Measure of noise intensity (7)
I believe the answer is:
decibel
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">measure of noise intensity</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for decibel that I've seen before include "Noise unit" , "Unit relating to sound or power measurement" , "Measure of sound" , "Unit of measurement for loudness" , "Sound level unit" .)