<< Chapter < Page Chapter >> Page >

Physics of the ear and hearing

Diagram of the human ear.

The human ear is divided into three main sections: the outer, middle, and inner ear. Let's follow the journey of a sound wave from the pinna (outermost part) to the auditory nerve (innermost part) which transmits a signal to the brain. The pinna is the part of the ear we typically think of when we refer to the ear. Its mainfunction is to collect and focus an incident sound wave. The wave then travels through the ear canal until it meets the eardrum. Thepressure fluctuations of the sound wave make the eardrum vibrate. The three very small bones of the middle ear, the malleus (hammer),the incus (anvil), and the stapes (stirrup), transmit the signal through to the elliptical window. The elliptical window is the beginning of theinner ear. From the elliptical window the sound waves are transmitted through the liquid in the inner ear and interpreted as sounds by the brain.The inner ear, made of the semicircular canals, the cochlea, and the auditory nerve, is filled with fluid. The fluid allows the body todetect quick movements and maintain balance. The snail-shaped cochlea is covered in nerve cells. There are more than 25 000 hairlikenerve cells. Different nerve cells vibrate with different frequencies. When a nerve cell vibrates, it releases electrical impulsesto the auditory nerve. The impulses are sent to the brain through the auditory nerve and understood as sound.

Intensity of sound

Intensity is one indicator of amplitude. Intensity is the energy transmitted over a unit of area each second.

Intensity

Intensity is defined as:

Intensity = energy time × area = power area

By the definition of intensity, we can see that the units of intensity are

Joules s · m 2 = Watts m 2

The unit of intensity is the decibel (symbol: dB). This reduces to an SI equivalent of W · m - 2 .

The average threshold of hearing is 10 - 12 W · m - 2 . Below this intensity, the sound is too soft for the ear to hear. The threshold of pain is 1 . 0 W · m - 2 . Above this intensity a sound is so loud it becomes uncomfortable for the ear.

Notice that there is a factor of 10 12 between the thresholds of hearing and pain. This is one reason we define the decibel (dB) scale.

Db scale

The intensity in dB of a sound of intensity I , is given by:

β = 10 log I I o I o = 10 - 12 W · m - 2

In this way we can compress the whole hearing intensity scale into a range from 0 dB to 120 dB.

Examples of sound intensities.
Source Intensity (dB) Times greater than hearing threshold
Rocket Launch 180 10 18
Jet Plane 140 10 14
Threshold of Pain 120 10 12
Rock Band 110 10 11
Subway Train 90 10 9
Factory 80 10 8
City Traffic 70 10 7
Normal Conversation 60 10 6
Library 40 10 4
Whisper 20 10 2
Threshold of hearing 0 0

Notice that there are sounds which exceed the threshold of pain. Exposure to these sounds can cause immediate damage to hearing.In fact, exposure to sounds from 80 dB and above can damage hearing over time. Measurescan be taken to avoid damage, such as wearing earplugs or ear muffs. Limiting exposure time andincreasing distance between you and the source are also important steps for protecting your hearing.

Questions & Answers

I'm interested in biological psychology and cognitive psychology
Tanya Reply
what does preconceived mean
sammie Reply
physiological Psychology
Nwosu Reply
How can I develope my cognitive domain
Amanyire Reply
why is communication effective
Dakolo Reply
Communication is effective because it allows individuals to share ideas, thoughts, and information with others.
effective communication can lead to improved outcomes in various settings, including personal relationships, business environments, and educational settings. By communicating effectively, individuals can negotiate effectively, solve problems collaboratively, and work towards common goals.
it starts up serve and return practice/assessments.it helps find voice talking therapy also assessments through relaxed conversation.
miss
Every time someone flushes a toilet in the apartment building, the person begins to jumb back automatically after hearing the flush, before the water temperature changes. Identify the types of learning, if it is classical conditioning identify the NS, UCS, CS and CR. If it is operant conditioning, identify the type of consequence positive reinforcement, negative reinforcement or punishment
Wekolamo Reply
please i need answer
Wekolamo
because it helps many people around the world to understand how to interact with other people and understand them well, for example at work (job).
Manix Reply
Agreed 👍 There are many parts of our brains and behaviors, we really need to get to know. Blessings for everyone and happy Sunday!
ARC
A child is a member of community not society elucidate ?
JESSY Reply
Isn't practices worldwide, be it psychology, be it science. isn't much just a false belief of control over something the mind cannot truly comprehend?
Simon Reply
compare and contrast skinner's perspective on personality development on freud
namakula Reply
Skinner skipped the whole unconscious phenomenon and rather emphasized on classical conditioning
war
explain how nature and nurture affect the development and later the productivity of an individual.
Amesalu Reply
nature is an hereditary factor while nurture is an environmental factor which constitute an individual personality. so if an individual's parent has a deviant behavior and was also brought up in an deviant environment, observation of the behavior and the inborn trait we make the individual deviant.
Samuel
I am taking this course because I am hoping that I could somehow learn more about my chosen field of interest and due to the fact that being a PsyD really ignites my passion as an individual the more I hope to learn about developing and literally explore the complexity of my critical thinking skills
Zyryn Reply
good👍
Jonathan
and having a good philosophy of the world is like a sandwich and a peanut butter 👍
Jonathan
generally amnesi how long yrs memory loss
Kelu Reply
interpersonal relationships
Abdulfatai Reply
What would be the best educational aid(s) for gifted kids/savants?
Heidi Reply
treat them normal, if they want help then give them. that will make everyone happy
Saurabh
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Siyavula textbooks: grade 11 physical science. OpenStax CNX. Jul 29, 2011 Download for free at http://cnx.org/content/col11241/1.2
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Siyavula textbooks: grade 11 physical science' conversation and receive update notifications?

Ask