2006 Rayleigh-lecture | ResearchGate

Proceedings of the Institute of Acoustics

THE DEVELOPMENT OF CONCERT HALL DESIGN – A 111 YEAR EXPERIENCE Mike Barron

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Department of Architecture and Civil Engineering, University of Bath, Bath BA2 7AY

INTRODUCTION

My title mentions 111 years ago, which takes us back to 1895. Here are some events which occurred that year: Oscar Wilde was sentenced to 2 years imprisonment The Lumière brothers display their first moving picture film in Paris Wilhelm Röntgen discovered X-rays A new edition published of Roger Smith’s “Acoustics of public buildings” Wallace Sabine is asked to look at the acoustics of the Fogg Art Museum lecture theatre. It is of course the last of these that led to the choice of the year 1895. This lecture will follow a historical course since Sabine’s arrival on the scene. It cannot hope to be a full history and there will be some emphasis on topics with which I have myself been involved. There are several comments one can make about what was happening during the 1890s. In the world of physics this was the period of the first discoveries in nuclear physics; only 5 months after Röntgen’s discovery, Becquerel discovered a new type of radiation, what we now call radioactivity. Yet in spite of these advances in what at the time must have seemed obscure areas of physics, noone had achieved a meaningful explanation of the phenomenon of reverberation in rooms, something which anyone with access to large buildings can experience for themselves. Perhaps the statistical nature of reverberation was a deterrent here. Even Lord Rayleigh found the topic confusing. His only mention of it in his extensive “Theory of sound” of 1877 (Vol. 2, §287) is: ‘In connection with the acoustics of public buildings there are many points which remain obscure. … In order to prevent reverberation it may often be necessary to introduce carpets or hangings to absorb sound. In some cases the presence of an audience is found sufficient to produce the desired effect.’ As an example of the confusion which reigned, Roger Smith’s book, originally of 1861 which was republished in 1895, contains a discussion of reflections including Figure 1 here. Smith introduces the concept of a conducted proportion of the sound, in order to explain unpleasant shrill echoes heard in rooms. Fortunately we now just consider sound to consistently follow a simple law of reflection. Returning to Sabine, his first publication begins as follows (“Reverberation” from 1900 included in Collected papers of 1922): ‘The following investigation was not undertaken at first by choice, but devolved on the writer in 1895 through instructions from the Corporation of Harvard University to propose changes for remedying the acoustical difficulties in the lecture-room of the Fogg Art Museum, a building that had just been completed. About two years were spent in experimenting on this room, and permanent changes were then made. …

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No one can appreciate the condition of architectural acoustics – the science of sound as applied to buildings – who has not with a pressing case in hand sought through the scattered literature for some safe guidance. Responsibility in a large and irretrievable expenditure of money compels a careful consideration, and emphasises the meagreness and inconsistency of the current suggestions. …’ Though from the above, it appears that Sabine viewed his new task as a chore, he had before then done no work in acoustics, he soon decided to undertake a fundamental study of the determinants of reverberation time. This of course resulted in his famous reverberation time equation, that is used to this day. It is probable that his scientific colleagues were amazed by the simplicity of his result.

Figure 1. The ‘conducted’ portion of the sound responsible for echoes in a rectangular room as postulated by Smith. The speaker is at S. (Smith, 1861) Students may wonder why so much emphasis is often placed on the work of Sabine, in the same way that young teenagers studying English literature wonder why such fuss is made of Shakespeare. Sabine’s great achievement was to develop a rational understanding of acoustic behaviour and thereby lay a solid foundation for its later study. Anyone who has taught architectural acoustics will know the challenge of converting a layman’s view of sound in rooms into a scientific one. Yet Sabine apparently achieved for the first time this large conceptual journey on his own. The lecture-room of the Fogg Art Museum proved to be a space with multiple acoustic failings some of which were never satisfactorily resolved; the lecture room was eventually demolished in 1973. The enduring memorial to Sabine’s expertise is Boston Symphony Hall, which opened in 1900. This was the first auditorium to be designed in one respect at least on a scientific basis, though Sabine demonstrated himself very much a pragmatist regarding aspects of the design other than reverberation time. The design was considerably influenced by experience of its predecessor, the Boston Music Hall. The new hall was significantly longer than the old but Sabine considered that, by having the orchestra in a recess, the loudness of sound for the audience would be ‘more than compensated’. From a world perspective the acoustic reputation of Boston Symphony Hall is among the best.

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FORM OF CONCERT HALLS

The basic architectural form of the Boston Symphony Hall was rectangular or shoebox, with parallel side walls and two balconies which run across the rear and along the side walls. The ceiling is high at 19m in order to give an appropriate reverberation time. The design was very much in the th tradition of European 19 century halls, with plaster decoration applied to walls and ceiling which, we now know, promotes diffusion. Table A1 lists the principal parallel-sided large concert halls up to this century. Describing the plan form in a single word is not easy, but all these halls can be considered to be part of the rectangular plan tradition inspired originally by ballrooms, such as the Redoutensaal of 1752 in Vienna. The list in Table A1 is far from complete and the choice of halls is no doubt somewhat personal. Many of these halls are to be found in Beranek (2004). Vol. 28. Pt.1. 2006

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th

Virtually all halls in the 19 century followed the parallel-sided tradition. The listed halls in Vienna, Amsterdam and Boston are now frequently considered to have the best acoustics in the world; see th Bradley (1991) for a discussion of their objective characteristics. Yet in the first 60 years of the 20 century the form was all but abandoned. The rectangular plan form was revived by C.M. Harris for the Kennedy Center Concert Hall, Washington, DC in 1971 (Harris, 1972). The parallel-sided plan was subsequently taken up by R. Johnson for the new concert hall for Dallas of 1989. Since then it has been one of the most popular forms for new concert halls.

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6 6 5 5 4 4 3 3 2 2 1 1 0 0 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Shoebox/rectangular ,

Theatre form ,

Fan-shape ,

Terraced ,

Other (Oval, hexagon, surround, in-the-round)

Figure 2a. Numbers of concert halls built during decades between 1850 and 2000 of different forms. 7

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6 6 5 5 4 4 3 3 2 2 1 1 0 0 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Shoebox/rectangular ,

Theatre form ,

Fan-shape ,

Terraced ,

Other (Oval, hexagon, surround, in-the-round)

Figure 2b. Black and white version of Figure 2a. In Figure 1, which shows the forms of 69 major concert halls over one and a half centuries, the trends over time are clear to see. Construction before 1870 was sporadic but developed over the th last three decades of the 19 century. Construction was again modest until 1950, since when many concert halls have been erected. In terms of concert hall form, the first major watershed is around 1900, or more precisely 1925. Two forms were used prior to 1925: the rectangular shoebox and what is called here ‘theatre form’. The classical shoebox hall is rectangular in plan with one or two balconies opposite the stage which th extend along the two side walls; the 19 century versions are also noted for the extensive plaster decoration on the walls and ceiling, which provide acoustic scattering. The theatre form is designed as a theatre with one or two balconies with curved balcony fronts, which extend some way along the side walls from the back; the stage is in a recess. Several of these halls had higher ceilings than one expects for a drama theatre; the design keeps distances from the stage to a minimum. Vol. 28. Pt.1. 2006

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Examples of this form are Carnegie Hall in New York and the Usher Hall in Edinburgh. acoustics of these theatre-form concert halls have in the main been disappointing.

The

The new favourite form in the 1920s was the fan-shape plan, such as the Salle Pleyel in Paris. The plan form allows for a maximum audience within a certain angle centred on the stage. Its acoustic limitations have gradually become apparent yet new examples were still appearing in the 1980s. What is also apparent is that between 1910 and 1970 no large shoebox/rectangular halls were built, Figure 3. The reason for this must surely have been architectural taste; the modern movement in th architecture sought to distance itself from 19 century styles. 7

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6 6 5 5 4 4 3 3 2 2 1 1 0 0 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Shoebox/rectangular ,

Terraced ,

Figure 3. Shoebox/rectangular halls and terraced halls extracted from Figure 2. The realisation that the classical rectangular halls had the most reliable reputations led to return to that form in the 1970s to the present. Also shown in Figure 4 is the growth in terraced concert halls, pioneered in the Berlin Philharmonie. These two forms can be considered to be the main precedents of today (Barron, 1993). Halls which are categorised as ‘Other’ in terms of their form cannot be combined easily as a group, other than noting that halls in this category are generally examples of experimentation in design. Plan form Shoebox/rectangular plan Theatre form Fan-shaped plan Terraced hall

Dates 1850 – 1905, 1970 – present 1850 – 1935 1925 – 1985 1960 - present

Table 1. The principal periods for concert halls of different plan forms. The forms of concert halls have followed a clear pattern, but how has science influenced decisions, why have certain forms been abandoned, are present forms in any way optimised? In the design of Boston Symphony Hall, we know that Sabine’s new theory was applied and it seems that for several other decisions he relied on precedents. To what extent is reliance placed on precedents today?

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THE SCIENCE OF AUDITORIUM ACOUSTICS

3.1

Scientific progress from 1900

Sabine pressed his new equation into service during the remainder of his professional acoustic life. The formula has stood the test of time but there have been difficulties with accurate prediction due to ignorance of absorption coefficients, particularly for audience and audience seating. Several auditoria from the 30s and beyond are disappointing both due to their form and short reverberations times. Even in the 1950s, we find the Royal Festival Hall, London and Frederic Mann Auditorium, Vol. 28. Pt.1. 2006

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Tel Aviv, for example, constructed with insufficient volumes and hence short reverberation times. The question of audience absorption was only finally resolved by Beranek (1960); one key change of approach was to treat audience absorption on the basis of floor area covered instead of absorption per person. It is now rare for large concert halls to have reverberation times which fall outside the recommended range at mid-frequencies of 1.8 – 2.2 seconds. By 1950 it had become clear that there were aspects other than reverberation time which influenced acoustic quality, but how could this be resolved? Simulation systems in acoustic laboratories starting from around 1950 proved a promising resource. These systems can generate the sort of sound field experienced by a listener in a concert hall, with direct sound, reflections and reverberation simulated in an anechoic chamber. An early discovery by Thiele (1953) was that clarity for music and intelligibility for speech is related to the ratio of early-to-late energy received by the listener; the interval of 50ms has remained for speech and 80ms for music. In 1952, from listening to such a simulation system Meyer and Schodder (1952) observed that “… the presence of a secondary [lateral] loudspeaker creates an apparent enlargement of the spatial extent of the primary source and with a delay of some 10ms also a certain ‘reverberance’” (translated from German). This was an entirely accurate observation, yet it was not pursued, presumably as they did not consider it important for concert halls listening. Also around this time, experiments suggested that, for a judgement of the amount of reverberation, the traditional reverberation time measure was not ideal, but that rather the decay rate of earlier sound was important subjectively (Atal, Schroeder and Sessler, 1965). The early decay time, measured over the first 10dB of the decay, has now become the standard measure of reverberance. While the above was valuable progress by scientists, it was not clear what were the design implications of these findings. In 1966, Harold Marshall was asked to advise the jury of the design competition for a new concert hall for Christchurch in his native New Zealand. The Sabine equation was only concerned with room volume and total absorption, but “Marshall found that there was at that time, in the literature, no rational basis for the selection of one shape over another, once the obvious focusing problems were overcome and given adequate reverberant volume. The Sabine reverberation equation is notoriously silent on the effect of room shape and yet in the literature there was a substantial preference for the narrow rectangular halls.” (Marshall and Barron, 2001). From listening in the Royal Festival Hall, Marshall came to realise that sound from the side was particularly important and wrote his seminal paper “On the importance of room cross section in concert halls” (Marshall, 1967). Sufficient lateral reflections are now universally accepted as a necessary component of the best concert hall acoustics.

3.2

Research at Southampton 1967 – 1969

At this point a rather timid graduate appeared at the Institute of Sound and Vibration Research enquiring if it would be possible to do research in architectural acoustics. Phil Doak (at the time not yet a professor) welcomed me onto a project to test Harold Marshall’s ideas about early lateral reflections. The simulation equipment had been bought but a researcher was needed. Incidentally at the time I knew no acoustics, but this was rectified by my attending the MSc. course. It was only several years later that I realised that getting involved in this project was a major piece of good luck for me. As an office I was offered part of a garden shed behind a house in University Road. I shared the shed with David Fleming, who 20 years later became my consultancy partner. On a visit to Southampton a year ago, I took a look at the site of the shed to discover that unsurprisingly the shed had gone but also the house has disappeared! After two years in Southampton (Barron, 1971), I joined Harold Marshall in Perth, Western Australia, where he was a lecturer; a simulator in an anechoic chamber had also been built there. The outcome of the research was a measurable quantity for the degree of spatial impression: the early Vol. 28. Pt.1. 2006

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lateral energy fraction (Barron and Marshall, 1981), which is the ratio between the lateral sound within 80ms of the direct sound and the omni-directional sound, also arriving within 80ms. The subjective effective is now described as source broadening.

3.3

Five objective measures for music auditoria

The fifth objective measure is perhaps the most obvious, indeed Sabine in his first paper “Reverberation” of 1900 (Sabine, 1922) listed as the first of his necessary and entirely sufficient conditions for good hearing that sound should be sufficiently loud. The sound level heard by the listener is determined by the sound emitted by the players and the corresponding sound pressure level at relevant positions in the hall. For the case of upgrading sound insulation in a building, a 5dB improvement is usually taken as necessary for worthwhile remedial action. The thinking had been that the same criterion should be applied to auditoria; the level changes within an auditorium were rarely much more than 5dB. Experiments in Germany involving subjective assessments of music recordings made in actual halls, particularly those in Berlin (Lehmann and Wilkens, 1980), showed that sound level was significant, changes of only about a decibel can be perceived. The sound level relative to the sound power level of the source is thus an important objective measure for concert halls; it is often referred to as strength. Subjective quality Clarity Reverberance Intimacy Souce broadening Loudness

Objective measure Clarity index (C80) Early decay time (EDT) Sound strength (level) Early lateral fraction and strength Sound strength and source-receiver distance

Table 2. The main subjective qualities in concert halls and their possible objective correlates. Table 2 includes the following four acoustic objective measures: clarity index, early decay time, early lateral fraction and relative sound level; they are enshrined in ISO3382. One notes the absence of reverberation time (RT); the early decay time appears better correlated to the subjective effect of reverberance. In many halls, RT and EDT are very similar but certain design details create EDTs shorter than the RT (Barron, 1995a). In parallel with advances on the objective front, Hawkes and Douglas (1971) showed that concert hall listening was subjectively a multi-dimensional process with listeners having individual preferences. This conceptual realisation clearly complicates the study of auditorium acoustics.

3.4

Models and full-size concert halls

My second piece of luck was to be asked in 1975 by Peter Parkin, then at the Building Research Station, to join a project on acoustic scale models at Cambridge. We had moved up in the world, instead of a garden shed, our laboratory was a large glasshouse! The models were at a scale of 1:8 so required a higher than usual ceiling height, which this glasshouse could provide. We were soon measuring the quantities mentioned above but there was little evidence available regarding what were desirable and unsuitable values for them for concert hall listening. There was also little evidence of the way in which design influenced the new quantities. The link between objective behaviour and design became an on-going search for me in the following years; in a sense this quest was aimed at answering Harold Marshall’s query from 1966 (section 3.1). By testing at smaller scales, such as 1:50 (Barron and Chinoy, 1979), designs can be assessed according to objective measures within the time scale of building projects. Testing actual designs at this scale proved to be a fruitful exercise in the period 1977 – 1994 (Barron, 1997). The end of that period occurred partly due to the coming of age of computer simulation models. With time however, it has become apparent that the accuracy of scale modelling remains generally more reliable than computer simulation models (Barron, 2002). Vol. 28. Pt.1. 2006

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Scale modelling is particularly valuable for investigation of diffraction. Two recent examples are illustrated here (Barron and Dammerud, 2006). Figure 4 shows reflection off a long 2m wide surface. In the case of modest source and receiver distances, there is significant scattering. At lower frequencies, reflections along the geometrical paths become weaker. Figure 5 shows what happens in the case of a corner reflection off the cornice between a wall and a finite size horizontal surface, such as occurs with a narrow (~2m) balcony against a concert hall balcony. Because of the presence of the wall, the horizontal surface with width d behaves as if the surface was double the width, 2d. The consequence of this is that the frequency below which diffraction effects become significant is lowered by two octaves. This behaviour has been checked by scale model; a narrow balcony like this may be valuable to assist reflections back to performers on stage (Barron and Dammerud, 2006).

Figure 4. Polar plot of reflection from a 2m wide panel, source and receiver distances 11 and 5m. Real space

d

Image space

Source

Receiver (image) Wall

Figure 5. Illustration using image space of how reflection from a cornice (balcony shelf and wall) is equivalent to reflection from a double width horizontal panel. In the quest for the link between design and objective behaviour, models have a lot to offer. As a resource however, full-size halls are more valuable, not least because they can be assessed subjectively as well. Hence the Acoustic Survey of British Auditoria (Barron, 1993), which proved invaluable in demonstrating several novel results. One of these results related to sound level behaviour in concert halls.

3.5

Sound levels in auditoria

Traditional theory says that sound level can be separated into the direct and reflected sound and that the reflected component is constant throughout the space. Evidence from many auditorium spaces showed however that the reflected sound level decreases as one moves away from the source. This can be explained by a simple model of sound decays within a room. It is assumed that as sound decays in a room the instantaneous sound level is the same throughout the room. The sound decay is assumed to consist of the initial direct sound and thereafter a linear decay; because of the same sound level throughout the room these decays are superimposed. However since the reflected sound can only arrive after the direct sound, there is more reflected sound at positions closer to the source, as illustrated in Figure 6. A simple theory, known as revised theory, Vol. 28. Pt.1. 2006

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expresses the reflected sound level as a function of room volume, reverberation time and sourcereceiver distance (Barron and Lee, 1988). The theory can also be used to predict early and late reflected levels, which can then be compared with measured values, Figures 7 and 8. Revised theory appears to match average behaviour in concert halls well. It has also been demonstrated to apply in diffuse spaces (Chiles and Barron, 2004). a b Level (dB)

c

0 ta

tb

tc

Time

Figure 6. Integrated impulse curves at three receiver distances from a source in a room according to revised theory. Time t=0 is the moment when sound is emitted from the source. The magnitude of each trace on the y-axis is the total level for that receiver position. Two of the standard measured quantities for auditoria are the Clarity Index (the early-to-late ratio in dB) and Strength (relative sound pressure level). Since the latter is the sum of early and late sound, it is easy to extract the early and late levels separately; the temporal boundary is usually taken as 80ms after the direct sound.

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4

5

3

Late sound level (dB)

Early sound level (dB)

Two clear examples of use of revised theory relate to measurements made in the Colston Hall, Bristol and the Barbican Concert Hall, London (Barron, 1993). Figure 7 shows the early and late sound compared with revised theory in the Colston Hall. The behaviour of the early sound is typical, following revised theory with some scatter. With the late sound however, points are following two lines, one relating to the stalls seating, the other the balcony seating. This hall has a single balcony with an excessive overhang, and this reduces the late sound but not the early.

S

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S 3 S

B

O

2 B

1

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BS B

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B B

2 S

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40

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Source-receiver distance (m)

Figure 7. Measured early and late sound levels in the Colston Hall, Bristol. Lines indicate revised theory prediction. S – stalls, O – stalls overhung seats, B – balcony. Figure 8 shows measured early sound levels from 1984 in the Barbican Concert Hall compared with revised theory, the early sound decreases with distance more than one would expect. This was attributed to the deeply profiled ceiling in this hall which provides only weak ceiling reflections to remote seats. The hall has since been modified with new reflecting ceiling panels.

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Early sound level (dB)

4 3 2 1 0 -1 -2 -3 -4 -5 0

10

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Figure 8. Measured early sound levels in the Barbican Concert Hall, London. Line indicates revised theory prediction. Using revised theory for comparison with measured values appears to be a useful tool, though there are several exceptions to revised theory performance to be found in actual halls. It is not known how much this technique is used by consultants. It is also a valuable aid for scale model testing of auditoria.

3.6

Balcony overhangs

On the subject of balcony overhangs, behaviour under nine balconies in six British concert halls was investigated (Barron, 1995b). This found that the average change in total sound level under these overhangs compared with expected values was -1.3dB at mid-frequencies, the average change in early-to-late index (clarity index) relative to expectations was 2.6dB and the average change of Early Decay Time (EDT) was -16%. In terms of the number of difference limen, these changes were greatest for EDT with 9 difference limen. This suggests that, as they go further under an overhang, listeners are going to hear a reduction in reverberance before they notice reduction in sound level. Figure 9(a) illustrates the concept of vertical angle of view from the listeners seat, while Figure 9(b) shows the average proportional reduction of EDT as a function of vertical angle of view. 1.1 Regression line

Early decay time ratio

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D H

θ

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0.7

θ = Vertical angle of view 0.6 10

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Vertical angle of view (degrees)

Figure 9. a) Section through balcony overhang illustrating the vertical angle of view, b) average relative reduction of EDT as a function of angle of view (Barron, 1995b).

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RECENT DEVELOPMENTS IN CONCERT HALLS

It is important in a discussion like this not to ignore the political dimension, what is the relationship between client and designers and what is the situation of the acoustician within the design team? Vol. 28. Pt.1. 2006

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Up to the 1970s, it was not unusual for clients to place their trust in the ‘experts’, a group usually strongly dominated by the architect. In some cases, the acoustician had little influence on the design. The importance of concert hall form was not widely acknowledged, so certain forms which now have bad acoustic reputations were common. The fan-shaped plan is an obvious example of this; as a form it accommodates a large audience within a modest distance from the stage, but its acoustic reputation is poor. Around the middle of the 1980s, a change of approach took place in which clients became aware that the reputation of a new auditorium was linked to its acoustics and that acoustics perhaps influenced future financial success. The status of the acoustician was raised allowing them to influence auditorium design more than previously. With these changes came greater responsibility for acoustic consultants, which led to less risks being taken. By this time, two concert hall forms had emerged as acoustically reliable: the rectangular plan and the terraced hall. Experience with rectangular halls had of course been much more extensive. The return to rectangular halls began in America in the 1970s, several years ahead of Europe. The second precedent, the terraced hall, has a much shorter history. Pioneered by the architect Hans Scharoun with Prof. Cremer as consultant, the Berlin Philharmonie of 1963 (2340 seats) was a seriously radical design (Cremer, 1964). Audience surrounds the orchestra platform and is divided into blocks of 100 – 200 seats. This provides a more involving experience for both performers and audience. From an acoustic perspective, Cremer knew of the importance of early reflections, which necessitated in this design placing the audience blocks at different levels so that surfaces separating them could be used to provide additional early reflections. For this reason, the form is often referred to as having vineyard terraces. The design challenge is demanding particularly to maintain uniformity throughout the seating area. With two concert hall forms dominating present design, what are the pros and cons of these two forms? The rectangular concert hall Advantages: Acoustics are pretty reliable A known ‘quantity’ expected to have good acoustics Liked by many musicians Disadvantages:

Formal relationship of audience to performers Limited involvement of the audience ‘Looking through a tunnel’ from rear audience seats Poor sightlines at high levels on the sides Limited seat capacity

Table 3. The advantages and disadvantages of the rectangular concert hall form. The terraced concert hall Advantages: Acoustician has more control over acoustics Involving relationship between performers and audience Good sightlines Larger audience capacity possible Greater freedom in design Disadvantages:

Poor balance for audience to the sides of the stage Demanding to get good acoustics

Table 4. The advantages and disadvantages of the terraced concert hall form. The safe solution is the rectangular hall, while the terraced hall offers greater freedom of design and potentially more exciting performance spaces. Vol. 28. Pt.1. 2006

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Over the last 20 years, the size of several acoustic consultancies has grown to the point where they now dominate ‘the market’. Not surprisingly, many clients feel more confident using a large as opposed to a small consultancy. A by-product of this development is that less information is available in the public domain regarding the principles consultants are using and the techniques that they use. To what extent is a scientific approach being used? Are either computer simulation models or physical scale models being employed? Of course, auditorium acoustic design is both an art and a science; features which appear valuable can be repeated and visa versa. Secrets are likely to take longer to emerge than before.

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CONCLUSIONS th

Concert hall design has come a long way from the 19 century, when it appears no-one alone took th responsibility for the acoustic design. In the early years of the 20 century, there are some wellknown names associated some of the halls, but usually it was the case that a single individual was involved. After 1950, design by consultancy firm gradually became the norm; today acoustic design is usually a shared responsibility. In the mid-‘60s, there was only one objective measure available for concert hall acoustics and prediction of reverberation time had finally become more reliable. It was thought that the acoustics of almost any form of space could be resolved by remedial action. Subsequently it has been learnt that appropriate form is essential for good acoustics. The understanding of the subjective listening process has grown substantially. New objective measures are now widely accepted as useful for design. The science of acoustics and design aids in the shape of computer or physical models have made great progress but it is often not obvious to what extent they are currently used. Some mysteries remain! One mystery concerns the appropriate degree of diffusion. To what extent is diffusion subjectively perceived, which surfaces are most valuable to make scattering and to what extent is this th necessary? One of the characteristics of the 19 century halls is that the walls and ceiling are highly decorated in line with the architectural style of the time. Does this contribute to their good acoustic reputation?

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ACKNOWLEDGEMENTS

I owe a serious debt to the following for their help and inspiration in the earlier part of my working life: Hugh Creighton, Prof. Phil Doak, Prof. Harold Marshall and Prof. Peter Parkin. And I must also thank my principal co-workers: Dr. Raf Orlowski, Lee-Jong Lee, Dr. Stephen Chiles and Jens Jørgen Dammerud.

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REFERENCES

Atal, B.S., Schroeder, M.R. and Sessler, G.M. ‘Subjective reverberation time and its relation to th sound decay’, 5 International Congress on Acoustics, Liège, Paper G 32 (1965). Barron, M. ‘The subjective effects of first reflections in concert halls - the need for lateral reflections’, J. Sound Vib., 15, 475-494 (1971). Barron, M. and Chinoy, C.B. ‘1:50 scale acoustic models for objective testing of auditoria’, Applied Acoustics, 12, 361-375 (1979). Barron, M. Auditorium acoustics and architectural design, Spon, London (1993). Barron, M. ‘Interpretation of early decay times in concert auditoria’, Acustica 81, 320-331 (1995a). Barron, M. ‘Balcony overhangs in concert auditoria’, J. Acous. Soc. America, 98, 2580-2589 (1995b). Barron, M. ‘Acoustic scale model testing over 21 years’, Acoustics Bulletin, 22, No. 3, 5-12 (1997). Barron, M. ‘The accuracy of acoustic scale modelling at 1:50 scale’, Proc. of the Institute of Acoustics, 24, Part 4 (2002). Vol. 28. Pt.1. 2006

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Barron, M. and Dammerud, J.J. ‘Stage acoustics in concert halls – early investigations’, Proc. of the Institute of Acoustics, 28, Part 2 (2006). Barron, M. and Lee L-J. ‘Energy relations in concert auditoriums, I’, J. Acous. Soc. America, 84, 618-628 (1988). Barron, M. and Marshall A.H. ‘Spatial impression due to early lateral reflections in concert halls: the derivation of a physical measure’ J. Sound Vib. 77, 211-232 (1981). Beranek, L. L. ‘Audience and seat absorption in large halls’, J. Acoust. Soc. Amer., 32, 661-670 (1960). nd Beranek, L.L. Concert halls and opera houses: music, acoustics and architecture, 2 ed Springer, New York (2004). Bradley, J.S. ‘A comparison of three classical concert halls’, J. Acous. Soc. America, 89, 1176-91 (1991). Chiles, S. and Barron, M. ‘Sound level distribution and scatter in proportionate spaces’, J. Acous. Soc. America, 116, 1585 – 1595 (2004). Cremer, L. ‘Die raum- und bauakustischen Massnahmen beim Wiederaufbau der Berliner Philharmonie’, Die Schalltechnik, 57, 1-11 (1964). Harris, C.M. ‘Acoustical designing of the J.F. Kennedy Center for the Performing Arts’, J. Acoust. Soc. America 51, 1113-1126 (1972). Hawkes, R.J. and Douglas, H. ‘Subjective acoustic experience in concert auditoria’, Acustica, 24, 235-250 (1971). Lehmann, P. and Wilkens, H. ‘Zusammenhang subjektiver Beurteilungen von Konzertsälen mit Raumakustischen Kriterien’, Acustica, 45, 256-268 (1980). Marshall, A.H. ‘A note on the importance of room cross-section in concert halls’, J. Sound Vib., 5, 100-112 (1967). Marshall, A.H. and Barron, M. ‘Spatial responsiveness in concert halls and the origins of spatial impression’, Applied Acoustics, 62, 91-108 (2001). Meyer, E and Schodder G.R. ‘Über den Einfluss von Schallrückwürfen auf Richtungslokalisation und Lautstärke bei Sprache’, Nachrichten der Akademie der Wissenschaften in Göttingen Mathematisch-Physikalische Klasse IIa, 6, 31-42 (1952). Rayleigh, Lord (J.W. Strutt). The theory of sound, Vols. 1 and 2, Macmillan, London (1877, reprinted by Dover, New York, 1964). Sabine, W.C. Collected papers on acoustics, Harvard University Press (1922, reprinted by Dover, New York, 1964). Smith, T.R. Acoustics of public buildings, Crosby Lockwood, London (1861, reprinted 1895). Thiele, R. ‘Richtungsverteilung und Zeitfolge der Schallrückwürfe in Raümen’, Acustica, 3, 291-302 (1953).

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APPENDIX The list of concert halls represented in Figure 2 is divided into two. Table A1 contains halls which can be categorised as rectangular, shoe-box shape halls. Some are referred to as parallel-sided, in most cases because the ends are not flat and not at right-angles to the walls. In all cases these th halls can be considered as descendents of the 19 century rectangular halls. Table A2 contains halls of all other forms. The listed plan forms will in some cases seem inappropriate to individual readers, but this is unlikely to alter the main conclusions drawn. th

Table A1. Halls derived from the 19 century shoebox halls Concert hall Philharmonic Hall, Liverpool Mechanics Hall, Worcester, Mass. Grosser Musikvereinssaal, Vienna Music Hall, Troy, NY Stadt Casino, Basel St. Andrew’s Hall, Glasgow Neues Gewandhaus, Leipzig Concertgebouw, Amsterdam Grosser Tonhallesaal, Zurich Symphony Hall, Boston Palau de la Musica Catalana, Barcelona Town Hall, Watford, UK Herkulessaal, Munich Kennedy Center, Concert Hall, Washington, DC Orchestra Hall, Minneapolis Avery Fisher Hall, New York Alte Oper, Grosser Konzertsaal, Frankfurt Konzerthaus, Berlin Dr. Anton Philips Hall, The Hague McDermott Concert Hall, Dallas Orchard Hall, Tokyo Symphony Hall, Birmingham, UK Seiji Ozawa Hall, Tanglewood, Lenox, Mass. Concert Hall, Kyoto Opera City Concert Hall, Tokyo Winspear Centre for Music, Edmonton Benaroya Hall, Seattle Culture and Congress Centre, Lucerne

Date

Plan form

Capacity

1849-1933 1857 1870 1875 1876 1877-1962 1884-1944 1888 1895 1900 1908 1940 1953 1971 1974 1976 1981 1986 1987 1989 1989 1991 1994 1995 1997 1997 1998 1998

Rectangular Rectangular Rectangular Rectangular Rectangular Rectangular Rectangular Rectangular Rectangular Rectangular Parallel-sided Rectangular Rectangular Rectangular Rectangular Rectangular Rectangular Rectangular Rectangular Parallel-sided Parallel-sided Parallel-sided Rectangular Rectangular Rectangular Parallel-sided Rectangular Rectangular

2100 1280 1680 1255 1400 2130 1560 2205 1550 2630 1970 1590 1290 2450 2450 2740 2500 1600 1900 2065 2150 2210 1180 1830 1630 1960 2500 1840

Date

Plan form

Capacity

1857 1891 1893-1941 1904 1914 1923 1927 1929

Opera form Theatre form Theatre form Theatre form Theatre form Theatre form Fan-shape ‘Oval’

2980 2760 2050 2580 2550 3340 2400 2150

Table A2. Non-rectangular halls Concert hall Academy of Music, Philadelphia Carnegie Hall, New York Queen’s Hall, London Orchestra Hall, Chicago Usher Hall, Edinburgh Eastman Theatre, Rochester, NY Salle Pleyel, Paris Palais des Beaux-Arts, Brussels Vol. 28. Pt.1. 2006

Proceedings of the Institute of Acoustics

Severance Hall, Cleveland Konserthus, Gothenburg Philharmonic Hall, Liverpool Kleinhans Music Hall, Buffalo, NY Royal Festival Hall, London Colston Hall, Bristol Alberta Jubilee Halls, Calgary and Edmonton Frederic Mann Auditorium, Tel Aviv Beethovenhalle, Bonn Festspielhaus, Salzburg Philharmonic Hall, New York Philharmonie, Berlin De Doelen Concert Hall, Rotterdam Finlandia Concert Hall, Helsinki Town Hall, Christchurch, New Zealand Concert Hall, Sydney Opera House Boettcher Concert Hall, Denver Muziekcentrum Vredenburg, Utrecht Louise Davies Symphony Hall, San Francisco Neues Gewandhaus, Leipzig Roy Thomson Hall, Toronto Barbican Concert Hall, London Symphony Hall, Osaka Joseph Meyerhoff Symphony Hall, Baltimore St. David’s Hall, Cardiff Philharmonie am Gasteig, Munich Suntory Hall, Tokyo Segerstrom Hall, Orange County, California Cultural Centre Concert Hall, Hong Kong Royal Concert Hall, Glasgow Bridgewater Hall, Manchester, UK Waterfront Hall, Belfast Kitara Concert Hall, Sapporo, Japan

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1931 1935 1939 1940 1951 1951 1957 1957 1959 1960 1962-1976 1963 1966 1972 1972 1973 1978 1979 1980 1981 1982 1982 1982 1982 1982 1985 1986 1986 1989 1990 1996 1997 1997

Theatre form Segmented fan Fan-shape Fan-shape Wide rectangular Extended rect’lar Fan-shape Fan-shape Fan-shape Fan-shape Fan-shape Terraced Elongated hexagon Fan-shape Elliptical Elongated hexagon Surround In-the-round Surround Terraced Surround Fan-shape Wide rectangular Surround Terraced Fan-shape Terraced Split fan-shape Surround Surround ‘Terraced’ Terraced Terraced

1890 1370 1970 2840 2900 2020 2700 2710 1400 2160 2650 2340 2230 1750 2660 2700 2750 1550 2740 1900 2800 1920 1700 2470 1950 2490 2000 2900 2020 2460 2360 2250 2010