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Re: Impacts from ultrasound and infrasound

On 12 Aug 2009 at 22:04, Henrik Møller wrote:

> Hi Amy
> Please let me mention the common misunderstanding that the human hearing 
> "stops" st around 16-20 Hz. We do denote sound below 20 Hz as 
> "infrasound", but it is not inaudible. Below these frequencies, the 
> perception changes, and the tonal sensation disappears. But tones at 
> least down to a couple of hertz can indeed be perceived by everyone. The 
> lower the frequency, the higher the threshold. The sensation goes 
> through the ear, not the body as often claimed. I think it is still 
> unclear, if the sensation is from the cochlear or elsewhere in the ear.
> For a fairly recent review, please allow me to promote our article: 
> Henrik Møller, Christian Sejer Pedersen: "Hearing at low and infrasonic 
> frequencies", Noise & Health, Vol. 6(23), pp. 37-57 (2004).
> The idea of infrasound being inaudible has caused a number of 
> misunderstandings, in particular in the popular press (but also in the 
> academic literature).
> Best regards,
> Henrik

The fact that a sound may be processed through the ear does 
not eliminate other paths, such as through the viscera. 
There were many tests on the effects of vibration in the 
early years of space flight, and at visceral resonance 
frequencies these effects could be profound (nausea, and 
worse).  I seem to recall 7 Hz as being a particular 

Best regards,

Bob Masta
            D A Q A R T A
Data AcQuisition And Real-Time Analysis
Scope, Spectrum, Spectrogram, Signal Generator
    Science with your sound card!