Hearing


Read here about a sensory capability and its treatment in the comprehension of scale.

Overview


Human hearing is a special case of mechanoreception and baroception.

About Hearing

Rhythmic alterations of pressure in the atmosphere are detected in the portion of the atmosphere contained by the ear canal. Cells in the inner ear detect these vibrations, Hair cells on a spiral cochlea aresympathetic to different frequency components of the pressure oscillation. The external auditory canal originates outside the ear and terminates in the auditory tube. Across this passage the eardrum is suspended, intimately connected to the tensor tympani muscle, malleus, incus, and the exquisite spiral of the tiniest bone in the body. The Malleus Incus and stapes have several ligaments anchoring them in place.

Lack of hearing


The inability to hear is called deafness.

Space And Vibration In Hearing

In physiology, tonotopy (from Greek tono- and topos = place) is the spatial arrangement of where sounds of different frequency are processed in the brain. Tones close to each other in terms of frequency are represented in topologically neighboring regions in the brain. Tonotopic maps are a particular case of topographic organization, similar to retinotopy in the visual system.
Tonotopy in the auditory system begins at the cochlea, the small snail-like structure in the inner ear that sends information about sound to the brain. Different regions of the basilar membrane vibrate at different sinusoidal frequencies. The auditory nerves that transmit information from different regions of the basilar membrane therefore encode frequency tonotopically. This tonotopy is maintained in the human vestibule cochlea nerves cortex, that part of the brain that receives and interprets sound information:
  • sounds of low pitch project into the anterolateral aspect of Heschl's gyrus
  • sounds of high pitch project deeply into the lateral fissure (which houses Heschl's gyrus).
Tonotopy is present in animals including humans and in crickets, where it is part of echolocation and ultrasound avoidance.

Ultrasonic hearing

Echolocation, also known as biosonar, is used by bats, whales, dolphins and shrews to emit calls out to the environment, attend to the echo, and thus discern environmental features. Microbats issue these calls in frequencies from 14,000 to well over 100,000 Hz, well beyond the range of the human ear (typical human hearing range is considered to be from 20 Hz to 20,000 Hz).