The Ear

Exam 3

Physical sound

the loudness, pitch, and timbre of sound

psychological sound

what and how we process and perceive sound

Frequency

the number of sound waves per second, is measured in hertz, and determines pitch

Amplitude

the vertical size of sound waves, is measured in decibels, and determines the loudness of a sound

Complexity

the characteristics of a sound when different harmonics are emphasized (piano vs flute). This creates “shaped” sound waves because of the different overtonal structures

Sound

air pressure. the more compressed, the louder it is

sine waves

pure tones and the simplest sound waves

Hearing thresholds

we are most sensitive to 4000 hz (consonant speech) and can here between 15-20,000 hz

Outer Ear

• Pinna

• external auditory canal

Pinna

the fleshy outer part of the ear that funnels sound into the ear

External Auditory Canal

The tunnel that resonates sound from 300-400 hz (human speaking sound)

Middle Ear

• Eardrum/tympanic membrane

• Ossicles

• Oval window

Tympanic Membrane

aka the ear drum, transmits sound through vibration and regulates air pressure so the it can vibrate

Ossicles

Consists of the malleus, incus, and stapes that work together like a hammer to increase force to send sound into the cochlea

Oval Window

concentrates force from the tympanic membrane

Inner Ear

• Cochlea

• semicircular canals

• Basilar membrane

Semicircular canal

the part of the vestibular system that regulates balance

Cochlea

a fluid filled structure that receives the strengthened message from the ossicles and contains the basilar membrane

Basilar Membrane

tonotopically organized to push cilia against the tectorial membrane to turn sound into electrical signals. If one frequency is present, the respective area on the membrane will activate. If many frequencies are present, multiple areas on the membrane will activate.

Place Theory

The area of the cochlea that activates is related the area that activates in the auditory cortex. It is tonotopically organized. Most of the right ear goes to the left hemisphere of the auditory cortex of the temporal lobe

• lower frequency → center

• high → outside

• middle → in-between

Conductive Hearing Loss

sound cannot be efficiently conducted into the cochlea and usually can be corrected (similar to cataracts)

Sensorineural Hearing loss

there is something wrong with the hearing system structures and is extremely difficult to repair. Cumulative and irreversible damage

Conduction Problems

caused by anything that prevents the ear drum from being able to vibrate

Presbycusis

impaired hearing caused by old age and decreased flexibility in the system. higher frequencies are lost first which creates muffled hearing, loss of consonants, and is treated with hearing aids

Sensorineural Problems

caused by damage to the inner ear, often the cilia, which can result in tinnitus

Cochlear Implants

a microphone sends sounds through a magnetic coil and wire that mimics the tonotopic organization of the basilar membrane. It usually feeds into 15-20 different electrodes to preserve speech sounds above all.

Music is often too complicated for cochlear implants to fully translate, but many people still listen to music with them.