Properties of Sound Waves Flashcards
What is a transverse wave?
A wave where particles move perpendicular to the direction the wave propagates
What is a longitudinal wave?
A wave where particles move parallel to the direction the wave propagates
What is compression?
When wave molecules are squeezed together
What is rarefaction?
When wave molecules are stretched apart
What is pressure?
The concentration of force in a certain area
What is density?
The mass concentration in a volume
What are the seven acoustic parameters?
Period, frequency, amplitude, power, intensity, wavelength, and propagation speed.
What is constructive interference?
When in-phase waves combine to form one larger wave with a higher amplitude than either component wave
What is destructive interference?
When out-of-phase waves combine to form one wave smaller and with less amplitude than at least one component
What is period?
The time it takes for the wave to complete one full cycle
What determines period?
Sound source
What is frequency?
The number of particular events that occur in a specific amount of time
US = (cycles per second)
What determines frequency?
Sound source
How are period and frequency related?
Inversely related
Reciprocals
What is the frequency of infrasound?
< 20Hz
What is the frequency of ultrasound?
> 20,000 Hz
> 20 kHz
What is the frequency of audible sound?
between 20Hz and 20,000Hz
What are hertz (Hz)?
Units per second
What is amplitude?
Difference between an acoustic variable’s maximum value and average value
What determines amplitude?
Initially sound source;
Decreases as sound moves through the body
What is power?
The rate at which energy is transferred or work is performed
How are power and amplitude related?
Power is proportional to amplitude squared
Power increases by 2, amplitude increases by 4
What is intensity?
Energy concentration in a sound beam
What is the formula for intensity?
Intensity = beam power/area
How are intensity and power related?
Intensity is proportional to power.
Power is doubled, intensity is doubled
How are intensity and amplitude related?
Intensity is proportional to amplitude squared.
Amplitude doubled, intensity quadrupled
What is wavelength?
The distance of one cycle
What is the formula for wavelength?
Wavelength = propagation speed/frequency
Unit is in length
What determines wavelength?
The source and medium
How are wavelength and frequency related?
Inversely
As frequency increases, wavelength decreases
What is propagation speed?
The rate at which a sound wave travels through a specific medium
What determines propagation speed?
The medium
What is the speed of sound in soft tissue?
1540 m/s
1.54 mm/us
What is stiffness?
An object’s ability to resist compression
How does stiffness affect speed?
Directly related
The stiffer the material, the faster the sound
What is density?
The relative weight of a material
How does density affect speed?
Inversely
The denser the object, the slower the speed
What is bulk modulus?
Synonym for stiffness
Does stiffness or density have a greater effect on speed?
Stiffness
How does sound speed compare through different mediums?
Fastest through solids, slower through liquids, slowest through gases.
