Sound Quiz #2 Review
Why does the pitch of an ambulance siren sound higher as it drives towards you.
Does the siren actually change the pitch coming from the speaker as it approaches and passes you standing on
the side of the road?
What is natural frequency? Give an example.
Give two examples of resonance.
Explain the Doppler effect.
One sound has a wavelength of 196 m and the second has a wavelength of 223 m. Which sound would have the
highest pitch? Why?
How are P and S wave similar? How are they different?
What types of waves cause the most damage during an earthquake?
What is an epicenter?
Explain how noise cancelling headphones work.
Draw two examples of constructive interference with transverse waves.
Draw an example of constructive interference with compressional waves.
Draw an example of destructive interference with longitudinal waves.
What is the wavelength of a sound with a frequency of 317 hz?
What is the frequency of a sound wave with a wavelength of 4.2 m?
What is the speed of a wave if the wavelength is 12.5 m and the frequency is 98 hz?
If 214 geese fly by in 57 minutes, what is the frequency?
If a 4.5 m wave goes by in 1.1 seconds, what is the speed of the wave? What is the wave’s frequency? (hint – 2
steps)
What happens to a sound wave when it undergoes constructive interference? What change do we hear?
What happens to a light wave (transverse wave) when it undergoes destructive interference? What change do
we see?
Sound Quiz #2 Review
Why does the pitch of an ambulance siren sound higher as it drives towards you.
As a vehicle makes sound (siren) and travels in the same direction as the sound, the distance between the
waves decreases and the pitch increases (a wave goes out in front of the ambulance, but the ambulance
drives behind it so the distance to the next wave is less).
This is not making the sound louder!!
Does the siren actually change the pitch coming from the speaker as it approaches and passes you standing on
the side of the road?
No – the change in pitch after passing is because now the ambulance is driving away as it makes waves –
this makes the distance between waves longer and the pitch decreases.
What is natural frequency? Give an example.
The frequency at which an object naturally resonates – the wine classes in myth busters rang at a specific
frequency when hit – that is its natural frequency.
Give two examples of resonance.
Two tuning forks in class – hit one and the 2nd starts to vibrate
Your car shaking when another car next to you has music turned up
Breaking glass by singing
Explain the Doppler effect.
As an object is making sound, it is moving (or the hearer is moving). If the movement is in the direction
of the sound travelling, the distance between sound waves is less and the pitch is higher. If the movement
is in the opposite direction of the sound travelling, the distance between waves is greater and the pitch is
lower.
One sound has a wavelength of 196 m and the second has a wavelength of 223 m. Which sound would have the
highest pitch? Why?
Higher pitch is higher frequency.
The 196 m wavelength is shorter than 223 m, so it would have a higher frequency, therefore, higher pitch
How are P and S wave similar? How are they different?
They are both seismic waves, specifically body waves, that travel through the earth.
P waves are faster and can travel through all the earth. S waves are slower and can’t travel through
liquids
What types of waves cause the most damage during an earthquake?
Surface waves do the most damage – Raleigh and Love waves
What is an epicenter?
The place directly above where the earthquake took place
Explain how noise cancelling headphones work.
They make the inverse wave of the sound going to the ear. The naturally occurring sound wave and the
inverse then go through destructive interference and cancel each other out.
Draw two examples of constructive interference with transverse waves.
Draw an example of constructive interference with compressional waves.
Draw an example of destructive interference with longitudinal waves.
What is the wavelength of a sound with a frequency of 317 hz?
V=340 m/s
v=λf
f = 317 hz
340 m/s = λ(317 hz)
λ=?
λ=1.07 m
What is the frequency of a sound wave with a wavelength of 4.2 m?
V=340 m/s
v=λf
f=?
340 m/s = (4.2 m) f
λ = 4.2 m
f=80.95 hz
What is the speed of a wave if the wavelength is 12.5 m and the frequency is 98 hz?
V=?
v=λf
f = 98 hz
v = (12.5 m)(98 hz)
λ = 12.5 m
v = 1225 hz
If 214 geese fly by in 57 minutes, what is the frequency?
# = 214
f = #/t
T = 57 min
f = 214 geese/57 min
f=?
f = 3.75 geese/min
If a 4.5 m wave goes by in 1.1 seconds, what is the speed of the wave? What is the wave’s frequency? (hint – 2
steps)
λ = 4.5 m
f = 1/period
t (or period) = 1.1 seconds
f = 1/1.1
v=?
f = .91 hz
f=?
v=λf
v = (4.5 m)(.91 hz)
v = 4.1 m/s
or
v=d/t
v=4.5 m/ 1.1 sec
v = 4.1 m/s
What happens to a sound wave when it undergoes constructive interference? What change do we hear?
Sound waves align their compressions and rarefactions, making each bigger – the result is a louder sound
What happens to a light wave (transverse wave) when it undergoes destructive interference? What change do
we see?
Light waves align the crest of one wave with the trough of the next – this leads to cancelling that
particular frequency – making the light color dimmer or completely removing it