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.


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