7.2 Sound

Question 1

sound

Answer 1

a longitudinal wave transmitted by the oscillation of particles in a deformable medium

(sound cannot travel through a vacuum)

Question 2

speed of sound equation

Answer 2

Question 3

bulk modulus

Answer 3

a measure of the medium’s resistance to compression

increases from gas to liquid to solid

Question 4

pitch

Answer 4

the frequency of a sound

Question 5

lower frequency = ____ pitch

Answer 5

lower

Question 6

higher frequency = ____ pitch

Answer 6

higher

Question 7

infrasonic waves

Answer 7

soundwaves with frequencies below 20Hz

(humans cannot hear)

Question 8

ultrasonic waves

Answer 8

sound waves with frequencies above 20,000 Hz

(humans cannot hear)

Question 9

doppler effect

Answer 9

describes the difference between the actual frequency of a sound and its perceived frequency when the source of the sound and the sound detector are moving relative to one another

example: an ambulance with its sirens blaring has a distinct drop in pitch as it passes your car

Question 10

doppler effect equation

Answer 10

f = perceived frequency
f0 = actual emitted frequency

Question 11

shock waves

Answer 11

the highly condensed wave front that results when an object moves faster than the speed of sound

Question 12

sonic boom

Answer 12

the nouse heard from the shockwave of an object travelling at or faster than the speed of sound

Question 13

sound volume

Answer 13

this is subjective

depends on brain function, damage to the ear, etc.

Question 14

sound intensity

Answer 14

objectively measureable

the average rate of energy transfer per area across a surface that is perpendicular to the wave

the power carried by sound waves per unit area in a direction perpendicular to that area

Question 15

SI unit for intensity

Answer 15

watts per square meter

Question 16

sound intensity equation

Answer 16

Intensity = power / area

watts / square meter

Question 17

relationship between intensity and amplitude

Answer 17

intensity = amplitude squared

(doubling the amplitude quadruples the intensity)

Question 18

Sound level (β)

Answer 18

used to measure the intensity of sound within an easier to measure range

Question 19

sound level unit

Answer 19

decibels (dB)

Question 20

sound level equation

Answer 20

I = intensity of sound
I0 = threshold of hearing = 1 x 10^-12 W/m^2

Question 21

attenuation/damping

Answer 21

the system decreases in amplitude during each oscillation due to friction and nonconservative forces

this is why it is more difficult to hear in a cluttered space; the friction from the surface of objects decreases the amplitude of sound waves

Question 22

sound damping does NOT affect __________

Answer 22

frequency/pitch

Question 23

beat frequency

Answer 23

when two sounds of slightly difference frequencies play in proximity at the same time, it sounds like volume is oscillating between loud and quiet

the rate of this oscillation is the difference between the two frequencies

Question 24

objects that support standing waves have:

Answer 24

boundaries at both ends

Question 25

how is ultrasound used in medicine

Answer 25

ultrasound is used to visualize organs, anatomy, and pathology

high frequency sound waves outside the range of human hearing is used to compare the relative densities of tissues in the body

Question 26

components of an ultrasound machine

Answer 26

transmitter: generates a pressure gradient

receiver: processes the reflected sound

usually packaged in a single device

Question 27

how does ultrasound imaging work?

Answer 27

the speed of the wave and travel time is known

the machine can then generate a graphical representation of borders and edges within the body by calculating the traversed distance

Question 28

sound travels fastest through —– and slowest through —–

Answer 28

sound travels fastest through solids and slowest through gases

(less resistance to compression = faster speed)

Question 29

which is faster, speed of light or speed of sound?

Answer 29

light travels faster than sound