The number of repeating occurrences of a particular distinct and complete element (the positive and negative crest and trough of a single sound wave in audio) in a given time (one second). Frequency is measured in hertz (Hz). A 20 Hz frequency contains 20 cycles of individual components each second (think of 20 distinct waves passing by in one second). A 20 kHz (kilohertz) frequency contains 20,000 cycles per second. n a sound wave, frequency measures the number of waves sent out per second and in effect can be used to measure the length of the individual waves (the wavelength). Since a sound signal travels at a certain speed, it can travel a specific distance in one second. Since the distance then is set for one second and the frequency measures cycles in a second, the frequency measurement dictates how many cycles or individual waves are placed into that length. If we divide the distance the sound wave travels in one second by the number of cycles (the frequency as measured in Hz), we get the size of the individual waves (the wavelength). Sound travels about 3,960,000 feet per hour or 1,100 feet per second. By dividing the feet per second by a frequency of 20 Hz we get a wavelength of about 55 feet (the true value is given as 56 feet). At 20 kHz (20,000 cycles per second), the wavelength is about 0.66 inches or two thirds of an inch.