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Principles of Noise. GCA Safety Committee March 22, 2005. Susan Geier Fahmy, CSP, CCC-A Lovell Safety Management Co., LLC. “ Vision relates people to nature. Sound relates humans to each other.”. Health Effects Attributed to Excessive Exposure to Noise. Lower reading scores

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principles of noise
Principles of Noise

GCA Safety Committee

March 22, 2005

Susan Geier Fahmy, CSP, CCC-A

Lovell Safety Management Co., LLC

health effects attributed to excessive exposure to noise
Health Effects Attributed to Excessive Exposure to Noise
  • Lower reading scores
  • Lower quality of work
    • disturbs concentration
    • disruptive
    • fatigue
    • aggravation and frustration
  • Stress - “fight or flight response”
    • adrenalin surge
    • heart and breathing rate increases
    • muscles tense
health effects attributed to excessive exposure to noise4
Elevated blood pressure



Vasoconstriction of peripheral blood vessels

Sore throat

Gastrointestinal disorders


Allergic reactions

Sleeping disorders

Damage to the brain stem

Health Effects Attributed to Excessive Exposure to Noise
sources of noise
Motor vehicles

Air traffic






Power tools

Emergency vehicles



Sources of Noise

Unwanted sound

what is sound
What is Sound ?
  • An oscillation in pressure in a medium (such as air)
  • The oscillation travels through the medium at a certain speed and magnitude
properties of sound
Properties of Sound
  • Frequency (Pitch)
  • Intensity (Loudness)
frequency pitch
Frequency - Pitch

# of cycles a wave passes by a point in space per unit of time

Cycles/ second or Hertz (Hz)


The Height of the Wave

Sound Pressure Level – Decibel

how do we hear
How Do We Hear?
  • Outer Ear
  • Middle Ear
  • Inner Ear
The Inner Ear

Sensori Neural Hearing Loss

Noise Induced Hearing Loss

effects of noise
Effects of Noise
  • Sensorineural Hearing Loss
    • Destruction of hair cells in the cochlea
    • Outer hair cells (high frequency receptors) are first affected
    • Continued exposure collapses other hair cells

**Damage is initially temporary and then permanent!

how do we measure all of this
How Do We Measure All of This?

Measuring Pitch (Frequency)

  • Hertz or Cycles Per Second
measuring loudness
Measuring Loudness

Measure intensity or sound pressure

  • Pressure = force/ area
  • Unit of pressure is measured in “Pascals”
  • 0.00002 Pascals 100,000 pascals
the decibel
The Decibel

Means Nothing Without a Reference

dB SPL – Sound Pressure Level 20 micropascals = 0 dBSPL

dB HTL – Hearing Threshold Level Frequency Dependent

dB A Mimics Human Hearing

db C Mimics Flat SPL

normal hearing frequency range
‘Normal’ Hearing Frequency Range

Intensity: 0 dbHTL – 25 dBHTL

Frequencies: 500 Hz - 2 kHz

Noise Induced Hearing Loss

Loss of high frequency acuity

s’s, x’s, f’s difficult to distinguish

decibels are logarithmic

Decibels are Logarithmic

Cannot Add and Subtract - Are Not Linear

Difference between 5 dBSPL and 10 dBSPL


The Difference between 10 dBSPL and 15 dBSPL

  • Ear responds to logs (dB) as if the sound pressure is a linear increment
  • Doubling of perceived loudness is approximately a 3 dBSPL increase
common noise levels dbspl

Common Noise Levels - dBSPL

Barely Audible 10 dBWatch Ticking 20 dBStreet With out Traffic 40 dBNormal Conversation 60 dBHeavy truck 90 dB

Pneumatic chipper 100 dB

Typical Rock Concert 100 dBJet Engine (800 ft away) 120 dBJackhammer 120 dB


Orb. Sand.

Table Saw


Belt Sander


Metal Shear

Hand Drill

Circular Saw

Tile Saw

Impact Wrench

Miter Saw

Chop Saw

Chain Saw

Hammer Drill










Noise Levels forCommon Tools


a scale dba
A - Scale (dBA)
  • Attenuation of low frequencies
  • Enhances high frequency perception
  • Human ears attenuate sounds below 1 kHz
  • We perceive high frequency sounds to be louder than low frequency sounds, though they might have equal sound pressure
measurement of sound
Measurement of Sound
  • Sound Level Meters (type 1 or 2)
    • Measures continuous sound pressure instantaneously
    • A scale, slow response
    • Set to “max” or Lmax (for OSHA/NYC measurements)
    • Gives instantaneous readout
    • Measurement done in hearing zone
noise dosimeters
Noise Dosimeters
  • Will measure sound levels which are constantly fluctuating
  • Integrate sound pressure with time
  • Worn by the worker for the entire shift
  • Readout indicates percentage of the permissible exposure limit (90 dBA @ 8 hours) to which employee was exposed
ambient sound
Ambient Sound

Measurements taken at a comparable site in the

nearby area

noise control
Noise Control

Source Receiver


source control
Source Control
  • Quieter Work Process
    • Internal damping
  • Enclose Equipment
    • Walls with high Transmission Loss
    • Lead rubber fabric draperies
    • Noise jackets
  • Alter/ modify equipment
    • Internal damping
    • Mufflers
    • Prevent/ reduce impact between machine parts
    • Replace metal parts with plastic parts
path control
Sound level is reduced 6 dBSP for
  • each doubling of distance from noise source
Path Control
  • Sound reduction by distance
  • Sound Barriers


Hearing Protection

Reduce time exposed - HCP

Increase distance of nearby workers

new york city noise code
New York City Noise Code

Construction: Work, Device and Material

New Definitions:

Extraneous Sound: intense, intermittent < 50% of sound source – excluded when measuring sound

Impulsive Sound: Each peak of sound lasts < 2 seconds

Plainly Audible Sound: does not requirement measurement

Unreasonable Noise: >15’ from source; 7dBA over ambient

10 pm–7am; 10dBA over ambient 7am-10pm – Impulse 15dBA over ambient on fast scale - Not Construction!


New subchapter (24-219) will be added with new rules prescribing noise mitigation strategies (in addition to those already listed (Perimeter fences, blanket insulation etc.)

Noise Mitigation Plan – adopted at beginning of construction

After hours work cannot exceed 8dBA over ambient measured inside “residential receiving property”

Subchapter 5 – standards for specific noise sources

24-228 – Construction devices/exhausts

>85dBA measured 50’ or more outside property line of source.

Impulsive: < 15dBA over ambient

24-229 – Containers and construction material

>7dBA over ambient – night

>10dBA over ambient – day

measured 15’ or more from source

>15dBA over ambient – impulsive

24-230 – Paving breakers

Not operated electrically or hydraulically

Must have pneumatic discharge muffler