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SIZING UP THE HALL
Two halls may look very much alike, but
one may have excellent acoustics and the other may be
terrible. The single most important consideration which
determines whether you will be successful in providing
good sound is its REVERBERATION TIME. This is the number
of seconds that it takes for a single sound to die away
in a single hall. A hall with low reverberation time will
be easy to sound. A hall with a high reverberation time
will be difficult if not impossible to sound properly. To
measure the reverb time, stand in the center of the empty
hall and clap your hands. Count very carefully the
seconds it takes for the sound to die away completely. If
your watch has a second hand, use it; or you can count
one thousand one, one thousand two, etc.
If the reverb time is more than three seconds the sound
will not be good. With a music tempo of 120 beats per
minute and a reverb time of two seconds, along with each
music beat the dancers hear, they will also still be
hearing the last three beats. This is what causes the
music to run together and make it hard to distinguish the
rhythm and the melody.
Let's look at the things that affect reverb time.
Reverberation is caused by sound reflecting back and
fourth from one flat surface to another. The harder and
flatter the surface, the more reverb will be present.
Conversely, soft and irregular surfaces tend to absorb
sound and reduce the reverb time. A ceiling of acoustic
tile or blown fiberglass will greatly reduce
reverberation. Heavy velour drapes covering a hard
surface will also reduce reverb. A wall covered with
acoustic tile will not reflect sound and will reduce
reverberation.
Here are some suggestions to help minimize reverberation.
If there is one wall which reflects more sound than the
others, never aim speakers at that wall. If there is one
wall which absorbs more sound than the others, direct
speakers towards that wall. Try to aim speakers downward,
at the dancers, so the sound won't bounce directly off
the opposite wall. Think of the sound as a beam of light,
and aim it at the dancers, not at a surface from which it
will bounce back. In a reverberant hall, the less volume
you can use the better the sound will be; if your
speakers are well above the dancers' heads you can reach
the farthest dancers with less volume than if they are at
head height or lower. There are things you can do with
the volume and tone controls on your sound system which
will be of some help in a reverberant hall; they will be
discussed later.
Reverberation time is important. One and a half seconds
or less is a good indication that a hall has good
acoustics. If you don't have good sound in such a hall,
either your sound system is inadequate or you are doing
something wrong. Two seconds of reverb is usually
acceptable. If you set up correctly and use care in
operation of the sound system, your sound should be at
least passable. If the reverb is three seconds or more
it's unlikely any type of sound equipment or amount of
expertise will produce truly good sound in this hall.
Certain things can be done, as mentioned above, to make
it less bad, but nothing short of acoustical treatment of
the hall will produce good sound with such a reverb time.
Follow our bird to the next topic
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 Contact
Information
For a complete information package contact Dick
Henschel at:
HILTON AUDIO
PRODUCTS, INC.
1033-E Shary Circle, Concord, California 94518
Phone: 925-682-8390 - Fax: 925-682-8497 - E-mail: hiltonaud@aol.com
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© 2007 - Hilton Audio Products, Inc.
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