Follow Slashdot blog updates by subscribing to our blog RSS feed

 



Forgot your password?
typodupeerror
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. ×

Comment Re:levitating humans (Score 1) 182

20mm wavelength seems to be 17KHz (at sealevel in air), which isn't very "ultra" sound. To levitate the 3 meters radius of adult humans (with extended arms/legs), we'd need 6m wavelength.
Which is about 57Hz.

How much power...well lots. Area of human (one side) about 1sq. m. mass, (order of magnitude) 100Kg, say 1KN force required = 1Megapascal. That's 10bar pressure, implying an acoustic pressure of 10dB above atmospheric..or 203dB into 4pi space.

Imagine you had a 'regular' hifi speaker, radiating into half space..and that it behaved in a perfectly linear manner to power input (no chance!) at the typical 1% efficiency of electrical-to-acoustic conversion, you' need to hit it with, oh, about a half megawatt. Really. Which means poor sorry-assed-but-levitated-human falls apart.

(assumptions: 87dB/watt for reasonable speaker; +3dB gain for half-space; power required = 10^ [(200-87)/20] )

Slashdot Top Deals

Top Ten Things Overheard At The ANSI C Draft Committee Meetings: (8) I'm on the committee and I *still* don't know what the hell #pragma is for.

Working...