Re: "white noise" monitoring?

From: Martin Brown (|||newspam|||_at_nezumi.demon.co.uk)
Date: 01/24/05 

Date: Mon, 24 Jan 2005 09:14:41 +0000

Chris L Peterson wrote:

> On Sat, 22 Jan 2005 13:01:21 -0700, Tim Killian <TJK@notmyrealemail.com>
> wrote:
>
>>Spread spectrum signals can be broadcast at extremely low levels and
>>they don't alter the spectrum enough to be detectable without tremendous
>>effort. A receiver with the proper chipping sequence can extract the
>>signals from what appears to be random noise.
>
> Yes, but I think what is being discussed is _people_ directly hearing or
> seeing messages in noise. That's quite different from a spread spectrum
> receiver doing it (and as you say, it just appears to be noise in that
> case... it isn't really.)

I don't think people ever hear voices in noise that are not signal
breakthrough in badly designed experiments or pure imagination. Our
brain is geared to recognising patterns even where none exists - witness
the ink-blot test.

In radio astronomy the interference problem is usually from reflections
from the underside of commercial airliners (or for the VLA from White
Sands test range). Listen to enough white noise and you will eventually
believe you hear whatever you want to hear.

>>On the subject of anomalous detection, how do you suppose all of those
>>wild animals detected the imminent tsunami danger last month?
>
> I have seen no convincing evidence at all that any animals detected the
> tsunami. In fact, I've seen no convincing evidence that animals ever
> routinely sense seismic activity, at least not more than a few seconds
> earlier than people. I remember a couple of occasions when living in
> California where the cat got spooked before a big earthquake- maybe five
> seconds before I first heart them. Nothing too mysterious there.

It is explainable by conventional physics, but very few humans seem to
be aware of sounds at 18kHz and above. I have (had) acutely good high
frequency hearing and heard a couple of moderate sized earthquakes where
I was near the epicentre for several seconds before any sense of ground
movement was obvious. I never heard a distant big one.

They sounded to me like an express train approaching for want of a
better description. It doesn't surprise me at all that animals with even
better extended high frequency hearing can sense the initial stage of an
earthquake (at least near to the fault line).

> Certainly, in the areas affected by the recent tsunami, massive numbers
> of dead animals are contributing to the disease problem.

A tsunami is different. Apart from knowing what it means when the sea
goes out unexpectedly there is nothing much that humans can do about it.
(except run for high ground)

I doubt that any animals have innate knowledge of tsunamis - they are
far too rare. Fish got caught out by the rapidly receeding tide prior to
the inrush. Most people are unaware of the warning signs.

Regards,
Martin Brown

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