Audition and Mechanical Senses

Sound waves

Periodic compressions of air, water, or other media.

Rube Goldberg (1883–1970)

drew cartoons of complicated, far-fetched inventions.

What animals hear best at lower pitches

large animals ex. elephant

timbre (TAM-ber)

• tone quality or tone complexity.

• People communicate emotion by alterations in pitch, loudness and _

Amplitude of a sound wave

The magnitude of the maximum disturbance in a sound wave.

Intensity

The amount of energy transmitted through a unit area in the direction of wave propagation.

Frequency of a sound

The number of compressions per second in a sound wave.

Hertz (Hz)

The unit used to measure frequency, representing cycles per second.

Pitch

A related aspect of perception where sounds higher in frequency are perceived as higher in pitch.

Range of frequency that adult humans can hear

starting at about 15 to 20 Hz and extending up to nearly 20,000 Hz.

Lowest sound that can be detected by the human ear

= usually around 15 to 20 Hz.

The highest frequency that can be heard by adult humans

reaching close to 20,000 Hz.

Pinna

• the familiar structure of flesh and cartilage attached to each side of the head.

• by altering the reflections of sound waves, it helps us locate the source of a sound.

• each person’s _ is shaped differently from anyone else’s

Outer ear

The part of the ear that includes the pinna

children hear high frequencies than adults

the ability to perceive high frequencies decreases with age and exposure to loud noises

3 aspects of sound

frequency, amplitude, timbre

What animals hear best at higher pitches

Mice (smaller animals)

prosody

Conveying emotional information by tone of voice

tympanic membrane is also known as the

eardrum

these are the smallest bones in the body

• hammer, anvil, and stirrup

The tympanic membrane

connects to three tiny bones that transmit the vibrations to the oval window, a membrane of the inner ear.

cochlea

snail-shaped structure of the inner ear
- Contains 3 fluid filled tunnels

Place theory

Each frequency activates the hair cells at only one place along the basilar membrane (which resembles the strings of a piano, with each area along the membrane tuned to a specific frequency) and the nervous system distinguishes among frequencies based on which neurons respond

Frequency theory

Basilar membrane vibrates in synchrony with a sound, causing auditory nerve axons to produce action potentials at the same frequency

Height of each wave corresponds to....

amplitude

Number of waves per second corresponds to...

Frequency

oval window

Membrane of the inner ear

Malleus (hammer) Incus (anvil) Stapes (stirrup)

3 tiny bones that convert the sound waves into stronger vibrations in the fluid filled cochlea

Hair cells

Auditory receptors that lie between the basilar membrane of the cochlea on one side and the tectorial membrane on the other

Ossicles

Term for the 3 tiny bones in the middle ear

primary auditory cortex (area A1)

• in the superior temporal cortex

Tinnitus

Frequent/constant ringing in the ears. Associated with phantom limb because it is a result of damage to the cochlea, like an amputation.

Conductive deafness (Middle-ear deafness)

happens when disease, infections, or tumorous bone growth prevent the middle ear from transmitting sound waves properly to the cochlea. Sometimes temporary. Can be corrected with surgery and hearing aids.

Nerve deafness (inner-ear deafness)

Results from damage to the cochlea, the hair cells, or the auditory nerve. May be confined to one part of the cochlea and not others

Absolute pitch

The ability to hear a note and identify it

Absolute pitch

Genetic predisposition contributes to this and is more common among people who speak tonal languages

Amusia

(Tone deafness) Impaired detection of frequency changes.

People with __________ have a thicker than average auditory cortex in the right hemisphere but fewer than average connections from it to the frontal cortex

amusia

Basilar Membrane of the Cochlea

Stiff at it's base where the stirrup meets it, to floppy at the apex

transduction

External stimuli transducing into an internal stimuli (transduce: to convert energy from one form to another)

Stereocilia

Crescent shaped structures atop hair cells. Sound waves bend them triggering responses from the hair cells

downfall of place theory

Various parts of the basilar membrane are bound together too tightly for any part to resonate like a piano string

Auditory "what" pathway

Sensitive to patterns of sound in the anterior temporal cortex

Auditory "where" pathway

Sensitive to sound location in the posterior temporal cortex and parietal cortex

time of arrival

Most useful for localizing sounds with a sudden onset.

sound shadow

For high frequency sounds, with a wave length shorter than the width of the head, the head creates this, making the sound louder for the closer ear

phase difference

Humans localize low frequencies by this. It provides information that is useful for localizing sounds with frequencies up to about 1500 Hz in humans