Acoustic Impedance
Attenuation is the loss of energy from the ultrasound beam as it travels through tissue layers. Attenuation is determined by the acoustic impedance of the tissue being imaged. The variation between diverse tissues can be enormous, as shown in the table below.
| Material |
Speed of sound (m/s) |
Density (Kg/m3/103) |
Acoustic Imp Z (kg/m2/s)/106 |
| Air | 330 | 1.2 | 0.0004 |
| Water | 1480 | 1000 | 1.48 |
| Steel | 5000 | 7800 | 39.0 |
| Blood | 1575 | 1057 | 1.62 |
| Fat | 1459 | 952 | 1.38 |
| Muscle | 1580 | 1080 | 1.7 |
| Bone | 4080 | 1912 | 7.8 |
Reflection coefficient:
