A decibel, abbreviated dB, is a logarithmic unit used to express the ratio between two sound intensities. In ultrasound, decibels are used to describe how much the sound beam weakens as it travels through tissue (attenuation), how much the signal is amplified by the machine’s gain controls, and the relative strength of echoes returning from different tissues. Because the decibel scale is logarithmic, every 3 dB increase represents a doubling of sound intensity, and every 10 dB increase represents a tenfold increase. Understanding decibels helps sonography students grasp how the ultrasound machine processes and displays the signals it receives.
Sonography Term