16.01.2013 Views

Handbook of air conditioning and refrigeration / Shan K

Handbook of air conditioning and refrigeration / Shan K

Handbook of air conditioning and refrigeration / Shan K

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

CHAPTER 19<br />

SOUND CONTROL<br />

19.1 SOUND CONTROL AND SOUND<br />

PATHS 19.1<br />

Sound Control 19.1<br />

Sound Paths 19.2<br />

Control at Design Stage 19.3<br />

Recommended Procedure for<br />

Noise Control 19.3<br />

19.2 FAN, COMPRESSOR, PUMP, AND<br />

AIRFLOW NOISE 19.4<br />

Fan Noise 19.4<br />

Noise from Chillers <strong>and</strong> Pumps 19.4<br />

Airflow Noise 19.5<br />

19.3 SOUND ATTENUATION ALONG<br />

DUCT-BORNE PATH 19.6<br />

Sound Attenuation in Ducts 19.6<br />

Sound Attenuation at Elbows <strong>and</strong> Branch<br />

Take<strong>of</strong>fs 19.9<br />

End Reflection Loss 19.10<br />

Duct-Borne Crosstalk 19.11<br />

Attenuation along Duct-Borne<br />

Path 19.11<br />

19.4 SILENCERS 19.12<br />

Types <strong>of</strong> Silencers 19.13<br />

Characteristics <strong>of</strong> Silencers 19.14<br />

Location <strong>of</strong> Silencers 19.15<br />

Active Silencers 19.16<br />

Selection <strong>of</strong> Silencers 19.17<br />

19.5 FIBERGLASS IN HVAC&R<br />

SYSTEMS 19.17<br />

Problems 19.17<br />

Recommendations 19.18<br />

19.1 SOUND CONTROL AND SOUND PATHS<br />

Sound Control<br />

19.6 RADIATED NOISE AND<br />

TRANSMISSION LOSSES 19.18<br />

Breakout <strong>and</strong> Break-in 19.18<br />

Duct Rumble 19.19<br />

Transmission Losses 19.19<br />

Breakout <strong>and</strong> Break-in Sound<br />

Power Level 19.19<br />

Transmission Loss for Selected Building<br />

Structures 19.23<br />

19.7 RELATIONSHIP BETWEEN ROOM<br />

SOUND POWER LEVEL AND ROOM<br />

SOUND PRESSURE LEVEL 19.23<br />

Single or Multiple Sound<br />

Sources 19.23<br />

Array <strong>of</strong> Ceiling Diffusers 19.24<br />

19.8 NOISE CONTROL FOR A TYPICAL<br />

AIR SYSTEM 19.25<br />

Combination <strong>of</strong> Supply Fan Noise <strong>and</strong><br />

Terminal Noise 19.25<br />

Estimate Sound Pressure Level<br />

for Spaces Served by Terminal<br />

Units 19.25<br />

Environmental Adjustment Factor 19.26<br />

Plenum Ceiling Effect 19.26<br />

19.9 ROOFTOP PACKAGED UNITS 19.29<br />

Basics 19.29<br />

Sound Sources <strong>and</strong> Paths 19.30<br />

Discharge Side Duct Breakout 19.31<br />

Sound Path on Return Side 19.31<br />

Structure-Borne Noise 19.32<br />

REFERENCES 19.32<br />

Sound control for an <strong>air</strong> conditioned space or, more accurately, an occupied zone is provided to attenuate<br />

the HVAC&R equipment sound to an acceptable background level <strong>and</strong> to provide a suitable acoustic<br />

environment for people in the occupied zone. A suitable acoustic environment is as important as a comfortable<br />

thermal environment to the occupants. Noise, or any unwanted sound, is always annoying.<br />

The objective <strong>of</strong> sound control should also be to provide an unobtrusive background sound at a<br />

level low enough that it does not interfere with human activities. Sound quality depends on the relative<br />

intensities <strong>of</strong> the sound levels in various octave b<strong>and</strong>s <strong>of</strong> the audible spectrum. Unobtrusive<br />

sound quality means the following: a balanced distribution over a wide frequency range; no tonal<br />

characteristics such as hiss, whistle, or rumble; <strong>and</strong> a steady sound level.<br />

19.1

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!