Topic 8.2 sound

Question 1

Describe how sound sensation is recieved

Answer 1

• Compressions = close molecules
• Rarefactions = sparse molecules
• When either strike ear drum = sound

Question 2

Describe the different types of frequencies

Answer 2

• Above 20 kHz = ultrasonic
• Below 20 kHz = infrasonic

Question 3

How can speed of sound be predicted?

Answer 3

c = √ bulk modulus / density

Question 4

Describe speed of sounds

Answer 4

• 0C = 331
• 20C = 343
• Increases by 0.61m/s each 1C rise

Question 5

What factors is speed of sound independant of?

Answer 5

• Pressure
• Frequency
• Wavelength

Question 6

Define pure tone

Answer 6

• Sound wave = amplitude varies sinusoidally

Question 7

Define pitch

Answer 7

• High/low sounds = determined by wave frequency
• Higher frequency = higher pitch

Question 8

Define loudness

Answer 8

• Measure of human perception of sound
• Higher intensity = louder
• Sensation of sound proportional to log of sound intensity

Question 9

What is the value of 0 on the intensity scale?

Answer 9

1x10-2 W/m2

Question 10

Define decibel

Answer 10

• Dimensionless unit = represents relative magnitude of intensities

Question 11

What are different values of intensity on the dB scale?

Answer 11

• Normal conversation = 60-70 dB
• Speech = 70-80 dB
• Pain threshold = 120 dB
• Window break = 163 dB

Question 12

Describe the vocal organs function in creating sound

Answer 12

• Cavities in mouth + nasal + pharynx = vocal tract
• Changes in shape = produce different sound
• To create sound = energy source needed = using air from lungs as exhaling
• Air vibrations = produced in larynx = vocal cords = band of muscular tissue
• Space between vocal cords = glottis

Question 13

Describe the outer ear

Answer 13

• Function = catch sound waves
• Pinna has curves = catch sound + determine direction
• Guided to middle ear via ear canal until reaches eardrum

Question 14

Describe middle ear

Answer 14

• Function = magnify sound pressure
• Ossicles = small bones suspended by ligaments
• Connected to oral cavity via eustachian tube
• Malleus attached to ear drum > incus > stapes
• Stapes attached to oval window = causes ossicle movent to move fluid in cochlea

Question 15

Describe inner ear

Answer 15

• Cochlea = coiled up bone = filled with fluid
• It is divided = 2 halves via membrane = membrane turn waves > signals
• Cochlea does spectral analysis = stimulus split into frequency bands = critical bands

Question 16

Describe 4 steps of hearing

Answer 16

1) Sound wave enter outer ear
2) Movement of tympanic membrane = transfer conduction via ossicles > oval window
3) Movement of oval window = compressional wave in cochlea fluid
4) Wave move membrane = primary auditory receptors = electrical signals generated = sent to brain

Question 17

What is the normal auditory sensitivity?

Answer 17

• 20 Hz - 20kHz
• Ear most sensitive between 100-4000Hz

Question 18

What levels of sound are harmful?

Answer 18

• Above 85 = harmful
• Pain threshold = 120
• Above 150 = physical damage
• 190-198 = eardrums rupture
• Around 200 can cause death in humans

Question 19

Define doppler effect

Answer 19

• Apparent shift in frequency of sound when source + observer are in relative motion