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190 CHAPTER 13 TERMINAL EQUIPMENT Control applications for the. following types of terminal equipment are described in their respective chapters of the 1964 Gums And Data Book. Radiant Panels--'Warm Air Ceiling, Chapter 14 --rHot Water, Chapter 14 .. , --Electric, Chapter 15 --Air Conditioning, Chapter 5 Snow Melting, Chapter.83 ; Induction Units, Chapter 3 - DuahDuct Mixing Units, Chapter 2 Room Fan-Coil Units, Chapter 4 Unit heaters, .unit ventilators, and classroom heatingcooling units are disnigswl in Chapter 54 of this volume. Radiators and Convectors When individual room control is used, each radiator and convector is equipped with an automatic control valve. Depending upon the size of the room, one thermostat may control one valve or several valves in unison. Volume Damper or Single-Duct Units When individual,room control is used, each volume damper 1965 Guide And Data Book is equipped with an operator. Often, several air outlets am supplied through one damper. The damper operation is usually controlled by a room-type thermostat. The volume dainper . is. usually set to provide for minimum ventilation requirements, regardless of thermostat demand. When the airsupply system is used for heating as well as cooling, it is necessary to use a heating-cooling thermostat. REFERENCE 1E. J. Brown and J. R. Fellows: Pressure losses and flow characteristics of multiple-leaf dampers (ASHAE Journal Section, Heating, Piping and Air Conditioning, August 1957 p. 119). ' BIBLIOGRAPHY -Automatic Control Terminology (American Society of Me chanical Engineers, 1954). R. H. MacMillan: An Introduction to the Theory oj Control tn Mechanical Engineering (Cambridge University Press. New York, 1951). E. W. F. Feller*. Instrument end-Control Manual Jot Operating Engineer* (McGraw-Hill Book Co, New York. 1947). J. E. Haines: Automatic Control of Heating and Air Con ditioning (McGraw-Hill Book Co, New York, 1953, 1st edj. CHAPTER 14 SOUND CONTROL Terminology, Sound Confro/ Procedure, Determination of Design Criteria, Selection of Room Terminal Units, Required Duct Attenuation, Acoustical Treatment for Duct Systems, Selection of Outdoor Equipment, fro/of/on of Machine Vibration, Checking Completed Installation OUND conditioning, the creation of an acoustical envi /Measured quantityx S ronment'equally as comfortable as the thermal environ ment, has become an accepted part of building design. The Level, in db 8l# \ Reference value / (1) responsibility for specifying what constitutes a proper acous The reference value for a particular quantity identifipa the tic environment for various parts of the building should rest 0 db point of the level scale of that quantity. with the architect, because he alone is in a position to eval Fig. 1 is a graphical presentation of Equation 1. An in uate all factors involved. The air-conditioning system cannot crease in level means that the magnitude.of the sound is in provide the specified acoustic environment but must be com- creased in a certain ratio. For a 3 db increase, the ratio is jratiWt with it This means that the engineer designing the doubled (the quantity is twice its original value). A reduc air-conditioning system must establish not only heating, cool tion in the quantity (and the resulting ratio) to half its original ing, and air Sow performance requirements, but also acoustic value is expressed by a 3 db reduction in level performance Emits for the various components, and must The decibel notation simplifies the process of dealing with specify pertinent installation details. The American Society the tremendous range of sound magnitudes which the human of Heating, Refrigerating and Air-Conditioning Engineers ear can hear. Anywhere within this range, a change of one to has established standards1-*-* for acoustic performance meas two db is about the smallest change the ear can detect. urement so that components can be uniformly and accurately Since the decibel is a measure of ratio only, it is always rated necessary to specify the kind of ratio and the reference value. The purpose of this chapter is to provide a step-by-step pro Two kinds of levels must be distinguished, (1) sound pressure cedure for the acoustic calculations for air-conditioning sys level and (2) sound power lead. The relationship between tems and to present the available design information in a sound power and sound pressure corresponds to that between readily usable form. The information given will include both heat and temperature. The ear and instruments respond to . fundamental principles and relationships derived therefrom; sound pressure, but equipment sound ratings are best ex and also empirical data and generalized results of experience. pressed in terms of sound power, output. like heat, sound Some of the statements and expressions given here will be power cannot be measured directly; it has totbe computed qualified or presented as useful approximations or rules of from sound pressure measurements.1 thumb. This is done to make the content of this chapter rigor Sound pressure levels are always based on the square of the ously correct where possible, and to provide the best avail sound pressure because the acoustical energy is proportional able useful data in all areas, even those where convenient pro to the square of the sound pressure. cedures have not been fully developed. Sound pressure level Lp, in decibels re 0.0002 microbar, is: The basis of this chapter is a procedure for designing the acoustic performance of an air-conditioning installation- This MorSPLl-lOlog,.^)' approach creates a useful framework in which to present the fundamentals of sound control, and indicates the BignifirAnro of various component parts of the installation. It is intended 20lE,(o^m) <2> that much of the information given will be of value to the designer of specific air-conditioning equipment. Due to the diverse nature of such products, however, it is beyond the scope of this chapter to present specific procedures for all such design work. References 4 to 7. will be found useful in this regard. where p '=* sound pressure in microbars or dynes per square centimeter. Sound power Usd Lw in decibels re 10~tt watt, is defined'as: . Lr (or PWL) - 10 log,. (y~) (3) More complete coverage of sound and sound control run be found in References 8 to 13; and information on architec tural acoustics in Reference 14. TERMINOLOGY Levels and Decibels In controlling sound, both the quality (or frequency spectfum) and the magnitude have to be considered. Magnitudes expressed as levels above a standard reference value. The is a measure of the ratio of sound power, or a similar <fuantity, to a reference value, and is "expressed in decibels. wpoaibffity for thi. chapter ta tanked WTC L7. Sound end RATIO Rg. 1 .,.. Graph of Equation 1 for Expressing a Ratio of Sound Power in Terms ofDeabeb 191