Cubase records ambient noise even tho no mic is plugged in!

Cubase
1

Hi:
I am attempting to record audio from my Yamaha MX 88 . For some reason, Cubase is also picking up ambient sounds , evenm though no microphone is plugged in. Is there something I have to disable on my laptop? Please help me! Thanx Bruce in Dorset

2

More info is required here Bruce.

3

What audio interface do you have selected, is it possible you have a mic coming in to the MX88?