Sough wihle recording audiotrack

I´m trying to make an audiotrack by using my epiano via audiointerface. Everytime when I have recorded a few notes theres a sough in the backround. It sounds some kind of digital - Its not a sough created by the room I´m recording in. I can hear the notes i´ve played, but they are very silent. Any Idea??
Thanks for Help!

First of all, check the cables and especially the power supply. I had a similar problem with connecting my USB soundcard to a mixing console. Removing power supply and working on battery only helped. If your piano has any built-in DSP (reverb, chorus etc), try switching those off. Also make sure your PC is grounded and don’t forget that your piano’s amplification circuit can produce such kind of noise too if soundcard in and keyboard out impedance values don’t match.

Which audio interface, and which electronic piano? Possibly the signal level from the piano is just too low compared to what the interface input was designed to accept, and so the signal to noise ratio is too low.
Is the volume control of the piano turned up to maximum? Does the interface have a gain control that is perhaps set too low? Or perhaps the gain control is set too high, forcing you to turn the output level of the piano too low.
When you play, what is the peak level displayed on the meters in Ardour?