Re: freq
- From: don@xxxxxxxxxxxxxx (Don Klipstein)
- Date: Thu, 7 Feb 2008 23:36:31 +0000 (UTC)
In article <IZ-dnaVal87fqzbanZ2dnUVZ_g2dnZ2d@xxxxxxxxxxxx>, BobW wrote:
"Bob Masta" <NoSpam@xxxxxxxxxxx> wrote in message
news:47aaf9ac.910101@xxxxxxxxxxxxxxxxxxxxx
On Thu, 7 Feb 2008 00:32:32 -0800 (PST), drjamilurrahman@xxxxxxxxx
wrote:
can any one tell me about scan of body's viberation frequency
Just remember: Seven HURTS!
(7 Hertz is the approximate resonant frequency of the gut.
At high levels, it is reported to cause extreme discomfort and
nausea.)
Best regards,
Bob Masta
There was a MythBusters episode that dealt with this subject. I'm not sure
if they went down to 7Hz, but I think they did, and they did refer to the
so-called "brown noise". At the frequencies they did use, at (at
least)120dBspl (iirc), there were no ill effects.
On the other hand, SouthPark did a related episode, too. The results were
much different.
Achieving 120 dB at 7 Hz is a tall order.
Consider what dort of loudspeakers are needed to achieve 120 dB at 30 or
50 Hz. Go ahead with an SPL meter, loudspeakers, sinewave oscillator, and
amplifier. Outdoors that gets to be a tall order much past point blank
range.
Ever see a local band or a DJ with really good really loud deep bass?
My experience is that the most impressive deep bass was from bass bins
whose frequency response was full blast only down to about 50 Hz.
Maintaining high loudspeaker efficiency to lower frequencies requires the
loudspeakers to be proportionately larger.
For example, one in "ideal half space" needs to have a volume around
..01% of a cubic wavelength of the lowest frequency at which it works well
to have efficiency only about 1-2% from that frequency on up. (Narrowband
designs can be smaller.) Efficiency increases roughly with volume, though
significantly begins to level off around 20% (at which point you can
maintain increase in "sensitivity" by having the loudspeaker large enough
to be directional).
.01% of a cubic wavelength is roughly a 6 foot cube at 7 Hz.
- Don Klipstein (don@xxxxxxxxx)
.
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