Defining Ultrasound:
Audible 20Hz and 20 000Hz.
Infra sound Below 20Hz
Ultrasound Above 20 000Hz
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When an ultrasound wave passes through tissues:
- Attenuation: Reduction in amplitude and intensity of wave
- Refraction: Change in direction & velocity of wave
Attenuation is the rate at which intensity wave diminishes with the depth it covers or its penetration.
3 Types:
- Reflection.
- Scattering
- Absorption: the main form of attenuation - loss of sound energy occurs and heat is produced
Affecting attenuation:
- Frequency of wave - Higher the frequency, higher the attenuation and less penetration of the wave
- Type of tissue the wave is traveling
- Depth the wave travels - more distance wave has to travel the more energy is lost.
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