Sound

Question 1

intensity

Answer 1

amount of power delivered per unit of area

Question 2

decibel scale

Answer 2

used to determine intensity

dB = 10log(I/10^-12)

I = attenuated signal intensity = P/A
measured in W/m^2

decrease of 10 fold is -10dB
decrease of 100 fold is -20dB

Question 3

Blood flowing away from the Doppler ultrasound

Answer 3

will have a positive blood velocity because will be increasing the distance

will have a decreasing frequency shift because will be increasing the space in between waves. Velocity decreases when moving away from the source

Question 4

blood flowing toward the Doppler ultrasound

Answer 4

will have negative blood velocity because will decrease the distance

will have positive frequency shift because will be moving towards the source

Question 5

relationship between doppler shift and wave speed

Answer 5

doppler shift is inversely proportional to the speed of the wave

the faster the wave, the less shift that occurs

Question 6

sound intensity

Answer 6

intensity decreases when crossing between mediums because energy is reflected

Question 7

sound velocity

Answer 7

velocity will increase with temperature, in solids, and with stiffness
velocity will decrease with density

V = √(B/p) 
bulk modulus (how stiff object is)/density

the bulk modulus usually compensates for the density when both increase –> so will have increased speed

Question 8

bulk modulus

Answer 8

measure of how resistant an object is to compression
B = Change in pressure/(change in volume/volume)

units of Pascals
- how much pressure is required to compress something

marshmallows = smaller B
metals = higher B

Question 9

period

Answer 9

cycles/second

signified as “T”

T = 1/frequency

Question 10

What range of sounds are audible for the human ear?

Answer 10

20 - 20,000 Hz

Question 11

frequency

Answer 11

the amount of time it takes for one cycle

measured in 1/s = Hz

determines pitch that is heard

Question 12

what is the speed of sound through air

Answer 12

340 m/s

Question 13

Speed of sound equation

Answer 13

c = wavelength x frequency

or wavelength/period

Question 14

what does the speed of sound depend on

Answer 14

the medium
aka the substance through which a wave travels

the only way for the speed of change is if it went through a different medium

the stiffer the medium, the faster sound will travel (moves faster through solids > liquids > gases)

also depends on density (the more dense = slower)

Question 15

amplitude

Answer 15

how loud something is

Question 16

timbre

Answer 16

overall quality of the voice that results from overlapping waves

Question 17

Which of the following properties explains why sound wave velocity increases as it travels from air to a liquid medium at the same temperature?

Answer 17

bulk modulus explains better than density because bulk modulus has a greater affect than density

Question 18

Shock wave ultrasound

Answer 18

ultrasound waves are outside of human hearing

they have a small wavelength that allows them to propagate through body tissue without diffracting significantly which allows for medical imaging to occur

high amplitude vibrations can destroy tissues when shock wave frequency = resonance frequency and the tissue begins to vibrate

resonance frequency of disease structures may change in accordance to size and material composition

Question 19

MHz to Hz

Answer 19

1 MHz = 10^6 Hz

Question 20

Doppler effect formula

Answer 20

Δf/f = v/c

Δf = frequency shift
f = original frequency
v = relative velocity
c = speed of wave in the medium

magnitude of Doppler shift is inversely related to the speed of the wave

Question 21

Laser Doppler flowmetry uses an infrared laser to measure blood flow velocity. Compared to ultrasound, the observed frequency shift using this technique is:

Answer 21

smaller

because light travels faster than sound and will be able to be reflected back quicker so there will be less doppler shift by the time it returns to the original place

Question 22

When sound passes from air to the tympanic membrane, what changes occur to the sound’s intensity and velocity?

Answer 22

velocity increases because moving from gas –> solid

intensity decreases because when sound propagates across different media, attenuation occurs due to reflection. Therefore some energy is lost which would decrease the intensity.

Intensity decreases when passes from gas –> solid structures

Question 23

Propagation velocity of sound waves depends on properties of medium including

Answer 23

• velocity increases with temperature
• velocity is slowest in gases, and fastest in solids
• within a phase of matter, velocity increases with stiffness (bulk modulus) and decreases with density