• What are the elements of acoustics? What should come to our minds when acoustics and acoustics in architecture is mentioned?
Sound and acoustics are everywhere: from the resonant, immersive sound in a grand concert hall or a cathedral to the hopefully intimate sound of our offices, schools and homes. Sound and music are used to signify and celebrate important events in our communities and our lives, they define cultures and provide common ground. Music is vital for our psychological well-being, artistic and emotional expression and relaxation. From this introduction, it should be clear that, first of all, the acoustics of a space should reflect its uses – the long reverberation in a cathedral would not work well as a cinema, nor would an office provide the dramatic immersion required for symphony concerts!
Secondly: there is no acoustics without architecture, and there is no architecture without acoustics! In fact, the size of sound waves that humans can hear ranges from a few millimeters to many meters – and these are exactly the same dimensions the architects are interested in: from the microstructure and “texture” of finishes to the larger elements such as balcony fronts, undersides or acoustic reflectors, to the overall shape and volume of a room. Architecture and acoustics go hand in hand, and I often say that “fine acoustics is not there to be seen, it should become part of the architecture.” This is why collaboration between architect and acoustician is so important when designing performing arts spaces, and in good collaborations, at the end, it is often no longer possible to say who has designed what part or aspect of the room.
• Why it is an important issue to make acoustically good spaces?
For a building to be an overall success it must have good acoustics – acoustics that are optimized for its uses, culture and community – not just great ‘visual architecture’. When we experience architectural spaces, be they performing arts venues, schools or urban spaces, we use all of our senses. We are only at the very beginning of understanding how our senses combine to provide us with a multi-modal overall impression of our surroundings, but we do know that acoustics play an important role. An intimate acoustic (sound reflections arriving quickly) can make us feel visually closer and more emotionally connected to a music or drama performance and, to give a totally different example, the spectrum of noise on an air plane affects the taste of the food!
For a performing arts venue to be considered a success requires that it becomes a focal point of its community, is financially sustainable and, for the largest venues, becomes a landmark on the world stage. In this type of building it is of course clear that excellent acoustics are essential for performers to play at their best and to create an engaging, immersive experience for their audiences. Artists, audiences and the media spread the word about the acoustical quality of the venue, which builds its reputation, and that of its home institutions. One of the key reasons London is considering a new concert hall (at great cost) is that the reputation of the British classical music industry is perceived to be restricted by the quality of venues in London. For a new room, we try to develop a unique ‘acoustic character’, adapted to the aspirations of the community. At first this character is in our ‘minds ear’ – just as the architect imagines how the space should look and feel from every perspective. From this basis we work in close collaboration with the architects and engineers to develop a room shape and geometry, audience layout and material choices to bring the ‘acoustic character’ to life.
• In which stage and how acoustics should be handled in newly constructed buildings?
We believe that the best design is holistic, where all acoustical and engineering aspects are seamlessly integrated into the architectural design. Many people seem to think that ‘good acoustics’ can be achieved by hanging panels on the walls or suspending acoustic reflectors. While in renovations or acoustic tuning interventions these are definitely options, the best results are when architecture and acoustics are one.
For this integration to happen, the acousticians must be involved in the design from the very start – architects, acousticians and theatre planners, together with the client, should develop the concept for the building in close collaboration. This takes a great deal of understanding from all sides and the best projects result from teams where everybody assimilates each other’s views and constraints into their own design thinking.
A great example of this is the Fartein Valen, a 1,500-seat concert hall in Stavanger, Norway. Working together with Ratio Architekter of Oslo, we created a harmonious architecture that subtly incorporates significant acoustical complexity: the side balconies hang free of the walls to improve sound propagation along the hall, every balcony front shape and angle is optimized to provide reflections to the audience and for excellent listening conditions on stage, the ceiling of the hall can move 5 m to vary the acoustical volume and resonance of the hall to accommodate different size ensembles, from symphony orchestras to chamber and contemporary music. That the hall now has acoustics considered as some of the best in the world is down to the excellent collaboration within the design team. And the architects took advantage of the acoustic complexity to create a stunning mixture of ‘harmonious simplicity’ and ‘interesting complexity’ in a seemingly classic, wood-finished concert hall.
• How should acoustics design process be for buildings under renovation?
Renovation projects can range from a complete reworking of the interior of a venue, to light-touch (but often still highly significant) acoustical improvements, to safeguarding a beloved concert venue during a refurbishment. Each type of renovation has its own challenges, but they all begin with thoroughly understanding the acoustics of the existing building. This comprises three parts:
Firstly, when a building has experienced users, such as a home orchestra or theatre company, discussions with them are the most important step in understanding what the important acoustical characteristics are that should be preserved andwhat any deficiencies might be. Next, our own listening during performances and rehearsals is essential so that we have a good subjective sense of the character of the room. For historic venues such as La Monnaie opera house in Brussels or Victoria Hall in Geneva, where the existing acoustic is enjoyed by local audiences, it is paramount for us to subjectively understand the character of the room so that we can maintain it through the renovation. Finally, we carry out thorough acoustical measurements – and more listening – to document the characteristics of the building. We seek connections between the measurements and our subjective experience to put our recommendations on a good scientific basis.
We particularly enjoy working on renovations because they involve a different type of creativity to new-build projects – you have an often long history of the building to draw upon, and any design decisions have to be in the context of that history and the existing architecture – this could range from the Louis XIV style at our current Kulturcasino project in Bern, Switzerland to Art Deco at the Flagey concert hall in Brussels, or anything in between. Furthermore, the audience returning to their cherished hall will be serious critics if anything is not to their liking!
• Tuning / Interventions projects are also an important part of your portfolio. Will you please tell us how this aspect of acoustics design is realized?
I think this is because of our background! All acousticians from Kahle Acoustics have a background and education both in music and in natural sciences. I myself have studied physics and have a PhD in acoustics, and at the same time I have worked as a professional musician playing the viola in different international groups. So I know what it feels like to play on a stage – and what can go wrong there; and I know how to design rooms – and what can go wrong there as well. In tunings/interventions, a lot of time is spent “translating”: translating the observations and complaints of the musicians into what this means acoustically, and translating the acoustic deficiencies to features of the room and/or architectural elements. The aim is to find out why a room is creating a problem, and then how to fix it.
Sometimes we feel like a physio-therapist, “listening” to a body and making slight changes so that “all falls in place”. In some venues the acoustical issues are specific to one part of the room, or can be attributed to a particular architectural element. In these cases, significant acoustical improvements can be made by locally tuning surfaces or with discreet interventions.
In other cases, the venue cannot be closed for a long period (often a large renovation requires a venue to be closed for a year or two) and a series of discreet, smaller projects can be fit in between performances or during downtime, for instance during the summer. These kinds of projects allow us to collaborate particularly closely with the conductor, musicians and management since unlike a continuous project we can get productive feedback after each step and use this to steer the next step of intervention.
We have made improvements at a number of venues where conditions for musicians to hear themselves and each other were not good enough. At the Casa da Música in Porto, Portugal, Winterthur Stadthaus concert hall in Switzerland and Stockholm’s Konserthus we developed architecturally integrated acoustical reflectors and strategically located sound absorbing surfaces to improve on-stage hearing and to better balance the louder percussion and brass instruments against the quieter strings and woodwinds. In Stockholm, a further improvement has been to increase the strength and audibility of reverberation from the upper room by installing an electroacoustic enhancement system above the technical grid level-actually using an electro-acoustic solution to solve an architectural acoustics problem. The technical grid was added during a previous renovation for simplified access and covers the whole hall. The grid was attenuating the sound travelling from the stage to the ceiling, creating a transmission loss and a resulting lack of reverberation. The enhancement system subtly amplifies the hall’s own reverberation to replace the resonance lost due to the technical grid. The ceiling has, once again, “fallen in place acoustically” and this is how the hall now sounds.
• Please tell us about your recently completed project of Philharmonie
de Paris. How was the design process?
The Philharmonie de Paris was a particularly challenging and fun project! Not only was this the most prestigious building project in France in living memory, with France’s most wellknown architect Jean Nouvel but in all there were 4 acoustics consultants involved! Kahle Acoustics were acousticians to the client and defined the acoustical brief, supervised the design development, construction and opening. Marshall Day Acoustics of Auckland were the design acousticians with Yasuhisa Toyota of Nagata Acoustics, Los Angeles acting as special advisor to the architect.
Kahle Acoustics’ brief ensured that the acoustics for this iconic hall would be totally unique, contemporary and based on stateof- the-art principles. The new typology sees a compact, intimate inner room for the audience floating within a reverberant outer volume. In this way acoustical intimacy and immediacy is generated by the surfaces of the inner room with resonance and reverberation delivered by the larger volume. The design team worked extremely well together and we congratulate our colleagues – and the architects – on translating our acoustic brief into a beautiful looking and great sounding hall!
• Aside from methods coming from past to date in acoustics field what are the new materials and applications that come out by technological developments?
Acoustics is a relatively young science – although the Greeks established the basic principles of acoustics in designing structures such as the Amphitheatre at Epidaurus, it was not until Helmholtz and W.C. Sabine working in the late 19th Century that the physics of sound began to be thoroughly developed.
The science of acoustics is currently in a very exciting period. On many fronts, the science of acoustics is being improved at a rapid pace: from a better psychological underpinning of how humans hear, to 3D acoustical measurement and playback
techniques and real-time acoustic simulation tools.
The ability to trace sound reflection paths and see the effects of adjustments directly in the architect’s model is a major advancement from the last few years. We can now work at the same pace as architects and propose alternative geometries or parametrics to acoustically optimize the design. The halls in Stavanger and Paris could not have been acoustically optimized to the extent they are without these tools. We have also used these methods to determine the angles of wall panels at the temporary Opéra des Nations and the new Théâtre de Carouge (both in Geneva) and to determine the interior shape of the Fuzhou Opera Hall, China via reverse engineering from acoustical parameters. In many instances we can sit with the architects and make changes together, without having to return to the office for lengthy acoustic computer modeling, which is enormously beneficial for creating a holistic design with acoustics integrated seamlessly into the architecture.
• Recently which project/ space is the most successful one from the viewpoint of acoustics? Why?
Stavanger, a beautiful hall next to a fjord that produces some of the best orchestral sound you have ever heard… Philharmonie de Paris, a novel space, innovative architecture and a relationship between performers and audience (both visually and acoustically) that is different, and exciting… And Bochum, the new concert hall for the Bochumer Symphoniker. Perhaps this is because I was there last week for the first rehearsals of the orchestra in their new space, in a hall that is still not quite yet finished. But the sound is already there and it is beautiful! Or is it just beautiful so see all the happy faces of musicians that discover their new home?
• Will you please tell us about your recent projects and future aims?
Excellent acoustics is the result of excellent collaborations and we hope that our deepening understanding of acoustics makes us better collaborators. At the same time, our aim is always to incorporate the latest developments in acoustics research and psychology into our designs. In recent years we have worked hard to improved our abilities to collaborate even more closely (and quickly) with architects by developing acoustical modeling techniques that operate in the architects’ own 3D model. But acoustics is ultimately all about sound, and these techniques still rely on us converting a visual result into an imagined acoustic result. The next steps will be for us to be able to listen to the effect of architectural changes as we make adjustments to the model in real-time. Yet the ultimate test will always stay the same: listening to real music by real musicians with your own, real ears – this is where the emotions come in and this is where the real excitement is…