Chapter 3: Describing Sound Waves Flashcards
Sound Wave Parameters
features of a sound wave
Examples of sound wave parameters
-speed
-period
-frequency
-amplitude
-power
-intensity
-wavelength
Frequency
-affects penetration and image quality
-measured in hertz (Hz)
-“cycles per second”
Cycle
Compression
_______________
Rarefaction
Period
-time it takes to complete a single cycle
-PERIOD and FREQUENCY are INVERSELY related
-if one remains constant, the other remains unchanged
Period and frequency are reciprocals
Ex:
8 Hz = 1/8 period
4 Hz= 1/4 period
6 Hz= 1/6 period
9 Hz= 1/9 period
Wavelength
-measured in units of length: mm, meters,etc.
-distance of a single cycle
-inversely related to frequency
-shorter wavelengths= high frequency
THREE “BIGNESS” Parameters
-size, magnitude or strength of a sound wave:
-amplitude
-power
-intensity
Amplitude
“BIGNESS” of a wave
-difference between the minimum and average value of acoustic variable
-difference between the maximum and average value of acoustic variable
(measured from the baseline to the maximum or from the baseline to the minimum)
Facts about amplitude
-determined by sound source initially
-decreases as sound propagates
peak-to-peak amplitude
-difference between maximum and minimum values of an acoustic variable
-twice the value of the amplitude
Power
-rate of energy transfer
-rate at which work is performed
-also describes the “bigness” of a wave
-if power ^, then so does amplitude
-direct relationship
Facts about Power
-determined by sound source initially
-decreases as sound propagates
-expressed in watts (W)
Intensity
-concentration of energy in a sound beam
- describes “bigness” of a wave
-relates to how the wave power spreads in space
- W/cm^2
-changes as sound propagates through body
* WHEN INTENSITY INCREASES, POWER AND AMPLITUDE ALSO INCREASE*
Propagation Speed
-rate at which sound travels through a medium
- m/s
- distance/time
-depends on the medium
Propogation speed and medium
-All sound travels through a specific medium at a specific speed
- Speed of sound changes only when the medium is different
Characteristics of a medium that affect the sound
-Stiffness
-Density
Stiffness
-Ability of an object to resist compression
-Directly related to speed
-Elasticity and compressibility are the opposite of stiffness
Density
-Relative weight of a material
-Inversely related to speed
-Sound travels faster in media with low density
Single Mediums
All Acoustic waves, even those with different frequencies, travel at the same speed within a single medium
