Problem with built-in microphone

I took today my laptop to service for cleaning the vents with compressed air,I just came back home turn it on and noticed that my mic is picking up sounds when I put my hand on palmrest or when I tap the mic.And I can hear this sounds only on my left speaker.Microphone volume is at max level and has always been on max.
I can hear taping even if the music is playing.

I am not shure is this a problem at all,is this the case with your notebooks also???
I didn't notice this before so I am not shure is this normal or did cleaning with compressed air damage something.Compressed air was pretty strong.

 

The microphone shares the same channel as the audio port. Thats why when you install your drivers on your laptop it says microphone on HD-Audio etc. It shares the same IRQ channel and as a result will pick up any sounds that occur as a result.

Get a USB microphone to fix this problem, or mute the internal mic by default when it is not in use.

--ssx--

 

Ok ssx thanks.

But what confuses me is that I hear sounds ONLY on left speaker.I own this lappy for about 6 months and I can't belive that I noticed this today after so much time.
I am still afraid that something got damaged today in service...