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Trane TRG-TRC007-EN manual Free-FieldMethod, Equipment Sound Rating, period four

Models: TRG-TRC007-EN

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period four

Equipment Sound Rating

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Free-Field Method

Figure 61

The free-field method is commonly used for HVAC equipment that is too large to be tested in a reverberant room. This includes water chillers, cooling towers, and the outdoor sound from packaged rooftop air conditioners and air-cooled condensers.

This type of equipment is placed on a hard surface in an anechoic (or sound- absorbing) room or on a large parking lot outdoors. This approximates the characteristics of sound in a free field above a reflecting plane. That is, the sound-pressure waves travel evenly in a hemispherical pattern, away from the equipment. Sound-power levels are determined by measuring sound-pressure levels on an imaginary hemispherical surface surrounding the equipment.

56	TRG-TRC007-EN

Page 63

Image 63

Trane TRG-TRC007-EN manual Free-FieldMethod, Equipment Sound Rating, period four

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 HVACOne of the Fundamental Series A publication of Trane, an American Standard CompanyFundamentals of HVAC Acoustics Preface Fundamentals of HVAC AcousticsA 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?Sound Wave and Frequency Fundamentals of Soundperiod one Wavelength Fundamentals of Soundperiod 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 BandsOne-ThirdOctave Bands Fundamentals of Soundperiod 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 Methodsperiod two Loudness ContoursSound Perception and Rating Methods period two Response to TonesSingle-NumberRating Methods Sound Perception and Rating MethodsA-B-CWeighting Sound Perception and Rating Methodsperiod two A-WeightingExample Sound Perception and Rating Methodsperiod two A-Weighting Sound Perception and Rating Methodsperiod two Noise Criteria NC Curves Sound Perception and Rating Methodsperiod two NC-39 Sound Perception and Rating Methodsperiod two Noise Criteria NC CurvesRoom Criteria RC Curves Sound Perception and Rating Methodsperiod two dB ref Sound Perception and Rating Methodsperiod two Room Criteria RC CurvesSound Perception and Rating Methods period twonPerceptible 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 CurvesPhon and Sone Sound Perception and Rating Methodsperiod 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 threeSource-Path-ReceiverModel Acoustical Analysisperiod 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 PathsAlgorithms for Sound-PathModeling Acoustical Analysisperiod three Computerized Analysis Tools Acoustical Analysisperiod three Terms Used in Sound-PathModeling Attenuation and RegenerationAcoustical Analysis period threeSound Transmission Acoustical Analysisperiod three IInsertion loss IL INoise reduction NR Acoustical Analysisperiod three Sound TransmissionAbsorption Acoustical Analysisperiod three Reflected Sound Acoustical Analysisperiod three Receiver Sound Correction Acoustical Analysisperiod 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 FieldNear Field Equipment Sound Ratingperiod four source reflective walls Reverberant FieldEquipment Sound Rating period fourSemireverberant Field Equipment Sound Ratingperiod four HVAC Equipment Sound Rating Rating HVAC EquipmentEquipment Sound Rating period fourReverberant-RoomMethod Equipment Sound Ratingperiod four Free-FieldMethod Equipment Sound Ratingperiod four Industry Standards Equipment Sound Ratingperiod four supply-airoutlet Ducted Air-HandlingEquipmentEquipment Sound Rating period fourAir Handler Test Configurations Equipment Sound Ratingperiod 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-PeriodThree Reviewperiod five Review-PeriodFour Reviewperiod five Review period fivenTrane Acoustics Program TAP Quiz Questions for PeriodQuestions 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