Hearing Assistance

Hearing, is one of the traditional five senses and refers to the ability to detect sound. In humans and other vertebrates, hearing is performed primarily by the auditory system: sound is detected by the ear and transduced into nerve impulses that are perceived by the brain. more...

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Like the sense of touch, audition requires sensitivity to the movement of molecules in the world outside the organism. Both hearing and touch are types of mechanosensation.

Hearing in animals

Not all sounds are normally audible to all animals. Each species has a range of normal hearing for both loudness (amplitude) and pitch (frequency). Many animals use sound in order to communicate with each other and hearing in these species is particularly important for survival and reproduction. In species using sound as a primary means of communication, hearing is typically most acute for the range of pitches produced in calls and speech.

Frequencies capable of being heard by humans are called audio or sonic. Frequencies higher than audio are referred to as ultrasonic, while frequencies below audio are referred to as infrasonic. Some bats use ultrasound for echo location while in flight. Dogs are able to hear ultrasound, which is the principle of 'silent' dog whistles. Snakes sense infrasound through their bellies, and whales, giraffes and elephants use it for communication.

The physiology of hearing in vertebrates is not fully understood at this time. The molecular mechanism of sound transduction within the cochlea and the processing of sound by the brain, (the auditory cortex) are two areas that remain largely unknown.

Hearing in humans

Humans can generally hear sounds with frequencies between 20 Hz and 20 kHz. Human hearing is able to discriminate small differences in loudness (intensity) and pitch (frequency) over that large range of audible sound. This healthy human range of frequency detection varies significantly with age, occupational hearing damage, and gender; some individuals are able to hear pitches up to 22 kHz and perhaps beyond, while others are limited to about 16 kHz. The ability of most adults to hear sounds above about 8000 Hz begins to deteriorate in early middle age.

Mechanism

Human hearing takes place by a complex mechanism involving the transformation of sound waves into nerve impulses.

Outer ear

The visible portion of the outer ear in humans is called the auricle or the pinna. It is a convoluted cup that arises from the opening of the ear canal on either side of the head. The auricle helps direct sound to the ear canal. Both the auricle and the ear canal amplify and guide sound waves to the tympanic membrane or eardrum.

Read more at Wikipedia.org