Basic Documentation
Table Of Contents
- Getting a Handle on Decibels
- The Frequency Component
- The Octave Bands
- Sound Curves
- Now Come the Complications and Confusion
- NC Sound Curves
- Attaining Acceptable Ventilation Related Sound Levels in Laboratory Rooms
- Equipment Sound Ratings
- Fume Hood Sound
- Attaining an Acceptable Room Sound Level
- Example Analysis of a VAV Research Laboratory Room Supply Air System
- Item 1: Supply Air Sound Level
- Item 2: Space Effect Sound Attenuation
- Item 3: Multiple Sources of Sound
- Item 4: Allowable Supply Air Sound at Diffusers
- Item 5: End Reflection Sound Attenuation at Supply Diffuser Inlet
- Item 6: Supply Air Terminal Duct Attenuation
- Item 7: Duct Division
- Item 8: Allowable Supply Terminal Discharge Sound
- Allowable Room Sound Level
- Room General Exhaust Terminal
- VAV Fume Hoods
- Suggestions for Reducing Excess Room Related Ventilation System Sound
- Conclusion
Example Analysis of a Room General Exhaust and a
VAV Fume Hood
Room Size: 12 ft W × 25 ft L × 9 ft H (2,592
cubic feet)
Fume Hood Exhaust: 1200 cfm maximum
Room General Exhaust: 400 cfm max. with a 6-
inch unlined round duct to general exhaust
terminal.
Six feet exists between the general exhaust grill
and where the sound level would be measured.
Page 10 of 12
Siemens Industry, Inc.
Figure 5 illustrates this arrangement.
Since the room general exhaust duct is round and
unlined it provides very little attenuation and is not
included as an item in the summation chart below.
Item
125
Hz
250
Hz
500
Hz
1000
Hz
2000
Hz
4000
Hz
1 67 62 58 56 54 53
2 +6 +7 +8 +9 +10 +11
3 73 69 66 65 64 64
4 +14 +9 +5 +2 +1 0
5 87 78 71 67 65 64
ROOM GENERAL
EXHAUST TERMINAL
FUME HOOD
EXHAUST TERMINAL
Figure 5. Fume Hood and Room General Exhaust Discharge Sound.
Document No. 1
49-979