Trane TRG-TRC007-EN - Manuals

Preface © 20 01 American Standard Inc. All rights reserved TRG-TRC007-EN ii Trane believes that it is incumbent on manufacturers to serve the industry by regularly disseminating information gathered through laboratory research, testing programs, and field experience. The Trane Air Conditioning Clini...

TRG-TRC0 07-EN iii Contents period one Fundamentals of Sound ..................................... 1 What is Sound? ....................................................... 2 Octave Bands ......................................................... 6 Sound Power and Sound Pressure .........................

TRG-TRC0 07-EN 1 notes period one Fundamentals of Sound People have become increasingly conscious of acoustics as a component of a comfortable environment. Sound levels, both indoor and outdoor, can be affected to varying degrees by HVAC equipment and systems. The degree to which the HVAC system aff...

2 TRG-TRC007-EN notes period one Fundamentals of Sound What is Sound? Sound is the audible emissions resulting from the vibration of molecules within an elastic medium. It is generated by either a vibrating surface or the movement of a fluid. In the context of building HVAC systems, this elastic med...

TRG-TRC0 07-EN 3 period one Fundamentals of Sound notes Airborne sound is transmitted away from a vibrating body through the transfer of energy from one air molecule to the next. The vibrating body alternately compresses and rarefies (expands) the air molecules. The pressure fluctuations that result...

4 TRG-TRC007-EN notes period one Fundamentals of Sound The wavelength of the sound is the linear measurement of one complete cycle. The wavelength and frequency of a sound are related by using the following equation: The speed of sound transmission is a physical property of the medium. For air, the ...

TRG-TRC0 07-EN 5 period one Fundamentals of Sound notes The wave form shown in Figure 5 represents sound occurring at a single frequency. This is called a pure tone . A pure sinusoidal wave form, however, is very rare in HVAC acoustics. Typically, sounds are of a broadband nature, meaning that the s...

6 TRG-TRC007-EN notes period one Fundamentals of Sound Again, a pure tone has a single frequency. If a sound in a narrow band of frequencies is significantly greater than the sound at adjacent frequencies, it would be similar to a tone. Tones that stand out enough from the background sound can be ob...

8 TRG-TRC007-EN notes period one Fundamentals of Sound Middle ground between octave-band analysis and full-spectrum analysis is provided by one-third octave-band analysis. One-third octave bands divide the full octaves into thirds. The upper cutoff frequency of each third octave is greater than the ...

TRG-TRC0 07-EN 9 period one Fundamentals of Sound notes Sound Power and Sound Pressure Sound power and sound pressure are two distinct and commonly confused characteristics of sound. Both are generally described using the term decibel (dB), and the term “sound level” is commonly substituted for each...

10 TRG-TRC007-EN notes period one Fundamentals of Sound The following comparison of sound and light may help illustrate the distinction between these two properties. Think of sound power as the wattage rating of a light bulb. Both measure a fixed amount of energy. Whether you put a 100-watt light bu...

TRG-TRC0 07-EN 11 period one Fundamentals of Sound notes Sounds encompass a wide range of volumes, or levels. The loudest sound the human ear can hear without damage due to prolonged exposure is about 1,000,000,000 times greater than the quietest perceptible sound. A range of this magnitude makes us...

12 TRG-TRC007-EN notes period one Fundamentals of Sound A logarithm is the exponent power of the base. In this case, the base is ten. For example, the log 10 of 10 (or 10 1 ) equals 1, the log 10 of 100 (or 10 2 ) equals 2, and the log 10 of 1,000,000,000 (or 10 9 ) equals 9. As mentioned earlier, t...

TRG-TRC0 07-EN 13 period one Fundamentals of Sound notes When a reference value is established and placed in the denominator of the ratio, the dB can be calculated for any value entered into the numerator. The reference value used for calculating sound-power level is 1 picowatt (pW), or 10 -12 watts...

14 TRG-TRC007-EN notes period one Fundamentals of Sound Again, these reference values can be considered the threshold of hearing. The multiplier 20 is used in the sound-pressure level equation instead of 10 because sound power is proportional to the square of sound pressure. Measuring sound using a ...

TRG-TRC0 07-EN 15 notes The study of acoustics is affected by the response of the human ear to sound pressure. Unlike electronic sound-measuring equipment, which provides a repeatable, unbiased analysis of sound pressure, the sensitivity of the human ear varies by frequency and magnitude. Our ears a...

16 TRG-TRC007-EN notes period two Sound Perception and Rating Methods The sensation of loudness is principally a function of sound pressure, however, it also depends upon frequency. As a selective sensory organ, the human ear is more sensitive to high frequencies than to low frequencies. Also, the e...

TRG-TRC0 07-EN 17 period two Sound Perception and Rating Methods notes Additionally, tones evoke a particularly strong response. Recall that a tone is a sound that occurs at a single frequency. Chalk squeaking on a blackboard, for example, produces a tone that is extremely irritating to many people....

18 TRG-TRC007-EN notes period two Sound Perception and Rating Methods shall be X ,” where X is a single-number descriptor conveying the desired quality of sound. The most frequently used single-number descriptors are the A-weighting network, noise criteria (NC), and room criteria (RC). All three sha...

TRG-TRC0 07-EN 19 period two Sound Perception and Rating Methods notes The following steps describe how to calculate an A-weighted value. 1 Starting with the actual sound-pressure levels for the eight octave bands, add or subtract the decibel values represented by the A-weighting curve shown in Figu...

20 TRG-TRC007-EN notes period two Sound Perception and Rating Methods A-weighting is often used to define sound in outdoor environments. For example, local sound ordinances typically regulate dBA levels at property lines. Hearing-related safety standards, written by organizations such as the Occupat...

TRG-TRC0 07-EN 27 period two Sound Perception and Rating Methods notes The phon is another descriptor used to indicate loudness with a single number. The loudness of a sound, expressed in phons, is equal to the sound- pressure level of a standard sound, at 1,000 Hz, that is considered equally loud. ...

28 TRG-TRC007-EN notes period two Sound Perception and Rating Methods Octave-Band Rating Method A more useful method of rating sound level is to use the octave bands discussed earlier. While octave-band data is not as simple to interpret as a single-number rating, it provides much more information a...

TRG-TRC0 07-EN 29 notes period three Acoustical Analysis The primary acoustical design goal for an HVAC system is to achieve a background noise level that is quiet enough so that it does not interfere with the activity requirements of the space and is not obtrusive in sound quality. What is consider...

30 TRG-TRC007-EN notes period three Acoustical Analysis Setting a Design Goal The first step of an acoustical design is to quantify the goal. Period Two introduced several single-number descriptors that designers commonly use to define the acoustical design goal for a space. Each descriptor has its ...

32 TRG-TRC007-EN notes period three Acoustical Analysis Source–Path–Receiver Analysis Achieving the desired acoustical characteristics in a space, however, requires more than selecting an appropriate single-number descriptor. Including a single-number descriptor in a HVAC system specification means ...

TRG-TRC0 07-EN 33 period three Acoustical Analysis notes Predicting the sound level in a given space requires making a model of the system. A source–path–receiver model provides a systematic approach to predict the acoustical characteristics in a space. As the name suggests, this modeling method tra...

34 TRG-TRC007-EN notes period three Acoustical Analysis The work, and art, of an acoustical analysis is in identifying and quantifying the various paths that sound travels from the source to the receiver. There are primarily three different types of sound paths. n Airborne: This is a path where soun...

TRG-TRC0 07-EN 35 period three Acoustical Analysis notes Sound can travel between a single source and the receiver along one or multiple paths. In the case of an air-cooled chiller sitting on the roof of a building, and a receiver located across a parking lot at the edge of the property, sound trave...

36 TRG-TRC007-EN notes period three Acoustical Analysis 1 Supply airborne through the supply ductwork and diffusers and into the space 2 Supply breakout as the sound travels through the walls of the supply ductwork, through the ceiling tile, and into the space 3 Return airborne through the air-handl...

TRG-TRC0 07-EN 37 period three Acoustical Analysis notes Sound-Path Modeling When all the paths have been identified, they can be individually modeled to determine the contribution of each to the total sound heard by the receiver. Sound-path modeling studies how sound from a source changes on its wa...

TRG-TRC0 07-EN 39 period three Acoustical Analysis notes Theoretical equations aid the analysis of some path elements, but prediction equations based on test data and experience prevail. For example, an acoustical lab may have measured the attenuation and regenerated sound from a number of different...

40 TRG-TRC007-EN notes period three Acoustical Analysis Solving these algorithms manually can be tedious and time consuming, especially when one or more paths need further attenuation and the calculations have to be repeated. Fortunately, computer software tools are available to spare analysts from ...

TRG-TRC0 07-EN 41 period three Acoustical Analysis notes Terms Used in Sound-Path Modeling This section introduces several terms that are fairly specific to the science of acoustics. Attenuation refers to the reduction in sound level as sound travels along the path from a source to a receiver. It is...

42 TRG-TRC007-EN notes period three Acoustical Analysis The total sound energy that strikes a surface (W i ) is either reflected (W r ), absorbed by the material (W a ), or transmitted through the material (W t ). A material provides a barrier to the incident sound energy (W i ) when it reduces the ...

44 TRG-TRC007-EN notes period three Acoustical Analysis Absorptive materials work by converting acoustical energy into heat energy. The absorbed energy (W a ) is the portion of the incident sound energy (W i ) that is neither transmitted through the material nor reflected off the material. The absor...

TRG-TRC0 07-EN 45 period three Acoustical Analysis notes Finally, some of the incident sound energy (W i ) bounces off of (or is reflected from) the material. Reflected sound becomes especially important when the sound source and the receiver are located in the same room. Consider a mechanical equip...

46 TRG-TRC007-EN notes period three Acoustical Analysis Receiver sound correction , also called room effect , is the relationship between the sound energy (sound power) entering the room and the sound pressure at a given point in the room where the receiver hears the sound. This reduction in sound i...

TRG-TRC0 07-EN 47 notes period four Equipment Sound Rating As explained in Period One, sound pressure can be directly measured, however, sound power cannot. Because sound pressure is influenced by the surroundings, the most accurate sound data that can be provided for a piece of equipment is sound p...

48 TRG-TRC007-EN notes period four Equipment Sound Rating Fields of Measurement To measure sound pressure correctly, it is important to understand the behavior of sound in various environments, or fields. In theory, a free field is a homogeneous, isotropic medium that is free from boundaries. In pra...

TRG-TRC0 07-EN 49 period four Equipment Sound Rating notes This type of relationship between distance and surface area provides the following simple mathematical model for estimating how sound will change as the distance from the source increases. L p2 = L p1 - 20 log 10 [r 2 / r 1 ] where, L p2 = s...

TRG-TRC0 07-EN 51 period four Equipment Sound Rating notes The near field is an area adjacent to the source where sound does not behave as it would in a free field. Most sound sources, including all HVAC equipment, do not radiate sound in perfectly spherical waves. This is due to the irregular shape...

52 TRG-TRC007-EN notes period four Equipment Sound Rating A reverberant field is nearly the opposite of a free field. Reverberant fields exist in rooms with reflective walls, floors, and ceilings. When a sound source is placed in an enclosed room, the sound waves from the source bounce back and fort...

TRG-TRC0 07-EN 53 period four Equipment Sound Rating notes Most rooms in buildings are somewhere between a free field and a reverberant field environment. Called a semireverberant field , these spaces have some characteristics of both free field and reverberant field environments. The walls, floor, ...

54 TRG-TRC007-EN notes period four Equipment Sound Rating HVAC Equipment Sound Rating As mentioned earlier, because sound pressure is influenced by the surroundings, often the best way for an equipment manufacturer to provide sound data is to provide sound-power levels. Sound-power levels for many t...

TRG-TRC0 07-EN 55 period four Equipment Sound Rating notes The most common test method for HVAC equipment is the reverberant-room method . The objective of a reverberant room is to create a uniform, or diffuse, sound field by reflecting and mixing the sound waves. The walls, floor, and ceiling of th...

TRG-TRC0 07-EN 57 period four Equipment Sound Rating notes Formal standards are written by industry organizations to promote uniformity of data between different manufacturers. Air-Conditioning & Refrigeration Institute (ARI), the Air Movement and Control Association International (AMCA), and th...

58 TRG-TRC007-EN notes period four Equipment Sound Rating One of the best examples to demonstrate the complexity of gathering complete and accurate sound data is air-handling equipment. This involves any type of HVAC equipment that contains a fan and is used to condition and move air through a duct ...

TRG-TRC0 07-EN 59 period four Equipment Sound Rating notes In order to isolate these different paths, the air handler must be tested using a number of different configurations. For example, to determine the portion of the sound that is discharged with the air into the supply ductwork, the air handle...

60 TRG-TRC007-EN notes period four Equipment Sound Rating Historically, there have been several methods used to generate sound data for air handling equipment. Though increasingly less common, there are still cases where fan-sound levels are based on prediction equations such as the generic fan algo...

62 TRG-TRC007-EN notes period four Equipment Sound Rating Depending on the type of equipment, sound ratings for HVAC equipment are typically given as sound-power levels by octave band or as a single dBA rating. Outdoor equipment, such as an air-cooled chiller or condensing unit, may be rated in term...

TRG-TRC0 07-EN 63 notes We will now review the main concepts that were covered in this clinic on the fundamentals of HVAC acoustics. Period One explained some of the basic concepts of sound. Sound is the audible emissions resulting from the vibration of molecules within an elastic medium. It is gene...

64 TRG-TRC007-EN notes period five Review Period Two discussed how the human ear perceives sound. As a selective sensory organ, the human ear is more sensitive to high frequencies than to low frequencies. The sensitivity of the human ear at a particular frequency also changes with loudness. Many sin...

TRG-TRC0 07-EN 65 period five Review notes Period Three walked through the steps of an acoustical analysis, including setting the design target for the indoor or outdoor environment, and performing a source–path–receiver analysis. This method of analysis traces sound from the source to the location ...

66 TRG-TRC007-EN notes period five Review Period Four introduced two common methods used by HVAC equipment manufacturers to provide accurate sound data. Because sound pressure is influenced by the surroundings, the most useful sound data that can be provided for most pieces of equipment is sound pow...

68 TRG-TRC007-EN Questions for Period 1 1 What unit of measure is used to describe frequency? 2 Define a tone. 3 Sound _______ (power or pressure) is what our ears hear and is influenced by the surroundings. Questions for Period 2 4 Which of these two single-number descriptors, A-weighted sound pres...

TRG-TRC0 07-EN 69 Quiz notes Questions for Period 3 7 True or False: Sound can only travel from a source to the receiver along one path. 8 True or False: One piece of HVAC equipment may contain several sound sources. 9 What term is used to describe the reduction in sound that enters a room as it tra...

70 TRG-TRC007-EN 1 Hertz (cycles per second) 2 A sound at a single frequency. A sound at a narrow band of frequencies that is significantly greater than the sound at adjacent frequencies would be similar to a tone. 3 Sound pressure 4 A-weighted sound-pressure level is better for describing outdoor s...

TRG-TRC0 07-EN 71 absorbed sound Sound energy that strikes a material and is converted from sound energy to heat energy within the material. absorption coefficient The ratio of the sound energy absorbed by the material to the total sound energy incident upon the surface of that material. AMCA Air Mo...

74 TRG-TRC007-EN notes Glossary the receiver, and everything it encounters as it travels along the way, constitutes the path. tone A sound in a single frequency. A sound in a narrow band of frequencies that is significantly greater than the sound at adjacent frequencies would be similar to a tone. t...