I assume you are talking about audible noise.
Your description makes me think you are hearing the focus motor.
I believe you have the camera set for continuous auto focus.
That means that every time you move the camera, it will automatically focus.
You can turn off continuous auto focus.
I have noticed that my canon S5 IS makes noise in the action/sport mode. Did it always do this and I just never noticed before or did I do something (got a couple snowflakes on the lens shortly before I noticed the noise)???
Also get the same noise in the Custom mode whenever I move the camera to a different scene, ie. pan or tilt to a different area with minor variations in lighting.