In a previous post, I argued that some artificial sounds might be wrongly presented as if they were not natural, because ecological environments are complex and so natural sounds are diverse. But what if they were actually not natural? Perhaps these particular sounds can be encountered in a natural environment, but there might be other sounds that can be synthesized and heard but that are never encountered in nature.

Why exactly do we care about this question? If we are interested in knowing whether these sounds exist in nature, it is because we hypothesize that they acquire a particular meaning that is related to the context in which they appear (e.g. a binaural sound with a large ITD is produced by a source located on the ipsilateral leading side). This is a form of objectivism: it is argued that if we subjectively lateralize a binaural sound with a 10 ms ITD to the right, it is because in nature, such a sound would actually be produced by a source located on the right. So in fact, what we are interested in is not only whether these sounds exist in nature, but also additionally whether we have encountered them in a meaningful situation.

So have we previously encountered all the sounds that we subjectively localize? Certainly this cannot be literally true, for a new sound (e.g. in a new acoustical environment) could then never be localized. Therefore there must be some level of extrapolation in our perception. It cannot be that what we perceive is a direct reflection of the world. In fact, there is a relationship between this point and the question of inductivism in philosophy of science. Inductivism is the position that a scientific theory can be deduced from the facts. But this cannot be true, for a scientific theory is a universal statement about the world, and no finite set of observations can imply a universal statement. No scientific theory is ever “true”: rather, it agrees with a large body of data collected so far, and it is understood that any theory is bound to be amended or changed for a new theory at some point. The same can be said about perception, for example sound localization: given a number of past observations, a perceptual theory can be formed that relates some acoustical properties and the spatial location of the source. This implies that there should be sounds that have never been heard but that can still be associated with a specific source location.

Now we reach an interesting point, because it means that there may be a relationship between phenomenology and biology. When sounds are presented that deviate from the set of natural sounds, their perceived quality says something about the perceptual theory that the individual has developed. This provides some credit to the idea that the fact we lateralize binaural sounds with large ITDs might say something about the way the auditory system processes binaural sounds – but of course this is probably not the best example since it may well be in agreement with an objectivist viewpoint.