Section 2: Physics of Ultrasound

The Decibel
The equation used to describe the difference in intensity between two
ultrasonic or other sound measurements is:
where: ∆I is the difference in sound intensity expressed in decibels (dB), P1
and P2 are two different sound pressure measurements, and the log is to
base 10.
What exactly is a decibel?
The decibel (dB) is one tenth of a Bel, which is a unit of measure that was
developed by engineers at Bell Telephone Laboratories and named for
Alexander Graham Bell. The dB is a logarithmic unit that describes a ratio of
two measurements. The basic equation that describes the difference in
decibels between two measurements is: