Frequency
of wave cycle in a second
Frequency units
Hz
Infrasound
<20hz
Audible
20hz to 20000 hz
Ultrasound
> 20000hz
Imaging frequency
2 MHz to 10 MHz
Frequency determined by
Source
Frequency affects the depth of penetration
Increase frequency
Decrease depth
Frequency improves axial resolution by
Decreasing wavelength, spl length, period and pulse duration
Increasing Frequency improves lateral resolution by
Extending the near zone, decreasing be diameter and angle divergence