Discover truth about noise (6)
I believe the answer is:
rumble
This could be a double definition.
'discover truth' is the first definition.
'rumble' can be an answer for 'discover' (to rumble someone is to discover their secret). I am unsure of the 'truth' bit.
'noise' is the second definition.
(I know that rumble is a type of noise)
'about' acts as a link.
Can you help me to learn more?
(Other definitions for rumble that I've seen before include "Heavy vibration; US gang fight" , "Discover the truth about" , "Utter in deep voice, of have a slang fight - in the jungle?" , "Low, vibrating (traffic) noise" , "Tummy sound - discover (an illicit activity)" .)