Room Acoustics and Speech Intelligibility

Every church worship service has two elements: SPEECH and MUSIC. Typically, when a church considers the need for upgrading their sound system, they are interested in improving one or both of these elements. It is important to have a basic understanding of the relationship between speech, music and the acoustical characteristics of the worship space.

Speech

Speech is less understandable in rooms that are highly reverberant.

Traditional Music

Where speech intelligibility is degraded by highly reverberant rooms, traditional music is enhanced by higher reverberation in worship spaces.

Contemporary Music

Contemporary music sounds best in spaces that are not reverberant. Put this in an environment with relatively high reverberation and the results can be disastrous.

The Sound System to the Rescue

A properly designed sound system that is installed and aligned correctly will greatly IMPROVE problems associated with room acoustics, music and speech. But please notice, I DID NOT say that a sound system will ELIMINATE acoustical problems.

A sound system can help reduce the effects of highly reverberant levels in a room by doing one or more of the following:

1. Increase the Directionality of the Sound Source

When shouting to someone across the room, you can improve the intelligibility of your voice by cupping your hand around your mouth. A sound system can do the same thing. Using highly directional loudspeakers, a sound system designer can focus the sound energy into areas where people are sitting. This helps improve speech and vocal intelligibility.

 
Too much reflected sound energy

More concentrated sound where it's needed

2. Decrease the Effective Distance Between the Sound Source and the Listener

When standing next to someone in a room, conversation is easy. However, move across the room and intelligibility is hindered. In general, the closer the sound source is to the listener, the higher the intelligibility. In some cases, this is the only effective approach for sound system design. For example, if the sanctuary is highly reverberant and the distance from the loudspeaker to the last pew is 60 feet or greater, one solution for providing good speech intelligibility is to add a delayed loudspeaker (Figure 1).

 
Figure 1

3. Reduce Unnecessary Sound Energy

Events, such as small weddings, that use 20% or less of the seating area actually degrade the sound system's intelligibility. Because empty, unpadded pews are a hard surface, they cause the room to be more reverberant. If possible, turn off any unnecessary loudspeaker components.

As a professional sound system contractor, we have the tools and experience to determine how simple or complex a sound system must be in order to provide adequate intelligibility. We can measure the reverberation characteristics of the room and can predict whether a particular loudspeaker system will provide sufficient intelligibility.

There are some cases where a properly designed and installed sound system will provide adequate intelligibility, but specific acoustical problems in the room may prevent the sound system from providing optimum performance. Many of these situations can be corrected with simple acoustical treatment of the room.

Sometimes the acoustics of the room will prevent the use of any cost-effective sound system solution. At this point, the customer has several options. In some cases, simple acoustical treatment can be included in the sound system design package. There are times, however, when an acoustical consultant should become a part of the project.

The Bottom Line

No matter what specific acoustical problems your church may have, there is only one prudent method for finding the best solution:

• Hire a professional sound system contractor that can accurately measure the acoustical characteristics of the room. If the project involves new construction, there are software tools that can be used to predict the reverberant characteristics of a proposed facility.
• Make-certain that you provide us with ALL the pertinent information regarding styles of music worship.

by Travis Ludwig © 1996 Internet Sound Institute (www.soundinstitute.com). This article is for personal use only. Any commercial reproduction is not permitted without permission. To obtain permission, contact ISI at hopi@soundinstitute.com

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