frequency of a tortoises hearing begins to drop off at 1K which makes sense. He does not hear bird chirping. I have witnessed this. But what is the frequency center of the theoretical maximum recording level? 1K. What is "A" weighting with regard to a real time analyzer? Right. centered on 1K. This is also why they would be able to hear a phone conversation over a cell phone. Just like a triangle. You can hear someone hitting a triangle at 1K in a loud concert or over an entire orchestra.
This must be why their hearing was designed in that way.
