Chapter 3: describing sound waves Flashcards by Emily Espinoza

Define Parameters

describe features of a sound wave.

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what the seven paramets are used for?

they are values used to characterize a sound wave

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list the seven parameters

PERIOD
FREQUENCY
INTENSITY
POWER
AMPLITUDE
WAVELENGTH
PROPAGATION SPEED

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PETER
FELL
IN
PRACTICE
AFTER
WAVING
(AT) SALLY

PERIOD
FREQUENCY
INTENSITY
POWER
AMPLITUDE
WAVELENGTH
SPEED

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source

the transducer and the ultrasound system

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medium

soft tissue

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period

Define

the time it takes a wave to vibrate a single cycle.

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the time from the start of one cycle to the start of the next.

period

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Units for period

time (seconds,microseconds

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what is period determined by?

the sound source only

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is period adjustable?

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What are the seven acoustic parameters?

Frequency
period,
wavelength,
propagation of speed,
intensity,
amplitude
and power.

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Frequency

the number of events that occur in a specific duration of time

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in diagnostic ultrasound, the frequency of a wave is described as

the number of cycles that occur in one second

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Unit for frequency

per seconds, 1/second, hertz, Hz

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Hertz is another way to say

per second

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Is frequency adjustable?

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what is frequency determined by?

the sound source only

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frequency for infrasound

less than 20 Hz

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frequency for ultrasound

greater than 20 kHz or 20,000 Hz

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frequency for audible

Between 20Hz and 20 kHz

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frequency for diagnostic ultrasound

1MHz to 20MHz

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Why is frequency important?

It affects the penetration and image quality

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What is the relationship between period and frequency?

Period and frequency are inversely related to each other

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As frequency increases, period____

decreases

As frequency decreases, period____

increases

Period and Frequency have a special relationship called....

Reciprocal

Formula for period and frequency

period x frequency =1

A wave takes up 1/8 of a second to vibrate up and down. What is the period and the frequency?

Period = 1/8 Frequency = 8 1/8x8=1`

The higher the frequency

the lower the period

which of the following waves is infrasonic? 4 Mhz 400 kHz 28 Hz 2 Hz

2 Hz less than 20Hz cannot be heard

which wave is ultrasonic? 400 mHz 4 MHz 28 Hz 2 Hz

4 MHz greater than 20kHz cannot be heard

indetify all which are audiable 4 MHz 400 kHz 28 Hz 2 Hz

4 MHz, 400kHz,2 Hz are all audiable

which of the following has the longest period 2MHz 4,000 Hz 6 Hz 1 kHz

6Hz

which has the highest frequency 8 s 80 µseconds 8 Ms 8000 ks

8 µseconds

The three bigness parameters

IPA intensity power amplitude

Three parameters used to describe the size, magnitude, or strength of a sound wave

the three bigness parameters, Intensity, power, amplitude

define amplitude

The difference between the maximum value and the average value of an acoustic variable

which parameter defines the "bigness" of a wave

amplitude

Units for amplitude

decibels (dB) any units associated with acoustic variables -pressure; pascals (pa) -density; grams/cubic cm -particle motion; units of distance

what is amplitude determined by?

sound source

is amplitude adjustable?

Yes!

what is the difference between amplitude and peak-to-peak amplitude

amplitude is measured by the MIDDLE or UNDISTURBED, value to the maximum value

Peak-to-peak amplitude

the difference between maximum and minimum values of an acoustic variable, (twice the value of amplitude)

Power

the rate of energy transferor rate at which work is performed

power is like what other parameter? in what sense?

power is like amplitude. they both describe the "bigness" of a wave

units for power

Watts or (W)

is power adjustable?

Yes!

what is power determined by?

They are determined by the sound source`

how are power and amplitude related?

both amplitude and power describe the size or magnitude of a wave.

when power increases..... amplitude

increases

Power is proportional to the waves amplitude squared

power ∝ amplitude^2

what relationship does power and amplitude have

the are directly proportional

what happens to power if amp^2 is increased by a factor of 3

power is increased by a power of 9

what happens to power if amp^2 is decreased by a factor of 2

power is decreased by a power of 4

Intensity

The concentration of energy in a sound beam

units for Intensity

W/cm^2

what is intensity determined by?

Source

Is intensity adjustable?

Yes!

intensity relates

to how the power in a wave is spread or is distributed in a space, therefore making it dependent on power and area

Intensity is proportional to

power

Intensity (W/cm^2)=

power (w)/ area (cm^2)

intensity is proportional to

amplitude ^2

what happens to intensity if a waves power is doubled?

Intensity is also doubled

what three parameters tend to be directly related

intensity, power, and amplitude

what happens to intensity when a waves amplitude^2 is doubled

the intensity increases four times its original value.

Wavelength

The distance or length of one complete cycle

unit for wavelength

length (mm,meters,inches,feet...)

what is wavelength determined by?

source and the medium

true or false? is wavelength the only parameter determined by both source and the medium

true

is wavelength adjustable?

λ = c/f

wavelength (mm) = propagation speed (µs)/frequency (MHz

What is the difference between period and wavelength

-period refers to the TIME it takes to complete a single cycle -wavelength refers to the LENGTH or DISTANCE of a single cycle

What is the relationship between wavelength and frequency?

wavelength and frequency are INVERSELY related. As f increases w decreases.

the lower the frequency ... (wl)

the longer the wavelength

If a waves frequency is twice that of another

wavelength will be half as much

what is the wavelength of 1MHz in soft tissue?

1.54 mm

to find the wavelength in soft tissue

divide 1.54 mm by the frequency in MHz

why is wavelength important in diagnostic imaging?

shorter wavelengths are created by high frequency; resulting in higher quality images with greater detail

Propagation Speed

the rate at which sound travels through a medium

what is the unit for speed?

m/s or mm/s

what is speed determined by?

the medium ONLY

is speed adjustable?

what is the speed of sound in soft tissue?

1,540 m/s or1.54 mm/s or 1.54 km/s

list the speed of sound in biologic tissue

-lung -fat SOFT TISSUE -liver -blood -muscle -tendon -bone

order of sound traveling fastest to slowest

solids>liquids>gases

formula for speed

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

two characteristics that affect speed

-stiffness (bulk modulus) :how squishy something is -density; object weight/mass

what relationship do stiffness and speed have

direct relationship

the opposite of stiffness

elasticity and compressability

what relationship do density and speed have?

they are inversely related

Chapter 3: describing sound waves Flashcards

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