Frequency: The number of vibrations or cycles per second of a sound wave, measured in hertz (Hz), determining the pitch of the sound. Redshift (Sound): The decrease in frequency (and increase in wavel...Frequency: The number of vibrations or cycles per second of a sound wave, measured in hertz (Hz), determining the pitch of the sound. Redshift (Sound): The decrease in frequency (and increase in wavelength) of a sound wave as the source moves away from the observer. Blueshift (Sound): The increase in frequency (and decrease in wavelength) of a sound wave as the source moves toward the observer.
