1. ACOUSTICS REAL-WORLD HVAC ACOUSTICS BRD Noise and Vibration Control, Inc A presentation by Steffan Kollevoll of BRD Noise and Vibration Control, Inc.

2. ACOUSTICS 101

3. TERMINOLOGY  Sound  Noise  Ambient Noise  Flanking Transmission  Airborne noise  Structure borne noise  Transmission Loss  Insertion Loss Reverberated Noise Reverberated Noise Sound Power Sound Power Sound Pressure Sound Pressure Sound Transmission Class (STC) Sound Transmission Class (STC) Noise Reduction Coefficient (NRC) Noise Reduction Coefficient (NRC) Near Field Near Field Far Field Far Field

4. SOUND POWER VS. SOUND PRESSURE  Critical to understanding manufacturer supplied sound data  AHRI  Specification Impact  Scheduling sound power vs. sound pressure

5. A-WEIGHTING OF DECIBELS Correction factors that turn dB into dBA

6. SOUND DECAY (NEAR VS. FAR)  Near Field Noise  Decay rate of the sound 4 dB per doubling of distance  {Insert decay rate of sound equation}  5’-30’ 4 dB decay rate  Far Field Noise  Decay rate of the sound 6 dB per doubling of distance  {Insert decay rate of sound equation}  30’ or greater 6 dB decay rate

7. INDOOR CHILLER APPLICATIONS

8. DESIGN QUESTIONS TO CONSIDER Where are we now? Baseline data AHRI 575 Where do we need to be? Acceptance Criteria (NC/dBA) Dealing with subjective criteria “Don’t want to hear anything” What needs to be done to achieve compliance? How much will it cost?

9. TRANSMISSION PATHWAYS  Vibration energy transferred from unit to building structure(s).  Airborne radiated noise from equipment components.  Mechanical shaft considerations.  Wall and Ceiling penetrations.

10. SOURCE VS. PATH TREATMENTS  Source Treatment Attenuation  Entry Level  Typical reductions range from 5-7 dBA  Airborne and structure borne transmission pathway addressed at the equipment  Testing  Path Treatment Attenuation  Direct Path vs. Indirect Path  A bit more cost effective, can get expensive for full enclosures  Typical reductions range from 8-20 dBA  Testing

11. SOURCE VS. PATH TREATMENTS (EXAMPLES)  Source Direct PathIndirect Path

12. DEVELOPING THE SPECIFICATION  Schedule vs. written specification  Details to support written specification  Clarity for the contractor/equipment bidders  Ideally embedded in the specification with the equipment (Div 23)  Performance accountability  NC/dBA requirements  May require dialogue with acoustic consultant (path analysis)  Product performance test data  “Factory” or “Off the Shelf” Acoustic Packages  Evaluate for basis and other bidders  Approved bidders

13. OTHER CONSIDERATION  Developing the budget  Installation  Remedial applications  May be limited in attenuation strategies  Limited funds available at the end of the project  Building Occupants

14. OUTDOOR CHILLER / CONDENSING UNIT APPLICATIONS

15. QUESTIONS TO CONSIDER  Where are we now? Baseline data  AHRI 370, AHRI 270  Inside the building  Residential property lines  Where do we need to be?  Acceptance Criteria (NC/dBA)  Dealing with subjective criteria “We don’t want any compliants”  Risk Management approach  What needs to be done to achieve compliance?  How much will it cost?

16. TRANSMISSION PATHWAYS Vibration energy transferred from unit. Grade vs. Rooftop Airborne radiated noise Air intakes, compressor/circuit, condenser fans Window, wall and roof construction. Concern for noise in building unit(s) service Neighboring Property Lines Ambient Noise Ordinances/Codes

17. SOURCE VS. PATH TREATMENTS  Source Treatment Attenuation  Entry Level  Typical reductions range from 2-10 dBA  Airborne and structure borne transmission pathway addressed at the equipment  Testing  Path Treatment Attenuation  Direct Path vs. Indirect Path  A bit more cost effective, can get expensive for full enclosures  Typical reductions range from 10-25 dBA  Testing

18. SOURCE VS. PATH TREATMENTS (EXAMPLES)  Source

19. SOURCE VS. PATH TREATMENTS (EXAMPLES)  Path Indirect

20. SOURCE VS. PATH TREATMENTS (EXAMPLES)  Path Direct

21. DEVELOPING THE SPECIFICATION  Boiler plate specification vs. Custom developed specification  Schedule vs. written specification  Details to support written specification  Clarity for the contractor/equipment bidders  Ideally embedded in the specification with the equipment (Div 23)  Performance accountability  NC/dBA requirements  May require dialogue with acoustic consultant (path analysis)  Product performance test data  “Factory” or “Off the Shelf” Acoustic Packages  Evaluate for BOD and other bidders  Approved bidders

22. OTHER CONSIDERATIONS  Value Engineering  Serviceability and Airflow Considerations  Unit placement  Cost benefit analysis  Installation

23. CURB MOUNTED ROOFTOP EQUIPMENT APPLICATION

24. TRANSMISSION PATHWAYS  In-Duct Fan Noise  Radiated Noise  Ductwork Breakout Noise  Structure-borne Transmission  Outdoor Noise

25. ADDRESSING TRANSMISSION (SOLUTIONS)  In-Duct Fan Noise  Duct Liner and Silencers  Placement  Noise reduction required to obtain NC level desired  Radiated Noise  In-curb acoustic treatment  Old approach vs. newer technologies/products  Ductwork Breakout Noise  Acoustical lagging  Acoustic panel discharge plenums  Structure-borne Transmission  External vs. unit supplied (internal) vibration isolation  Old approach vs. Newer technologies  Penetrations in the roof curb  Noise leaks around duct drops and pipe chases

26. DEVELOPING THE SPECIFICATION  Needs to address multiple noise transmission pathways  Performance Accountability  Specified NC values  Product test data  Scheduled performance embedded with the equipment.  Aerodynamic performance  Pitfalls of a “loose” specification  Inspection/Commissioning

27. CASE HISTORIES

28. INDOOR CHILLER APPLICATION – HAMPSTEAD HILL ACADEMY  Chiller installed in mechanical room with concrete walls and ceiling  Mechanical shaft for refrigerant piping connects mechanical room with classrooms on the next 4 levels  Screw chiller installed without vibration isolation for the connected piping or treatment to address airborne radiated noise entering mechanical shaft  Boiler plate specification with entry level sound attenuation may have prevented the problem  NC 45-40 in core learning classrooms  Building owner highly energized and aggravated at current state of classroom noise  No money left in the budget for a remedial fix, finger pointing

29. OUTDOOR CHILLER APPLICATION – CABANA HILTON  Days INN hotel converted to Cabana Hilton Hotel  New chillers adding during renovation  225 ton air cooled screw chillers  Bare chillers placed on roof of the building, no attenuation provided on chillers  High rise apartments in downtown Miami FL overlooking Cabana Hilton’s roof  Legal action taken by tenants  Building owner fined $10K a day for being out of compliance with governing noise ordinance for city of Miami

30. ROOFTOP APPLICATION-NORRISVILLE ES  Packaged rooftop air-conditioning units installed for in a school building renovation  All units provided with external vibration isolation and silencers in the ductwork  Problems with (1) out of (8) rooftop units; unit directly over the stage area in gymnasium  Space was split between gym, teacher’s office and music classroom  NC 56  Inside of the curb left untreated  Light Gauge sheet metal roof construction, Light Gauge sheet metal curb bottom  Overcut duct drop openings  Tonal noise from the supply and return fans flanking the curb floor and roof deck around duct drop penetrations  Break-in/Break-out noise  Light Gauge ductwork

31. CONCLUSION / RECAP  Sound Power vs Sound Pressure/Terminology Review  Acoustic Design Review  4 questions  Assessment and Problem Definition Review  Transmission pathways  Project Specific  Subjective vs Objective Criteria Review Specification Review