Speedster Hearing
An observer travelling very fast, perceiving a stationary sound source, would hear frequency-shifted sounds, compared with what would be heard when at rest. Whether the observer is an acoustical transducer on a land vehicle or aircraft, or a fictional speedster, the shift observed depends only on the relative velocity, ignoring wind effects and sperical spreading.
The following are audio samples created for a presentation presented at the 178th Meeting of the Acoustical Society of America, and published here in the open-source Proceedings of Meetings on Acoustics (POMA), these sound files were created in Mathematica using the formula for Doppler shift.
The original evil laugh heard in the first file is what the observer would hear at rest. The folloing clips assume the observer is in the proximally audible range of the sound source for an impossible amount of time, since the sound pressure propegation would not last the long distances covered at these speeds. While running Assuming a sound speed (c) of 343 m/s, and running at 0.5*c away from the villain, the vocal frequencies shift down considerably, resulting in a much more maniacal and thus terrifying production. Running at 0.5*c toward the villain, an increased frequency is heard compared to the original. When supersonic at 2.0*c, the villain's voice sounds embarrassingly high. This should motivate our heroes and us civilians alike to tackle our fears head on at full speed ahead!
What does a speedster hear when running very, very fast?