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Good acoustic conditions in offices and meeting rooms affect
and improve both concentration and the communication between people. When
using conference phones, good room acoustic is even more
important.
The Human Ear
The human ear picks up the complete
sound picture when people are talking inside a room. This means
that not only does the ear hear the direct sound,
but also the sound reflected from walls and
ceilings (echo) as well as any background noise in the
room. Reflections and background noise affects the clarity of the speech.
While the human air can to a large extent filter out "unwanted"
noise, conference phones can not. Consequently, the need for good
acoustic condition is even more true when conferencing via speakerphones.
The Eclipse conference system from
Gemini Communication connected up to a mobile phone.
Sound Reflections
Echo is sound waves
reflected back and forth between the surfaces in a room. Each time a sound
wave hits a surface, some of it is absorb and some of it is reflected. The
surface's ability to absorb sound waves directly affects the amount of
echo created in the room. There is an obvious time delay between the
direct sound waves and the reflected waves. The delay time depends on the
distance the reflected waves has to travel compared the direct sound. The
higher the reflections are in a room, the less clarity of the speech. The
reflected and delayed sound waves in a room are often referred to as
reverberation time. The lower the reverberation time the better and
typically recommendations are less than 0.5 seconds.
Background Noise
Background noise in an office building is typically
consists of noise from the ventilation system, fans from electronic
devices and outside road traffic. A high background noise reduces the
quality and clarity of the speech as it mixes with the spoken words. We
recommend that the background noise does not exceed 35 dB for office and
30 dB for meeting rooms.
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Using Conference Phones
In addition to
offering high qUality microphones and loudspeakers, a good conference
phone should offer full duplex speech. This means that both parties can
speak at the same time and still hear each other just as one can when
speaking eye to eye. In large rooms and rooms with a high reverberation
time, one can reduce the negative effect of the sound reflections using a
system offering extension microphones. This brings each participant closer
to their microphone which will reduce and possibly cancel out the
reflected sound waves. In rooms with high reverberation time, one may also
experience that the party at the other end hears an echo of his/her own
voice when speaking. A good conference phone should have echo cancelling
to reduce this problem to a minimum.
Ways to Improve the Room Acoustics
The reverberation time in a room depends on the material's
ability to absorb sound waves, the physical size of the
surfaces, the interaction between surfaces of different
materials, the position of the surfaces and the total size
of the room. The ways to improve the acoustics are therefore
different from room to room. It is, however, possible to give
some general guidelines that normally helps in most types of
rooms.
Offices
Most offices have reasonable good acoustics and but if it
has few furniture you will find it advantages to add some
sort of sound absorbent material. This is particularly true
if using a conference phone in the office. We recommend
mounting mineral wool coated plates in the ceiling covering
about 50% of the ceiling. You can further improve the
acoustics by using thick textiles hanging approximately
5 to 10 cm from the wall, e.g. deep fold curtains and wall
rugs.
Floor carpets on the other hand, do not have much
impact of the acoustics in the room.
An example of mounting of sound absorbing mineral wool coated plates in the ceiling.
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Conference Rooms
For smaller conference rooms (6-8 persons), we recommend
a good sound absorbing ceiling in the form of mineral wool coated plates.
If changing to the ceiling is not possible or if you need to further
improve the room, we recommend the same wall decoration as in offices
(deep fold curtains and wall rugs). In rooms where glass is heavily
applied, the room may have an unfortunate reflection between parallel
surfaces. Here we recommend using sound absorbing plates on the wall as
well as the ceiling.
Larger conference rooms may prove more difficult.
In addition to adding sound absorbing material in the ceiling and on the
walls, we also recommend to install a horizontal mounted sound absorbing
surface above the conference table. Required alteration will vary much
more from room to room than when dealing with smaller conference rooms. It
is therefore recommendable to consult acoustic experts when designing or
redesign a room. This is even more important if the room is to have
telephone conference equipment installed.
Installing Conference Phones
The position of microphones and loudspeaker can also
affect the clarity of the speech. You should choose a system that allows
flexibility in positioning of the microphones and loudspeakers and also
carefully follow the recommendation outlined by the manufacturer.
It
is important to remember that conference phone can do little to compensate
for poor room acoustics. An optimal solution can only taken the necessary
action to improve the acoustic quality of the room. Remember that this
also helps on concentration and generally improves the communication
between people.
For exert advice
on acoustics, please contact:
Techno Consult AS
on:
Phone +47 67 57 18 00
Fax: +47 67 57 18 49
or email us at .
Please also
visit our web site www.techno.no.
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