 Consider first the fact that sounds are sometimes loud and sometimes soft; as we have seen, in the wave theory this feature is correlated with amplitude of the sound waves. However, the location of the sound plays a role in establishing the correlation. A loud sound, which is heard as being far from us, is different from a soft sound, which is heard as being close to us. The spectra of the two sounds are different. If you want a vivid example, consider what happens if you amplify the sound of a person who is speaking low. You do not have the impression of a person who speaks loud. You have, on the other hand, the impression of having come very close to a low-speaking giant.