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Trane TRG-TRC007-EN Typical Sound Paths, Acoustical Analysis, period three, IAirborne, I Breakout

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Typical Sound Paths

period three

Acoustical Analysis

notes

Typical Sound Paths

IAirborne

KSound that travels through supply ductwork, return ductwork, or an open plenum

KCan travel with or against the direction of airflow

I Breakout

KSound that breaks out through the walls of the supply or return ductwork

ITransmission

KSound that travels through walls, floors, or ceilings

Figure 38

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.

nAirborne: This is a path where sound travels with, or against, the direction of airflow. In a HVAC system, sound travels along this type of path through the supply ductwork, return ductwork, or an open plenum.

nBreakout: This type of path is typically associated with sound breaking out through the duct walls and into the space.

nTransmission: This is a path where sound travels through walls, floors, and ceilings. In its simplest form, this path involves sound traveling directly through the air from the source to the receiver.

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Trane TRG-TRC007-EN manual Typical Sound Paths, Acoustical Analysis, period three, IAirborne, I Breakout, ITransmission

Contents

Fundamentals of HVAC Acoustics Air Conditioning ClinicOne of the Fundamental Series TRG-TRC007-ENBUSINESS REPLY MAIL BUSINESS REPLY MAILTRANE Attn Applications Engineering 3600 Pammel Creek Road La Crosse WIResponse Card Comment CardFundamentals of HVAC AcousticsFundamentals of HVAC Acoustics One of the Fundamental Series A publication ofTrane, an American Standard Company A Trane Air Conditioning Clinic PrefaceFundamentals of HVAC Acoustics period two Sound Perception and Rating Methods Contentsperiod three period fiveTRG-TRC007-EN Fundamentals of Sound period oneFundamentals of Sound period oneperiod one What is Sound?What is Sound? Fundamentals of Soundperiod one Sound Wave and FrequencyFundamentals of Sound period one WavelengthFundamentals of Sound Broadband Sound and Tones Broadband SoundFundamentals of Sound period oneFundamentals of Sound Octave Bandsperiod one Octave Bandsperiod one Fundamentals of SoundOctave Bands Octave 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 bandperiod one One-ThirdOctave BandsFundamentals of Sound Sound Power and Sound Pressure Sound Power and Sound PressureFundamentals of Sound period oneFundamentals of Sound An Analogyperiod one K Correlates to bulb wattageDecibel dB = 10 log10Fundamentals of Sound period oneFundamentals of Sound Logarithmic Scaleperiod one ratio= 10 log10 Equation for Sound Power= 20 log10 Equation for Sound Pressure50 dB + 44 dB = 51 dB Logarithmic Addition of DecibelsFundamentals of Sound period oneSound Perception and Rating Methods period twoSound Perception and Rating Methods period twoSound Perception and Rating Methods period twoLoudness Contours Single-NumberRating Methods Response to TonesSound Perception and Rating Methods period twoperiod two A-B-CWeightingSound Perception and Rating Methods period two A-WeightingExampleSound Perception and Rating Methods period two A-WeightingSound Perception and Rating Methods period two Noise Criteria NC CurvesSound Perception and Rating Methods period two Sound Perception and Rating MethodsNoise Criteria NC Curves NC-39period two Room Criteria RC CurvesSound Perception and Rating Methods period two Sound Perception and Rating MethodsRoom Criteria RC Curves dB refnPerceptible 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 Sound Perception and Rating Methodsperiod two period two Sound Perception and Rating MethodsRoom Criteria RC Curves RC-31Rperiod two Phon and SoneSound Perception and Rating Methods Sound Perception and Rating Methods Octave-BandRating Methodperiod two Octave-BandRating MethodAcoustical Analysis period threeAcoustical Analysis period threeperiod three Setting a Design GoalSetting a Design Goal Acoustical AnalysisWhen 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 Setting a Design GoalAcoustical Analysis period threeAcoustical Analysis Acoustical Analysisperiod three Source-Path-ReceiverAnalysisperiod three Source-Path-ReceiverModelAcoustical Analysis Acoustical Analysis Typical Sound Pathsperiod three IAirborneExample of Multiple Sound Paths Examples of a Single Sound PathAcoustical Analysis period threeAcoustical Analysis Identifying Sound Sources and Pathsperiod three packaged rooftop air conditionerAcoustical Analysis Modeling Sound Pathsperiod three Sound-PathModelingperiod three Acoustical AnalysisExample of Multiple Sound Paths supplyperiod three Algorithms for Sound-PathModelingAcoustical Analysis period three Computerized Analysis ToolsAcoustical Analysis Acoustical Analysis Attenuation and Regenerationperiod three Terms Used in Sound-PathModelingperiod three Sound TransmissionAcoustical Analysis period three Acoustical AnalysisSound Transmission IInsertion loss IL INoise reduction NRperiod three AbsorptionAcoustical Analysis period three Reflected SoundAcoustical Analysis period three Receiver Sound CorrectionAcoustical Analysis Equipment Sound Rating period fourEquipment Sound Rating period fourFree Field period fourEquipment Sound Rating Fields of Measurement20 log10 = Lp1Distance Correction in a Free Field Equipment Sound Ratingperiod four Equipment Sound RatingDistance Correction in a Free Field Lp2 = 95 dB - 20 log10 120 ft / 30 ft = 83 dBperiod four Near FieldEquipment Sound Rating Equipment Sound Rating Reverberant Fieldperiod four source reflective wallsperiod four Semireverberant FieldEquipment Sound Rating Equipment Sound Rating Rating HVAC Equipmentperiod four HVAC Equipment Sound Ratingperiod four Reverberant-RoomMethodEquipment Sound Rating period four Free-FieldMethodEquipment Sound Rating period four Industry StandardsEquipment Sound Rating Equipment Sound Rating Ducted Air-HandlingEquipmentperiod four supply-airoutletperiod four Air Handler Test ConfigurationsEquipment Sound Rating Equipment Sound Rating Former Methods of Sound Testingperiod four I ASHRAE generic fan algorithmEquipment Sound Rating ARI Standardperiod four IUses reverberant- room methodEquipment Sound Rating Sound Power by Octave Bandperiod four 1 2 3Review period fiveReview period fiveReview-PeriodTwo period fiveReview TRG-TRC007-ENperiod five Review-PeriodThreeReview period five Review-PeriodFourReview nTrane Acoustics Program TAP Reviewperiod five Questions for Period QuizQuestions for Period Questions for Period QuizQuestions for Period 7True or False Sound can only travel from a source to the receiver along one pathAnswers 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 GlossaryTRG-TRC007-EN Literature Order NumberFile Number E/AV-FND-TRG-TRC007-1101-EN