Basic Documentation

Table 2. Acceptable Laboratory Sound Levels at Various Octave Bands.
Laboratory Type
31
Hz
63
Hz
125
Hz
250
Hz
500
Hz
1000
Hz
2000
Hz
4000
Hz
A. Teaching lab with extensive
speech capability required.
60 to 70 55 to 65 50 to 60 45 to 55 40 to 50 35 to 45 30 to 40 25 to 35
B. Research lab with appreciable
speech capability required.
65 to 75 60 to 70 55 to 65 50 to 60 45 to 55 40 to 50 35 to 45 30 to 40
C. Research lab with minimal
speech capability required.
70 to 80 65 to 75 60 to 70 55 to 65 50 to 60 45 to 55 40 to 50 35 to 45
Fume Hood Sound
If a laboratory room has many fume hoods, the fume
hood sound usually becomes the dominant
component of the room sound. It is generally
accepted that a user located directly in front of a
fume hood with an open sash will experience a
sound level that approximates a NC 55 curve.
Therefore, a good laboratory room layout is very
important. Areas where communication must take
place (such as an integral office area) should be
located as far as possible from the fume hoods and
preferably separated by a partition. VAV ventilation
systems offer the advantage of reducing fume hood
and room airflow as sash openings are reduced,
thus lowering the sound level. Since CAV ventilation
systems do not reduce fume hood or room airflow in
relationship to fume hood sash position, they will
invariably result in higher room sound levels.
Fume hood sound levels should also be a part of
their overall selection criteria. Although fume hood
manufacturers do not normally include certified
sound data with fume hood technical specifications,
they usually provide sound level data upon request.
Attaining an Acceptable Room Sound
Level
The starting point for ensuring attainment of an
acceptable room sound level is establishing the
room's sound criteria. Once the room sound criteria
is established, then the systematic ventilation sound
analysis presented in this report can be followed to
yield the required ventilation equipment sound
ratings. This approach differs from other sound
analysis procedures in that most other procedures
analyze a given ventilation system design to predict
the resulting room sound level.
The chart in Figure 2 enables you to use this
system
atic approach to obtain the required
equipment sound ratings so they can then be
included in the project specifications. (You can
reproduce copies of Figure 2 for your own use.) The
example sou
nd analysis procedure shows how to
use the Figure 2 chart to obtain the required
equipm
ent sound ratings for a typical VAV laboratory
room's supply air system.
Siemens Industry, Inc.
Page 5 of 12
Document No. 1
49-979