Waves/sound

Question 1

velocity of wave

Answer 1

v = wavelength x frequency

Question 2

period

Answer 2

T = 1/f

Question 3

angular frequency

Answer 3

w = 2pi(f) or 2pi/T

Question 4

natural resonant freq

Answer 4

< 20Hz infrasonic
20Hz- 20,000 Hz
> 20,000 Hz ultrasonic

Question 5

forced oscillation

Answer 5

external force causing oscillation so
frequency of force = freq of oscillation
if force close to natural frequency then inc in amplitude

Question 6

speed of sound

Answer 6

v = square root ( B/ rho) 
B = bulk modulus medium resistance 
rho = density of medium

Question 7

pitch

Answer 7

frequency

Question 8

Doppler effect

Answer 8

f’ = f x (v +- vo)/(v +- vs)

v= speed of sound in medium 
vo = speed of detector (m/s)
vs = speed of source (m/s) 

+ is toward
- is away

ie- me driving away from ambulance but ambulance driving toward me

Question 9

intensity

Answer 9

= energy transfer/area in watts/m^2
I = P/A
p= power

proportional to amplitude squared
so double intensity = quadruple the amplitude

inversely proportional to distance squared
d =2 —> A=4 —> I=P/4A

Question 10

sound level?

Answer 10

B = 10log (I/Io) measured in dB 
Bf = Bi + 10 log (If/Ii)

Question 11

damping

Answer 11

no effect on frequency/pitch, only amplitude, intensity,, volume

Question 12

fbeat

Answer 12

= | f1 - f2 |

Question 13

Strings/ standing wave: wavelength

Answer 13

lambda = (2L / n)

L= length 
n= harmonic

Question 14

possible frequency of harmonic?

Answer 14

f = nv/ 2L

v= wave speed

Question 15

open pipe harmonics

Answer 15

just like string

lambda = (2L / n) 
f = nv/ 2L

Question 16

closed pipe harmonics

Answer 16

only odd harmonics

lambda = 4L/n 
f = nv/4L 

L= n (lambda) / 4

Question 17

ultrasound imaging

Answer 17

use high frequency to determine relative densities

Question 18

doppler ultrasound- blood flow

Answer 18

faster healing - direct blood flow

focus to ablate kidney stones/ cataract