Exam 2 Hearing 1

Question 1

How do sound vibrations travel?

Answer 1

As longitudinal waves

Question 2

•Sound travels faster in water or in air?

Answer 2

Sound waves travel faster in water

–The velocity of sound in air is 343 m/sec or 767 mph.

–The velocity of sound in water is 1500 m/sec, 3400 mph.

Question 3

What is the simplest, most fundamental type of vibration, contains only one single frequency of vibration (similar to a pure, spectral color in light).

Answer 3

Pure tones

Question 4

What is the number of compressed or rarefied patches of molecules that pass by our ears each second.

-One cycle of sound is the distance between successive compressed patches

Answer 4

Frequency

Question 5

What is the time duration of one cycle of vibration in seconds. The inverse of frequency.

–Note: Frequency and ______ depend on the source of the sound alone.

Answer 5

period

Question 6

What is the the number of cycles per second?

Answer 6

Hertz

Question 7

What is the spacing between cycles, in meters.

-it depends on both the source of the sound and the medium in which it travels.

Answer 7

Wavelength

–The wavelength of a 1000 Hz tone is 300/1000 = 0.3 meters in air and 1500/1000 = 1.5 meters in water.

–Our range of hearing is 20-20,000 Hz. Church organ low note is 20 Hz, piccolo high note is 10,000 Hz.

Question 8

What is the difference in pressure between the compressed and rarefied patches of air.

–_______ determines loudness.

Answer 8

Intensity

Question 9

Describe this image

Answer 9

High-frequency waves are perceived as high pitch (a)

High intensity as louder (b)

Question 10

_______ and its components can be decomposed into a spectrum of pure tones, each of a different frequency.

________ having no dominant rhythmicity get perceived as noise, hisses, or scratches.

–When a dominant rhythmicity exists, we perceive a pitch corresponding to the rhythmicity.

Answer 10

•A complex sound

Question 11

What is a measure of sound intensity.

Answer 11

Decibel

-we can hear best from 20 hz to 20k hz

Question 12

What is it called to lose your hearing as you age?

-at higher frequencies (higher pitch) you need higher decibels (sound intesntiy)

Answer 12

Presbycusis

Question 13

What includes the pinna and the auditory canal?

Answer 13

The outer ear

Question 14

What acts as a funnel to magnify pressure?

Answer 14

Pinna

Question 15

What is the eardrum.

-Vibrates relative to frequency

Answer 15

•The tympanic membrane

Question 16

What are the malleus, incus, and stapes all called together?

–amplify sound force at the oval window.

•Sound waves have to travel from air in the middle ear to water in the inner ear. The problem is that air and water have different acoustical properties.

Answer 16

Ossicles

-The three bones together act as a leaver

Question 17

–In air, sound waves have _____ pressures and cause large displacements of air molecules (low impedance).

–In water, sound waves have ______ pressures and cause small displacements of molecules (high impedance).

Answer 17

1) Low
2) High

Question 18

explain this image

Answer 18

Middle ear mechanics

In the ear, the “matching device” is the ossicles.

The pressure on the oval window must be greater than the pressure on the tympanic membrane in order for the sound waves traveling through air to pass into the fluid of the cochlea.

Question 19

The pressure on a membrane in middle ear mechanics is increased by?

Answer 19

Pressure = Force/surface area

The pressure on a membrane is increased by

–Increasing the force on the membrane.

-This is done by the movement of the ossicles which act like levers on the oval window.

–Reducing the surface area of the membrane.

• The surface area of the oval window is much less than that of the tympanic membrane.
• If the same amount of force is exerted on both membranes, the smaller membrane will receive the greater pressure.

Question 20

•The middle ear magnifies the sound force at the oval window ______ times and reduces the displacement of air molecules ________ times. These factors combine to make the pressure at the oval window about _______ times greater than that at the tympanic membrane.

Answer 20

1) 1.5
2) 1.5
3) 20x

Question 21

•The middle ear is capable of nearly perfect __________.

-Loss of the matching effect would reduce the sensitivity of the ear by 30 db.

Answer 21

impedance matching

Question 22

Mechanical control of ear sensitivity is regulated by the ________

Answer 22

tensor tympani and stapedius muscles

–Contraction reduces sound transmission by 20 db.

–These muscles maintain fidelity of sound transmission at high sound levels. Ossicle joints could otherwise separate causing distortion of the sound.

Question 23

What reflex?

–The tensor tympani and stapedius muscles contract reflexively at loud sounds to protect the auditory apparatus.

–This reflex has a delay of 50-100 msec so it does not protect the ear against sudden loud sounds.

–Contraction of these muscles also occurs just prior to speaking.

Answer 23

•Attenuation reflex:

Question 24

•The inner ear includes the ______________.

Answer 24

cochlea and labyrinth

Question 25

The organ of Corti and associated structures contain auditory receptors that are ___________

Answer 25

hair cells with stereocilia

–Hair cells synapse on neurons whose axons enter the auditory nerve and whose cell bodies are located in the spiral ganglion within the modiolus.

-they are the transducers

Question 26

The basilar membrane ________ toward the apex.

The _______ is a hole at the apex of the basilar membrane, which connects the scala vestibuli and scala tympani.

Answer 26

1) widens
2) helicotrema

Question 27

Why can the basilar membrane vibrate easily at sound frequencies?

Answer 27

•The basilar membrane holding the hair cells vibrates easily at sound frequencies.

–This is due partly to the coiling of the cochlea.

–This is due mainly to how the structure of the membrane varies along its length.

• It is wider at its apex than its base by a factor of 5.
• The stiffness of the membrane decreases from base to apex.

–If a sound frequency is high, the stiffer base will vibrate and the pressure wave will not propagate to the apex.

–If a sound frequency is low, the stiffer base will not vibrate but the wave will move to the floppy apex.

Question 28

•The _______________ holding the tips of the hairs has a very flexible attachment, but considerable mass.

–It bends freely with slow movements, but acts very stiff with fast movements (at sound frequencies).

•The mechanical arrangement of these membranes provides magnification of the hair movement which increases the sensitivity of the system.

Answer 28

tectorial membrane

Question 29

Bending of the stereocilia is produced by the upward motion of the ___________

Answer 29

basilar membrane

• (a) Membrane at rest.
• (b) Membrane deflected upward.