Sound waves Flashcards
Sound
Experential or physical
Experential sound
What we hear with our human auditory system
Physical sound
What travels from the source of the sound of the listener
Infrasound
Sound waves of less than 20Hz
Audible sound
Frequency between 20Hz and 20kHz
Ultrasound
Sound waves greater than 20kHz
Use of ultrasound
Diagnostic sonography uses ultrasound to produce images of anatomy, motion and flow
Transducer
Source of the sound waves
Tissue
Medium through which the sound travels
Sound
A traveling variation in pressure, when the speaker speaks variation in pressure are produced in the throat and mouth. These pressure variation travel through the air to the listener where they stimulate the auditory response in the ear and brain.
The acoustic variables
Pressure
Density
Distance
It is a sound wave when…
One of these acoustic variables have rhythmic oscillations
Wave
A traveling variation in one or more quantities called variables.
Pressure
Variation in soun waves cause the particles of the medium to vibrate back and forth
Acoustic variables becuase of quantities vary in sound wave
Density
The concentration of matter. Acoustic variables because of quantities that vary sound waves.
Rarefraction
Regions of low pressure and density
Compression
Regionscof high pressure and density
Longitudinal wave
A mechanical, compressional wave in which back and forth particle motion is parallel to the direction of the wave eg. sound wave
Transverse waves
Particles move in a direction perpendicular to the direction of that the wave propagates. Involves no particular motion.
Sound wave characteristics
- The molecules in the medium vibrate back and forth in a fixed position.
- cannot travel through a vacuum
- Sound molecules are compressed and rarefied
- travels in a straight line
- longitudinal
In phase
Pair of waves when their peaks occur at the same time and the troughs, at the same location
Out phase
Pair waves when their peaks and troughs occur at different times
Interference
The waves lose their individual characteristics at that moment and combine to form a single wave.
Constructive interference
Pair of in phase waves results in the formation of a single wave or greater amplitudes than either of its components
Deconstructive interference
Pair out of phase waves results in the formation of a single wave of lesser amplitude than either of its components
Sound wave parameters
- Period
- Frequency
- Amplitude
- Power
- Intensity
- Wavelength
- Speed
Period
The time it takes to generate a single wave cycle
Determined by the sound source, not adjustable
Frequency
The number of wave cycles that occur in a second. Has an impact on resolutions and penetration images. Not controlled by medium. Not adjustable.
Bigness parameters
Parameters that describe the size, magnitude of the wave.
Amplitude, power, intensity
Amplitude
Size/magnitude/ straight of the wave.
Difference between the max value and the average of an acoustic variable. Determined by the source and adjustable
Power
The rate of energy transfer, describes the bigness of the wave. Decreases as the sound propagates depending on the characteristics of the medium. Is adjustable.
Intensity
The concentration of energy in the sound beam. How the power I spread or distributed in space. Depends on the power of the beam and the area over which the power is applied.
Wavelength
The distance of one complete cycle.
Shorter wavelength = higher quality image
= high frequency transducer
Propagation of speed
The distance that a sound wave travels through a medium in 1 sec.
Stiffness
The ability of an object to resist compression
Density
The relative weight of an material
Speed and medium characteristics
If two media are equally stiff, the denser medium will, have a lower speed
