Headphone music and Spatial manipulation

“The Composition of Auditory Space: Recent Developments in Headphone Music”
Author: Durand R. Begault

Source: Leonardo, Vol. 23, No. 1 (1990), pp. 45-52

Published by: The MIT Press

http://www.jstor.org/stable/1578456

Summary: In this article, Durand R. Begault discusses the potential for composition of spatial music, meaning music that is written to occupy specific space, as opposed to music that is performed under any context, regardless of the space the sound occupies. Durand writes, “The composition manipulation of the spatial aspect of music was as inevitable as the manipulation of pitch, timbre or duration...”. Using psychoacoustically-based digital signal-processing techniques, composers of today are able to create music that is based on spatial hearing in the composition of music for headphones. Musical-spatial intentions can be conveyed through the use of headphones, and can create various effects including the illusion of distance and manipulation of the environmental context of the sounds.

Begault writes about “four so-called separable musical elements (with their corresponding psychological descriptions); frequency (pitch), spectral content (timbre), intensity (loudness) and duration (perceived duration)”. These categories are restricting, according to Begault, so he has added a fifth element of musical sound- space. It is a problem, according to Begault, when an undesired perceptual mismatch occurs between the composer’s intent and the listener’s perception. This translates to a source-medium-receptor (SMR) model, the source being the composer’s spatial conception for a sound, the medium involves the effects of loudspeakers and room acoustics (which can have a huge impact on the sound before it arrives at the listener), and the receptor is the listener who experiences these sound waves in some manner. The receptor experiences what Begault calls “immediate perceptual recognition” of the spatial aspects of the sound, as given by cues based on non-aural and binaural differences in intensity, spectra and time-delay, and the higher-level cognition of spatial manipulation experienced by the listener”. What Begault claims is an advantage of headphone music is the elimination of the “medium” and the freedom of the composer to control the auditory space in which the listener experiences the music. Signals sent to each ear can be predicted and controlled very carefully. There are several types of headphone presentations, diotic, dichotic and binaural. Diotic headphone presentation involves a single signal being sent to both ears. A dichotic presentation involves two different signals being fed differently to each ear, and a binaural presentation essentially involves a dichotic presentation in which the content of one of the two signals is to some degree present in the other. These signals can be used simultaneously. When done, music can sound as though it is coming from above, behind, in front or to the side of a person wearing the headphones. The perceptual experience is altered significantly. Begault has designed a digital signal-processing algorithm called REFL which is used for creating spatialized versions of a digital sound file according to an arbitrary model. The algorithm allows compositional specification of a model that includes the position of the listener and of the sound source within a variable environmental context. These filters create spatial-listening cues by “modifying an input sound in the same way that the outer ears (or pinnae) and the head would modify a sound in an actual environmental context”. The filtering effect is altered as a function of the angle of incidence of the sound source. Listeners would interpret what is happening as changes in the spatial position of the sound source. Begault has used these techniques in many of his own compositions for headphones, and is continually expanding his work and his research as an innovative and creative composer with fascinating techniques. He ends his article with the anticipation, that “We should expect our mind’s ‘aural eye’ to be surprised and challenged in the future.”

Reflection: This field is entirely new to me, and fascinating as I have never considered the possibilities for creating music that caters specifically to the manipulation of auditory space. The notion of auditory space itself has only ever come up for me when considering acoustics of a performance venue or the effect of a room’s acoustics on an instrument on a smaller scale. The manipulation of auditory space leads me to think about what else we as listeners might be lacking by experiencing music through the filter Begault calls the “medium”, be it concert hall space, loudspeakers, etc. Is our experience lessened because of the filters through which the music has to travel? Do these filters take away from what is intrinsically enjoyable about music (whatever that may be)? Could we someday manipulate our concert halls to cater to each individual listener in the way that headphones cater to the individual listener?

Although there may be elements of music lacking when auditory space is not controlled, the opposite may also be true. The negative effects of eliminating the medium must be considered. What is offered through the medium that provides us as listeners with something unique? For example, to take away the concert hall essentially takes away the social aspect of music. In many cases, headphone listening is usually a secluded activity which allows for the listener to block out her or his environment. When we cater to this style of listening to and experiencing music, are we in fact cutting ourselves off from a very important aspect of music? By eliminating the social aspect of the musical experience, we eliminate the energy brought to us by other people and we don’t have an opportunity to consciously offer our own energy to the people around us, like the effect of a high-energy rock concert. By eliminating the social experience, music may become an introverted activity. This is not to say that seclusion and introversion are bad when it comes to music; this is to point out the combination of elements that make up a musical experience, and how by eliminating one (in this case, the social aspect) many other facets are necessarily altered.

Despite whatever drawbacks headphone music may have in terms of music’s social aspect, the exciting part of this work is how much manipulation can be done in terms of finite details and sound wave altering. Clearly, there is so much more to music than meets the ear.