Shoebox

Early concert halls consisted mostly of cuboid spaces. This "shoebox" shape emerged from the palace chambers where music was played to entertain aristocrats. The finding that these shoebox volumes provided excellent acoustic experiences for audiences was particularly acknowledged when other, more unusual, shapes failed to succeed.

Fan shape

As public concerts became more and more popular, the ambition to accommodate larger audiences grew in parallel. This explains the evolution of the shoebox shape into the fan shape. With wider walls, fan-shaped halls are very efficient at locating a large number of listeners close to the stage. However, the acoustics of this experimental typology disappointed spectators and so other shapes were explored.

Vineyard

An innovative shape was subsequently developed where the audience surrounds the stage, in the form of staggered terraces like those of a vineyard. Vineyard halls enable listeners to be within close proximity to the stage and provide a democratic experience. However, the acoustics have to be finely tuned in order to provide a sonic experience that can match the impressive architectural effect, or live up to the simple shoebox.

Buro Happold have developed an in-house software package that enables the real-time prototyping of performance spaces and visualisation of sound. Scroll on to find out how this tool helps to "sculpt" the sound in concert halls of different shapes.

Shoebox

Introduction to the Shoebox

The traditional cuboid concert hall shape has built arguably the best reputation for “good acoustics” throughout the course of history.

The key to the excellent acoustic experience in shoebox shaped-halls lies largely in the narrow walls. Sound reflecting off the side walls can provide a remarkable sonic experience in these cuboid halls.

Click on the arrow to visualise influence of lateral sound reflections.

Advantages

The strong early reflections (from the lower parts of the side walls) play a crucial role in the perception of the acoustical quality of a concert hall. The side reflections arriving later (from the upper walls) can also promote a sense of envelopment, spaciousness and richness at the listener’s ears.

The narrow walls provide these traditional halls with spatial and dynamic responsiveness, which naturally leads to highly expressive music with noticeable contrasts. This is optimised when these side walls have a structured or textured finish, promoting reflections to all areas of the room equally.

Challenges

The downside of the shoebox shape, however, is that the audience size is limited (typically < 2000 seats).

When the width of the hall is increased to accommodate a larger audience, the strength of the side reflections notably decreases towards the centre of the hall. This leads to an uneven sound environment across the audience plane and a poorer sonic experience.

Challenges

Lengthening the hall whilst maintaining the narrow side walls maintains the benefits of lateral reflections. However, it brings to light a different issue: the lack of intimacy (and sound strength), both visually and sonically.

As sound travels from the stage towards the back of the hall, it loses energy. The greater the distance between the stage and the back seats, the weaker the direct (unreflected) sound is likely to be perceived. This naturally leads to poor clarity of sound, with the direct sound having very low presence.

This also results in the audience feeling visually disconnected from the performance due to the long distance to the stage.

Fan shape

Introduction to the Fan Shape

The fan shape resembles the configuration of ancient Greek amphitheatres. These outdoor venues relied on the direct sound, which could be maximised by locating the audience as close as possible to the stage in a radial setting. This configuration can accommodate large audiences, which can be located a relatively short distance from the stage.

However, in contrast to the outdoor amphitheatres, the sonic experience in an enclosed space is radically different as the sound environment consists of not only direct sound but also reverberant sound – sound being reflected off room surfaces.

Advantages

The great advantage of this hall typology is the large number of seats it can accommodate. With wide side walls and limited depth, these spaces bring a large audience close to the stage. This contributes to the important circuit of energy between player and patron.

Further to this, the typically raked seating enables clear sightlines with a range of visual distances and seat-to-stage relationships.

Challenges

The very wide, non-parallel walls result in sound being reflected towards the back of the hall, rather than at the audience. The central areas of the hall receive very few early sound reflections, which can be perceived as a lack of sound clarity.

There is very little sense of envelopment, which has a detrimental impact on the perceived sound quality of the hall.

Challenges

The wider the hall, the poorer the musical sound experience is likely to be. Despite the audience being physically close to the stage, the hall may not be perceived as being acoustically intimate as the lateral sound reflections arrive significantly later than the direct sound due to the distance to the side walls.

The sense of fullness of tone is often limited due to the commonly adopted lower ceiling configurations and the higher sound absorption provided by the large audience.

Vineyard

Introduction to the Vineyard

Half way through the 20th century, an unconventional hall typology was developed in the pursuit of novelty and larger audiences.

The vineyard shape emerged as an aesthetically interesting hall breaking with tradition. This innovative shape typically consists of seating blocks or terraces surrounding the stage and with high tent-like ceilings.

Advantages

Given the surround seating arrangement of this type of hall, most seats benefit from a sense of visual and acoustic intimacy. The close proximity to the stage and the raked seating provide clear sightlines and strong direct sound reception for a significant percentage of the audience.

The staggered nature and surround setting of the ‘vineyard terraces’ also enables the audience to be aware of itself and promote a positive atmosphere and concert experience.

Challenges

Clarity of sound is provided through early sound reflections off the vertical surfaces that delimit the individual ‘vineyard terraces’. These surfaces are carefully designed to direct reflections towards seating areas. However, they very rarely provide lateral reflections to the listeners due to their orientation. This can affect the perception of the acoustic quality of the hall given the lack of sense of envelopment and spaciousness.

On the other hand, later reflections off the complex geometry of the entire space contribute towards a sense of fullness.

Challenges

A disadvantage of this concert hall typology is that imbalances in the sound environment across the space can be experienced.

Most musical instruments project sound predominantly forward. This is especially true of solo instruments, where the performer’s body or head may partially obstruct the sound.

Further to this, the seating arrangement of the orchestra has an associated ‘image’, which is characterised by the precise location of the different instrument groups and for which composers have written music specifically.

This means that the audience sitting behind the stage perceives a reversed image of the orchestra, and experiences an incorrect timbre from many instruments.

How we make it work

All concert hall typologies naturally have advantages and disadvantages from an acoustics perspective. At Buro Happold, we fully understand these and can help optimise the architectural design to promote acoustical excellence.

Limit dimensions

Scattering on side walls

The sound experience at the back of a shoebox hall can be enhanced by limiting the dimensions of the auditorium. This can avoid lateral reflections arriving too late (decreasing clarity of sound) or too early (masking the direct sound).

Incorporating irregular surfaces on the side walls helps to provide a more diffuse sound environment with more blended, less discrete sound reflections.

Side panels to direct side reflections towards audience

High ceilings and overhead reflecting panels

Whilst shoebox halls are restricted in seat capacity, fan shaped halls are a good alternative when there is an aspiration to accommodate large audiences.

The lack of clarity and envelopment associated with this hall typology can be overcome by optimising the shape of the side walls to direct reflections towards the audience. This helps provide a sense of envelopment and improve the perceived acoustic quality of the hall.

Similarly, overhead reflecting panels can also help reflect early sound towards the audience and increase the perception of acoustical intimacy.

Limit listeners’ distance to stage

Suspended reflecting panels

Vineyard halls can generally accommodate larger audiences than shoebox halls (typically ~3000 seats). However, the audience size should still be limited to avoid sound from becoming too weak. This can be achieved by restricting the length and width of the hall.

To maximise the orchestra’s sound output, suspended reflecting panels can be installed above the stage to provide support to the performers and help project the sound towards the audience areas to the sides and back of the stage.