imac onboard mic

[bp mad]

hello 
just wondering if anyone can assist 
problem is with an imac machine and the on board mic.
when you try to burn a disc  the mic activates and 
goes into the mix . discouraging part is have been
told that the only way to rectify this is to
disconnect it internally . surely this cant be so
?!!!!
 any advice would be greatly appreciated 
machine is running 10.3.2
                               bmad

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