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Fwd = [SeeSat] Satellites making supersonic noises?

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  • Frits Westra
    Forwarded by: fwestra@hetnet.nl Originally from: SeeSat-D-request@blackadder.lmsal.com Original Subject: SeeSat-D Digest V00 #237 Original Date: Sun, 4
    Message 1 of 1 , Jun 4, 2000
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      Forwarded by: fwestra@...
      Originally from: SeeSat-D-request@...
      Original Subject: SeeSat-D Digest V00 #237
      Original Date: Sun, 4 Jun 2000 12:19:24 -0700 (PDT)

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      Date: Sun, 04 Jun 2000 17:42:07 +0930
      From: Tony Beresford <starman@...>
      To: RocketKevin@..., seesat-l@...
      Subject: Re: Satellites making supersonic noises.

      At 16:09 4/06/00 , RocketKevin@... wrote:
      >The question has popped in and out of my mind for many years is do
      >very Low Orbiting satellites make supersonic noises until I saw a very
      >fast pass of #13576 over my friends house recently.about 25 seconds after
      >the pass there was a very soft to medium noise almost like a supersonic jet.

      Kevin, firstly a question of applying the right names. Supersonic just
      means faster than sound, nothing else. In relation to your question I
      assume you meant ultasonic, the sound equivalent of ultraviolet, the high
      pitched sounds we humans cant hear ( > 20 kilohertz for most of us, and >
      14khz for me) The upper atmosphere is too low a densiy to progogate sound
      waves in the audible range when you get above 30,000 metres (100,000
      feet). The circumstances are even worse for ultrasonic frequencies. This
      is shown by the observations that only meteoroids that penetrate below
      this height make a sonic boom. Since the satellite you mentioned would
      have been at at least 150Km, it seems unlikely to be source of the
      whooshing sound you heard. The length of the time delay you quoted is
      really what kills your explanation though. A delay of 25 seconds implies a
      distance of some 9Km, as the speed of sound is about 330 meters/second.
      Tony Beresford

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