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Concert Hall Acoustics: Art and Science
The shape we're in
Over the centuries, trial and error had established the ‘shoe box’ shape as good for concert halls because of beneficial side reflections. The shoe box is long, tall and narrow. An example of a shoe box shape is the Royal Festival Hall.
The influence of amphitheatres, theatre and early cinema can be seen in fan-shaped halls, but this design can lead to problems due to a lack of side reflections. Examples of fan-shaped halls are the Barbican Hall, London and the Liverpool Philharmonic Hall.
Acoustic science has created new concert hall shapes over the last half of the 20th century. An example is the ‘Vineyard Terrace’ where the audience is subdivided, providing more beneficial reflections from the dividing walls. Examples of such halls are St. David’s Hall, Cardiff and Bridgewater Hall, Manchester.
Circular and elliptical shapes risk focusing sound on ‘hot spots’. These shapes are favoured by architects, but usually make acousticians nervous! The Royal Albert Hall is elliptical.
The story of the Berlin Philharmonie – a landmark hall
The Berlin Philharmonie was developed in line with the architect’s socialist views and, by a combination of skill and accident, revealed a new way forward for acoustics – vineyard terracing. It also used the radical concept of ‘music in the round’. Hans Scharoun, it’s architect, noted the “people always gather in circles when listening to music informally”, and built on this idea in the design of the concert hall.
Transcript of audio commentary on panel
In this audio demonstration, we will show how the shape of a concert hall influences the music we hear. Music outside may be popular with fireworks, but the quality of the sound is hardly likely to set the world on fire. Move indoors and the sound comes alive, enveloping and involving the listener in the music-making process.Outdoors, we receive sound straight from the orchestra, there are no reflections from the walls, and the sound appears distant. When we play music inside, reflections from the walls, ceiling and floor embellish the sound. With the right type of reflections we make a pleasing sound, especially if there are plenty of reflections arriving from the side.
In shoe box shape halls, plenty of reflections arrive from the side. Halls which are too wide and low lack these important lateral reflections.
When sound reaches the listener from the stage, the same sound signal is received at both ears. This is because the head is symmetrical and the sound to both ears travel an identical path.
When reflections come from the side, the sound at each ear is different. Sound to the furthest ear has to bend around the head. This means the sound arrives later and is significantly altered. The brain senses it is in a room, and a feeling of being enveloped by the music occurs.
In a fan shape hall, the sound often lacks side reflections. But in modern designs, such as a vineyard terrace, plenty of side reflections can be provided. Some of the major work on the importance of lateral reflections was done by a British Acoustician, Mike Barron. These facts now enable us to know why shoe box halls were successful, the narrow tall shape provides plenty of lateral reflections. Knowing this has also been a catalyst for radical designs of halls, particularly in the 1970s and 80s.
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(c) Bridget Shield, Trevor Cox 1999/2000. The material maybe re-used provided a link to the website is provided and a clear acknowledgement to the curators given.