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Trane TRG-TRC007-EN manual Sound Wave and Frequency, Fundamentals of Sound, period one

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Sound Wave and Frequency

period one

Fundamentals of Sound

notes

Sound Wave and Frequency
	one cycle
+	frequency, Hz =	cycles
+	frequency, Hz =	seconds
amplitude
-
	time	Figure 4

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 from the displacement of these air molecules take the form of a harmonic, or sine, wave. The amplitude of the wave depicts pressure. The higher the amplitude, the louder the sound.

This transfer of energy takes time. Each complete sequence of motion (compression and rarefaction) constitutes a cycle, and the time required to complete one cycle is the cycle period. The frequency of the periodic motion is the number of cycles that occur in a second. The unit of measure for frequency is the hertz (Hz). One hertz is equal to one cycle per second.

cycles

frequency, Hz = ----------------------

seconds

The terms pitch and frequency are often (incorrectly) used interchangeably. Frequency is an objective quantity that is independent of sound-pressure level. Pitch, however, is a subjective quantity that is primarily based on frequency, but is also dependent on sound-pressure level and composition. Pitch is not measured, but is described with terms like bass, tenor, and soprano.

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Trane TRG-TRC007-EN manual Sound Wave and Frequency, Fundamentals of Sound, period one

Contents

One of the Fundamental Series Air Conditioning ClinicFundamentals of HVAC Acoustics TRG-TRC007-ENTRANE Attn Applications Engineering BUSINESS REPLY MAILBUSINESS REPLY MAIL 3600 Pammel Creek Road La Crosse WIFundamentals of HVAC Comment CardResponse Card AcousticsTrane, 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 three Contentsperiod two Sound Perception and Rating Methods period fiveTRG-TRC007-EN Fundamentals of Sound period oneFundamentals of Sound period oneWhat is Sound? What is Sound?period one Fundamentals of SoundFundamentals of Sound Sound Wave and Frequencyperiod one Fundamentals of Sound Wavelengthperiod one Fundamentals of Sound Broadband SoundBroadband Sound and Tones period oneperiod one Octave BandsFundamentals of Sound Octave BandsOctave Bands Fundamentals of Soundperiod one 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 bandFundamentals of Sound One-ThirdOctave Bandsperiod one Fundamentals of Sound Sound Power and Sound PressureSound Power and Sound Pressure period oneperiod one An AnalogyFundamentals of Sound K Correlates to bulb wattageFundamentals of Sound dB = 10 log10Decibel period oneperiod one Logarithmic ScaleFundamentals of Sound ratio= 20 log10 Equation for Sound Power= 10 log10 Equation for Sound PressureFundamentals of Sound Logarithmic Addition of Decibels50 dB + 44 dB = 51 dB period oneSound Perception and Rating Methods period twoSound Perception and Rating Methods period twoLoudness Contours period twoSound Perception and Rating Methods Sound Perception and Rating Methods Response to TonesSingle-NumberRating Methods period twoSound 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 Noise Criteria NC Curves Sound Perception and Rating Methodsperiod two NC-39Sound Perception and Rating Methods Room Criteria RC Curvesperiod two Room Criteria RC Curves Sound Perception and Rating Methodsperiod two dB refperiod 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 Room Criteria RC Curves Sound Perception and Rating Methodsperiod two RC-31RSound Perception and Rating Methods Phon and Soneperiod two period two Octave-BandRating MethodSound Perception and Rating Methods Octave-BandRating MethodAcoustical Analysis period threeAcoustical Analysis period threeSetting a Design Goal Setting a Design Goalperiod three Acoustical AnalysisAcoustical Analysis 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 period threeperiod three Acoustical AnalysisAcoustical Analysis Source-Path-ReceiverAnalysisAcoustical Analysis Source-Path-ReceiverModelperiod three period three Typical Sound PathsAcoustical Analysis IAirborneAcoustical Analysis Examples of a Single Sound PathExample of Multiple Sound Paths period threeperiod three Identifying Sound Sources and PathsAcoustical Analysis packaged rooftop air conditionerperiod three Modeling Sound PathsAcoustical Analysis Sound-PathModelingExample of Multiple Sound Paths Acoustical Analysisperiod three supplyAcoustical Analysis Algorithms for Sound-PathModelingperiod three Acoustical Analysis Computerized Analysis Toolsperiod three period three Attenuation and RegenerationAcoustical Analysis Terms Used in Sound-PathModelingAcoustical Analysis Sound Transmissionperiod three Sound Transmission Acoustical Analysisperiod three IInsertion loss IL INoise reduction NRAcoustical Analysis Absorptionperiod three Acoustical Analysis Reflected Soundperiod three Acoustical Analysis Receiver Sound Correctionperiod three Equipment Sound Rating period fourEquipment Sound Rating period fourEquipment Sound Rating period fourFree Field Fields of MeasurementDistance Correction in a Free Field = Lp120 log10 Equipment Sound RatingDistance Correction in a Free Field Equipment Sound Ratingperiod four Lp2 = 95 dB - 20 log10 120 ft / 30 ft = 83 dBEquipment Sound Rating Near Fieldperiod four period four Reverberant FieldEquipment Sound Rating source reflective wallsEquipment Sound Rating Semireverberant Fieldperiod four period four Rating HVAC EquipmentEquipment Sound Rating HVAC Equipment Sound RatingEquipment Sound Rating Reverberant-RoomMethodperiod four Equipment Sound Rating Free-FieldMethodperiod four Equipment Sound Rating Industry Standardsperiod four period four Ducted Air-HandlingEquipmentEquipment Sound Rating supply-airoutletEquipment Sound Rating Air Handler Test Configurationsperiod four period four Former Methods of Sound TestingEquipment Sound Rating I ASHRAE generic fan algorithmperiod four ARI StandardEquipment Sound Rating IUses reverberant- room methodperiod four Sound Power by Octave BandEquipment Sound Rating 1 2 3Review period fiveReview period fiveReview period fiveReview-PeriodTwo TRG-TRC007-ENReview Review-PeriodThreeperiod five Review Review-PeriodFourperiod five period five ReviewnTrane Acoustics Program TAP 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 Glossary hertz Hz The unit of measure for frequency. One hertz is equal to one cycle per secondGlossary reverberant 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 pointsGlossary the receiver, and everything it encounters as it travels along the way, constitutes the pathFile Number Literature Order NumberTRG-TRC007-EN E/AV-FND-TRG-TRC007-1101-EN