• What are the elements of acoustics? What should come to our minds when acoustics and acoustics in architecture is mentioned?
Vision and sound are our most important means of perception. Architecture is very focused on the visual aspects. Acoustics is ignored in many cases. Nevertheless, sound has major impact on our wellbeing and our communication. Acoustics in spaces is determined by size, geometry and surface materials. In a big space each individual sound source will sound less loud, but it might also last longer. There
is more reverberation. By application of materials that do not reflect but absorb the sound, the reverberation can be reduced. So, this is one of the ways to influence the acoustics of spaces, but it might also impact the visual appearance of a space, so a good collaboration between acoustician and architects is essential. The goal is to let the acoustics be a part of the architecture, so acoustic elements should not be visible as such. Sometimes there is no other option and the acoustical elements are necessarily visible, like suspended reflectors that support the audibility between musicians on stage.
• Why it is an important issue to make acoustically good spaces?
Acoustics of spaces determines how we perceive a sound. How we experience music, if we can understand someone speaking, if we can concentrate in a noisy environment or if we can sleep when noise from outside like road traffic or aircraft enters our homes. Hear impaired people feel a detachment from their surroundings. So, sound and acoustics is very important.
The goals regarding obtaining adequate acoustics can be different, depending on the situation. In many cases it has to do with loudness control, absorbing excess of sound, removing reflections, so the environment is less loud. Examples of these are public spaces like shopping malls, airport halls, but also office spaces, reception halls and museums.
The acoustics create an atmosphere: for example, a quiet, confident atmosphere as opposed to a noisy and aggressive atmosphere. But adequate acoustics can also be a very functional issue: There is no sense to have a speech evacuation system if you can’t understand what is being said. This speech intelligibility issue can only be solved by a good loudspeaker design in combination with adequate acoustics with a lot of sound absorption, especially for large spaces. So, in many cases we work on both: the loudspeaker design and acoustics (e.g. for Abu Dhabi Airport or Amsterdam Airport Schiphol).
In open plan offices we try to do the opposite, obtain a very low speech intelligibility, so people are less disturbed by each other. Not for the meeting rooms of course, in meeting and presentation rooms a high speech intelligibility is needed. This is done by sound reflecting and sound absorbing surfaces, at the right places.
But there are also spaces where good acoustics is of vital importance, like theatres and music venues. A theatre is useless if you can’t understand the actor and a music venue is useless if the music sounds bad. So good acoustics is the prime goal for these spaces.
• How should acoustics design process be in the buildings under renovation?
Renovation is a special situation, especially for performance spaces. There is an existing space, where we can listen how it sounds and we can measure the acoustic properties. And we get feedback from the user, how it the acoustics is experienced. So, we analyze the situation, and then make calculations or do scale model research and propose alterations to the building to improve the acoustics.
This is very interesting work, we learned a lot of these projects. For example, we did the renovation of the Amsterdam Concertgebouw, a world famous building for its marvellous acoustics for symphonic music. Especially interesting are the renovation projects where the acoustics is not good need to be improved. By careful analyzing the existing situation we were able to propose alterations that had a big impact on the acoustic quality. Examples are the concert hall Tonhalle in Düsseldorf and the recent renovation of the Staatsoper Unter den Linden in Berlin. In the latter case we raised the ceiling by 5 meters to create more volume and more reverberance.
• In which stage and how acoustics should be handled in newly constructed buildings?
This is different for different types of buildings, but mostly it is something that has to be considered already at an early stage. For example, if an architect makes a design with as key element the use of brickwork for all surfaces, a later addition of sound absorbing materials could be strongly conflicting his architectural concept.
A very early exploration of the options could be helpful for the architect to focus on an architectural concept that can incorporate the functional, acoustical, requirements.
For performance spaces the geometry is essential for the right acoustics. The reflecting surfaces are directed in a way to provide the right reflections. Sometimes the acoustician makes a design even before an architect is hired. For example, we have been consulting a new theatre that was also intended for opera, musicals and concerts of symphonic music. So, we made a conceptual design with the main dimensions and later an architect was hired to implement this acoustical concept, together with us, into an architectural design.
• What are the acoustic solutions applied to open-air spaces?
Acoustics is typically referring to indoor situations. In outdoor situations there are little reflections, so there is not much acoustics and usually the sound is amplified. However, in outdoor situation the distances are large and when there is a reflection, for example from a building, this might quickly be disturbing. For the classical music festival in Bodrum we covered a building with sound absorption to get rid of the disturbing reflection.
• Would you tell us about your recently completed projects?
We work on about 3000 projects ranging from very small to very large. The most eye-catching projects are the large performance spaces. Last year we finished two concert halls for symphonic music: in Dresden, Germany and in Arnhem, Netherlands and the renovation of the Staatsoper Unter den Linden in Berlin. Although the type of halls is different, the Dresden concert hall is a vineyard shape concert hall and the Arnhem concert hall as a rectangular shape, the sound in all 3 projects has a common feature: a very warm and rich sound. This is also our goal and we are very pleased that this works out so well. Feedback from musicians, audience and critics is overwhelming positive. A few years ago, we realized the Volkswagen Arena in Istanbul. These kinds of venues have much different requirement for the acoustics. It is like the open air spaces: individual reflections can be disturbing so all surfaces, even the audience areas are sound absorptive. Together with the Heineken Music hall (now: Afas Live) and Ziggo Dome Amsterdam, projects we realized a number of years earlier, the Volkswagen Arena has the best acoustics in Europe for amplified music.
• What is the most successful project / venue in terms of acoustics in the recent period? Why?
I would like to mention two: both Staatsoper Berlin and Kulturpalast Dresden. In Dresden we made the vineyard hall sound like a shoebox hall at stalls level. By providing early reflections we were able to realize a very spaciousness and intimate sound at the balconies. Event at the most far away position it feels close to the stage. The critics were laudatory: for example, ‘Romantics of the 21st century.’ (FAZ)
The Opera Berlin was a renovation. We reduced the sound absorption of the walls and by doing so, we created strong side wall reflections. In combination with the creation of a reverberation gallery with a raised ceiling, an overwhelmingly warm sound was created. Also, here the critics were very positive, for example, ‘The acoustic is fabulous.’ (FAZ)
• Aside from methods coming from past to date in acoustics field what are the new materials and applications that come out by technological developments?
Innovation in materials is continuing. All kinds of materials are developed, because of new needs and new developments. For example, finishing materials made from recycling of plastic bottles, with interesting properties like high durability and low air flow resistance. These materials can, mostly in combination with other materials, be applied for acoustic purposes. We have our own, accredited acoustics laboratory and we perform measurements to these products, for example sound absorption, sound insulation or even sound power of equipment. Mostly we discuss results with clients to see if the products can be improved further.