Hissing noise around doors and emergency exits is a result of the door/exit seals leaking slightly.

In some cases it can also cause a drop in temperature around the area with a fairly leaky seal.

The noise or whistling that may occur from any leak in a cabin door is normally more of an issue than the small amount of air that leaks past, as the aircraft's pressurization system can more than compensate for that.

Probably not noticeable on aircraft with good seals.