~Proceedings ICMCISMCI2014 14-20 September 2014, Athens, Greece
Towards Defining the Potential of
Electroacoustic Infrasonic Music
Alexis Story Crawshaw
Media Arts and Technology; University of
California, Santa Barbara
Ecole Doctorale Esth6thique, Sciences et
Technologies des Arts;
Universit6 Paris 8 Vincennes-Saint-Denis
alexis@mat.ucsb.edu
ABSTRACT
Infrasounds, frequencies < 20 Hz, occupying the sonic
landscape beyond pitch, offer a wide terrain of musical
potential to the contemporary electroacoustic composer, a
potential that has so far been poorly defined or exploited.
This paper is a brief tutorial on employing infrasounds in
electroacoustic composition. Infrasounds possess musical
potential within the auditory and tactile modalites as either airborne and solidean vibrations, either containing or
psychoacoustically suggesting a fundamental wave < 20
Hz. The infrasonic composer must consider a range of
issues with respect to 1) equal-loudness contours (the
detection threshold being > 70 dB below 20 Hz), 2) intersubject variability within these contours, 3) obstacles in
finding hardware to diffuse these oscillations at the SPL
needed for their detection, 4) their safe usage (anticipating harmonic distortion in hardware when working at
high SPLs), as well as engineering an aesthetic context
through interactivity and sensory conditioning to optimize a positive-valence response. There is great potential
for sonic, vibrotactile, and intersensorial composition
with respect to space and the body, e.g., interacting with
or conveying large architectural spaces, evoking psychosomatic interactions through biorhythmic suggestion, and
exploring the musicality of the body through its peak
resonances.
1. INTRODUCTION
This paper evokes and addresses some practical issues
concerning infrasonic composition, touching a range of
subjects including hardware, perception (auditory and
tactile), and music cognition (specifically factors contributing to emotional response). I equally outline infrasounds' aesthetic potential to resonate with architectural
space, the human body, and more metaphorically with the
(embodied) mind, evoking the state of the art as well as
several of my own projects. As such, I hope to better inform and inspire the curious composer.
Copyright: ~ 2014 Alexis Story Crawshaw. This is an open-access article
distributed under the terms of the CreeCmoAtrgnion s.i n ewhich permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Infrasonic oscillations have previously made appearances
in electroacoustic music through use of low frequency
oscillators (LFOs), "sub-audio" FM, and monaural and
binaural beating. Most notably, in Kontakte (1959-1960),
Stockhausen famously investigated the continuity of pitch
to rhythm. Outside composition, infrasounds have notoriously been used in acoustic weaponry (at extremely high
SPLs) but also on the other extreme, as a means of relaxation in music therapy. Our typical encounters with
infrasounds include situations where we come into contact with vehicles of transportation, machinery, wind turbines, large architectural structures as well as with more
natural occurrences like earthquakes and waterfalls. Lastly, the biorhythms of the body are certainly the infrasonic
oscillations most familiar to us as living creatures.
2. DEFINING INFRASOUND
For the purposes of this paper, infrasound is defined here
as any frequency at or below 20 Hz, 16-20 Hz being the
approximate threshold of pitch to rhythm [1, 2]. Infrasounds may be thought of in numerous ways. They exist
as mechanical waves: vibrations effectuating a rarefaction
and compression of molecules, propagating in air or any
other medium, either as part of a sound source consisting
of a sinusoidal wave at an infrasonic frequency or as an
acoustic by-product, such as (monaural) beating. Yet, to
speak of infrasonic oscillations is to also speak of
rhythm; as such, a regularly occurring pulse under 20 Hz
consisting of any variety of other frequencies may also be
considered as an infrasound or perhaps, more precisely,
as simply being infrasonic. Infrasounds may also, of
course, be evoked psychoacoustically, such as through
binaural beating [3] or through the missing fundamental
phenomenon [4].
Acoustically propagated infrasounds are perceived multimodally, through both audition and tactility at high sound
pressure levels (SPLs); under 10 Hz, one can distinguish
individual oscillations and such frequencies are characterized by a sensation of pressure at the ears [2].
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