Decibels are one of the most confusing units of measurement that we use. It’s not like other measurements in that it stays the same every time. It’s not a set size or distance .

The thing you must understand is that a Decibel is a relationship between two values of power.

Generally the numbers that are being compared are of a vastly different magnitude.
Think of human hearing. You can hear your finger brush a paper as well as a gunshot. To compare the sounds to one another would be like comparing the softest audible sound (0.000000000001 watt/m2) to a sound that will actually cause pain in your ear (1 watt/m2).
The numbers are so far apart that we need a way to compare them that is easily understood. This is where Decibels come in.
If a sound is 10 times more powerful (10dB) than the original sound it sounds twice as loud. If we only double the power (3dB), the change might not even be noticeable.
Decibels are a generally a ratio between units of power, intensity or amplitude.


Deci-bell     If the decibel is positive then the unit is increasing. 3dB means twice as big.

  •      6dB = 2 x 2 = 4X the original
  •      9dB = 2 x 2 x 2= 8X the original
  •      20dB = 10 x 10= 100X the original
  •      30dB = 10 x 10 x 10= 1000X the original



Decibel Conversion Table (Positive and Negative Decibels)

Ultrasound decibel conversion chart for physics

The following two tabs change content below.
I am the founder and lead Instructor here at I strive to help those that are entering the field of Ultrasound to be the best that they can be. Ultrasound is my passion.

Latest posts by Franco (see all)


  1. halimur rahman says:

    You are Really a Wonderful teacher!

Speak Your Mind