Trout can hear and see you. It's a game of hide and seek. Fish are as sensitive to noise and vibration as they are to visual warnings.
It is important when stalking fish to approach low using any cover you can like long grass rushes and bushes. If possible try to keep a low profile especially on high banks with the skyline behind you. Remember fish that are deep can see you from farther away than fish that are close to the surface. This is due to how they see - fish have amazing vision. Their ability to see is uniquely adapted to locate food and distinguish predators from above both things that anglers should consider.
DEAD DRIFT ~ 9" x12" watercolour painting is all about trying to blend into your surroundings when fly fishing.