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By the end of this section, you will be able to:
  • Describe the relationship of amplitude and frequency of a sound wave to attributes of sound
  • Trace the path of sound through the auditory system to the site of transduction of sound
  • Identify the structures of the vestibular system that respond to gravity

Audition , or hearing, is important to humans and to other animals for many different interactions. It enables an organism to detect and receive information about danger, such as an approaching predator, and to participate in communal exchanges like those concerning territories or mating. On the other hand, although it is physically linked to the auditory system, the vestibular system is not involved in hearing. Instead, an animal’s vestibular system detects its own movement, both linear and angular acceleration and deceleration, and balance.

Sound

Auditory stimuli are sound waves, which are mechanical, pressure waves that move through a medium, such as air or water. There are no sound waves in a vacuum since there are no air molecules to move in waves. The speed of sound waves differs, based on altitude, temperature, and medium, but at sea level and a temperature of 20º C (68º F), sound waves travel in the air at about 343 meters per second.

As is true for all waves, there are four main characteristics of a sound wave: frequency, wavelength, period, and amplitude. Frequency is the number of waves per unit of time, and in sound is heard as pitch. High-frequency (≥15.000Hz) sounds are higher-pitched (short wavelength) than low-frequency (long wavelengths; ≤100Hz) sounds. Frequency is measured in cycles per second, and for sound, the most commonly used unit is hertz (Hz), or cycles per second. Most humans can perceive sounds with frequencies between 30 and 20,000 Hz. Women are typically better at hearing high frequencies, but everyone’s ability to hear high frequencies decreases with age. Dogs detect up to about 40,000 Hz; cats, 60,000 Hz; bats, 100,000 Hz; and dolphins 150,000 Hz, and American shad ( Alosa sapidissima ), a fish, can hear 180,000 Hz. Those frequencies above the human range are called ultrasound    .

Amplitude, or the dimension of a wave from peak to trough, in sound is heard as volume and is illustrated in [link] . The sound waves of louder sounds have greater amplitude than those of softer sounds. For sound, volume is measured in decibels (dB). The softest sound that a human can hear is the zero point. Humans speak normally at 60 decibels.

A graph shows a regularly repeating sine wave that goes gradually up, then down, then up again. The distance between two crests is the wavelength. The amplitude is the height of the wave. On the graph, two waves with different wavelengths but the same amplitude are superimposed on one another.
For sound waves, wavelength corresponds to pitch. Amplitude of the wave corresponds to volume. The sound wave shown with a dashed line is softer in volume than the sound wave shown with a solid line. (credit: NIH)

Reception of sound

In mammals, sound waves are collected by the external, cartilaginous part of the ear called the pinna    , then travel through the auditory canal and cause vibration of the thin diaphragm called the tympanum    or ear drum, the innermost part of the outer ear    (illustrated in [link] ). Interior to the tympanum is the middle ear    . The middle ear holds three small bones called the ossicles , which transfer energy from the moving tympanum to the inner ear. The three ossicles are the malleus    (also known as the hammer), the incus    (the anvil), and stapes    (the stirrup). The aptly named stapes looks very much like a stirrup. The three ossicles are unique to mammals, and each plays a role in hearing. The malleus attaches at three points to the interior surface of the tympanic membrane. The incus attaches the malleus to the stapes. In humans, the stapes is not long enough to reach the tympanum. If we did not have the malleus and the incus, then the vibrations of the tympanum would never reach the inner ear. These bones also function to collect force and amplify sounds. The ear ossicles are homologous to bones in a fish mouth: the bones that support gills in fish are thought to be adapted for use in the vertebrate ear over evolutionary time. Many animals (frogs, reptiles, and birds, for example) use the stapes of the middle ear to transmit vibrations to the middle ear.

Questions & Answers

Please what is ovulation
Adusei Reply
What is cell division?
Adusei
What is copulation?
Adusei
what is a metaborism
Beatrice Reply
this is a specialized part of the cell eg Nucleus
David Reply
what are the organelles?
Faith Reply
what is reproduction
mana Reply
reproduction is the process by which living organisms give rise to young ones of their own kind
Miriam
What is evolution
Wengelawit
the production of new forms of life over time as documented in the fossil record.
mana
hmm
Marvin
give two parasites where secondary host is water snail?
Kevin Reply
what is treats
Raih Reply
what are the organelles in cell that involves in protein sythenis
Rita Reply
what is a melanin?
Judith Reply
what is telophase
Elphas
melanin in that black color we posse in our skins
Marvin
Why do parasites take on a parasitic life?
Asadullah Reply
what is cell
Ousman Reply
A cell is the basic structure unit of an organ
Yaa
what is respiration
Igwe
what is organisms?
Bashir
Organisms are living things that can function on their own
EZEA
A cell is a functional basic unit of an organisms.
Evelyn
Organisms is a entity which consists of one or more cells and are able to undergo all life processes
Evelyn
A respiration is the physical and chemical break down of complex food substance into absorbable or simple form.
Evelyn
What will to a cell if the nucleus is removed..?
Goodrick Reply
When a cell nucleus removed then the cell will not be able to function properly, it will not be able to grow .All the metabolic functioning of the cell will stop .Without nucleus the cell will lose it's control. It can not carry out cellular reproduction .
Evelyn
defin peroxesome
walid
write a short note on how the kidney carry out osmoregulation in man
Rhoda Reply
Kidney play a very large role in human osoregulation by regulating the amount of water reabsorbed from glomerular filtrate in kidney as tubules, which is controlled by hormones such as antrdiuvetic hormone (ADH) , aldosterone and angiotensin.
Evelyn
kidney is capable of osmoregulation in mammal ,
Judith
simple definition for respiratory system
Gift Reply
Respiratory system is a network of organs and tissues that helps you to breathe or help in getting the rids of oxygen and discharge of carbon dioxide in the body.
Ruhiyatu
What are uses of respiratory system
Joster
how it functions
Ousman
what is inresparetion
Fikkabex
Why do parasites take on a parasitic life?
Asadullah
A respiratory system is a biological system consisting of specific organs and structures used for gas exchange in animals and plant
Evelyn
diseases of respiration
walid
when air enters to the body called inresparetion
walid
explain why plants responds to stimuli slowly than animals
Bekoe
how is a aerenchyma tissue adapted to its function
fatuma Reply
Have large air spaces that store air for gaseous exchange... Large air spaces also facilitate bouyancy.
Goodrick

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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