The term "20 Hz" refers to a frequency of 20 hertz, which means that a wave oscillates 20 times per second. This frequency is at the lower end of the human hearing range, typically starting around 20 Hz and going up to about 20,000 Hz (20 kHz). Sounds at this frequency are often felt as vibrations rather than heard clearly, such as the rumble of thunder or the deep bass in music. In various fields, including audio engineering and acoustics, 20 Hz is significant for understanding sound design and the impact of low-frequency sounds. It is also relevant in medical imaging and seismology, where low-frequency waves can provide important information about physical phenomena.