Mark W

The purpose of this experiment is to find out if you
can determine the speed of a car based on the change
in the pitch of its horn.

Drive a car past a tape recorder with its horn at 0
Kph, 10 Kph, 20 Kph, 30 Kph, 40 Kph, and 50 Kph.
Record data and use a frequency analyzer to check the
hertz. Average after the 3 runs.

When the car was still the pitch was an F Sharp or 344
Hz. When the car was moving at 10 Kph the pitch was a
G or 365 Hz then it changed to an F or323 Hz. The
difference is 12 %. At 20 Kph the pitch was an A or
440 Hz then an F or 323 Hz. The difference is 27%.
At 30 Kph the horn's pitch was an A Sharp or 447 Hz
and then an E or 281 Hz. The difference is 37%. At
40 Kph the pitch was a B or 454 Hz then a B sharp or
467 Hz. The difference is 3%. At 50 Kph the car
horn's pitch was a B or 454 Hz then a D sharp or 534
Hz. The difference is 18%.

When an object is moving towards some one the sound

waves are condensed and the pitch sounds higher and as
an object moves away humans hear a lower pitch.