akuTEK www.akutek.info PRESENTS The PhD thesis by Jens Jørgen Dammerud: Stage Acoustics for Symphony Orchestras in Concert Halls This is the medium resolution (96dpi) version. Click for full resolution (5.5MB) akuTEK navigation: Home Papers Title Index Stage Acoustics Concert Hall Acoustics STAGE ACOUSTICS FOR SYMPHONY ORCHESTRAS IN CONCERT HALLS Submitted by Jens Jørgen Dammerud for the degree of Doctor of Philosophy of the University of Bath September 2009 COPYRIGHT Attention is drawn to the fact that copyright of this thesis rests with its author. This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and no information derived from it may be published without the prior written consent of the author. This thesis may be made available for consultation within the University library and may be photocopied or lent to other libraries for the purposes of consultation. Acknowledgments I would like to thank everyone who has generously contributed to the work forming this thesis: First of all the musicians of professional symphony orchestras who have taken part in discussions (in alphabetical order): David Daly, Chris Gale, Gunnar Ihlen, Kevin Morgan, Finn Orestad, Torbjørn Ottersen, Mike Smith, Geir Solum and Bengt Arstad.˚ I would also like to thank all the musicians who responded to questionnaires, the contact persons within all the symphony orchestras who kindly collaborated in this project and my wife Silje Marie Skeie for all useful input as a musician. People from within the disciplines of acoustics, audio and science who have shared their own results and given valuable input to this research (in alphabetical order): Niels Werner Adelman- Larsen, Johan Andersson, Peter D’Antonio, Steve Barbar, Alf Berntson, Bertie van den Braak, Anders Buen, Eddy Bøgh Brixen, Stephen Chiles, Bengt-Inge Dalenback,¨ Anders Christian Gade, Maria Giovannini, David Griesinger, Tor Halmrast, Masahiro Ikeda, Eckhard Kahle, John O’Keefe, Asbjørn Krokstad, Russell Mason, Bob McCarthy, J¨urgen Meyer, Geoff Miles, Eckard Mommertz, Lars Henrik Morset, Francis Rumsey, Anssi Ruusuvuori, Magne Skalevik,˚ Olav Skutlaberg, Audun Strype, Peter Svensson, Kanako Ueno, Ian Walker and members of the Syn-Aud-Con forum and the AUDITORY list. All fellow players who have tolerated the squeaks from my clarinets and saxophones, allowing me to get valuable experience on how it is to play within acoustic ensembles over the last five years: Nordre Aker Janitsjar (Oslo), Wind Band and University Orchestra (University of Bath) and Bath All Comers Orchestra. Also a big thank you to all fellow postgraduates, academic and support staff at the University of Bath and the people at Brekke & Strand akustikk. I am also very thankful to Eckhard Kahle, Andy Shea, Bengt-Inge Dalenback,¨ Gunnar Ihlen and Magne Skalevik˚ for providing valuable comments on preliminary versions of the thesis. Last but not least, I am most grateful to my supervisor Mike Barron for inviting me to take part in this project and for generously sharing his knowledge and guiding me towards completion of this thesis – and my wife and son for all support and inspiration. The research project on which this thesis is based was funded by the Engineering and Physical Sciences Research Council (EPSRC), UK. 3 Abstract The main goals for this study were to better understand what are the acoustic conditions physically within a symphony orchestra on concert hall stages, how these physical conditions affect the players and ultimately how to design venues suitable for symphony orchestras. This was investigated by use of several different approaches, including questionnaire surveys and dialogue with musicians, scale and computer modelling and measurements of existing stages. The results from the orchestra collaborations indicate that the following are of most concern for players regarding acoustic conditions: hearing all other players in the orchestra clearly and having sound from others well balanced with the sound of their own instrument and the acoustic response from the main auditorium. These subjective aspects appear to relate to complex perceptual effects like the precedence effect, masking effects and the cocktail-party effect. When relating these effects to physical conditions, a narrow and high stage enclosure with the stage highly exposed to the main auditorium appears most beneficial. Regarding musicians’ impressions of actual stages and objective measurement results, existing methods for assessing the stage acoustically by use of omnidirectional transducers without the orchestra present were found to have only limited relevance. The reliability and validity of the most common acoustic measures (including ST ) were studied in detail. For the assessment and design of stage enclosures, new methods and objective architectural measures have been proposed. A combination of acoustic and architectural measures are found to successfully discriminate the most preferred from the least preferred stages of purpose-built concert halls. The results from judgements of existing stages support the finding of a narrow and high stage enclosure with a highly exposed stage being most beneficial. The objective measures studied are simplified representations of real acoustic conditions. How to improve the assessment of acoustic conditions on stage is also discussed. 5 Preface This thesis is split into nine main chapters: Chapter 1: Introduction. Chapter 2: Background of the study. The literature review. Chapter 3: Musicians’ impressions of acoustic conditions. Studies of impressions of acous- tic conditions on stage in general terms. Chapter 4: Sound propagation within a symphony orchestra. Studies of how the sym- phony orchestra itself affect sound propagation between players. Chapter 5: The effect of reflected sound back towards a symphony orchestra. Studies of how reflected sound may affect perceived conditions among the players. Chapter 6: Computer modelling of stage enclosures including a full symphony orchestra. Studies of how to represent a symphony orchestra in computer models. The developed representation of an orchestra is used to study resulting acoustic responses under different stage enclosure designs, with a symphony orchestra present on stage. Chapter 7: Acoustic measures for assessing acoustic conditions on stage. Studies of the validity and reliability of acoustic responses and measures, assessed without a sym- phony orchestra present on stage. Values of the acoustic measures are compared with subjective impressions for a set of existing stages. Chapter 8: Impressions of eight performance spaces visited regularly. Studies of one or- chestra’s impressions of acoustic conditions in eight performance spaces they visit regularly. Chapter 9: Overall discussion and conclusions. Preliminary results from the research project forming this thesis were presented at interna- tional conferences on acoustics (Barron & Dammerud (2006), Dammerud & Barron (2007) and Dammerud & Barron (2008)). Copies of these papers are not included in this thesis. This thesis was prepared in LATEX (set for double-sided printing) using MiKTeX and LEd. 7 Contents 1 Introduction 15 2 Background of the study 19 2.1 Physical objective sound behaviour within symphony orchestras ........ 19 2.2 The impressions of acoustic conditions on stage ................. 22 2.2.1 Studies of general impressions ....................... 23 2.2.2 Studies of impressions of specific stages ................. 24 2.2.3 Laboratory experiments ........................... 25 2.3 Proposed acoustic measures ............................ 28 2.4 Effect of stage enclosure for conductor and audience ............... 31 2.5 Approaches used for this study ........................... 33 3 Musicians’ impressions of acoustic conditions 35 3.1 Introduction ...................................... 35 3.2 Questionnaire method ................................ 36 3.3 Questionnaire results in general .......................... 36 3.4 Open questions .................................... 37 3.4.1 Non-acoustic issues important on stage .................. 37 3.4.2 Favourite halls ................................ 37 3.4.3 Preference for risers ............................. 38 3.4.4 Hearing others and oneself ......................... 39 3.4.5 Statements on good acoustics for performers ............... 39 3.4.6 Information contained in, and direction of reverberant sound ....... 40 3.4.7 Bloom and projection ............................ 40 9 3.4.8 Discussion and conclusions of results for open questions ........ 41 3.5 Preference rating questions ............................. 42 3.5.1 Comments on loud instruments ....................... 45 3.5.2 Comments on problems with focusing on particular instruments ..... 45 3.5.3 Comments on awareness of reflecting surfaces .............. 45 3.5.4 Correlation of the rating responses ..................... 46 3.5.5 Discussion and conclusions of preference rating results ......... 46 3.6 Specific halls rated by the players .......................... 48 3.6.1 The effect of which orchestras judging acoustic conditions ........ 49 3.6.2 Objective measures associated with the purpose-built concert halls .. 50 3.6.3 Relationships between average overall acoustic impression and objective measures ........................... 52 3.6.4 Comparison of high and medium scoring halls .............. 54 3.6.5 Discussion and conclusions of results for specific halls .......... 55 3.7 Overall conclusions