I have had the opportunity to communicate with Eddy at Amulet Devices via email and ask him some questions. Here is part of our conversation:
Q: I notice there are two holes next to the stop button, presumably for the microphone. Does it use some kind of "microphone-array" technology to filter out background noise?
A: The two holes beside the stop button are indeed for the mic (or rather, one of them is; the other one is a dummy for aesthetic purposes, so it doesn't look unbalanced). There is no microphone array; a microphone array is most useful for electronic direction setting, and we have the luxury of not needing that as the physical operation ensures optimal mic direction and distance setting.
Q: What is the expected range for the RF connection. I will test this myself, but I'm wondering what your data says on this.
A: Our range is ~90 feet in free space; less if travelling through walls etc. (At home, I find I can easily use the Amulet from the kitchen two rooms away from the living room where the Media Center is, though I lose the connection at the far end of the kitchen. I feed my Media Center into a Sonos multi-room audio system, so it's nice to be able to control the music I'm listening to in the kitchen by voice.)
Q: If one were to leave the remote upright (i.e. microphone on) how long would the battery be expected to last when new and fully charged.
A: We've measured 3-4 hours of continuous operation for the mic/link -- the battery is quite powerful for its size. However, the product isn't designed to operate with an open channel while noise is present. Its designed to be used only when there is someone talking, i.e. tilt to talk. If we had to operate in an environment while its constantly on, we would do things different (e.g. force a command prefix keyword), but operating constantly on is not a mode we recommend.
A: Re hands-free operation, we've had some internal discussions about follow-on products that use alternative types of operation...
Q: What can you tell me about the RF connection w.r.t. sound transmission. Frequency, compression etc.
A: We send uncompressed audio over a 2.4 Ghz link, with lots of proprietary forward error correction and interference avoidance smarts; the link will dynamically frequency hop as needed in realtime to avoid new sources of interference that come online.
Q: Have you done any drop tests?
A: It's designed to withstand drop test from waist height (not the waist height of a midget ;-) We had some minor issues with the original case design that were picked up in the initial drop tests, and have since been addressed by adding strengthening struts in a few key places. On a personal note, my prototype Amulet has been fairly well abused by my 2 year-old (not intentionally on my part, but he's hard to stop!) and is still continuing to tick along just fine. Also several falls from couch height onto a wooden floor with no ill effects, though obviously we don't recommend this!
