9 Sound, the Ear + Auditory Perception

Question 1

Q: What is sound in terms of air pressure?

Answer 1

A: Sound consists of waves with areas of high and low pressure, representing changes in air pressure over time.

Question 2

Q: What are the three characteristics of a sound wave?

Answer 2

A: The three characteristics of a sound wave are frequency (pitch), amplitude (loudness), and complexity (timbre).

Question 3

Q: How is frequency measured and what does it determine?

Answer 3

A: Frequency is measured in Hertz (Hz), which is the number of waves per second. It determines the pitch of the sound.

Question 4

Q: What is the range of human hearing in terms of frequency?

Answer 4

A: The range of human hearing is 20-20,000 Hz.

Question 5

Q: What happens to our ability to hear high frequencies as we age?

Answer 5

A: As we age, we lose the ability to hear higher frequencies.

Question 6

Q: What are infrasound and ultrasound?

Answer 6

A: Infrasound refers to sound frequencies below the human hearing range (less than 20 Hz), and ultrasound refers to frequencies above the human hearing range (greater than 20,000 Hz).

Question 7

Q: How is amplitude measured and what does it determine?

Answer 7

A: Amplitude is measured in decibels (dB) and determines the loudness of the sound.

Question 8

Q: What does a higher amplitude indicate in terms of sound?

Answer 8

A: A higher amplitude indicates a louder sound, which corresponds to higher pressure changes in the air.

Question 9

Q: What causes complex waves in sound?

Answer 9

A: Complex waves occur when the same musical note is played on different instruments, resulting in the same wavelength but different complexities.

Question 10

Q: What is Fourier analysis in the context of sound?

Answer 10

A: Fourier analysis is a method used to break down complex sounds into their fundamental frequency and harmonics.

Question 11

Q: What is the fundamental frequency?

Answer 11

A: The fundamental frequency is the wavelength of the longest component of a sound wave and determines the pitch of the sound.

Question 12

Q: What determines the timbre (sound quality) of a sound?

Answer 12

A: The harmonics, or the additional frequencies present in the sound wave, determine the timbre (sound quality) of the sound.

Question 13

Q: What role does the outer ear play in hearing?

Answer 13

A: The outer ear amplifies sound waves.

Question 14

Q: What happens when the eardrum vibrates?

Answer 14

A: When the eardrum vibrates, it changes air pressure and causes the ossicles in the middle ear to vibrate.

Question 15

Q: What is the vestibular system responsible for?

Answer 15

A: The vestibular system is responsible for balance.

Question 16

Q: What is the ocular reflex?

Answer 16

A: The ocular reflex detects head movements and allows the eyes to quickly compensate and maintain focus.

Question 17

Q: What is the cupula’s role in the vestibular system?

Answer 17

A: The cupula helps detect changes in head position by firing signals to the brain when the fluid inside the vestibular system moves.

Question 18

Q: What can cause the illusion of turning even when stationary?

Answer 18

A: The illusion of turning occurs because the fluid in the vestibular system keeps moving even when you are stationary.

Question 19

Q: What are the effects of damage to the vestibular system?

Answer 19

A: Damage to the vestibular system can cause vertigo and difficulty with balance.

Question 20

Q: What happens in the middle and inner ear when the eardrum vibrates?

Answer 20

A: Vibrations from the eardrum cause the ossicles to vibrate, which moves the oval window, leading to fluid movement in the cochlear duct.

Question 21

Q: How can we hear sound through bone conduction?

Answer 21

A: Sound can be heard through bone conduction without the involvement of the eardrum, as vibrations are transmitted directly to the cochlea through the bones of the skull.

Question 22

Q: What type of hearing aids can use bone conduction?

Answer 22

A: Bone conductor hearing aids can be used for some types of hearing loss that affect the outer or middle ear.

Question 23

Q: What happens in the cochlea when fluid moves through it?

Answer 23

A: Movement of fluid in the cochlea causes waves to pass through the basilar membrane, which is analyzed for frequency.

Question 24

Q: What is the role of hair cells in the cochlea?

Answer 24

A: Hair cells in the cochlea detect vibrations in the basilar membrane and change their firing rate when bent.

Question 25

Q: What does it mean that hair cells are tonotopic?

Answer 25

A: Hair cells are tonotopic, meaning they respond preferentially to particular frequencies.

Question 26

Q: How is the auditory system different from the visual system in terms of organization?

Answer 26

A: The auditory system is tonotopic (organized by frequency), whereas the visual system is retinotopic (organized by spatial location on the retina).

Question 27

Q: What is tonotopic cortical organization, and where is it maintained?

Answer 27

A: Tonotopic cortical organization is the spatial arrangement of neurons that respond to different frequencies. It is maintained as far as the primary auditory cortex in the temporal lobe, where neurons next to each other respond to neighboring frequencies.

Question 28

Q: What are the steps in auditory transduction?

Answer 28

A:

Air pressure changes (kinetic).
Vibration of the eardrum -> middle ear -> oval window (mechanical).
Cochlear fluid flows (kinetic).
Hair cells bend (mechanical).
Auditory nerves fire (neural).

Question 29

Q: What determines the pitch and loudness of a sound?

Answer 29

A: Pitch depends on the frequency of the sound wave, and loudness depends on the amplitude.

Question 30

Q: How are pitch and loudness perceived in relation to each other?

Answer 30

A: They are not completely independent; more intense low-frequency sounds are perceived as lower pitch, and the perception of loudness is affected by frequency, with low frequencies needing to be more intense to be perceived as equally loud.

Question 31

Q: How is space perception in hearing different from vision?

Answer 31

A: Unlike direct depth perception in vision, space perception in hearing is indirect, relying on cues such as loudness, the Doppler effect, interaural intensity differences, and interaural time differences.

Question 32

Q: What are monaural cues for auditory space perception?

Answer 32

A: Monaural cues (from one ear) include loudness and the Doppler effect, which is the change in frequency relative to distance.

Question 33

Q: Why are binaural cues important for perceiving direction of sound?

Answer 33

A: Binaural cues (using both ears) are important for perceiving direction because of interaural intensity differences, the head shadow effect, and interaural time differences.

Question 34

Q: What is the head shadow effect?

Answer 34

A: The head shadow effect occurs because sound to one ear must travel further and diffuse around the head, causing attenuation of the sound.

Question 35

Q: What is the significance of interaural time differences?

Answer 35

A: Interaural time differences, which can be up to 0.07 seconds, help in localizing the direction of sound.

Question 36

Q: How do head movements contribute to auditory space perception?

Answer 36

A: Head movements help in perceiving the vertical location of a sound source.

Question 37

Q: What is auditory grouping or streaming?

Answer 37

A: Auditory grouping or streaming is the process by which sounds are grouped into streams based on their proximity in space, time, and frequency, similar to figure-ground separation in vision.