INTRODUCTION
The single most important aspect regarding sound in a church, synagogue, mosque, or chapel is
intelligibility. In other words, making sure that all of those that are there to hear the message
are able to understand what is being said.
One of the biggest misconceptions of all is: purchasing a new sound system will solve the
problem. This in fact is rarely the case and only after many thousands of dollars are spent do
folks come to the realization that unless the acoustics in the room are managed, a louder PA
system will only cause the problem to get worse.
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THE CHALLENGES
For the most part, large assembly rooms are built with hard surfaces. Windows adorn the walls
and concrete surfaces abound. These hard surfaces allow sound to reflect off of them creating
a dense reverberant field and decay times that can exceed 5 seconds.
When you increase the sound level in a highly reverberant space, the room quickly becomes
o ere ited a d e eeds the roo s a ilit to aturall dissipate the energy. Echo on top of
echo elongates the reverb and the sound becomes an annoying nightmare.
Today, the House of Worship has changed. It is a place where ideas and guidance is
communicated. And with the advent of music performance, the acoustics in the room have
taken on an even more important role. It is therefore critical that the reverberant field be
reduced so that communicating to the patrons can be effectively achieved. This is known as
improving the intelligibility of the room. Ideally, one must reduce the reverb decay time to
below 1 second. In other words, if you clap your hands once loudly, the sound should dissipate
very quickly.
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FREQUENCIES AND THEIR RANGES
This graph shows the frequency range of a typical male voice. And as evident, most of the
energy contained in the human voice ranges between 300Hz and 2000Hz. Because we
communicate in this range, it makes sense that the treatment we plan to apply should, for
obvious reasons, be effective in this range. In other words, because we are most concerned
about controlling the sound in the vocal range, the choice of acoustic panel used to absorb the
energy sound should be one that performs well throughout the voice range.
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Shout
Loud Voice
Raised Voice
Normal Voice
Casual Voice
There is certainly truth to the statement that longer reverberant decay times will enhance
music. But this really only applies to classical instruments that employ the room as part of their
sou d. For i sta e ha er usi sou ds est i a re er era t space. But given the fact
that so a of toda s usi perfor a es are o te porar —controlling drums, bass and
electric guitars needs to be addressed differently. In these instances, increasing the absorption
by adding a greater number of acoustic panels (more surface coverage) and using thicker ones
will help absorb low frequencies.
If longer reverberation times are needed for a choral performance, this can easily be reintroduced into the room by using artificial means such as a digital reverb. This eliminates the
eed for o a le pa els hi h redu es the ost of the i stallatio .
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PANEL PLACEMENT
High and mid frequencies tend to beam like a flashlight. As such, any large flat wall surface will
reflect energy like a mirror. By drawing vectors from the loudspeakers to these hard surfaces to
the seating positions, you can predict where the most obvious problems will be. Strategically
distributing acoustic panels on the available wall surfaces will help attenuate room reflections.
For instance; in a long narrow room, most acousticians tend to focus treatment on the side
alls a d the rear re ei e-e d of the room so that powerful first order reflections are
eliminated and front to back flutter echo is reduced. In wider rooms than fan out, a greater
percentage of the acoustic treatment tends to be applied on the balconies where sound is in
direct line of fire from the speaker system.
Some ceilings are particularly problematic: Rooms that have vaulted ceilings tend to focus the
e erg to ards the iddle of the roo as sou d e hoes off the a gles. Do es a d tu els'
are even more problematic. In these types of spaces, treating the ceiling can be very beneficial.
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How much treatment is needed?
As a general rule of thumb, 15% to 30% wall coverage will provide adequate absorption for a
large assembly hall. The greater the surface coverage you treat with acoustic panels, the
shorter the decay time will be. And as can surmise, the more treatment you put up, the shorter
the reverb decay. A shorter decay of less than 1 second will help tremendously at improving
intelligibility.
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When treating large surfa e areas, usi g ultiple a ousti pa els together i a
odular
fashion' can create a very attractive and uniform appearance while providing significant cost
advantage over ordering custom made oversized panels.
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