World Class Indoor Acoustics

On January 15th, 2005, the $440 million, new Copenhagen Opera House opened with a Royal Command Performance and the tones of Carl Nielsen, Donizetti, and Rossini. Likening the sound to the gift of a Stradivarius, the Royal theatres musical director was thrilled. It is a world class acoustic he commented, that at the same time is analytical, warm and round. Every subtlety, even the very quietest, reaches out towards the rear seating rows with a clear and golden character. This opera house balances the intimate and the very loud.

The guest conductors, opera directors, music staff and the chairman of the orchestra were equally delighted with the sound achieved. English consulting company Arup Acoustics, responsible for the design of the new opera houses acoustics, chose ODEON modelling software for this and for many of its other major projects within architectural acoustics since 1991.

A Meeting of Music and Acoustics

The Copenhagen Opera House is designed by Danish architect Henning Larsen, and stands on Copenhagens waterfront. The 135,000 square foot buildings main auditorium is adorned with 105,000 sheets of 24-carat gold leaf, boasts seating for as many as 1500, and has an orchestra pit that can accommodate up to 110 musicians. However, as one of the most modern opera houses in the world, luxurious design and architecture are not enough. Technical excellence is also expected, especially for the acoustics. In opera houses and concert halls music and acoustics meet a meeting between art and science materialising in architecture.

Acoustic Simulation How will it Sound?

Acoustic simulations are carried out with sound sources on the stage and in the orchestra pit. Each calculation shows the volume and clarity of the singer and the orchestra. By comparing the two sets of calculations you can estimate the important balance between the singer and the orchestra. For a complete sound simulation you typically have to calculate sound reflections of up to approximately 2 s duration corresponding to a total distance of just under 700 m. This means that in the Opera House you have to calculate reflections up to about 70th order. Each sound reflection is characterised by an angle of incidence, a time delay and a frequency-dependent intensity. By combining this information with the human proportions concerning the position of the ears on the head, it is possible to divide the calculation of the sound into two contributions each reaching the two ears. The final result unequivocally shows how the sound reaches the two ears from the source. Afterwards, this result can be applied with an audio record of speech, song or music.

Subsequently, you can listen to the result with headphones and get an impression of how it will sound on the seat in question. Combining a singer on the stage and an orchestra in the pit in one simulation allows listening tests of the balance, which is so important in an opera house. During the design phase of Copenhagens new opera house, DTUs researchers went a step further and developed a technique allowing a presentation of the simulated sound though a number of loudspeakers as known from a surround system. This was first adopted by Arup Acoustics and is now included in ODEON Version. 7.

By choosing a huge number of receiver positions distributed on all audience areas, you can illustrate the calculated reverberation time as a coloured mapping. Similarly, you can also map the sound level, the clarity, the lateral energy fraction, etc. This technique is an important tool to investigate how evenly the sound is distributed over the audience, and for the specialist it is relatively easy to discover any acoustic problems in the hall.

Acclaimed as second to none, it certainly would appear that the acoustic design of the new opera house is the successful result of untiring research and close cooperation between researchers in architectural acoustics and the users of the research results, reaching the goal of providing acoustic quality that lives up to the highest expectations.

What is ODEON?

ODEON, a reliable, easy-to-use, modelling software tool for indoor acoustics, was developed at the Technical University of Denmark (DTU), and is based on twenty years of research into the development of an advanced method to calculate the sound in new buildings already during the initial planning phase. ODEON PC software simulates the interior acoustics of buildings where, from the geometry and properties of surfaces, acoustics can be calculated, illustrated and listened to. In fact, in addition to the acoustic calculations, you can listen from any seat in the hall solely based on a computer model of the room and the acoustic characteristics of the material surfaces.

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