Introduction to Acoustics

Noise
Noise is discussed in terms of a source–path–
receiver model. After an introduction to sound
propagation and radiation efficiency, the quantities
measured for noise control are defined, and
the instruments used for noise measurement and
control are described.
The noise emission of sources is discussed
with emphasis on the determination of the sound
power level of a variety of sources. The properties
of two very significant sources of environmental
noise, aircraft and motor vehicles, are presented.
Tire noise is identified as a major noise source for
motor vehicles. Criteria for the noise emission of
sources are given, and the basic principles of noise
control are presented. A section on active control
of noise is included.
The path from the source to the receiver includes
propagation in the atmosphere, noise
barriers, the use of sound-absorptive materials,
and silencers. Guidance is given on the determination
of sound pressure level in a room when the
sound power output of the source is known.
At the receiver, the effects of noise are
presented, including both hearing damage and
annoyance. A brief section is devoted to sound
quality.
Finally, noise regulations and policies are
discussed. Many activities of the US government
are discussed, and information on both state and
local noise policies and regulations are presented.
The activities of the European Union are included,
as are the noise policies in many countries.
23.0.1 The Source–Path–Receiver Model 961
23.0.2 Properties of Sound Waves ......... 962
23.0.3 Radiation Efficiency................... 963
23.0.4 Sound Pressure Level
of Common Sounds ................... 965
23.1 Instruments for Noise Measurements .... 965
23.1.1 Introduction ............................. 965
23.1.2 Sound Level.............................. 966
23. Noise
23.1.3 Sound Exposure
and Sound Exposure Level.......... 967
23.1.4 Frequency Weightings................ 967
23.1.5 Octave and One-Third-Octave
Bands ...................................... 967
23.1.6 Sound Level Meters ................... 968
23.1.7 Multichannel Instruments .......... 969
23.1.8 Sound Intensity Analyzers .......... 969
23.1.9 FFT Analyzers ............................ 969
23.2 Noise Sources ...................................... 970
23.2.1 Measures of Noise Emission ........ 970
23.2.2 International Standards for the
Determination of Sound Power ... 973
23.2.3 Emission Sound Pressure Level.... 977
23.2.4 Other Noise Emission Standards .. 978
23.2.5 Criteria for Noise Emissions......... 979
23.2.6 Principles of Noise Control.......... 981
23.2.7 Noise From Stationary Sources .... 984
23.2.8 Noise from Moving Sources......... 987
23.3 Propagation Paths ............................... 991
23.3.1 Sound Propagation Outdoors ...... 991
23.3.2 Sound Propagation Indoors ........ 993
23.3.3 Sound-Absorptive Materials ....... 995
23.3.4 Ducts and Silencers ................... 998
23.4 Noise and the Receiver......................... 999
23.4.1 Soundscapes............................. 999
23.4.2 Noise Metrics ............................1000
23.4.3 Measurement
of Immission Sound Pressure
Level .......................................1000
23.4.4 Criteria for Noise Immission........1000
23.4.5 Sound Quality ...........................1004
23.5 Regulations and Policy for Noise Control 1006
23.5.1 United States Noise Policies
and Regulations........................1006
23.5.2 European Noise Policy
and Regulations........................1009
23.6 Other Information Resources ................1010
References ..................................................1010
961
Part G 23