Absorption is a key concept in understanding the interaction of ultrasound with biological tissues, particularly in the context of safety.

Here's what you need to know about absorption:

* **Definition:** Absorption is one of the three components of attenuation, where sound energy is converted into heat energy as it travels through a medium.
* **Role in Attenuation:** Attenuation refers to the reduction in the intensity, power, and amplitude of sound waves as they propagate through a medium. Absorption contributes to this reduction, alongside scattering and reflection. The amount of attenuation, and thus absorption, increases with higher frequency and longer path length.
* **Thermal Bioeffect:** The absorption of ultrasound waves by biological tissues leads to an increase in temperature, which is known as the thermal effect. This is a potential bioeffect of ultrasound. Localized hot spots can also be caused by Rayleigh scattering, which might lead to thermal injury.
* **Tissue Variability:** The degree of absorption varies depending on the medium through which the sound wave travels.
* Air has significantly more attenuation than soft tissue.
* Bone and lung also have more attenuation than soft tissue due to absorption and reflection, respectively.
* Water exhibits much less attenuation than soft tissue.
* In blood, the attenuation of sound is approximately equal to that in soft tissue.