Sound

Question 1

what is bulk modulus?

Answer 1

a measure of a medium’s resistance to compression (increases from gas to liquid to solid)

Question 2

What is the equation for the speed of sound?

Question 3

What type of wave are sound waves?

Answer 3

longitudinal waves, particles move parallel to direction of wave propagation (compression, think slinky)

(the opposite wave type is transverse waves, think wave in a stadium where people move parallel to direction of wave propogation)

Question 4

What is pitch?

Answer 4

our perception of the frequency of sound

Question 5

What are ultrasonic and infrasonic waves?

Answer 5

ultrasonic waves have a frequency higher than the normal range of human hearing (>20,000 Hz) (ex. dog whistle, ultrasound machine)

infrasonic waves have a frequency lower than the normal range of human hearing (<20 Hz)

Question 6

What is the Doppler Effect?

Answer 6

it is the change in perceived frequency (pitch) when a sound source is moving relative to a sound detector

when source and detector are moving towards one another, perceived frequency is higher than actual frequency. when source and detector are moving away from one another, perceived frequency is lower than actual frequency,

Question 7

How does echolocation work and what phenomenon does it rely on?

Answer 7

relies on Doppler Effect, the animal is both the sound source and detector. the animal uses the time it takes for sound to come back and the pitch of the sound to identify the position and speed of objects.

Question 8

What is the difference between sound volume and sound intensity?

Answer 8

sound volume is our perception of sound intensity and its subjective.

sound volume is “the average rate of energy transfer (power) per unit area of surface that is perpendicular to the sound wave”. it is objective and measurable.

Question 9

What is the formula for sound intensity?

Answer 9

I = Power / Area

[I] = Watts / m²

Question 10

What is the relationship between sound intensity and sound wave amplitude?

Answer 10

Intensity is proportional to the amplitude squared.

Therefore, doubling sound wave amplitude, increases sound intensity by 4 times.

Question 11

What is the relatinoship between sound intensity and distance from source?

Answer 11

sound intensity is inversely proportional to the square of the distance from source.

Therefore, doubling the distance from source, decreases sound intensity by a factor of 4.

Question 12

What is the equation for sound level, and what are its units?

Answer 12

B = 10log(I/I_o)

B: sound level

I: intensity of sound wave

I_o: lowest intensity threshold of human hearing (ie. softest sound)

Question 13

What is attenuation?

Answer 13

gradual dampening of sound due to nonconservative forces (friction, air resistance, viscous drag)

attenuation affect amplitude, intensity, but it does not affect frequency (pitch)

Question 14

What is the formula for beat frequency?

Answer 14

f_beat = f₁ - f₂

f1 and f2 are the two frequencies that are being combined