Community

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Community EnvironmentalNoise Measurement
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Section IPhysics ofSound
1-20
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Definition of Sound
Fig. I-1 Suspended String
Section I
1
4
Definition of Sound
Fig. I-2 Sine Wave
Section I
1
5
Definition of Sound
Fig. I-3 Compression Rarefaction of air
molecules
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Section I
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Frequency
Fig. I-4 1Hz and 10Hz Sine Waves
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Section I
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Frequency Characteristics

• Low Frequency, Long Wavelength
• Makes for good propagation
• High Frequency, Short Wavelength
• Reflective

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Frequency Response Weighting

• The human ear is capable of responding to
  frequencies ranging from 20 Hz to 20 kHz
• The ear is less efficient at high and low
  frequencies
• In the range from 500 Hz to 4 kHz a normal human
  ear is very sensitive

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Section I
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Frequency Response Weighting
Fig. I-6 A and C weighting curves
Section I
5
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Sound Characteristics

• Directionality
• Reflection
• Pure Tones

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Distance Rules

• Point Source 6 dB
• Line Source 3 dB
• Affected by humidity, frequency, temperature
• Humidity Increase, Attenuation Decrease
• Temperature Increase, Attenuation Decrease
• Frequency Increase, Attenuation Increase

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Surface Influence

• Angle of Incidence and Source Frequency
• Surface Type
• Hard
• Water, asphalt, concrete
• Soft
• Grass, sand, top soil
• Very Soft
• Snow

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Sound Flow in Atmosphere
Warm
Cool
Cool
Warm
Night
Day
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Sound Pressure Level
Fig. I-7 Sine Waves with different sound
pressures
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Section I
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Typical Sound Levels
Fig. I-8 Typical sound levels, measured A
weighted slow response
70 Speech at 1 foot. 60 Background in large
retail store. Speech at 3 feet. 50 Private
business office. Typical home. 40 Quite
residential area. 20 Background in motion picture
studio. 0 Average threshold of hearing, 1 - 4 kHz.
Section I
7
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Typical Sound Levels
Fig. I-8 Typical sound levels, measured A
weighted slow response
140 Super Siren. Jet airplane takeoff at 50
feet 130 Approximate threshold of pain in the
human ear 120 Jet airplane takeoff at 200
feet 110 Riveting machine. Chain Saw. 90 Boiler
room. OSHA permissible exposure level
(PEL). 80 Pneumatic drill at 50 feet.
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Section I
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EPA 1974 Community Levels

• Rural 35 to 50 dBA Ldn
• Quiet Suburb 50
• Normal Suburb 55
• Urban Residential 60
• Noisy Urban 65
• Very Noisy Urban 70

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Addition of Decibels
If the difference between two levels to be added
is - 0 to 1 dB, then add 3 dB to the higher
number - 2 to 3 dB, then add 2 dB to the higher
number - 4 to 7 dB, then add 1 dB to the higher
number - 8 dB or more, then add 0 dB to the
higher number

• Decibels are logrithmic values
• They can not be directly added or subtracted

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Section I
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Response Time

• Fast 125 milliseconds
• Slow 1 second

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Typical Measures

• Leq Level Equivalent
• Lpk Level Peak
• Ln Exceedence Levels
• Ldn Level Day-Night
• CNEL Community Noise Equivalent Level
• OBA Octave Band Levels

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What We Measure
Fig. I-13 RMS (Root-Mean-Square)
Section I
12
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Exceedence Levels

• L01 Maximum
• L10
• L50
• L90 Ambient without Maximum

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Ldn CNEL

• Ldn
• 10 dB penalty between 10 pm 7 am
• CNEL
• 5 dB penalty between 7 pm 10 pm
• 10 dB penalty between 10 pm 7 am

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Octaves
Fig. I-11 Octave Bands

• Focus on the frequency content of the overall
  noise signal
• Important for noise control efforts

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Section I
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Types of Noises

• Noise can be divided into three groups
• Continuous
• Variable
• Impulsive

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Section I
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How The Human Ear Functions
Fig. I-19 Anatomy of the human ear
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Section I
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Major Irritants

• Low frequency signals
• Loud speech
• Impulsive noise
• Levels above 65 dB

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Section II

• Regulatory
• Background

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Typical Sources of Concern

• Vehicle Traffic, especially trucks motorcycles
• Amplified Music
• Rail Aircraft
• Heavy Equipment
• Compressors Pumps
• Firing Ranges
• Race Tracks
• Loud Voices

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Human Factors

• Sleep Disturbance
• Annoyance
• Stress
• Fatigue
• Communication Interference

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Mitigating Circumstances

• Expectations
• Time of Day
• Time of Year
• Duration of Signal
• Attitudes in General

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How Loud?

• Complaints begin typically when the offending
  source is 5 dB louder than the ambient
• Complaints become vigorous when the source is 20
  dB louder than the ambient

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Property Line Concept

• Three dimensional
• Often cited as the location for sampling

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Ambient Noise

• The background noise level without the offending
  noise source
• Typical levels for the locations make-up
• Characterized by L90

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Determining Ambient

• L90
• Stop Source in Question
• Find a Similar Location

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Agencies, Documents, Regulations

• Noise Control Act of 1972
• EPA, 1974
• HUD, 1979
• DOD, FAA
• Federal Highway Administration
• State Laws
• Community Ordinances

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Examples

• EPA 7455 dBA Ldn (770)
• HUD 7965 dBA Ldn (loans)65 to 75 (need
  controls)

• DOD FAA65 dBA Ldn
• Fed. Hwy. Admin.1 hr. Leq of67 dBA for barriers

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Estimating Acceptable Levels

• Ldn2610Log(of people/km2)

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Nuisance Ordinance

• Disorderly Conduct
• Disturbing the Peace
• Subjective Tests

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Community Sources

• Zoning Requirementsi.e. Residential 50 to 55
  Night 55 to 60 Day
• Health Codes
• Ordinances
• Neighboring Communities

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Examples
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Typical Content

• Purpose
• Definitions
• Powers Duties
• Measurement Procedures
• Limits
• Specifically Forbidden Acts
• Exceptions
• Enforcements Procedures

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Exceptions

• Emergency Signals
• Churches
• Civic Events with Permit
• Repairs

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Section IIISound Level Meters Measurement
26-39
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Components of a Sound Level Meter
Fig. III-1 Block Diagram of a Typical Sound
Level Meter
Microphone Amplifier Range
Frequency Control Filter(s)
C
A
Fast/Slow
Display
F
S
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Section III
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Classification of Sound Level Meters

• Three types of SLMs established by ANSI, and IEC
  Standards
• Type 0
• Laboratory grade instrument
• Type 1
• Precision instrument
• Type 2
• General purpose instrument
• For OSHA noise surveys a type 2 or better
  instrument must be used.

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Section III
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Types of Microphones

• Three different types of microphones
• Random Incidence
• Direct Incidence
• Pressure Microphone

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Section III
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Types of Microphones
Fig. III-2a-c Three Different Types of
Microphones
Random Direct Pressure Incidence Incidence Micro
phone
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Section III
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Acoustical Calibrators
Fig. III-4 Typical Calibrator
1
1) Loudspeaker 2) ON/OFF switch 3) Battery
indicator 4) Microphone adapter
2
4
3
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Section III
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Picture of a Model 2900 SLM
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Section III
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2900 SLM Key Pad Functions
Used to change display, logging and communication
SETUP
RANGE
Used to review studies and group studies in files
FUNCTION
MEMORY
Sets measurement range of 60dB from 20 to 80 dB
up to 80 to 140 dB
Selects SPL, Averaging, and Exposure Readouts
RUN PAUSE
Starts and Stops integration and storage
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Section III
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2900 SLM Key Pad Functions
FAST SLOW IMPULSE PEAK
Selects measurement response time
RESET EDIT
ON OFF
A C LIN
Press to turn ON hold for 5 seconds to turn OFF
Clears memory and selects menu setup changes
Selects frequency weighting
PRINT
ENTER
Used to lock in menu changes
Turns on backlight for display
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Section III
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Sound Level Meter Placement Keys

• Location, Location, Location
• Reflection
• Vibration

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Section III
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Meter Height

• 1.2 to 1.8 Meters
• Avoid ground reflection
• Tripods
• Weather Cases

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Measurement Goals

• Source Evaluation
• Lawn mower
• Environmental Affect
• Property owner

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How To Do A Noise Survey

• Check Battery
• Calibrate
• Place Unit
• Place Microphone

• Observe
• Remove Unit
• Record Data

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Section IV
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What To Record In Addition To Sound Levels

• Dates and Times
• Model and Serial Numbers
• Pre and Post Survey Calibration Levels
• Location Descriptions
• Task Descriptions
• Environmental Factors
• Instrument Settings
• Unusual Conditions

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Section IV
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Survey Pitfalls!!!

• Microphone Placement
• Project Assumption
• Geography, burms, buildings
• Wind, Rain, Snow, Clouds
• Battery Calibration

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Section IV
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Environmental Concerns

• Temperature
• Humidity
• Atmospheric Pressure
• Wind
• Radio Frequency Interference
• Magnetic Interference

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Section IV
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Critter Factor

• Birds
• Bugs
• Frogs
• Dogs

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Diagram of a Model Q-300 Noise Dosimeter
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Section IV
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Q-300 Noise Dosimeter Key Pad Functions
RUN PAUSE
Start or Stop integrations Scroll up through
menus, Scroll down through menus, and memory. or
incremental values. or incremental values.
DOSE
AVG
LEVELS
Display SPL, MAX, MIN and Display DOSE,
PDOSE Display LAV, TWA and SEL PEAK. And EXP.
MENU ON/OFF
TIMES
ENTER
Used in the menu to begin Display Pause, RUN
or Turn unit ON and OFF, and And end a change of
a UPPER Limit time in hours access reset (RES
5) Menu items value or or seconds and
minutes State, used during reset.
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Section IV
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Q-300 Dosimeter Parameters From QuestSuite for
Windows
TM
Q300 - Noise Dosimeter Setup (C\QSUITE\DEFQ300.NO
P)
General
Auto-On
Security
Print
Dosimeters
Dosimeter 1 Dosimeter 2 Dosimeter 3 Threshold
(Use 0 for off) Exchange Rate Upper
Limit Criterion Level Response Weighting
Close
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Section IV
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Practical Time

• Meter set-up
• Calibration
• Indoor sample, A/C, F/S, OBA, Peak
• Indoor sample with music
• Road noise, Leq, L10, L50, L90
• Lawn mower, A/C, OBA, Leq

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Section IVControls
26-39
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Typical Solution Techniques

• Barriers Reduces exposure through 1.
  Transmission loss 2. Absorption 3.
  DiffractionKey factor is height and path
  alteration N (2/wavelength) d1 d2 - d

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Other Possibilities

• Distance planning
• Noise Cancellation
• Masking

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Aircraft Noise Approach

• Quieter Aircraft
• Alter Flight Procedures
• Move Airports
• Spend
• Fixing Houses
• Buying Houses

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Conclusion

• There is No
• Substitute for
• Good Planning
• Common Sense