Re: [microsound] microwave beam weapon

[Alex Davies <alex@xxxxxxxxxxxxxx>]

> http://www.newscientist.com/news/news.jsp?id=ns99991470

curious article. there was some research done some time ago into the heating
effects of high frequency sound. this was interesting as it was still in the
audible acoustic spectrum but at extremely high spl's.

some investigations into high intensity acoustic devices i have developed is
available here  http://www.schizophonia.com/installation/trauma/index.htm

a paper i wrote surveying the whole area of acoustic
weapons/psycho-physiological effects of sound subject can be downloaded from
the same page.

an extract that may be of interest regarding high frequency sound is as
follows...

snip....

At medium to high audio frequencies the pronounced visceral effects that are
evident with low frequency vibration are absent. However, disturbance of the
equilibrium can be achieved at levels above 140 dB for unprotected ears. At
even higher levels, tickling sensations and heating may occur in air-filled
cavities such as those of the nose and mouth and gaps between the fingers. A
7kHz acoustic beam at a level of 165 dB produced the sensation of strong
heating between the fingers of the subject that were being held close
together. This was due to the high degree of friction that was created
although the effect vanished when the fingers were subsequently opened
apart.
High audio frequencies (above 10 kHz) and ultrasound (above 20kHz) have no
pronounced effect on the individual unless the level is in the range of
140dB with more prominent effects of heating of air cavities, hair and
textiles becoming apparent at levels of 160dB.....

snip....

all together a rather curious and in general not very well researched area
of acoustics....


regards

alex





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