is the length of time that it takes to complete a single cycle.
the number of certain events that occur in a specific duration of time. The frequency of a wave is the number of vibrations that a molecule in it makes per second or the number of times the cycle is repeated per second.
relates to the strength of the sound wave. Amplitude describes the magnitude of a wave. Amplitude is the maximum variation of a variable from its mean value.
relates to the strength of the sound wave. It is the rate in which work is performed or energy is transferred from the entire sound beam.
relates to the strength of the sound beam. It is the concentration of energy in a sound beam.
the distance or length that one complete cycle occupies: the cycle length.
the speed at which sound moves through a medium -- also called sound's speed, velocity of sound, or acoustic velocity.
Three parameters relate to the strength of a sound wave. They are:
• Amplitude dB Magnitude (volume) • Power Watts Work • Intensity Watts/cm2 Work per unit area
• period (sec) x frequency (Hz) = 1 • period (sec) = 1 / frequency (Hz)• frequency (Hz) = 1 / period (sec)• Remember to use complementary units for period and frequency; such as sec & Hz, or msec & kHz.
• Power is proportional to the amplitude squared.• Intensity is proportional to the amplitude squared.• Power is proportional to intensity.
• Wavelength is inversely related to frequency.o Higher frequency waves have shorter wavelengths.o Lower frequency waves have longer wavelengths.• Shorter wavelengths generally produce higher quality images. This explains why higher frequency transducers create better quality clinical images.
Propagation speed/wavelength Relationship
• This means that sound with a frequency of 3 MHz will travel with different speeds in different mediums. If the acoustic velocity is high in a medium the sound will have a higher speed and travel a greater distance. (this will be an increased wavelength)• If the acoustic velocity is slow in a medium the sound will travel at a lower speed and travel less distance. (this will be a decreased wavelength)
Propagation Speed (Units)
0.004 to .090 watts (4 to 90 mwatts)
0.01 mW/cm2 to 300 W/cm2
Propagation Speed (normal)
1.54 km/s1,540 m/s1.54 mm/us
Determined by Source
Period, Frequency, Power, Amplitude, Intensity
Determined by Source and medium
Determined by medium
Cannot be changed by user
Wavelength, Propagation Speed, Period
Can be changed by user
Can be changed only if transducer is changed
Can be changed after its initial presentation
Propagation Speed (measure)
Longer period lower pitch
determined by the period of a single cycle in the wave.
decreases as sound propagates through the body.
decreases as ultrasound travels through the body.
decreases as ultrasound propagates through the body
detail that is displayed in an image is substantially influenced by wavelength because wavelength determines longitudinal resolution.