The Tower Handbook

14.10: Sound control

a: What is sound control?

Sound control is a general term used for any measure that makes the sound of the bells quieter outside the tower. There are two basic types of sound control, each with a number of variants described below.

b: Can the sound be permanently reduced?

It can, if this is what is appropriate for your tower. There are two approaches:

• Total reduction
  Fill the openings with a sound absorbent material (normally immediately behind the louvres). This is often done in city churches.
• Close range reduction
  Seal the openings at the level of the bells and install a sound lantern on the roof, as shown in the diagram. This projects the sound more or less unaltered at a distance but is much quieter close to the church.

c: Can sound control be made variable?

Yes. It is more complicated than blocking the louvres, but far more appropriate to the situation of many towers because the sound can be reduced for practices, etc, and returned to normal for services and public occasions. There are two approaches:

• Mechanical shutters
  Some form of openable shutter is built into the openings [247]. Depending on design these can achieve about 20dB [248] difference between open and closed. The shutters are operated by cords in the ringing room.
• An all-bell simulator
  For practices the clappers are tied and the simulator [249] provides sound in the ringing room but not outside. This has the drawback that you must go up the tower to silence and un-silence the bells every time you use it.

d: Should we consider fitting sound control?

Do you have a problem? If your tower is close to houses and the residents complain about the bells, or if your ringing is greatly restricted because you fear they would complain about them, then sound control is a possible option. But doing it properly is not cheap and you may upset people who like to hear you ringing on practice night. In many ways the sound lantern is the ideal solution (with or without shutters) since it provides acceptable sound far and wide without deafening those close to the church. Unfortunately in most cases it would be the most expensive, and in many towers would be impossible. For many forms of sound control you may need a faculty, so check with the authorities.

e: What is the best type of sound control?

The pros and cons of the major types have been described above. Many different designs and materials have been used for shutters, ranging from heavy board, marine ply [250] or building slabs, through double layers of glass [251] in hardwood frames to proprietary industrial sound absorbing material [252]. How you fit the shutters is very dependent on the design of your louvre openings. If there is a ledge inside the louvres, you can build a wall of block work with the window in it. If the louvres are flush with the inside of the wall, then you need to find some way of fastening the shutters to the wall.

The opening part need not be as big as the original opening. With a large opening it can be much less [253], with the rest of the area permanently covered. The biggest cut in sound occurs when the last space closes. Putting draught strip round the edge of the shutters makes quite a difference!

f: How effective is sound control?

Many towers have installations that give very satisfactory results in their situation. It depends very much what you need. Do you just want to take the harshness out of the sound or do you want the bells to be inconspicuous when the shutters are closed? Of the solutions installed in towers, some would meet one requirement and some would meet the other. You could be disappointed if you went ahead and installed something that did not match your needs.

The best advice we can give is to talk to people who have installed sound control. Look at what they did, listen to the result. Ask about their experience. Think whether you could adapt their solution to your own tower. If possible, look at several different options before starting any serious design.

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