1
General Science / How fast is my Sonic Toothbrush?
« on: 11/04/2008 02:45:23 »
Hi, Gents! Love the show. I'm a fan from Iowa in the US.
I agree with Ben that this seems suspect. First, this assumes that the sound emitted from the toothbrush is produced solely by the a 30kHz (or whatever) oscillation of the mechanism and nothing else (like constant, garden-variety friction). Few things emit what approaches a pure periodic sound, though. So whatever sound you get will likely be a composite waveform, created by all sorts of constructive and destructive interference. While we're at it, we're also assuming that the microphone used is capable of capturing a 30kHz sound, which probably isn't the case. Since the upper frequency limit of human hearing is around 20kHz, most consumer (and even commercial) mics don't accurately capture sounds much above 20kHz. Even if they did, the frequency and amplitude of this component of the emitted sound would probably be buried in the waveform.
Cool idea, but too many flawed assumptions.
Thanks for all of your great work!
I agree with Ben that this seems suspect. First, this assumes that the sound emitted from the toothbrush is produced solely by the a 30kHz (or whatever) oscillation of the mechanism and nothing else (like constant, garden-variety friction). Few things emit what approaches a pure periodic sound, though. So whatever sound you get will likely be a composite waveform, created by all sorts of constructive and destructive interference. While we're at it, we're also assuming that the microphone used is capable of capturing a 30kHz sound, which probably isn't the case. Since the upper frequency limit of human hearing is around 20kHz, most consumer (and even commercial) mics don't accurately capture sounds much above 20kHz. Even if they did, the frequency and amplitude of this component of the emitted sound would probably be buried in the waveform.
Cool idea, but too many flawed assumptions.
Thanks for all of your great work!