Sound Diffusion Research Articles

An Interview with Hans Tutschku

Computer Music Journal, 27:4, pp. 14–26, Winter 2003 2003 Massachusetts Institute of Technology. Born in 1966, Hans Tutschku began to study music at an early age. In 1982, he joined the Ensemble fur Intuitive Musik Weimar, playing synthesizer and live electronics. He studied electroacoustic composition in Dresden, The Hague and Paris, and between 1989 and 1991 he accompanied Karlheinz Stockhausen on several concert tours to study sound diffusion. As a member of the Ensemble fur Intuitive Musik Weimar, Mr. Tutschku has realized multimedia productions, including those involving projection of images and choreography for dance. The ensemble has given numerous concerts in Europe, Latin America, and Asia. He has composed instrumental works, works for tape, works for musicians and electronics, and music for theater, film, and ballet. During 1995–1996, Mr. Tutschku was the professor of electroacoustic composition at the Liszt Conservatory in Weimar, and in 1996 he attended the Royaumont composition workshop with Klaus Huber and Brian Ferneyhough. During 1997–2001, he taught computer music at IRCAM. He has given master classes at the Universities of Sao Paulo, Buenos Aires, and Singapore, the Music Academy in Budapest, as well as in Darmstadt, Stuttgart, Florence, Milan, and Porto. He has served as a jury member of the CIMESP (Sao Paulo) and Metamorphoses (Brussels) international competitions for electroacoustic composition. He completed a D.E.A. degree at the Parisian Sorbonne and a Ph.D. in Composition at the University of Birmingham in the UK. He has taught electroacoustic composition at the conservatory of Montbeliard since 2001. Last summer, he held a DAAD professorship at the Technical University of Berlin. He is the recipient of several international composition prizes, including Bourges, HannsEisler-Preis, CIMESP Sao Paulo, Prix ARS Electronica, Prix Noroit, and Prix Musica Nova. This interview was conducted on 2 April 2003, at the Ecole Nationale de Musique in Montbeliard, France.

Compressor noise control with a two-dimensional enclosure

This paper is concerned with the use of a two-dimensional enclosure with masonry block wall to mitigate compressor noise in a northern California location for consistency with city standards. Sensitive receptors consist of a duplex and single residences across the street from the source. Background sound is provided primarily by a nearby highway that is elevated. Noise reduction is accomplished by the barrier effect of the wall along with sound absorption realized from a pegboard wall surface in the vicinity of the compressor, unpainted concrete block surface and acoustic treatment on the doors. Design considerations for the pegboard are discussed with the intention of balancing the overall low- and high-frequency noise reduction from the absorption and from the barrier effect and with the intention of reasonably reducing the number of pegboard holes required. Some considerations from the standpoint of ray acoustics are discussed. A complicating factor for the interior acoustics consists of three full height tanks in a row that serve as sound diffusers. Comments on vibration isolation for equipment and pipes are offered.

Critical thermal diffusivity in anisotropic magnets

We derive nonasymptotic expressions for the frequency- and temperature-dependent thermal diffusivity near a critical point in an Ising-type magnet. We consider a dynamic model which takes also into account the longitudinal sound mode. The asymptotic scaling function of the thermal diffusion constant at long wavelengths is given within the renormalization group formalism in one-loop order. A relation connecting longitudinal sound velocity and thermal diffusivity in a broad range of frequency and reduced temperature is obtained.

Resisting the auditing industry: the case of the Sound Diffusion Action Group

Protest groups and political activism are a common feature of modern societies. In pursuit of rights, justice and fairness, loosely organised protest groups frequently mount resistance to challenge contemporary power relations. In contrast, little is known about the actions of any protest groups challenging the hegemony of the UK accountancy firms who enjoy a statutory monopoly of the external audit function. Against the background of the contested terrain of auditor/accountant liability to third parties, this paper examines the formation and the actions of the Sound Diffusion Action Group (SDAG) which mobilised a group of small UK investors to seek compensation from an accountancy firm for alleged failures. Despite having little financial and legal resource, the SDAG organised nearly 2,000 court cases to secure compensation. The SDAG's tactics, modes of organisation and engagement offer some reflections on how ordinary people develop strategies to resist major organisations. The case study also offers some reflections upon the state‐profession relationship.

A study case of noise coming from road yard machines : experimental tests and theoretical formulas to evaluate sound impact on people

Sound levels emitted by road yard machines are correlated strictly to engine power, to level of power taken up during the different operative conditions, to ground morphologies and features, to maintenance state of machines and to meteo-climatic conditions during working period. If people could carry out a preventive evaluation of sound diffusion around working machines than they could single out the yard zones where the acoustic limits established by Italian environmental laws would be overcame and, consequently, people could prearrange the convenient technics of mitigations to reduce sound impact on environment. To this aim people analysed as study-case the experimental results coming from a campaign of measures of noise level generated by big yard machine, equipped with pneumatic demolition hammer and working in different operative condition. By correlation between sound values measured and that ones forecasted by formulas of sound diffusion it has been possible to mark up experimental acoustic maps, each of them linked with different operative condition of machine respectively.

Real-time control of sound diffusion parameters

Much electronic and computer music relies extensively on real-time diffusion of electronic sound in surround loudspeaker configurations. The most common method of sound diffusion in practice today is to use standard sound-reinforcement mixers whereby each fader controls the playback volume of a corresponding loudspeaker in a concert hall. Using the mixer this way, however, presents problems when one attempts to create sound trajectories, because complex, precise, and repeatable control of the individual faders is required. To address these interface issues, two different handheld controllers were created for real-time sound diffusion. The first controller is equipped accelerometers, force-sensing resistors, and joysticks and maps using input into diffusion parameters. The second controller mimics the operation of a standard mixer but allows more rapid movement of fader positions by replacing each fader with a bend sensor. To test the validity of each controller, twenty undergraduate music engineering students were asked to repeatedly perform various diffusion tasks (such as moving a monaural sound in a circle around the audience) using a standard mixer and each of the controllers. The accuracy and speed of their performances were tracked. The study concludes with lessons learned from the statistics gathered. [Research supported by the University of Miami.]

Inside-in, alternative paradigms for sound spatialization

Arrays of widely spaced mono-directional loudspeakers (P.A.-style stereo configurations or ‘‘outside-in’’ surround-sound systems) have long provided the dominant paradigms for electronic sound diffusion. So prevalent are these models that alternatives have largely been ignored and electronic sound, regardless of musical aesthetic, has come to be inseparably associated with single-channel speakers, or headphones. We recognize the value of these familiar paradigms, but believe that electronic sound can and should have many alternative, idiosyncratic voices. Through the design and construction of unique sound diffusion structures, one can reinvent the nature of electronic sound; when allied with new sensor technologies, these structures offer alternative modes of interaction with techniques of sonic computation. This paper describes several recent applications of spherical speakers (multichannel, outward-radiating geodesic speaker arrays) and Sensor-Speaker-Arrays (SenSAs: combinations of various sensor devices with outward-radiating multi-channel speaker arrays). This presentation introduces the development of four generations of spherical speakers—over a hundred individual speakers of various configurations—and their use in many different musical situations including live performance, recording, and sound installation. We describe the design and construction of these systems, and, more generally, the new ‘‘voices’’ they give to electronic sound.

Acoustic diffusers III

This acoustic diffusion research presents a pragmatic view, based more on effects than causes and 15 very useful in the project advance control process, where the sound field’s diffusion coefficient, sound field diffusivity (SFD), for its evaluation. Further research suggestions are presented to obtain an octave frequency resolution of the SFD for precise design or acoustical corrections.

Live interactive computer music performance practice

A live-performance musical instrument can be assembled around current lap-top computer technology. One adds a controller such as a keyboard or other gestural input device, a sound diffusion system, some form of connectivity processor(s) providing for audio I/O and gestural controller input, and reactive real-time native signal processing software. A system consisting of a hand gesture controller; software for gesture analysis and mapping, machine listening, composition, and sound synthesis; and a controllable radiation pattern loudspeaker are described. Interactivity begins in the set up wherein the speaker–room combination is tuned with an LMS procedure. This system was designed for improvisation. It is argued that software suitable for carrying out an improvised musical dialog with another performer poses special challenges. The processes underlying the generation of musical material must be very adaptable, capable of rapid changes in musical direction. Machine listening techniques are used to help the performer adapt to new contexts. Machine learning can play an important role in the development of such systems. In the end, as with any musical instrument, human skill is essential. Practice is required not only for the development of musically appropriate human motor programs but for the adaptation of the computer-based instrument as well.

The non-linear model of sound wave diffusion in Chrysanthemum callus

There are non-linear effects during sound wave diffusing in biological tissues. It is necessary to further research the process of sound wave diffusion. In this article, we have primarily established the non-linear model of sound diffusion in Chrysanthemum callus, which can theoretically predict the attenuation tendency of sound wave in biological tissues, and the intensity received by tissues, the model provides us a primary model to further explore the mechanism of sound wave. Generally, due to the non-linear effects in tissue for sound wave diffusion, the efficient factor η and the effective diffusion distance are reduced, the effective attenuation coefficient α eff is increased. On the other hand, the conversion relation of sound intensity and sound pressure is primarily explored in this paper. We can gain the magnitude of pressure in tissue, which provides the basis of stress–growth relation studies for tissues and cells.

Toward Reality Equivalence in Spatial Sound Diffusion

�The diffusion of sound in space has always been a major topic interest to many composers working with music composed, produced, or performed using electronic means. Despite the rich possibilities inherent in current sound diffusion and spatialization systems, none of the current systems can fully mimic the spatial characteristics of natural sound systems. By examining the nature of our spatial hearing and the history of sound spatialization systems, this article attempts to map possible routes, taking us closer to full ‘‘reality equivalent’’ sound diffusion systems. Since the remote transmission of sound became possible in the late 19th century, ways have been sought to enable sound systems to deal not only with the frequency and amplitude elements that make up a sound event, but also with the spatiotemporal ones. This is, naturally, of the greatest importance when the sounds being transmitted are musical in nature. Prior to the current era, all musical events were fixed in and wholly part of the acoustic location in which they were being performed. With the breaking of that age-old bond came enormous challenges for the audio engineer in finding ways of restoring the bond correctly after such space/time transmissions. Perhaps more importantly, enormous opportunities opened for composers explore and exploit the relatively little-known territory of space in music.

Mechanism of sound absorption by seated audience in halls.

Four methods are explored for predicting the reverberation times in fully occupied halls for music as related to the sound absorption by their audiences. The methods for providing audience absorptions include two that use reverberation chambers, namely, the ISO 354 method (and other similar standards) (ISO) and Kath and Kuhl's method (K & K) [Acustica 15, 127-131 (1965)], and two that use average data from halls, i.e., Beranek's method (COH) [Concert and Opera Halls: How They Sound (Acoustical Society of America, Melville, NY, 1996)], and the average audience power-per-seat absorption which in practice is multiplied by the number of seats (AA). These methods are applied to the calculation of reverberation times in six existing halls, fully occupied, and the results were compared with actual measurements. The COH method was best for predictions over the entire frequency range. The K & K method showed the highest accuracy at mid-frequencies. Both the ISO and the K & K methods yielded wide differences for the measurements in the 125- and 250-Hz bands. The AA method was as good as the COH method when the measurements for the six halls were averaged, but showed a wide spread in the predictions around the average because it does not consider the degree of upholstering of the seats. It was hypothecated by the authors that the principal reasons for the ISO and K & K discrepancies at low frequencies were (a) differences between the degree of sound diffusion in actual halls and that in reverberation chambers, and (b) lack of information on the mechanisms of absorption of sound by people seated side-by-side in rows, particularly for near-grazing incidence sound fields. First, this article explores the sound diffusivity in a reverberation chamber and in the halls using CAD models. A probability density function of the incident angles of the sound rays that impinge on the audiences is defined and was measured for each case. Using a unique method, the sound absorption coefficient of each portion of the body and chair in a seated audience was determined in an anechoic chamber as a function of the incident angle of a sound wave. With adjustments from these findings, the K & K method can be made to equal the COH method in accuracy at all frequencies. Its forte is that it can be used for the determination of the sound absorption of occupied chairs from measurements of a limited number in a reverberation chamber.

Concert hall acoustics—2001

A brief summary is made of major factors encountered in today’s acoustical design of concert halls, including preferred reverberation times, loudness, lateral reflections, seat absorption, suspended panels, need for irregular surfaces to create sound diffusion and eliminate acoustical ‘‘glare,’’ and objective measurement techniques developed from laboratory experiments that can be used to estimate subjective acoustical quality. Objective measurements of these factors have been made in over 70 halls. The results are plotted versus subjective rank-orderings of acoustical quality for these halls. The rank-orderings were obtained from interviews and questionnaires involving conductors, music critics, and music aficionados. The objective quantities plotted are reverberation time, early decay time, spaciousness, lateral fraction, interaural cross-correlation coefficient, initial-time-delay gap, strength factor (sound level), bass ratio, 125-Hz level, and surface diffusivity index.

Application of number theory sequences in architectural acoustics

One of the challenges in architectural acoustics is to develop contemporary diffusing surfaces that complement contemporary architecture in the way that statuary, columns, and relief ornamentation complemented classic architecture. Number theory sequences invented by Schroeder [J. Acoust. Soc. Am. 65, 958–963 (1979)] and further developed by D’Antonio et al. [Appl. Acoust. 60, 143–165 (2000)] have been used for two decades to design reflection phase gratings, which provide useful sound diffusion in architectural acoustics. The use of modulation techniques, to enhance performance, and the development of proof-of-performance techniques, to evaluate their performance, will be described. The development of flat and curve optimized binary amplitude gratings will also be presented. The current state-of-the-art utilizing boundary-element multidimensional optimization to design 1- and 2-D diffusors, which incorporate aesthetic constraints, will offer a view of future design possibilities. Photos of installations using these acoustic tools will also be presented to illustrate the usefulness of these devices and their impact on architectural acoustics.

The development of ‘‘21st century’’ acoustic and orchestral instruments

The work of the Centre for New Musical Instruments (CNMI), recently established at London Guildhall University, is reported. In addition, a wide range of original slides is shown, providing an overview of international innovations relevant to the development of new versions of existing acoustic orchestral instruments, especially those offering new forms of expression to composers and performers. In view of the overwhelming majority of developments of electronic as opposed to acoustic instruments during the 20th century, the purpose of CNMI is to encourage innovations of the latter. Acoustic instruments designates not only those traditionally referred to by this term, but also those in which elements of sound generation may be electromechanical or electroacoustic, although sound diffusion is not through a loudspeaker. Three areas of innovation are discussed: (i) purely mechanical instruments; (ii) electromechanical and electroacoustic hybrids; and (iii) instruments designed for alternative tuning systems. All the orchestral families are considered. The mutually reinforcing possibilities and limitations of these elements, together with the evolving aesthetic issues of contemporary and other musics, suggests the importance of specific areas of future research and instrument making. Amongst these is the necessity of interdisciplinary perspectives and collaboration.

Measuring Speed of Sound and Thermal Diffusivity in the Diamond-Anvil Cell

Transient grating spectroscopy in the diamond-anvil high-pressure cell permits, in favorable cases, determination of the equation of state and thermal transport properties of fluids at high temperatures and pressures. Measurements of the speed of sound and thermodynamic properties of aqueous Na2SO4to 3.4 GPa at 300°C and the thermal diffusivity of oxygen are reported as examples of the application of this technique.

The effects of cylindrical diffusers on sound diffusion in a rectangular concert hall

Acoustical measurements in a 1:20 scale model were conducted to investigate the influence of a 1/4-cylinder diffuser on sound diffusion in a rectangular concert hall. Diffusion was evaluated regarding temporal and directional distribution of acoustical energy at individual seats as well as energy distribution over all seats. With volume of 19,000 m3 and seating area of 1,200 m2, the size and shape of the hall were determined based on three classical rectangular concert halls. Overall, diffusers around the stage were more effective for the source at the center, front of the stage than the source at the side, rear of the stage. The hall average values of late interaural cross correlation (IACCL3) were reduced by using transversal diffusers on ceiling or longitudinal diffusers on the side walls. Although the influences on the hall average values of echo criteria (EC) and temporal diffusion (TD) were relatively small, diffusers on the rear stage wall were effective in reducing EC values for the seats near the side walls. Strength factor (G) at the seats under the balcony was significantly increased by placing diffusers on the ceiling. On-going research is conducted to evaluate the effects of diffusers in the audience section. [Work supported by the National Science Council of Taiwan.]

Privacy with intelligibility—A novel electroacoustic solution

The concept of electronic sound masking is a well-established and successful solution in helping to achieve adequate speech privacy either within or between office areas or similar spaces. In many instances, separate paging or voice-alarm systems are also installed. Whereas locating loudspeakers in the ceiling void or within a plenum assists sound diffusion and evenness of coverage, this also degrades speech intelligibility and causes significant nonlinear (frequency-dependent) transmission losses. Conversely, installing conventional loudspeakers directly into the ceiling can result in good intelligibility but poor sound diffusion, leading to uneven sound distribution and immediate localization of the loudspeaker as the sound source. The diffuse, substantially decorrelated and wide dispersion characteristics of the distributed mode loudspeaker suggests that systems employing this new class of device may simultaneously satisfy the requirements for both speech privacy and speech intelligibility. The paper presents the results of a study using a range of loudspeaker formats to establish whether these apparently opposing requirements can be achieved.

Alternative voices for electronic sound

Through the design and construction of unique sound diffusion structures, the nature of electronic sound can be reinvented. When allied with new sensor technologies, these structures offer alternative modes of interaction with techniques of sonic computation. This paper describes several recent applications of Geosonic Speakers (multichannel, outward-radiating geodesic speaker arrays) and Sensor-Speaker-Arrays (SenSAs: combinations of various sensor devices with outward-radiating multichannel speaker arrays). Geosonic Speakers, building on previous studies of the directivity of acoustic instruments (the NBody Project), attempt to reproduce some of the diffusion characteristics of conventional acoustic instruments; they engage the reverberant qualities of performance spaces, and allow electronic and acoustic instruments to blend more readily. In collaboration with the U.S. Enclosure Company, over a dozen Geosonic Speakers were produced, varying in size from 8 to 14 in. Their use in the performance and recording of two major new works by composer Steven Mackey is detailed. The electronic improvisation ensemble ‘‘Interface’’ has integrated a family of these Geosonic Speakers into their standard setup, completely replacing their previous P.A. diffusion model; this has encouraged them to substantially reinvent their approach to the performance of live interactive computer music.

Sound Diffusion in Composition and Performance: An Interview with Denis Smalley

have been conducting with leading composer-practitioners of electroacoustic and computer music whose contributions to the art and technology of sound diffusion have been key to its development and growing acceptance through the last four decades. These discussions cover the aesthetics of, compositional approaches to, and technological realizations of sound diffusion. Topics include the dynamics of sound diffusion; stereo and multitrack solo-tape diffusion with multispeaker configurations in composition and performance; spatial composing; the diffusion of tape-plus pieces; diffusion as drama or aural cinema; present and future developments in sound diffusion in loudspeaker orchestras and multispeaker diffusion systems such as the Acousmonium (Desantos 1997), the Gmebaphone (Clozier 1997), and BEAST (Harrison 1998); the Spatialisateur (Jot 1997); advances in the field of ambisonics and Digital Versatile Disc (DVD) multichannel systems (Elen 1998); and specialized multiple-speaker systems (Stockhausen 1996). The present interview with composer Denis Smalley (see Figure 1) took place at City University in London on 2 April 1998. Denis Smalley, composer, is professor and head of the Department of Music at City University, London. He received his first degrees in New Zealand, specializing in composition and performance. He studied with Olivier Messiaen at the Paris Conservatoire and investigated electroacoustic composition with the Groupe de Recherches Musicales in Paris before moving to the UK, where he completed his doctorate at the University of York. He was senior lecturer in music and director of the Electroacoustic Music Studio at the Univer-