Describing Sound Waves Flashcards
What are parameters?
They describe features of a sound wave.
What are the seven parameters?
- Period
- Frequency
- Propagation speed
- Wavelength
- Amplitude
- Power
- Intensity
What is a period?
It is the time it takes a wave to complete a single cycle.
What units is period reported in?
Units of time.
What is the period determined by?
Determined by the sound source only.
Is the period adjustable?
No.
What is frequency?
It is the number of events that occur in a specific duration of time.
The number of cycles that occurs in one second.
What unit is frequency reported in?
Reported in units of per second.
What is frequency determined by?
adjustable?
It is determined by the sound source only and it is not adjustable.
What is considered below the threshold of human hearing?
A frequency of a sound wave less than 20 Hz.
What is the name for sound waves that have a frequency lower than 20 Hz?
Infrasound.
What frequency range can humans hear?
Between 20 Hz and 20,000 Hz
Why is frequnecy important in diagnostic sonography?
It is important because it affects the penetration and image quality.
What is the relationship between frequency and period?
Inversely related.
What is the equation for period?
Period= 1/F
What frequency is audible?
Between 20 Hz and 20 kHz
What frequency is ultrasound?
Greater than 20 kHz
What are the 3 “bigness” parameters that describe the size, magnitude, or strength of a sound wave?
- Amplitude
- Power
- Intensity
What is amplitude?
It is the bigness of a wave.
What is the amplitude determined by?
It is determined by the sound source only.
What happens to amplitude as it travels through a medium?
It decreases as sound propagates.
Is amplitude adjustable?
Yes.
What is power?
It is the rate at which work is performed.
What is power determined by?
It is determined by the sound source only.
What happens to power as ir travels through the body?
Like amplitude, it decreases as sound propagates through the body.
Is power adjustable?
Yes.
How are power and amplitude related?
Directly related.
Power ≈ amplitude2
What is intensity?
It is the concentration of energy in a sound beam.
How do you calculate intensity?
Divide the the beams power by the beam’s area.
intensity (W/cm2)=Power (w)/area (cm2)
What does intensity relate to?
It relates to how the power in a wave spreads or is distributed in space.
What is the unit of intensity?
W/cm2
What is whats determined by?
initial intensity is determined by the sound source only.
Is intensity adjustable?
Yes.
How is intensity related to power?
It is directly proportional.
How is intensity related to power?
It is directly proportional to the waves amplituded squared.
What is wavelength?
It is the distance of one complete cycle.
What is the unit of wavelength?
It is measured in units of length.
What is the wavelength determined by?
Both sound source and medium.
Can wavelength be adjusted?
No.
What is the only parameter that is determined by both the sound source and medium?
Wavelength.
What is the relationship between wavelength and frequency?
Inversely related
What is the wavelength of 1 MHz sound in soft tissue?
1.54mm
What is the equation for wavelength?
wavelength (mm)= 1.54 (mm/us) / frequency (MHz)
What type of wavelength creates a better and clearer image?
Shorter wavelength because it is created by higher frequencies.
What is propagation speed?
It is the rate at which a sound wave travels through a medium.
What is the unit of speed?
It is measured in used of distance/time
What is speed determined by?
Speed is determined by the medium.
Can speed be adjusted?
No.
What is the speed of sound in soft tissues?
1540 m/s
What is the equation for speed?
Speed (m/s)= frequency (Hz) x wavelength (mm)
What characteristics of a medium determine the speed of sound in that medium?
stiffness and density.
What is stiffness?
It is the ability of an object to resist compression.
How does stiffness affect speed?
They are directly related.
*As materials become stiffer, the speed of sound in the material increases.
What is density?
Describes the weight of a material.
How does density affect speed?
Density and speed are inversely related.
* As materials become more dense, the speed of sound decreases.
