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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.


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

what is reproduction
smart Reply
it is d act of bringing young ones to life
to ensure survival of a species🚴‍♀️
what is a genotype
what is hazardous
a cell is the smallest unit of a living thing. so we all have cell
It is the formation of a zygote resulting from the fusion of the sperm cell with the ovum.Thus,this results in the production of new species which are genetically dissimilar from their parent cells.
what is size of cell
Mohd Reply
what is size of Hart
nanometers=um sign thingie
monomers and polymers of nucleic acids?
Jyrl Reply
dna and rna involvement
give me the elements of the soil
Iguma Reply
Air, water, organic matter, inorganic matter
soil water humus air
silica, iron
potassium, sulfur, calcium, carbon
what is cell
iyaji Reply
A cell is a smallest fundamental unit of a living organisms.
the basic structural and functional unit of life
what is size of cell
all things are made up of.....all things cannot exist without pre-exisiting cells...check out the 16th ce tury to learn more about microscope use and cells. i will give a hint: Mr. L.
we are all made of cells
Nutrition - sensitive intervention
Therowda Reply
what does the sori In fern mean
arhin Reply
biology is the study .exactly what is life?
i'm sorry , the study of life
how can U identify a person through his blood
Frankyx Reply
through genetic fingerprinting where specific DNA sequences in a person genome can be identified.
by help of genetics and DNA test
can it also be detected using an RNA test
environmental biology
Ojesola Reply
what is phytoplankton
What is anabolism
Treasure Reply
the break down of substance
how many teeth has an adult person
32 teeth
32 (or 36 including the wisdom teeth)
what is homoestastis
Ayo Reply
hypothalamus negative feedback vs. postive feedback systems.
it is the maintenance of a steady internal environment.it is controlled largely by the brain especially the hypothalamus.
What is a cell
Eric Reply
A cell is the building block of all organisms
yes it is , it also helps in functions .
cell is structural & functional unit of oraganisms
it is a building blocks of a living organism
it is the basic unit of life in living organisms
it is the basic unite of life in living organisms
it is the fundamental unit of life
it is the structural and functional unit of life
Why cells are classify as living and non living things
Millicent Reply
due to such as virus which acts as a living cell inside the cell of an organisms and out side of cell in form of crystals
because there are living cells which performs complex processes such as reproduction and metabolism then there are dead cells like the top most part of the epidermis or the bark
because there are living cells which performs complex function such as reproduction and metabolism
cause otherwise you could call fire alive
what's nomenclature
Joseph Reply
assigning scientific name to organism
yes, the genius name, and the species name
it is a scientific naming of organism
why drinking excess alcohol causes thirst and dehydration
uwikuzo Reply

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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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