Acoustics Research in Canada

Acoustics is the science of sound, and the study of its production, accommodation, uses, and effects. There are many applications of this science, some in areas one might not expect.

Acoustics is the science of sound, and the study of its production, accommodation, uses, and effects. There are many applications of this science, some in areas one might not expect. Medicine, the military, fisheries and, of course, music are just a few disciplines that have benefited from the efforts to uncover the mysteries of sound.

One of Canada's pioneers in this field was Oswald Michaud, a researcher and teacher of acoustics at the Conservatoire national in Montreal, beginning in 1928. The earliest Canadian research in acoustics was actually in a related field known as ultrasonics. This work began in the 1920s at the University of Alberta under the direction of R.W. Boyle. About 1930 Boyle moved to the National Research Council (NRC) where he became director of the Division of Physics and Engineering. Over the years, studies at the NRC have investigated a wide array of topics such as building acoustics, audiometry, machinery noise, muffler development, outdoor sound propagation, the structural effects of high intensity sound, guidance devices for the blind, and electronic music. In the 1980s work by NRC scientists and others clarified some of the vagaries of sound both in the concert hall and the living room.

The study of room acoustics, as an independent branch of science, began at the turn of the 20th century. Significant developments from 1950 on have begun to quantify some of the more important aspects of concert hall sound. One of the leaders in this field is John Bradley of the NRC. Bradley's measurements in Canadian and European halls have provided a systematic assessment of rooms, a foundation of knowledge that is indispensable if one is to make confident statements about what is or is not important in a concert hall. One of the more significant findings in the 1980s stemmed from studies such as this. Independent work in Britain, Denmark, and Canada has shed new light on the effects of acoustical diffusion. It turns out that diffusion, once thought to be a hallmark of good acoustics, can in fact cause some unwanted effects. It was discovered that concert halls with highly diffusing ceilings are not as loud at the back as they are at the front. These findings are quite consistent and by 1990 were being used to design better concert halls. The measurements that led to this discovery provide a new level of confidence in both the design and assessment of auditoria.

Another area where systematic studies have assisted the appreciation of music is loudspeaker design. Floyd Toole was one of the first to correlate quantifiable acoustic measurements of loudspeakers with listener preferences. The title of one of his early papers on the subject, "Turning opinion into fact," encapsulates the objective of acoustic research as it applies to music. Toole's studies on resonance detection and timbre are comprehensive and now provide quantifiable design guides with which to build better sounding loudspeakers.

With the increased understanding of how sound behaves and the way we perceive it, electroacoustic equipment, traditionally frowned on by performers and acousticians, has earned increased acceptance as a means of enhancing theatre and concert hall acoustics. The extreme example is the modern recording studio in which the musicians perform in acoustic isolation and achieve ensemble by way of signals fed back to them through earphones by the recording engineer.

In 1949 at the CMM Jean Papineau-Couture introduced courses which related acoustics directly to composition. He also gave classes along those lines 1953-70 at the University of Montreal; he was succeeded by Louise Gariépy. Speaking generally, however, research in musical acoustics has been limited to those few whose interest transcends the problem of finding funds for such work.

In the 1970s electronic music became a major activity. Stimulated by Hugh Le Caine's pioneering work at the NRC, and especially his development of electronic instruments in the early 1950s, work was undertaken at several universities (see Electroacoustic music). In the 1980s, Richard Armin successfully developed a solid body electric cello, one of the first of its kind.

At the NRC itself the computer has been utilized as a tool for the composer, facilitating the assembly, playback, and revision of thematic material. In the late 1970s, John Walsh of Vancouver developed one of the first computer programs to simulate the sound of a room before it was built. This allows acousticians and architects to 'hear' what a concert hall will sound like while the designs are still on the drawing board.

Also of interest are topics involving the interaction of sound waves and people. At the medical level are concerns relating to human speech and hearing. Studies of speech processes and related psychophysiological problems have been pursued at Dalhousie University, McGill University, the University of Saskatchewan, the University of Western Ontario, and the University of Calgary. Studies of hearing defects and, more particularly, development of audiometric testing procedures are of increasing importance in relation to working environments, where noise-induced deafness may be a hazard. Musicians, both orchestral and popular, are often exposed to sound levels that can and do cause noise-induced hearing loss. Several federal and provincial regulatory agencies were active in this area in the 1970s and have established criteria to protect the hearing of workers and the general population. Noise criteria addressing the particular needs of musicians have yet to be established.

Noise as a pollutant has come under wide scrutiny, with study projects in almost every Canadian university, several government agencies, and private consulting firms. Some have surveyed urban noise climates, notably those in Montreal, Toronto, Woodstock, Calgary, and Vancouver. A project of special interest, the World Soundscape Project organized by R. Murray Schafer at Simon Fraser University, has produced among other items a survey of community noise bylaws in Canada.

Research in ultrasonics, alluded to earlier, investigates the behaviour of sound waves at frequencies above the range audible to the human ear. Applications of ultrasonics are now familiar in the field of medicine. One typical example is a device for determining the internal dimensions of the heart developed at Lakehead University.

Closely related to research in acoustics is the development of standard methods of acoustical measurement, the development of subjective criteria of "noisiness," and the establishment of noise limits. Thomas Northwood and his colleagues at the NRC were instrumental in developing the standard procedures used to measure sound transmission through walls, floors, etc. Northwood's significant contributions to the understanding of building acoustics were recognized in 1982 when he was awarded the Wallace Clement Sabine medal. Northwood is one of only eight recipients of this award and the first Canadian. This medal takes its name from the man who designed Boston Symphony Hall and is considered to be the father of modern architectural acoustics.

The international nature of the acoustical research community makes the identification of exclusively Canadian projects practically impossible. Typically, Canadian researchers have maintained close contact with workers in the USA, Great Britain, and elsewhere Communication among Canadian acousticians is fostered by the Canadian Acoustical Association. This group grew out of a small committee formed by Thomas Northwood in 1962. The association by 1990 had a membership of approximately 400. It meets annually and publishes a quarterly journal, Canadian Acoustics/Acoustique Canadienne. In 1972 James Parrott, a librarian at the University of Waterloo, began the preparation of Bibliotheca Harmonicorum, a bibliography on acoustics and other sciences in their relation to music.

Bibliography

Cremer, L. & Muller, H.A., Principles and Applications of Room Acoustics (London 1979)

Doelle, L.L. Environmental Acoustics (New York 1972)

Northwood, T.D., ed. Benchmark Papers in Architectural Acoustics (New York 1977)

Schafer, R. Murray. The Book of Noise (Vancouver 1970)

A Survey of Community Noise By-Laws in Canada. Soundscape Document no. 4 (Vancouver 1972)

Journals

Applied Acoustics (London)

Acustica (Stuttgart)

Canadian Acoustics/Acoustique Canadienne (Ottawa)

J of the Acoustical Soc of America (New York)