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Trane TRG-TRC007-EN manual period four, Free Field, Equipment Sound Rating, Fields of Measurement

Models: TRG-TRC007-EN

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period four

Equipment Sound Rating

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Free Field

source

Figure 53

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 practice, an example of a free field over a reflecting plane would be a large open area void of obstructions, like a parking lot or meadow.

An ideal sound source, that is, one that radiates sound equally in all directions, placed in a free field generates sound-pressure waves in a spherical pattern. At equal distances from the source, the sound pressure is same in all directions. As the sound waves travel farther away from the source, the area of the sphere increases. Doubling of the distance from the source spreads the sound over four times as much surface area.

48	TRG-TRC007-EN

Page 55

Image 55

Trane TRG-TRC007-EN manual period four, Free Field, Equipment Sound Rating, Fields of Measurement

Contents

TRG-TRC007-EN Air Conditioning ClinicFundamentals of HVAC Acoustics One of the Fundamental Series3600 Pammel Creek Road La Crosse WI BUSINESS REPLY MAILBUSINESS REPLY MAIL TRANE Attn Applications EngineeringAcoustics Comment CardResponse Card Fundamentals of HVACTrane, an American Standard Company One of the Fundamental Series A publication ofFundamentals of HVAC Acoustics Fundamentals of HVAC Acoustics PrefaceA Trane Air Conditioning Clinic period five Contentsperiod two Sound Perception and Rating Methods period threeTRG-TRC007-EN period one period oneFundamentals of Sound Fundamentals of SoundFundamentals of Sound What is Sound?period one What is Sound?Fundamentals of Sound Sound Wave and Frequencyperiod one Fundamentals of Sound Wavelengthperiod one period one Broadband SoundBroadband Sound and Tones Fundamentals of SoundOctave Bands Octave BandsFundamentals of Sound period oneOctave bands compress the range of frequencies between the upper and lower ends of the band into a single value. Sound measured in an octave band is the logarithmic sum of the sound level at each of the frequencies within the band Fundamentals of Soundperiod one Octave BandsFundamentals of Sound One-ThirdOctave Bandsperiod one period one Sound Power and Sound PressureSound Power and Sound Pressure Fundamentals of SoundK Correlates to bulb wattage An AnalogyFundamentals of Sound period oneperiod one dB = 10 log10Decibel Fundamentals of Soundratio Logarithmic ScaleFundamentals of Sound period oneEquation for Sound Pressure Equation for Sound Power= 10 log10 = 20 log10period one Logarithmic Addition of Decibels50 dB + 44 dB = 51 dB Fundamentals of Soundperiod two period twoSound Perception and Rating Methods Sound Perception and Rating MethodsLoudness Contours period twoSound Perception and Rating Methods period two Response to TonesSingle-NumberRating Methods Sound Perception and Rating MethodsSound Perception and Rating Methods A-B-CWeightingperiod two Sound Perception and Rating Methods A-WeightingExampleperiod two Sound Perception and Rating Methods A-Weightingperiod two Sound Perception and Rating Methods Noise Criteria NC Curvesperiod two NC-39 Sound Perception and Rating Methodsperiod two Noise Criteria NC CurvesSound Perception and Rating Methods Room Criteria RC Curvesperiod two dB ref Sound Perception and Rating Methodsperiod two Room Criteria RC Curvesperiod two Sound Perception and Rating MethodsnPerceptible vibration RV The sound level in the octave bands between 16 Hz and 63 Hz falls in the shaded regions A and B. These regions indicate sound-pressurelevels at which walls and ceilings can vibrate perceptibly-rattlingcabinet doors, pictures, ceiling fixtures, and other furnishings in contact with them RC-31R Sound Perception and Rating Methodsperiod two Room Criteria RC CurvesSound Perception and Rating Methods Phon and Soneperiod two Octave-BandRating Method Octave-BandRating MethodSound Perception and Rating Methods period twoperiod three period threeAcoustical Analysis Acoustical AnalysisAcoustical Analysis Setting a Design Goalperiod three Setting a Design Goalperiod three Setting a Design GoalWhen defining the acoustical design goal for an outdoor environment, to meet a local noise ordinance for example, the A-weightedscale is typically used. This generally takes the form of a maximum A-weighted sound-pressurelevel at the lot line of the property Acoustical AnalysisSource-Path-ReceiverAnalysis Acoustical AnalysisAcoustical Analysis period threeAcoustical Analysis Source-Path-ReceiverModelperiod three IAirborne Typical Sound PathsAcoustical Analysis period threeperiod three Examples of a Single Sound PathExample of Multiple Sound Paths Acoustical Analysispackaged rooftop air conditioner Identifying Sound Sources and PathsAcoustical Analysis period threeSound-PathModeling Modeling Sound PathsAcoustical Analysis period threesupply Acoustical Analysisperiod three Example of Multiple Sound PathsAcoustical Analysis Algorithms for Sound-PathModelingperiod three Acoustical Analysis Computerized Analysis Toolsperiod three Terms Used in Sound-PathModeling Attenuation and RegenerationAcoustical Analysis period threeAcoustical Analysis Sound Transmissionperiod three IInsertion loss IL INoise reduction NR Acoustical Analysisperiod three Sound TransmissionAcoustical Analysis Absorptionperiod three Acoustical Analysis Reflected Soundperiod three Acoustical Analysis Receiver Sound Correctionperiod three period four period fourEquipment Sound Rating Equipment Sound RatingFields of Measurement period fourFree Field Equipment Sound RatingEquipment Sound Rating = Lp120 log10 Distance Correction in a Free FieldLp2 = 95 dB - 20 log10 120 ft / 30 ft = 83 dB Equipment Sound Ratingperiod four Distance Correction in a Free FieldEquipment Sound Rating Near Fieldperiod four source reflective walls Reverberant FieldEquipment Sound Rating period fourEquipment Sound Rating Semireverberant Fieldperiod four HVAC Equipment Sound Rating Rating HVAC EquipmentEquipment Sound Rating period fourEquipment Sound Rating Reverberant-RoomMethodperiod four Equipment Sound Rating Free-FieldMethodperiod four Equipment Sound Rating Industry Standardsperiod four supply-airoutlet Ducted Air-HandlingEquipmentEquipment Sound Rating period fourEquipment Sound Rating Air Handler Test Configurationsperiod four I ASHRAE generic fan algorithm Former Methods of Sound TestingEquipment Sound Rating period fourIUses reverberant- room method ARI StandardEquipment Sound Rating period four1 2 3 Sound Power by Octave BandEquipment Sound Rating period fourperiod five period fiveReview ReviewTRG-TRC007-EN period fiveReview-PeriodTwo ReviewReview Review-PeriodThreeperiod five Review Review-PeriodFourperiod five period five ReviewnTrane Acoustics Program TAP Questions for Period QuizQuestions for Period 7True or False Sound can only travel from a source to the receiver along one path QuizQuestions for Period Questions for PeriodAnswers Glossary hertz Hz The unit of measure for frequency. One hertz is equal to one cycle per second Glossaryreverberant field A uniform, or diffuse, sound field that is the opposite of a free field. In a perfectly reverberant field, the sound-pressurelevel is equal at all points Glossarythe receiver, and everything it encounters as it travels along the way, constitutes the path GlossaryE/AV-FND-TRG-TRC007-1101-EN Literature Order NumberTRG-TRC007-EN File Number