Week 8

Question 1

acoustics -

Answer 1

physics of sound waves is called acoustics

Question 2

transverse wave -

Answer 2

vibration direction is perpendicular to the direction of propagation

ex: electromagnetic waves

Question 3

longitudinal / compressional waves -

Answer 3

ex: sound waves

Question 4

crests -

Answer 4

top points on the wave

Question 5

troughs -

Answer 5

bottom points of the wave

Question 6

amplitude of a wave -

Answer 6

maximum disturbance undergone during a vibration cycle

Question 7

beats -

Answer 7

alternations of maximum and minimum intensity produced by the superposition of two waves of slightly different frequencies

Question 8

speed of compression waves

Answer 8

= speed of sound waves = c _sound on the formulae sheet

Question 9

pitch

Answer 9

how ‘high’ or ‘low’ sound sounds, determined by the wave frequency

Question 10

Hearing loss is defined as:

Answer 10

• slight (average value of 16–25 dB HL),
• mild (26–40 dB HL),
• moderate (41–55 dB HL),
• moderately severe (56–70 dB HL),
• severe (71–90 dB HL), and
• profound (>90 dB HL).

Question 11

Doppler effect:

Answer 11

apparent shift in frequency (and hence pitch) of a sound when the source and observer are in relative motion

𝑓′ = 𝑓 (𝑣 ± 𝑣_𝐷) / (𝑣 ± 𝑣_𝑠)

To remember which sign to use in the general formula, remember that if the detector or
source is moving towards the other, then the sign on its speed must give an increase in 𝑓′,and
if they are moving away, the corresponding speed has whichever sign would decrease 𝑓′

Question 12

waves above 20 kHz -

Answer 12

ultrasonic waves

Question 13

waves below 20 Hz -

Answer 13

infrasonic waves

Question 14

speed of sound at 0 C =

Answer 14

331 m/s

Question 15

speed of sound in 20 C =

Answer 15

343 m/s