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Suggested Reading

1. Rehearsal Rooms

Struggling to improve the acoustics in your band room? Check out how the Medan Band did it.

2. Concerned about playing swing music properly?

Check out my guidelines

3. Ear training exercises for bands

Unlike piano players, ear training is essential for wind band performers. But how many band directors bother to give their bands suitable exercises?

4. Intonation problems

While tuning is simple act of adjusting a length of tubing on a wind instrument (often by reference to a single note), intonation is an ongoing process in which a player strives to match the pitch of others in the ensemble during performance. 

5. “Blowing” a wind instrument

A common misconception among wind players is to believe that the air moves through the instrument in order to produce the sound. This is simply not true. 

6. Conducting – suggestions for home practice

The best way for a conductor to improve is in front of a live ensemble. The unfortunate reality, however, is that this is not always possible. Aspiring conductors therefore have little choice but to find other ways of honing their skills.

 

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Concert Halls

Introduction
Echoes and Sound Absorption
Curved Surfaces and High Ceilings
Flutter Echoes
The Grazing Effect
Sound Shadows
Sounding Boards
Electronic Amplifiers
Noises Originating Outside the Concert Hall

Introduction

Band directors and performers alike are all rightly concerned about the acoustics or sound properties of both their rehearsal rooms and the concert halls to which they have access.  Almost invariably, the complaint is that there is too much reverberation (or not enough!) and that the musicians are therefore unable to give of their best.  This is the reason a few simple guidelines on the subject have been included here. [More detailed, technical approaches can be found in a wide variety of references. See, for example, chapter 8 of Harry Olson's, Music Physics and Engineering, "Theatre, Studio and Room Acoustics", Dover Publications, 1967].  Strictly speaking, of course, it should all be quite unnecessary.  This is a job for architects, not musicians.  Sadly, few architects take the time to consider the acoustics of the buildings they design for low profile school halls or community centres.  In such circumstances it often falls to local musicians themselves to speak up in their capacity as the guardians of good sound production.

The study of acoustics in buildings is complicated by the wide variety of ways in which sound is conveyed, reflected, diffused and absorbed.  The following principles should provide a useful starting point, however.

Echoes and Sound Absorption

It is well known that sound waves are capable of being returned from a reflecting surface to produce echoes.  It is also popularly assumed that these echoes are undesirable in the concert hall.  The reality, however, is a little more complex.  Echoes, or (more accurately) reverberations on or near the stage, assist in hearing by merging with the original sound and increasing its volume.  It is the more distant echoes from other parts of the auditorium that require attention.  Fortunately, absorbent materials such as carpet and thick wall curtains can go a long way towards dampening such undesirable sounds.

The following table gives the absorption coefficients of various materials at different frequencies.  The closer the number is to one (1.00), the greater the absorptive capacity of the material concerned. As a general rule of thumb it may be said that hard surfaces reflect more sound than soft surfaces.  Smooth surfaces are also better reflectors than rough surfaces.

Absorption coefficients at Different Frequencies
Material 250Hz 500Hz 1000Hz
Brickwork 0.04 0.02 0.04
Concrete 0.02 0.02 0.04
Plaster (with solid backing) 0.03 0.02 0.03
Carpet (thick pile) 0.25 0.5 0.5
Audience (in upholstered seats) 0.4 0.46 0.46
Wooden seat (empty) n.a. 0.15 n.a.

Curved Surfaces and High Ceilings

Many band directors do not seem to realise that it is possible for a curved surface to reflect sound like a mirror in such a way that the sound becomes focused on a particular point in the auditorium.  When this happens, anyone located at the particular spot where the echoes converge can hear the sound many times louder than the original.  The result can be grotesque concert performances in which the sounds of particular instruments are greatly magnified in certain parts of the concert hall and barely audible in others.  It follows, therefore,that apses and rounded walls, especially when located behind the stage, are inimical to good music making and should be avoided.

Ceiling domes or other concave surfaces (such as the rear wall of a fan-shaped concert hall) can also produce annoying echoes, particularly in large auditoriums.  The most famous example is the dome above the stage of the Royal Albert Hall.  In this case the problem was addressed by suspending a series of convex “flying saucer” disks directly above the stage in order to prevent the direct sound reaching the concave surface overhead.

Flutter Echoes

Flutter echoes occur when stage or audience sounds such as coughing and programme rustling bounce back and forth across the sides of auditorium.  The problem is particularly noticeable in buildings with parallel walls.  Ideally, the walls of an auditorium should be angled slightly outwards so that the sound path of such noise is dispersed towards the rear of the building. [Of course, it is also true to say that parallel walls tend to add fullness to the tone of the music being performed on stage]. A similar effect can be achieved in an existing building by attaching angled panels to the main wall surface.  These can then act as reflectors, dispersing the sound towards the rear.  They will also help direct side reflections from the stage further down the hall.  This design has the added advantage of allowing stage and house lighting to be more effectively concealed.

The Grazing Effect

The audience themselves absorb much of the strength of the sound as it passes over their heads.  This phenomenon is called the grazing effect.  Combined with a general decrease in the decibel level as distance from the source increases, the grazing effect can make it very difficult for those at the back of the auditorium to hear.

The ideal solution is to introduce tiered seating, with each row of seats raised above the previous one.  Such a design can improve both hearing and sightlines significantly.  Unfortunately, such facilities are not popular in multipurpose community halls.  Apart from the expense, the floor area in such halls often needs to be permanently flat in order to cater for sports events, dances, exhibitions and other such functions.

In such circumstances, there may little that a secondary school band director can do apart from installing an electronic sound system, ensuring that the stage is raised as high as possible, and hoping for the best.  Yet another possibility may be to employ a removable stage that can be positioned in such a way that the audience can be seated on three sides.

Sound Shadows

Other potential interruptions in the path of the sound, such as columns and alcoves also need to be considered.  Fortunately, this problem is not as serious as it might at first appear.  Sound waves, being long, tend to work around objects in a way that light waves cannot.  Sound can also be transmitted fairly easily through certain types of solid objects.  Even so, the possibility of “sound shadows” cannot be completely ignored.

As a general rule of thumb, if a member of the audience cannot see the orchestra clearly, then he or she is not in a good position to hear the music being played.

Sounding Boards

An unresonant or “dead” hall may be improved by placing a flat sounding board behind the stage.  Care must be taken, however, to ensure that the sounding board is close enough to the musicians for the echo it produces to merge with the original sound.  In theatres it may also be necessary to construct some sort of reflector to prevent sound being lost in the fly tower above the stage.  Such a reflector, if it is used, should be made of hardboard or ply, not canvas.  This board may be readied so that it can be lowered into position above the performers by flying lines whenever it is needed.

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Electronic Amplifiers

Electronic amplifiers can also be used to great effect in improving the acoustics of a concert hall.  Generally speaking, loudspeakers should be directive in their transmission of the sound, set well above the heads of the audience and directed downwards.  In this way, the audience themselves will act as absorbers of the sound and thus minimize unwanted echoes.

Noises Originating Outside the Concert Hall

 Dealing with noises originating from outside the rehearsal room or concert hall, such as automobile traffic, can be more problematic.  Solid brick or concrete walls are usually effective in blocking out most of the sound.  Double shell buildings such as the Royal Festival Hall in London, are even more effective in preventing undesirable sounds from entering the building.

Windows and doors, however, present a more serious problem, especially when a lack or air-conditioning in school halls requires at least some windows to be open in order to provide relief from Southeast Asia’s tropical heat. While air-conditioning is clearly better, the fact remains that sound can still travel through closed windows.  Ideally, they should therefore be double.  Patterned or stain glass windows of the type found in churches can also be effective sound barriers because the small leaded panes tend to yield to the noise vibrations instead of passing them on.  Doors should be as heavy as possible.

And finally, if you do find yourself in the unenviable position of having to perform in a large hall characterized by an excessive degree of reverberation, consider altering your program in favour of less energetic pieces.  Under such horrendous acoustic conditions, slower tempos generally work better than faster ones.

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