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Important characteristics of sound waves that influence sonography.
Key Wave Properties
Sound waves with frequencies above the human hearing range, used in medical imaging.
Ultrasound
A branch of physics that studies sound and sound waves.
Acoustics
2 ways to define sound
Experiential and Physical
Sound as perceived through the human auditory system.
Experiential
Propagation of pressure variations through a medium from a sound source to a listener.
Physical
A form of energy causing mechanical disturbances through molecular vibrations in a medium.
Sound
Also refers to mechanical wave that travels to a medium
Sound
A type of mechanical wave where molecules vibrate parallel to the direction of wave travel.
Longitudinal or Compressed Wave
A type of mechanical wave where molecules vibrate perpendicular to the direction of the wave propagation.
Transverse or Shear wave
True or False. Sound does not require a medium with molecules to travel and cannot propagate through a vacuum.
False
Acoustic Variables includes
pressure, density, and particle motion that characterize sound.
A sound wave that travels in a sinusoidal form.
Ultrasound Wave
A type of ultrasound wave characterized by compression and rarefaction.
Longitudinal Wave
Regions of high pressure in a sound wave.
Compression
Regions of low pressure in a sound wave.
Rarefaction
The number of cycles per second, measured in Hertz (Hz)
Frequency
Ultrasound Imaging Frequency Range
2-20 MHz
Relationship of Frequency and Resolution
Lower frequency allows for higher penetration but lower resolution. (Direct with Resolution, Inverse with Penetration)
The time taken for a sound wave to complete one cycle, measured in seconds or microseconds.
Period (T)
Period Formula
Period= 1/Frequency (MHz)
Relationship of Frequency and Period
Frequency Increases, Period Decreases (Inverse)
The distance over which one cycle of a sound wave occurs. It is also the length of cycle.
Wavelength
The speed at which a sound wave travels through a medium (cm/sec), is influenced by density and stiffness or elasticity.
Propagation Velocity
Propagation velocity of Soft tissue
1540
Propagation velocity of Bone
4080
Propagation Velocity slowest in?
Air/Gas
Propagation Velocity Fastest in?
Solids
Propagation Velocity Formula
Velocity=wavelength x frequency
The strength or intensity of a sound wave affects image brightness in ultrasound. It is also the wave's height and the image's brightness.
Amplitude
Relationship of amplitude with brightness of the image
Amplitude Increases, Brightness of an image Increases (Direct)
Relationship of amplitude with Depth
Amplitude Decreases, Depth Increases (Inverse)
The rate at which energy is transmitted into the body, measured in watts (W). It varies over Time and Space.
Power (energy)
Unit of Power (energy)
W, mW
Unit of Frequency
Hertz (Hz)
Unit of Period (T)
sec, ms, us
Intensity of sound measures in
bel or decibel (dB)
The amount of energy passing through a specified area per second.
Intensity (energy per second)
True or False. Intensity of wave is proportional to the amplitude of the wave square.
True
The amount of force applied over a specific area, measured in Pascals (Pa), Megapascal.
Pressure
Relationship of pressure or force and volume of sound waves or intensity
Directly Proportional because these two deals with power
Relationship of pressure and Area
Inversely Proportional
