Is it normal for an amp to give off a high frequency sound with the engine?

DarylBurkitt

New member
just fitted my 4ch amp running 4 6x9s..i relised when my engines running or im driving, the amp seems to give off a high frequency sound..it seems to go wth my engine, higher the revs, higher the freguency goes..the only way i can bring it down is if i turn the levels down..can anyone explain why this happens and if its normal? cheers
 
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