From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Product data sheet for Burgess Acousti-Pad, a sound-absorbing duct lining, with charts and tables for noise level calculations.
| Identifier | ExFiles\Box 104\2\ scan0201 | |
| Date | 1st January 1936 | |
| Burgess Acousti-Pad Applications Noise from power-driven ventilating systems, which is audible above ordinary occupational room noises, is highly objectionable. This "undesired" sound may consist of three different noises. The first is from the fan or blower, the second is the friction of the air stream in the duct, the third source of noise may be from adjoining rooms served by the same air ducts. Intensities of duct noises for air velocities up to 2000 fpm range from 40 to 65 decibels. Burgess Acousti-Pad duct lining will satisfactorily suppress duct noises when installed in the proper proportion or as a part of ventilation air ducts. For Economical Design The effective silencing of noise created by the rush of air, accomplished by Burgess Acousti-Pad, permits the design of air-conditioning systems with smaller pipes and higher air velocities. This is especially advantageous where the ducts must be located within the wall partitions and are of necessity of a very oblong section. Burgess Acousti-Pad is most effective for a given length in a narrow oblong duct. Provides Thermal Insulation Balsam-Wool, the sound absorbent used in Burgess Acousti-Pad, is one of the best insulating materials known. That portion of an air duct containing Burgess Acousti-Pad does not require any additional insulation. (See page 4). The Acousti-Plate surface offers no more resistance to the flow of air than an ordinary ventilating duct. Burgess Acousti-Plate is treated to prevent corrosion. It may be painted or cleaned without harm to its acoustic function. The perforated metal surface protects the Balsam-Wool from fire just as the screen on a Davy lamp prevents the miner's lamp flame from igniting gas. In addition, the chemical treatment of the Balsam-Wool makes it flame-proof. Sectional and end view of an assembled length of duct lined with Burgess Acousti-Pad Burgess Acousti-Pad Chemically Treated The special process and chemical treatment of the Balsam-Wool makes it impervious to moisture, mold, rot, or decay. It has no odor in itself, and heat or moisture does not generate fumes which may cause complaints. Balsam-Wool does not support insect or germ life. Its fibers are resilient and of uniform density which does not change with heat or vibration. Burgess Acousti-Pad is the most remarkable sound absorbent ever developed for air ducts. Its high acoustic absorption efficiency provides the maximum silencing with the minimum length of lining. The metal facing permits the highest air velocities without harm. How to Calculate Correct Amount of Duct Lining First, determine the noise level of the room to be air-conditioned; second, locate the intersection of the db{Donald Bastow - Suspensions} level and the least dimension of the duct in inches on the Burgess Acousti-Pad chart. Read from this intersection straight down to the number of lineal feet of duct which must be lined. Air velocities, various fan speeds, sizes of ducts, bends, and all factors which cause noise have been taken into consideration in this chart. Occupational Room Noise Levels The list of noise levels is intended to serve as a guide — it is the result of actual measurements. Study the room noise conditions with the normal number of people in the room. If the noise level is above 65 db{Donald Bastow - Suspensions}, duct noise is relatively small and the only object of lining is to prevent that room's noise from traveling to other rooms. The Burgess Acousti-Pad chart is calculated upon the assumption that an increase of not more than three decibels may be tolerated. For more quiet results assume a lower occupational room noise level. Where greater noise (as in skating rinks or dance halls), is not objectionable, choose the higher noise level characteristic of the room. BURGESS ACOUSTI-PAD CHART Y-Axis: LEAST DIMENSION OF DUCT IN INCHES (0" to 78") X-Axis: DUCT LENGTH TO BE LINED — IN FEET (0' to 90') Chart Lines: 60 db{Donald Bastow - Suspensions}, 55 db{Donald Bastow - Suspensions}, 50 db{Donald Bastow - Suspensions}, 45 db{Donald Bastow - Suspensions}, 40 db{Donald Bastow - Suspensions}, 35 db{Donald Bastow - Suspensions}, 30 db{Donald Bastow - Suspensions}, 25 db{Donald Bastow - Suspensions}, 20 db.{Donald Bastow - Suspensions} Noise Levels in Decibels Table 1: Room Location, Levels in Decibels (Max. Min. Typical*) Sound Film Studios, 20, 10, 14 Radio Broadcasting Studios, 20, 10, 14 Planetarium, 25, 15, 20 Residence Apartments, etc., 40, 25, 35 Theaters — Legitimate, 35, 25, 30 Motion Picture, 40, 30, 35 Auditoriums, Concert Halls, etc., 40, 25, 30 Churches, 40, 30, 35 Executive Offices, Private Treated, 40, 25, 33 Untreated, 50, 40, 45 General Offices, 60, 50, 55 Hospitals, 70, 20, 50 Class Rooms, 50, 30, 40 Libraries, Museums, Art Galleries, 45, 30, 40 Public Buildings, Court Houses, Post Offices, etc., 60, 45, 55 Small Stores, 60, 40, 50 Upper Floors, Dept. Stores, 55, 40, 50 Table 2: Room Location, Levels in Decibels (Max. Min. Typical*) Stores, General, including Main Floor, 70, 50, 60 Dept. Stores, 60, 40, 50 Hotel Dining Rooms, 60, 40, 50 Restaurants and Cafeterias, 75, 55, 65 Banking Rooms, 60, 50, 55 Factories, 80, 60, 70 Office Machine Rooms, 80, 60, 70 Railroad Coaches, 80, 60**, 70 Pullman Cars, 75, 55**, 65 Automobiles, 80, 50, 65 Vehicular Tunnels, 95, 75, 85 Airplanes, 100, 80, 90 *It is assumed that if duct noise alone is not greater than these levels of background noise, at any frequency band, results will be commercially satisfactory. When both are heard together, an increase in total level of three db{Donald Bastow - Suspensions} can be anticipated. **For train standing in station a level of about 45 db{Donald Bastow - Suspensions} is the maximum which can ordinarily be tolerated. Copyright 1936, Burgess Battery Co. | ||