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DMS Physics (1st exam) > Ch. 1, & 2 > Flashcards

Ch. 1, & 2 Flashcards

Basics, Sound Variables, Sound Parameters & their Relationships

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1
Q

vertical axis

A

(Y)

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2
Q

horizontal axis

A

(X)

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3
Q

Unrelated

A
  • two items that are not associated with one another
    examples:
  • -propagation speed and frequency
  • -wavelength and intensity
  • -frequency and intensity
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4
Q

Related or Proportional

A
  • two items are associated, can either be inverse or directly
  • Power ∝ Intensity
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5
Q

Inversely Related

A

when one item increases the other decreases
ex) frequency and period
wavelength and frequency
acoustic velocity (speed) and density

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6
Q

Reciprocal relationships

A

Inverse numbers multiplied to equal 1

Example = period and frequency

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7
Q

Metric system

A 
G giga, billion, 10^9
M mega, million, 10^6
k killo, thousand, 10^3
h hecto, hundred, 10^2
da deca, ten, 10^1
 #
d deci, tenth, 10^-1
c centi, hundredth, 10^-2
m milli, thousandth, 10^-3
u(mu) micro, millionth, 10^-6
n nano, billionth, 10^-9
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8
Q

Acoustic propagation properties

A

effects medium have on wave/ what happens when sound wave hits something

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9
Q

Biological effects

A

effects of sound wave upon the biologic tissue through which it passes (heat)

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10
Q

to be a sound wave…

A
  • mechanical - vibrate back and forth in fixed position
  • cannot travel through vacuum - must have medium
  • molecules must have compression and rarefaction
  • travel in straight, longitudinal line
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11
Q

transverse waves

A

particles more in perpendicular motions, up and down along the wave in right angles

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12
Q

longitudinal waves

A

sound waves

more left to right in same direction as sound propagation

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13
Q

acoustic variables

A

pressure - pascals (Pa)
density - concentration of mass in volume (kg/cm^3)
distance - measure of particle motion (cm,mm)

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14
Q

Out of phase

A

peaks and troughs at different times

correlate to destructive interference for a wave lower in amplitude

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15
Q

In phase

A

when peaks and troughs are at the same time and location

correlate to constructive interference for a wave length higher in amplitude

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16
Q

Acoustic parameters

A
  • sound wave features/characteristics
  • period, frequency amplitude, intensity, power
    wavelength, propagation speed
17
Q

Period - define, units, typical values, determination, adjustability

A
  • time for a wave to vibrate a single cycle
  • microseconds μs
  • 0.06 - 0.5 μs
  • sound source
  • no adjusting
18
Q

Frequency - define, units, typical values, determination, adjustability

A
  • number of cycles in a given time
  • hertz (same as saying X per second)
  • 2 - 15 MHz
  • sound source
  • no adjusting
19
Q

Infrasound

A

less than 20 Hz - inaudible

20
Q

Audible

A

20 - 20,000 Hz (20 kHz)

21
Q

Ultrasound/ ultrasonic

A

greater than 20 kHz (20,000 Hz) - too high for humans

22
Q

Relationship between Frequency & Period

A
  • INVERSE (means they are repricals)
  • Frequency increases - Period decreases
  • As Frequency decreases - Period increases
  • Frequency X Period = 1
23
Q

“Bigness” Parameters

A

Amplitude, Power, Intensity = strength of sound wave

24
Q

Amplitude - define, units, typical values, determination, adjustability

A
  • difference between the max and baseline value (or peak to peak, max and min)
  • any of acoustic variables (Pa, g/cm^3, cm)
  • 1MPa - 3MPa
  • sound source
  • Initially adjustable
25
Q

Power - define, units, typical values, determination, adjustability

A
  • Rate of energy transfer, strength of beam
  • Watts
  • 0.004 to 0.090 watts (4 - 90 milliwats)
  • sound source
  • Initially adjustable
26
Q

Power & Amp. relationship

A

Power/Intensity ∝ Amp^2

- If amp decreases by a factor of 2, power is decreased by factor of 4

27
Q

Intensity - define, units, typical values, determination, adjustability

A
  • Concentration of energy in beam
  • W/cm^2, watts from power and cm^2 from beam area
  • 0.01 to 300 W/cm^2
  • sound source
  • initially can change

(intensity) W/cm^2 = (power) W ÷ cm^2 ( area)

28
Q

Relationship in Bigness Parameters

A
  • Intensity ∝ Power

- if amp doubles then power & intensity will quadruple

29
Q

Wavelength - define, units, typical values, determination, adjustability

A
  • Distance/ length of one complete cycle
  • Any unit of length (cm, mm, m)
  • Soft tissue wavelength typically 0.1 to 0.8 mm
  • Sound source AND media
  • Not adjustable

wavelength (mm) = 1.54 mm/μs ÷ frequency (MHz)

30
Q

Wavelength & Frequency relationship

A

INVERSE

  • Higher freq. has shorter wavelengths = higher quality
  • Lower freq. has longer wavelengths
31
Q

Propagation Speed - define, units, typical values, determination, adjustability

A
  • Rate of which sound travels through medium
  • mm/μs, or any distance divided by time
  • 1540 m/s or 1.54 mm/μs
  • Medium only
  • Not adjustable

speed (m/s) = frequency (Hz) X wavelength (m)

32
Q

Speed of sound in order of lowest to highest

A

Air (lung), soft tissues, liver, bone

33
Q

Medium characteristics that determine speed propagation

A

Stiffness & Density

34
Q

Stiffness

A
  • Resists compression, maintains its shape
  • Bulk modulus
  • Directly related to speed
  • –Increases & speed of sound increases
35
Q

Density

A
  • Relative weight
  • Inversely related to speed
  • –Increases & speed reduces

DMS Physics (1st exam) (2 decks)

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