What we experience as a conscious visual scene is a highly processed image, quite different from the raw input that we receive from the eyes.
We never see the world as our retina sees it. In fact, it would be a pretty horrible sight: a highly distorted set of light and dark pixels, blown up toward the center of the retina, masked by blood vessels, with a massive hole at the location of the "blind spot" where cables leave for the brain; the image would constantly blur and change as our gaze moved around. What we see, instead, is a three-dimensional scene, corrected for retinal defects, mended at the blind spot, stabilized for our eye and head movements, and massively reinterpreted based on our previous experience of similar visual scenes. All these operations unfold unconsciously. Whenever we open our eyes, a massively parallel operation takes place in our visual cortex -- but we are unaware of it. Uninformed of the inner workings of our vision, we believe that the brain works hard only when we feel that we are working hard -- for instance, when we are doing math or playing chess. We have no idea how hard it is also working behind the scenes to create this simple impression of a seamless visual world. As surprising as it seems, we do not hear the sound waves that reach our ears; nor do we see the photons entering our eyes. What we gain access to is not a raw sensation but an expert reconstruction of the outside world. Behind the scenes, our brain acts as a clever sleuth theat ponders all the separate pieces of sensory information we receive, weighs them according to their reliability, and binds them into a coherent whole. Subjectively, it does not feel like any of it is reconstructed. We do no have the impression of inferring the identity of the fused sound "da" -- we just hear it. Nevertheless, what we hear demonstrably arises from sight just as much as from sound.