Math, Sound, Parameters Flashcards
Unrelated
Two unassociated items
Related/proportional
Unspecific affiliation
Directly related or directly proportional
Two items that are associated
- when one increases, the other increases
Inversely related or inversely proportional
Two items that are opposingly associated
- when one increases, the other decreases
Reciprocal relation
Form of inverse relationship, when two items are multiplied together they equal 1
Ex. 2 and 1/2, 10 and 1/10
A positive exponent is
Greater than 10
A negative exponent is
Less than 1
Giga
10^9, G
Mega
10^6, M
Kilo
10^3, k
Hecto
10^2, h
Deca
10^1, da
Deci
10^-1, d
Centi
10^-2, c
Milli
10^-3, m
Micro
10^-6
Nano
10^-9, n
How are ultrasound images produced?
Transducer sends sound waves through media, reflections from boundaries between structures return and create images
What kind of waves are sound waves?
Mechanical
What is a mechanical wave?
Particles in the medium move
What is rarefaction?
Stretching apart of the molecules
What direction do soundwaves travel? What is the type of wave called?
Travel in a straight line, never backwards
They are longitudinal
What is a longitudinal wave?
The particles in the medium squeeze together and stretch apart as sound wave passes through
Peaks are compression, rarefaction is trough
What are acoustic propagation properties?
Effects of the medium upon the sound wave
What are biologic effects?
Effects of the sound wave upon tissue that it passes through
What three factors distinguish a sound wave?
Pressure, density, distance
What is pressure?
Concentration of a force in an area, unit pascals
What is density?
Concentration of mass in a volume, unit kg/m^3, g/cm^3
What is distance?
Measure of particle motion
What are the seven acoustic parameters?
- period
- frequency
- amplitude
- power
- intensity
- wavelength
- propagation speed
What is period? Unit? Value range? Controlled by? Adjustable?
- amount of time for wave to vibrate one cycle
- unit: time
- range: 0.06-0.5 microseconds
- controlled by source
- not adjustable
What is frequency? Unit? Value range? Controlled by? Adjustable?
- number of wave cycles that occur within 1 second
- units: units/second Hz
- range: 2-15MHz
- source
- not adjustable
What is infrasound?
Frequency less than 20 Hz
What is audible sound?
Frequency between 20 Hz-20 kHz
What is ultrasound?
Frequency greater than 20 kHz
What is the relationship between period and frequency?
Inverse, reciprocal
When frequency increases, period decreases
What is 1 hertz?
1cycle/second
If a wave has a period of 1/8 s, what is the frequency?
8 Hz
What are the 3 bigness parameters?
Amplitude, power, intensity
Describe magnitude
What is amplitude? Unit? Value range? Controlled by? Adjustable?
- difference between max or min value and the average, scale size of wave
- unit: pascal, density, distance, dB
- range: 1MPa-3 MPa
- controlled by source
- can be initially adjusted
What happens to amplitude as sound propagates?
It decreases depending on wave and medium characteristics
What is power? Unit? Value range? Controlled by? Adjustable?
- rate of energy transfer
- units: watts
- range: 4-90 milliwatts
- controlled by source
- initially adjustable
What happens to amplitude when power increases
Amplitude increases
Power is proportional to
Amplitude^2
What is intensity? Unit? Value range? Controlled by? Adjustable?
- Concentration of energy in a sound beam
- unit: watts/cm^2
- range: 0.01-300 w/cm^2
- controlled by source
- initially adjustable
Intensity is proportional to
Power and amplitude^2
What is wavelength? Unit? Value range? Controlled by? Adjustable?
- distance or length of one complete cycle
- units: length
- range: 0.1-0.8 mm
- controlled by source and medium
- not adjustable
Wavelength is the only parameter that is
Controlled by both source and medium
What is the difference between wavelength and period?
Wavelength is the distance of 1 cycle, period is the time to complete 1 cycle
What is the relation between wavelength and frequency?
Inverse
When frequency increases, wavelength decreases
What is the wavelength of sound with a frequency of 1 MHz in soft tissue?
1.54 mm
How do you find the wavelength of a sound wave?
1.54 mm/microsecond divided by frequency
What is an in-phase wave?
Peaks and troughs of two waves occur at same time and same location
What is an out-of-phase wave?
Peaks and troughs occur at different times
What is interference?
Multiple sound beams arrive at the same location at the same time and combine to form one wave
What is constructive interference?
In-phase waves form one wave with greater amplitude
What is destructive interference?
Out-of-phase waves form one wave with lesser amplitude
What is complete destructive interference?
Two out of phase waves with equal amplitude cancel each other out
What kind of interference happens to waves with different frequencies?
They are in and out of phase at different times so both constructive and destructive interference occur
What is propagation speed? Unit? Value range? Controlled by? Adjustable?
- rate that sound wave travels through a medium
- units: distance/time
- range: 500-4000 m/s
- controlled by medium
What is the propagation speed of sound in soft tissue?
1540 m/s
How do you calculate speed?
Frequency x wavelength
What is stiffness? How does it affect speed?
- the ability of an object to resist compression
- stiffer material = faster speed
What is density? How does it affect speed?
- relative weight of a material
- inverse relation
- denser material = decreased speed
If two media are equally stiff, the denser medium has a ______ speed.
Lower
What allows sound to travel fastest?
Stiff and not dense medium ex. Bone
What causes speed to travel at the slowest speed?
Not stiff and very dense medium
What has the biggest influence on speed?
Stiffness
