physics exam 1 study guide

What kind of wave is a sound wave?

mechanical

What do waves do?

carry energy from one location to another

sound waves travel in…

a medium

how do sound waves travel?

in a straight line

Are sound waves transverse or longitudinal?

longitudinal

Acoustic variables (3)

pressure, density, distance

Acoustic parameters (7)

period
frequency
amplitude
power
intensity
wavelength
propagation speed

Transverse waves move…

in perpendicular direction that the wave propagates

longitudinal waves move…

in the same direction the wave propagates

What happens with interference of two waves?

waves will combine into one single wave
individual characteristics of the wave will be lost

constructive interference

in phase waves combine to create a wave of greater amplitude

destructive interference

out of phase waves combine to create wave of lesser amplitude

constructive + destructive interference

both will occur

period definition?

time it takes for a single cycle

period is determined by?

sound source only

is period adjustable?

No

period has units of…

time

frequency definition

number of cycles in a duration of time

frequency is in units of…

Hz

frequency is determined by…

sound source only

is frequency adjustable?

No

Infrasound range

<20 Hz

Audible sound range

20-20k Hz

Ultrasound range

>20 kHz

period and frequency relationship

inversely related
reciprocal

Three bigness parameters of sound

amplitude
power
intensity

amplitude definition

difference between min/max value of an acoustic variable

amplitude units

any acoustic variable

amplitude is determined by…

sound source

Is amplitude adjustable?

Yes, it is adjustable.

Power definition

rate of energy transfer
rate at which work is performed

power units

watts

power is determined by…

sound source

Is power adjustable?

Yes

Power and amplitude are….

power is directly proportional to amp2

Intensity definition

concentration of energy in a sound beam

intensity units

watts/cm2

intensity is determined by…

sound source

is intensity adjustable?

Yes

Intensity formula

Intensity = power/area

intensity and power are…

directly proportional

intensity and amplitude are…

intensity directly proportional to amp2

wavelength definition

distance of one complete cycle

wavelength is in units of…

distance

wavelength is determined by…

both sound source and medium

Is wavelength adjustable?

No

1 MHz in soft tissue equals…

1.54 mm of wavelength

wavelength and frequency are…

inversely related

Wavelength formula

c/f

wavelength formula in soft tissue

1.54 mm/frequency

Propagation speed

rate at which a sound wave travels through a medium

propagation speed is determined by…

medium

is propagation speed adjustable?

No

Propagation speed formula

c = wavelength/freq

speed of sound in soft tissue

1540 m/s

What characteristics determine the speed of sound?

stiffness, density

stiffness and density are…

directly related

density and speed are…

inversely related

is density or stiffness more important for propagation speed?

stiffness

pulse definition

collection of cycles that travel together

two components of pulsed ultrasound?

transmit time and receiving time

pulse duration PD definition

time from start of pulse to end of pulse

pulse duration PD determined by?

sound source

is pulse duration adjustable?

No

Pulse duration formula

number cycles x period or number cycles/freq

pulse duration, number of cycles, and period are

directly related

pulse duration and frequency are…

inversely related

what kind of pulse duration is better for ultrasound?

shorter

spatial pulse length SPL definition

distance from start to end of a pulse

spatial pulse length SPL determined by…

sound source and medium

is SPL adjustable?

No

SPL formula

SPL = number of cycles x wavelength

SPL, number of cycles, and wavelength are…

directly proportional

A long SPL has…

many cycles in a pulse

In a long SPL, the individual cycles will have a ______ wavelength.

longer

A short SPL has…

few cycles in a pulse

In a short SPL, there are individual cycles with a _______ wavelength

shorter

Pulse repetition period PRP definition

time from start of one pulse to start of next pulse, includes listening time

PRP and period are…

unrelated

PRP is related to…

imaging depth

PRP is composed of…

transmit time, PD
receive time

How does PRP change when the depth becomes shallower?

PRP shortens

How does PRP change when the depth becomes deeper?

PRP lengthens

pulse repetition frequency PRF definition

number of pulses transmitted into the body each second

PRF determined by…

sound source, imaging depth

Is PRF adjustable?

Yes

PRF and frequency are…

unrelated

PRF and depth are…

inversely proportional

PRP and PRF are…

inversely proportional, reciprocal

Duty factor definition

percentage of time that a system transmits a pulse

Duty factor is determined by…

sound source

Is duty factor adjustable?

Yes, because you can adjust depth

Duty factor and depth are…

inversely proportional

Duty factor formula

PD/PRP x 100

Duty factor and PD are…

directly proportional

Duty factor and PRP are…

inversely proportional

Intensity: spatial definition

distance/space

Intensity: peak definition

max value

Intensity: average definition

mathematical middle value

Intensity: temporal definition

all time, transmit and receive time