Low in decibels (5)
I believe the answer is:
quiet
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">low in decibels</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for quiet that I've seen before include "Free from activity" , "Still" , "Noiseless" , "Without sound" , "Hushed; undisturbed" .)