We live in a noisy world. There is no place on the Earth where it is possible to have the experience of complete silence, not even the deepest place in the ocean. Billions of living and nonliving objects around us produce sounds, which are extremely different in their physical structure. Some of these sounds are noisy, some are harmonic, some are continuous, others are impulsive, soft, loud; the sound environment contains an infinite combination of all these characteristics and more. Evolving in such an environment has resulted in a human auditory system that is able to extract useful information from sounds. We are able to say whether a sound source is still or moving (and in the latter case, the direction of movement), what kind of object produced the sound, and the meaning of the message if the perceived sound is an intentional communicative signal. When we hear someone’s voice, for instance, we are able to extract useful information about talker identity apart from the meaning of the heard words. This thesis focuses on a particular kind of information that can be extracted from an acoustic signal: the apparent size of the sound-producing object.
