Pinna Versus Pitch Perception

8/14/2019 Pinna Versus Pitch Perception

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Bac

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Humans hear sounds(audition) through a partof the sensory systemcalled the auditorysystem.

Humans perceive thefrequencyof a sound

(how fast the soundwaves vibrate) bydetecting its pitch.

The average human can


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Sensoryanatomy of

audition Sound waves

travel through

the auditorycanal and causethe eardrum(tympanicmembrane) to

vibrate. This tympanic

vibration causesthe ossicles [thebones called the

hammer

This ossicular vibration pushes(the oval window a membranous

),hole pushing the fluid in the

.cochleaThis cochlear fluid stimulates apart of the cochlea called the

,organ of Corti which containsreceptors called hair cells (not

to be confused with hair).follicles


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Nervous anatomy ofaudition

Inside the organ of Corti, the cochlear fluidmoves the tectorial membrane, which isattached to the cilia (hairs) of the hair cells.

The hair cells send glutamate (a

neurotrasmitter) signals to communicate withthe neurons in the cochlear nerve, whichbecomes the vestibulocochlear nerve (orcranial nerve VIII).

These signals are processed multiple times at

sections of the brainstem, midbrain, andthalamus before reaching the primaryauditory cortexes in both temporal lobes.

These cortexes are the location where pitch isprocessed.


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Why people perceive pitchdifferently

Presbycusis (or hearing loss) is acondition in which humans graduallylose the ability to detect high-

frequency sounds. There are multitude of factors that

contribute to presbycusis: Overexposure to loud noises

Damage to hair cells Heart disease, high blood pressure,

diabetes, or other circulatory problems

Damage to eardrum or ossicles


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Designing a pitch perception test

Our group decided to test a population ofstudents and faculty in our school todetermine what the maximum frequency theycould hear was.

Besides the already-confirmed causes ofpresbycusis, we wanted to see whether therewas a correlation between the size of ones

pinna (the visible part of the outer ear) andpitch perception.

We proposed that the highest frequency onecan hear is proportional to pinna size, so ourhypothesis is if a population is tested todetermine what the maximum frequenciesthat they can detect are, then the subjectsthat can detect the highest maximum

frequencies with have the largest pinnae, andsub ects that detect lower maximum


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Designing a pitch perception test(cont.)

To test a subjects pitch perception, we used amobile phone application called Dog Whistle(pitcured below), which can generate high-pitched noises.

We played noises with frequencies ranging from12-20 kHz (increasing each subsequent noiseby 1 kHz, so that there were nine levels of theindependent variable).

When we played each noise, we asked the

subject if they could detect the noise. If theycould, we increased the frequency by 1 kHzand asked them again. If they could not, werecorded the frequency and then measuredthe size of their pinna.

To measure their pinna, we used a caliper andmeasured from the top of the helix to the


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DataStudent imit of pitch

( )erception kHzength of ear

( )mFemale 1 20 .2 0832 20 .1 9263 16 .2 1594 16 .2 0245 16 .2 0456 19 .2 2857 19 .1 9408 19 .1 9229 20 .2 14710 18 .1 88711 16 .2 13512 16 .2 11113 17 .2 026

Male 1 18 .2 1152 17 .2 6043 18 .2 1984 17 .2 2065 18 .2 1866 18 .2 081

7 18 .2 2108 19 .2 3309 16 .2 73110 16 .2 604


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Statistical analysis

According to the trendline, thecorrelation with


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Works cited

http://www.indiana.edu/~emusic/acoustics/pitc(average human pitch range)

http://www.dizziness-and-balance.com/disorder(animation)

http://commons.wikimedia.org/ (pictures) http://deafness.about.com/cs/earbasics/f/earba

(sensory anatomy) http://thalamus.wustl.edu/course/audvest.html

(nervous anatomy) http://www.nidcd.nih.gov/health/hearing/presby

(why people perceive pitch differently)
http://www.indiana.edu/~emusic/acoustics/pitch.htmhttp://www.dizziness-and-balance.com/disorders/hearing/hearing.htmlhttp://commons.wikimedia.org/http://deafness.about.com/cs/earbasics/f/earbasics.htmhttp://thalamus.wustl.edu/course/audvest.htmlhttp://www.nidcd.nih.gov/health/hearing/presbycusis.asphttp://www.nidcd.nih.gov/health/hearing/presbycusis.asphttp://thalamus.wustl.edu/course/audvest.htmlhttp://deafness.about.com/cs/earbasics/f/earbasics.htmhttp://commons.wikimedia.org/http://www.dizziness-and-balance.com/disorders/hearing/hearing.htmlhttp://www.indiana.edu/~emusic/acoustics/pitch.htm


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Copyright

The image loud by Rafael Pealoza isreleased under a Creative CommonsAttribution Non-CommericalShareAlike 3.0 License.

The image Dog Whistle bybaxiabhishek is released under aCreative Commons Attribution Non-Commercial 3.0 License.

The image Cochlea-crosssection byOarih is dual-licensed under aCreative Commons AttributionShareAlike 3.0 License and the GNU

Free Documentation License.

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Pinna Versus Pitch Perception