Ginny Carr WTC2 Impact Audio Recording - The Doppler Shift Problem
Ginny Carr was at a business meeting in
One Liberty Plaza on the Morning of September 11th 2001.
The proceedings were recorded with her voice dictation machine and
she accidently recorded the WTC2 impact sound.
The engine noise recorded is not reminiscent of the roaring sound
that should have been produced by the 2 bypass engines
used on a Boeing 767-200 and reveals no noticeable Doppler shift.
But the drop in pitch of the engine noise should have been even more pronounced than it was in the
Ginny Carr WTC1 Impact
Audio Recording due to the relatively higher airspeed of the UA175
aircraft and its closer proximity to One Liberty Plaza.
This can only imply that the sound source was either stationary, travelling very slow
or was approaching One Liberty Plaza from the west of
the World Trade Centre complex.
If you listen closely to the recording you will notice that
the engine noise continues after the impact sound and fades away gently.
This effect could have been caused by acoustic reflections off the
high rise buildings in Lower Manhattan.
To hear Ginny Carr's recording in full go to www.sonicmemorial.org,
enter the archive and search for "Ginny Carr" or alternatively the Ginny Carr
WTC2 Impact Audio Recording can be downloaded
here.
Compare the Ginny Carr WTC2 Impact Audio Recording to an
audio simulation
of the Doppler shift that should have been recorded by
the CNN Best Angle Video camera had a Boeing 767-200
flown into WTC2 at around 550mph in the same direction
as shown in the video.