Sound is a wave
Soundwaves are measured by their frequencies
the higher the frequency, the higher the pitch
frequency is measured in Hertz (abbreviated Hz)
16 Khz is 16,000 Hz
16,000 is a very very high pitch sound
500 Hz is lower end
20-120 Hz is about what a subwoofer put out, its the very deep sound rumbles.
An equalizer works by increasing or decreasing the volume of individual sound frequencies. For example: if you decrease everything except the 31,62, and 125 Hz then the only sound you will hear will be the deep rumbles and bass of the sound (or music). if you decrease everything but the 4, 8, and 16Khz range then you will hear the high pitches like taps, clicks, and high-pitch brass instruments. An equalize is used to correct inaccuracies in your speakers. Big speakers are better at making low rumbles while small speakers are better at making high pitch sounds. If you have just a couple small speakers and a subwoofer then you might need to correct with a boost in the midrange frequencies to compensate for the inaccuracies. Also, if all you have is a couple of cheap small desktop speakers then you can turn down the bass (lower frequencies) so that the bass doesn't harm the small, cheap speakers.
