Breaking the architectural sound barrier

While much current architectural discourse centres around the use of technology as it relates to design visualization and fabrication, there is a rising interest in the potential of digital applications to create multi-sensorial and sentient environments. Three genres of audio technology, first developed for non-architectural uses and adopted by designers wishing to explore issues of aurality in their work, are proving to have particular value. These are digital audio controllers, signal conversion, and electronic noise control systems.

Digital audio controllers Recent developments in the area of audio controllers, the electronic means through which sounds can be organized or modified, have potential for architectural uses. Both haptic (relying on touch or physical contact) and free-gesture (based on movements in space) controllers have been used by musicians and sound artists seeking to more directly interact with audio sources.

Free gesture controllers: The Son-O-House project in the Netherlands, by architect Lars Spuybroek (NOX) and composer Edwin van der Heide, provides an example of free-gesture controls applied architecturally. A large public pavilion located in an industrial park, the structure houses a sound work that continually generates new patterns based on visitors’ movements through the space. The composition that is produced is not based on the actions of a single visitor, but rather on the cumulative movement of all individuals entering the structure. Twenty-three sensors positioned at strategic locations provide real-time input, which influences the composition. The creators describe the work by saying, “The score is an evolutionary memoryscape that develops with the traced behavior of actual bodies in space.”

Signal conversion Recently, there have been significant innovations in how sounds are delivered from their source to the auditory system. Developments in audio transducers and piezoelectric diaphragms could allow building skins to act as both microphones and speakers. Especially promising, however, are innovations in bone conduction and ultrasonic technologies that are redefining our conventional understanding of hearing.

Bone mass transducers: That we are able to perceive sound through bone vibration has been known for centuries. Upon losing his hearing, Beethoven would place his forehead on the piano and pound out his compositions in an attempt to experience them physically. More recently, the idea has been used commercially in certain types of hearing aids.

A project experimenting with this technology in an architectural context was completed in a seminar at the Harvard Design School. Two mass drivers were placed behind a bench at a height just above the midpoint of an average user’s spine. A recording of automobile traffic was played using the wall as a transducer, conducting the sound through the person’s spine as he or she leaned back against the wall. The designer, Ean White, states, “The use of traffic sounds was designed to acousmatically disrupt the perceived geography of the building. With the use of bone conduction, whereby sound seems to inhabit one’s body, my intent was to conflate sensations of personal and public acoustic spaces.”

Ultrasonic audio transmission: This technology uses a piezoelectric emitter to transmit a highly focused steam (approximately three degrees of spread over 500 feet) of ultra-high frequency sound waves. Much like the beam from a flashlight, the hypersonic waves do not spread in all directions like the sound of a conventional loudspeaker, but remain locked inside a slender cone of supersonic energy. In order to hear the sound, the listener’s ears must be in line with the column of ultrasound. While the listener in line would be able to clearly hear the sounds, someone two feet off, and out of line, would not. Possible application in audio/video conferencing, simultaneous translation, home and commercial theatres, paging systems, and targeted advertising for retail sales are currently under development.

Two companies developing ultrasonic audio transmission systems are American Technology, developer of HyperSonic Sound; and Holosonic Research Labs, developer of Audio Spotlight.

Electronic noise control Stepping beyond the idea of basic noise masking (blanketing unwanted sounds beneath an unmitigated layer of static-like “white noise”), this new technology digitally negates undesirable sounds using a variety of strategies.

Active/adaptive noise cancellation (ANC): In this application, digital technology is used to analyse an audio environment and instantly generate reciprocal sound waves (anti-noises) that combine with, and thereby effectively cancel, the originals. Finding its first applications in consumer electronics such as noise reducing headphones and wireless telephone earpieces, manufacturers of open office furnishing systems are currently experimenting with this technology at an architectural scale. Media artist Paul Johnson has proposed an architectural installation for the Paris Metro using active noise cancellation technology to create a sound field by blocking sounds on a section of the subway platform.

Tunable pink noise: The latest variation on the use of white noise, tunable pink noise creates masking sounds specifically tailored to the acoustic characteristics of a particular space. By using digital processors to eliminate annoying frequencies across the audio spectrum, many of the undesirable aspects of outdated noise masking systems can be negated. Like ANC, this technology has thus far been used primarily in open office spaces. Tunable pink noise masking systems are commercially available through Dynasound and Logison.

Masking software: This technology creates acoustic privacy in a space, not by negating noises, but by introducing additional sounds into an acoustic environment. The system samples human speech and then uses software to deconstruct words into short, abstracted phoneme-like sound bites that are randomly played back into the immediate area. Again intended primarily for open workspace environments, the system is designed to make private conversations unintelligible in adjacent areas. Babble, a desktop masking system, is commercially produced by Sonare.

Sight has historically been the privileged sense with respect to architecture. However, technological advancements in sound generation, control, and reproduction in recent years have moved us closer to a conception of architecture in which the acoustic realm plays an increasingly important role. From Edison’s first phonograph to the development of the microchip and the advent of digital technology, it is now possible for sound to be legitimately considered an architectural medium. Many of the architectural applications discussed here are still in their nascent stages, and are subject to the pitfalls and false starts associated with emerging technology. Nevertheless, out of these early experiments will come technological advances that, in the near future, will fundamentally change the role of sound in the built environment.

While there are many ways to develop architectural applications for new and innovative audio technologies, the three aforementioned areas present the most immediate opportunities for meaningful integration and illustrate how the gap between architecture and emerging technologies can be successfully bridged.

Jim Lutz is an assistant professor in the architecture program at the University of Memphis, Memphis, Tenn.

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