what does low frequency mean
The number of cycles per second (Hertz) (abbreviated as, hz) of anything that oscillates is called the frequency. The electricity of an AC wall outlet is said to have a frequency of 60 Hertz as it cycles negative then positive 60 times each second. Sound is an oscillating wave, but it has a broad range of frequencies. A low frequency sound (say, 50 hz) might sound like a low rumble, while a high frequency sound (say 12,000 hz), might sound more like a sizzle. A person with normal hearing can hear all the way up to about 20,000 hz.