Trane TRG-TRC007-EN manual Sound Power and Sound Pressure

Page 16

period one

Fundamentals of Sound

notes

Sound Power and Sound Pressure

ISound power

KAcoustical energy emitted by the sound source

KUnaffected by the environment

ISound pressure

K Pressure disturbance in the atmosphere

K Affected by strength of source, surroundings, and distance between source and receiver

Figure 11

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. To understand how to measure and specify sound, however, one must first understand the difference between these two properties.

Sound power is the acoustical energy emitted by the sound source, and is expressed in terms of watts (W). It is not affected by the environment.

Sound pressure is a pressure disturbance in the atmosphere, expressed in terms of pascals (Pa), that can be measured directly. Sound pressure magnitude is influenced not only by the strength of the source, but also by the surroundings and the distance from the source to the listener. Sound pressure is what our ears hear and what sound meters measure.

While sound-producing pressure variations within the atmosphere can be measured directly, sound power cannot. It must be calculated from sound pressure, knowing both the character of the source and the modifying influences of the environment.

TRG-TRC007-EN

9

Image 16
Contents Air Conditioning Clinic Fundamentals of Hvac Acoustics Business Reply Mail Comment Card One of the Fundamental SeriesFundamentals of Hvac Acoustics Preface Fundamentals of Hvac AcousticsContents TRG-TRC007-EN Fundamentals of Sound Fundamentals of SoundWhat is Sound? What is Sound?Sound Wave and Frequency Wavelength Broadband Sound Broadband Sound and TonesOctave Bands Octave BandsLogarithmic sums One-Third Octave Bands Sound Power and Sound Pressure Sound Power and Sound PressureAn Analogy DB = 10 log DecibelLogarithmic Scale 10 ´ logEquation for Sound Power Equation for Sound PressureLogarithmic Addition of Decibels 50 dB + 44 dB = 51 dBHuman Ear Sound Perception Rating MethodsHuman Ear Response Loudness Contours Single-Number Rating Methods Response to TonesSingle-Number Rating Methods C Weighting Sound Perception and Rating MethodsWeighting Example Weighting Noise Criteria NC Curves NC-39 Room Criteria RC Curves MPa DB ref Pressure Sound Perception and Rating Methods RC-31 R Phon and Sone Octave-Band Rating Method Octave-Band Rating MethodAcoustical Analysis Acoustical AnalysisSetting a Design Goal Setting a Design GoalAcoustical Analysis Acoustical Analysis Source-Path-Receiver AnalysisSource-Path-Receiver Model Typical Sound Paths AirborneExamples of a Single Sound Path Example of Multiple Sound PathsIdentifying Sound Sources and Paths Modeling Sound Paths Sound-Path ModelingSupply Algorithms for Sound-Path Modeling Computerized Analysis Tools Attenuation and Regeneration Terms Used in Sound-Path ModelingSound Transmission Insertion loss IL Noise reduction NR Transmission loss TL Absorption Reflected Sound Receiver Sound Correction Equipment Sound Rating Equipment Sound RatingFree Field Fields of Measurement= L p1 20 log Distance Correction in a Free FieldLot Near Field Reverberant Field Semireverberant Field Rating Hvac Equipment Hvac Equipment Sound RatingReverberant-Room Method Free-Field Method Industry Standards Ducted Air-Handling Equipment Air Handler Test Configurations Former Methods of Sound Testing ARI Standard Sound Power by Octave Band Review Review-Period OneReview-Period Two Noise criteria NC Room criteria RCReview-Period Three Review-Period Four Review Quiz Questions for PeriodOctave-band frequency, Hz Answers Glossary Glossary Room effect See receiver room correction Glossary Trane