SEMAPHOR by Gerriet K. Sharma

“Semaphor” is a spatial sound-composition for two pioneering instruments, which are explored both practically and theoretically by the artists Susanne Fröhlich and Gerriet K. Sharma: Helder Tenor recorder and the Icosahedral loudspeaker (IKO). If one understands both instruments as sound projectors, sound textures in sculpturally entangled states, spatially demarcated sound layers and scenographies can be composed and perceived in a way, scarcely producible in this ensemble constellation until now. The piece attempts to discover the shared perceptual spectrum of both instruments in dialogue and thus to expand the aesthetic possibilities of spatial composition in the present.

Semaphor

A Spatial Composition

for two pioneering instruments

Helder Tenor Recorder & Icosahedral Loudspeaker

THE IKO

COMMON SPATIALIZATION SYSTEMS

THE NOVELTY

THE IEM ICOSAHEDRAL LOUDSPEAKER (IKO) consists of an icoshaedral housing carrying 20 individually driven loudspeakers and has been built in 2006, originally with the idea to holographically mimic musical instruments.

At the Institute of Electonic Muisic and Acoustics Graz (AT) Franz Zotter and Gerriet K. Sharma have been working on turning the IKO, built in 2006, into an instrument and composition tool from 2009-2018 targeting a new manifestation of spatial sound in contemporary computer music. As a result of this fruitful composer acoustician dialogue, the compositions grrawe (10’26’’) and firniss (11’23’’) could be developed. These two pieces were stepping stones to thinking about the technical device and its acoustical principles as a means of artistic expression and orchestration of sounds in space.

OSIL

The project "Orchestrating Space by Icosahedral Loudspeaker" (OSIL) from 2015 to 2018 aimed at increasing the practical and theoretical understanding of electroacoustic sound phenomena that are defined by their sculptural-choreographic nature, i.e., exhibiting localization, motion, and extent. Such auditory objects are new means of expression and as such they have already been subject of artistic research in the project "The Choreography of Sounds" (CoS), PEEK AR 41. In particular, the project focused on the icosahedral loudspeaker (IKO) constructed at IEM in order to project auditory objects into rooms, a feature that has already been successfully employed in various sonic art works that have been performed in concerts and installations in different halls and listening situations.
Within OSIL artists and scientists were working closely together trying to understand the field of 3D audio better with an multi-perspective approach to foster and extend aesthetical practice in this field.

>OSIL RC

Within theOSIL project Gerriet K. Sharma researched, composed and performed a series of 10 new sculptural works for IKO installing and conceptualising compositional and aesthetical approaches.

The common spatialization systems for computer music employ loudspeaker arrays that surround the listening area, such as the BEAST (University of Birmingham), the Espro (IRCAM), the Klangdom (ZKM), the CUBE and the MUMUTH (KUG). They either use the psychoacoustic phenomenon of a phantom source [Wen63, Pul97] to create auditory objects between the loudspeakers, e.g. VBAP and Ambisonics [Ger73, Dan01], or aim at recreating a physically accurate sound field, e.g. wave field synthesis [Ber88, SRA08].   The quality assessment of such systems is a current research topic [Fra13a, SWR+13, FZWS14, LEL+14, MZF14]. To a certain degree, these systems assume anechoic listening conditions and their accuracy suffers from reflections.

THE NOVELTY in contrast to common surrounding loudspeaker systems lies in controlling the strengths of the wall reflections that could be excited from a single performer’s location. Namely an icosahedral loudspeaker is employed as an instrument of adjustable directivity at this location.

In electroacoustic music, the notion of adjustable-directivity loudspeakers was introduced in Paris in the late 1980s by researchers at IRCAM. For the renowned concept study “la timée” [WDC97], a cube housing six separately controlled loudspeakers was built to achieve freely controllable directivity. Despite the ingenious idea and theory, loudness and focusing strength weren’t convincing enough to be employed in concerts. In 2006, researchers at IEM (University of Music and Performing Arts Graz) reconsidered theory aiming at an acoustically correct and powerful reproduction of musical instruments in their lower registers, including the entire 3D directivity pattern. The resulting icosahedral loudspeaker (IKO) is more powerful, of larger size, and larger number of loudspeakers. Moreover, a success in quality was achieved by reconsidering algorithms and acoustic calibration to control sound beams [Zot09] that are three times narrower than beams of earlier systems.

Except for the 120 channel array at CNMAT [AFKW06] that runs Zotter’s algorithm (from 2007), none of the few comparable arrays is employed with similar goals or algorithms (12 channel system at ITA RWTH-Aachen [PB09], 6 channel and experimental systems Stanford/Princeton [TCSW06, CETT98]).

Other than spherical arrays, a number of linear loudspeaker arrays is being sold for home theaters to simulate side/rear loudspeakers through wall reflections (Yamaha YSP series, BOSE VideoWave®). Planar, parametric arrays Acouspade and Audio Spotlight are being sold and are able to create the narrowest sound beams. However, spherical arrays are currently more flexible and more powerful.

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