While your dog does not show an orienting response, it could simply be that from his perspective the noise is just a neutral stimulus. In other words, the noise means nothing to him, it's irrelevant just as the birds chirping or the TV. Try to work in an area with low distractions, blow the whistle, immediately call your dog and give a treat to reward him. Repeat several times in a row. Afterwards, try to blow the whistle only. If your dog comes running (or at least turns around and seems to waiting to be called) most likely he hears it. It's just like the clicker, when you click it at first the dog cares less, then when you click and give a treat, it becomes a conditioned reinforcer, it has a meaning just as the noise of you getting the leash from a closet grabs his attention or the noise of the can opener if you feed canned food.
Of course, if this doesn't work and you tried to adjust the pitch already, maybe it's defective. What brand is it? Some of the best are produced by Acme.