Document vVL6EnqjLgqm437YN2Z3BGeEb

344 CHAPTER 24 1960 Guide * R. A. Nielsen: Dirt pattern on walls (ASHVE Transac tions, Vol. 46, 1941, p. 247). ` P. Drinker and T. Hatch: Industrial Dust (McGraw-Hill Co., New York). * Code for Testing Air Cleaning Devices Used in General Yeniiiaium. Section I, Unit or Panel Type Air Filtering De vices (Air Filter Institute, 1953). 1 ASHVE Standard Code for Testing and Bating Air Cleaning Devices Used in General Ventilation Work (ASHVE Transac tions, Voi. 39, 1933, p. 225). 1R. S. Dill: A test method for air filters (ASHVE Transac tions, Vol. 44,1938, p. 379). * H. L. Barnebey: Activated charcoal for air purification (ASHAE Journal Section, Heating, Piping and' Air Condi tioning, March 1958, p. 153). u Laboratory Design for Handling Radioactive Materials (Building Research Advisory Board, National Research Coun cil, Washington, D. C., Research Conference Report, 1952). BIBLIOGRAPHY H. C. Murphy: Design and application of oil-coated air filters (ASHVE Transactions, Vol. 33, 1927, p. 73). W. G. Frank: Operation and maintenance of air filters (Heat ing, Piping and Air Conditioning, May 1931, p. 378). W. G. Frank: Sise and characteristics of air-bome impurities (Heating, Piping and Air Conditioning, January 1932, p. 35). O. Wechaberg: Fundamental principles in the design of dry air filters (ASHvE Journal Section, Heating, Pipingand Axr Conditioning, April 1933, p. 217). H. E. Ziel ana Henry Sleik: The economic factors inconvert ing recirculated air for ventilation (ASHVE Journal Section, Heating, Piping and Air Conditioning, July 1943, p. 367). F. B. Rowley and R. C. Jordan: ASHVE Research Report No. 1094--Air filter performance as affected by kind of dust, rate of dust feed, and air velocity through filter (ASHVE Transactions, Vol. 44, 1938, p. 415). F. B. Rowley and R. C. Jordan: ASHVE Research Report No. 1122--Mr filter performance as affected by low rate of dust feed, various typos of carbon, and dust particle size and density (ASHVE Transactions, Vol. 45,1939, p. 339). F. B. Rowley and R. C. Jordan*. ASHVE Research Report No. 1145--The effect of lint on air filter performance (ASHVE Transactions, Vol. 46, 1940, p. 25). F. B. Rowley and R. C. Jordan: ASHVE Research Report No. 1169--Comparison of the weight, particle count and dis coloration methods of testing air filtcis (ASHVE Transac tions, Vol. 47, 1941, p. 29). F. B. Rowley and R. C. Jordan: ASHVE Research Report No. 1187--Economical air velocities for &jr filtra tion (ASHVE Transactions, Vol. 47, 1941, p. 391). F. B. Rowley and R. C. Jordan: ASHVE Research Report No. 1218--Overloading of viscous air filters during accelerated tests (ASHVE Transactions, Vol. 48,1942, p. 437). G. 'W. Penney: A new electrostatic precipitator (Electrical Engineering, January 1937, p. 159). H. E. Corbitt and N. J. Clark: Electrostatic precipitation for aircraft (Aero Digest, December 1940, p. 132). C. E. Miller: Pointers on selecting equipment for industrial gas cleaning (Chemical and Metallurgical Engineering, Maroh 1938, p. 132). W. A. Schmidt and E. Anderson: Electrical precipitation (Electrical Engineering, August 1938, p. 332). A. W. Simon and L. C. Kron: Electrical precipitation (Elec trical Engineering, February 1932, p. 93). E. Anderson: Some factors and principles involved in the separation and collection of dust, mist, and fume from gases (American Institute of Chemical Engineers Transactions. Vol. 16, 1924, p. 69). R. B. Rathbun: Electrical precipitation of solids from smelter gases (AmericanInstitute ofElectrical Engineers Trans actions, Vol. 41,1922, p. 816). A. C. Stern, J. Baliff, A. E. Perina, R. Crowley, B. Feiner, and A. A. Urbano: Characteristics of unit duat collectors (ASHVE Transactions, Vol. 52, 1946, p. 237). J. M. Kane: Operation, application and effectiveness of dust collection equipment (Reference Section, Heating and Ventilat ing, August 1952). C. A. L&pple: Chapter 9 (Air Pollution Abatement Manual, Manufacturing Chemists Association). S. K. Friedlander, L. Silverman, P. Drinker, mid M- W. First: Handbook on Air Cleaning (U. S. Atomic Energy Com mission, Washington,.D. C.). M. W. First, R. Moschella, L. Silverman, and E. Berly: Per formance of wet-cell washers for various aerosols (Industrial and Engineering Chemistry, Vol. 43, 1951, p. 1363). J. H. Perry: Chemical Engineers Handbook (McGraw-Hill Co., New York, 1950, 3rd ed.). American Industrial Hygiene Association Quarterly, March 1950. R. J. Ruff: Design factors in catalytic fume elimination (Heating and Ventilating, September 1953, p. 84). A. Nutting and R. F. Logsdon: New air filter code (Heating, Piping and Air Conditioning, June 1953, p. 77). li CHAPTER 25 SOUND CONTROL Acoustical Terminology; Apparatus for Measuring Sound; Approaches to the General Problem of Noise Control; Criferio for Noise Control; Kinds of Noise; Noise Generated by Fans, Grilles, and other Sources; Sound Attenuation in Ducts; Determination of Room levels; Cross Transmission between Rooms and through Duct Walls; Controlling Vibration from Machine Mountings THE NOISE created by heating, ventilating, and air- two powers; or It and h designate two sound intensities, and conditioning equipment has become an important factor let M designate the number of corresponding decibeb, then in modem building design. Related to this, and of equal im portance, is the problem of the transmission of speech or M = 10 TP. log -- (1) music from one part of the building to another through venti lating and air-conditioning ducts. The architect and the acous tical engineer cooperate to produce rooms that are satisfactory for speech, music, or other intended uses. The ventilation and or, M -- 10 log,, ~ It (2) acoustical engineers cooperate to ventilate and air condition these rooms to be physically comfortable without adding noise in excess of established requirements. This chapter is planned Alternatively, the ratio of two sound pressures squared b expressed in the same units, to supply part of the information needed to achieve adequate quietness in rooms that are ventilated and-air conditioned through supply ducts. The quieting of unit heaters and coolers M - 10 logit -- - 20 logu ^ P*' P* (3) is assumed to be the job of the manufacturers and is not covered here. Remaining information on cost, availability, durability, and ease of installation can come only through experience with practical installations. These relations tacitly assume that: W - jP/Z, which means that Z, the acoustic impedance, b real, and that for pi and p,, Zi = Zt. Thb b not usually the ease, but because sound pressure b the easiest variable to measure in a sound ACOUSTICAL TERMINOLOGY1 field, the relation: Sound Power W is the power in watts produced by a source of sound. This power may be (a) the total power radiated by the source over its entire frequency range, (6) the power radiated in a limited frequency range, (c) the power radiated in each of a series of contiguous frequency bands, or (d) the power radiated in a certain direction. The frequency range or frequency band should be clearly stated. Sound Intensity I is the power radiated in a specified direc tion through unit area normal to this direction, e.g., watts per square meter, watts per square foot, or watts per square centimeter. Sound Pressure p is the root-mean-square incremental pressure produced when a sound wave passes through an otherwise undisturbed medium. The unit b the microbar (l dyne per sq cm or 0-1 newton per sq m). Frequency f is the rate of repetition of a periodic phenome non. The frequency b the reciprocal of the period, or the time necessary for the phenomenon to repeat. The frequency / of a single tone sound wave b equal to the ratio of the speed of sound c to the wavelength A of the tone. / - c/\, or e * /A. The unit b the cycle per second, or cps. Decibel db b a dimensionless unit for expressing the ratio of two numerical values (usually electrical or mechanical power) on a logarithmic scale. The number of decibels b ten times the logarithm to the base 10 of the numerical ratio of the two quantities. For example, let VFi and Wj designate M - 20 log,, P* (4) is commonly used. Thus, in a sense when used in thb way, the decibel b redefined on the basis of a pressure squared ratio rather than a power ratio. Odaoe Frequency Bands. The frequency range of a noise b frequently broken up into octave frequency bands where, in principle, the upper frequency is twice the lower frequency of the band as shown in the following tabulation. tend Member Usual Frequency Utah Approximate Geometric Mean Frequency 1 20 to 75 cps* 40 2 75 to 150 105 3 150 to 300 210 4 300 to 600 425 5 600 to 1200 850 6 1200 to 2400 1700 7 2400 to 4800 3400 8 4800 to 10,000* 6900 * The highest aad Unrest dm ceteve u indicated. at utuftUjr used, emtain somewhat mate thea