### Theory:

Sound waves are longitudinal waves that can travel at different speeds through any medium (solids, liquids, or gases) depending on the properties of the medium. When sound travels through a medium, the medium's particles vibrate in the wave's propagation direction. Individual molecules are displaced longitudinally from their mean positions in this displacement. This causes compressions and rarefactions, which are a series of high and low-pressure areas.

Categories of sound waves based on their frequencies

(a) Audible waves:

These are sound waves with a frequency of $$20$$ to $$20,000$$ $$hertz$$. Vibrating bodies, such as stretched strings, vocal cords and so on, produce these sound waves.

Sound produced by guitar.

(b) Infrasonic waves:

Sound waves with a frequency less than $$20$$ $$Hz$$ that the human ear cannot detect are known as infrasonic waves.
Example:
Seismic waves, ocean waves, whale sounds, and so on.
Sound produced by whales

(c) Ultrasonic waves:

Ultrasonic waves are sound waves with a frequency greater than $$20$$ $$kHz$$ that are undetectable to the human ear but can be detected by certain animals such as mosquitos, dogs, bats, and dolphins.

Sound produced by bats
Reference:
maxpixel.net/Electric-Electric-Guitar-Tool-Guitar-Music-5386245
https://pixnio.com/fauna-animals/whales/whale-ocean-nature-animal-wave#
https://www.pxfuel.com/en/search?q=bats