There is disagreement as to whether this constitutes one, two or three senses. Neuroanatomists generally regard it as two senses, given that different receptors are responsible for the perception of colour (the frequency of photons of light) and brightness (amplitude/intensity – number of photons of light). Some argue that stereopsis, the perception of depth, also constitutes a sense, but it is generally regarded as a cognitive (that is, post-sensory) function of brain to interpret sensory input and to derive new information. The inability to see is called blindness.
Hearing or audition is the sense of sound perception. Since sound is vibrations propagating through a medium such as air, the detection of these vibrations, that is the sense of the hearing, is a mechanical sense akin to a sense of touch, albeit a very specialized one.
In humans, this perception is executed by tiny hair fibres in the inner ear which detect the motion of a membrane which vibrates in response to changes in the pressure exerted by atmospheric particles within a range of 20 to 22000 Hertz, with substantial variation between individuals. Sound can also be detected as vibrations conducted through the body by tactition. Lower and higher frequencies than that can be heard are detected this way only. The inability to hear is called deafness.