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WHAT’S ALL THE NOISE ABOUT?�

Presented By:

Angie Newton

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FUNDAMENTALS OF NOISE

Defined as unwanted sound
Measure unit is the decibel (dB)
Decibel is a logarithmic unit

50 dB + 50 dB = 53 dB (not 100 dB)

Noise is often measured in A-weighted scale (dBA) to closely represent the range of human hearing

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HUMAN PERCEPTION OF CHANGES IN SOUND LEVELS

2 to 3 dBA change is generally the smallest perceivable change
5 dBA change is readily perceived
10 dBA change is perceived as a double or halving of sound
Doubling traffic volume increases noise by 3 dBA

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WHAT TRIGGERS A NOISE ANALYSIS?

The construction of a highway
The physical alteration of an existing highway:

Substantial Horizontal Alteration. A project that halves the distance between the traffic noise source and the closest receptor between the existing condition to the future build condition;
Substantial Vertical Alteration. A project that removes shielding therefore, exposing the line-of-sight between the receptor and the traffic noise source.

The addition of a through-traffic lane(s). This includes the addition of a through-traffic lane that functions as a HOV lane, High-Occupancy Toll (HOT) lane, bus lane, or truck climbing lane; or
The addition of an auxiliary lane, except for when the auxiliary lane is a turn lane; or

*auxiliary lane is 2,500 feet or longer

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WHAT TRIGGERS A NOISE ANALYSIS?

The addition or relocation of interchange lanes or ramps added to a quadrant to complete an existing partial interchange; or
Restriping existing pavement for the purpose of adding a through-traffic lane or an auxiliary lane; or
The addition of a new or substantial alteration of a weigh station, rest stop, ride-share lot or toll plaza.
If a project is determined to be a Type I project under this definition then the entire project area as defined in the environmental document is a Type I.

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NOISE ANALYSIS PROCEDURES?

Seven Step Process:

Identify noise-sensitive land uses and receptor locations (NAC)
Determine existing noise levels – noise measurements
Noise Modeling - predict future (Design Year) noise levels
Determine noise impacts at receptors by comparing existing vs. future noise levels
Analysis of noise abatement measures – feasible and reasonable criteria
Coordination with Local Jurisdictions – provide noise prediction results for undeveloped lands within 300’ of right of way for zoning/permitting decisions
Identify any noise impacts resulting from project construction activities

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NOISE ABATEMENT CRITERIA

FHWA NOISE ABATEMENT CRITERIA
Activity Category	dBA, L_Aeq1h	Activity Description
A	57 (exterior)	Land on which serenity and quiet are of extraordinary significance and serve an important public need, and where the preservation of those qualities is essential if the area is to continue to serve its intended purpose.
B	67 (exterior)	Residential.
C	67 (exterior)	Active sports areas, amphitheaters, auditoriums, campgrounds, cemeteries, day care centers, hospitals, libraries, medical facilities, parks, picnic areas, places of worship, playgrounds, public meeting rooms, public or nonprofit institutional structures, radio studios, recording studios, recreation areas, Section 4(f) sites, schools, television studios, trails, and trail crossings.
D	52 (interior)	Auditoriums, day care centers, hospitals, libraries, medical facilities, places of worship, public meeting rooms, public or nonprofit institutional structures, radio structures, recording studios, schools, and television studios.
E	72 (exterior)	Hotels, motels, offices, restaurants/bars, and other developed lands, properties or activities not included in categories A–D or F.
F	---	Agriculture, airports, bus yards, emergency services, industrial, logging, maintenance facilities, manufacturing, mining, rail yards, retail facilities, shipyards, utilities (water resources, water treatment, electrical), and warehousing.
G	---	Undeveloped lands that are not permitted.

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ROADWAY NOISE MEASUREMENTS

Sound level meter
Measurement site selection
Ambient condition

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Roadway Noise Source�Noise Generators -

Automobiles
Buses
Medium & Heavy Trucks
Motorcycles

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FACTORS AFFECTING TRAFFIC NOISE LEVELS

Traffic Volume
Traffic Speed
Number of Trucks
Wind
Temperature Inversions

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PHYSICAL FACTORS

Traffic Volume - 2000 vehicles per hour is perceived as twice as loud as 200 vehicles per hour

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PHYSICAL FACTORS

Number of Trucks - A truck at 55 miles per hour sounds as loud as 13 cars at 55 miles per hour

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PHYSICAL FACTORS

Traffic Speed - Traffic at 65 miles per hour is perceived as twice as loud as traffic at 30 miles per hour

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ENVIRONMENTAL FACTORS

Wind - Speeds of 11 mph in the direction from the source to the receiver can increase noise levels by about 4 dB at 1000 feet.

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ENVIRONMENTAL FACTORS

Temperature Inversions - ADEQ: “Phoenix area nightly temperature inversions… are stronger in the winter… Every evening after sunset the surface of the land cools off more rapidly than the air above.”

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NOISE MEASUREMENTS

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FHWA SAYS: NOISE BARRIERS

Can reduce the loudness by as much as half
Do not completely block all traffic noise
Can be effective, regardless of the material used
Must be tall enough to break the line of sight and long with no openings
Are most effective within 200 feet (i.e., 1st row of homes)
Must be designed to be visually appealing
Must preserve aesthetic values and scenic vistas
Do not increase noise levels perceptibly on the opposite side of a highway
Substantially reduce noise levels for people living next to highways

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PAVEMENT EFFECTS

Noisiest to Quietest

Transversely Tined Concrete (+7 to +9 dBA)

Horizontally Tined Concrete

New non-tined concrete

Old non-tined Concrete

“AVERAGE”

Old Asphalt

New Dense Graded Asphalt Concrete

New Open Graded Asphalt Concrete

Diamond Grinded Concrete

(-4 to -6 dBA) Rubberized Asphalt

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QUIETEST PAVEMENTS

RA - “Asphalt rubber is a mixture of 20% crumb rubber particles derived from the grinding of waste tires with 80% paving grade asphalt. The resultant hot mixture is added to a specially graded aggregate in a hot plant. A one-inch resurfacing project with asphalt rubber uses 1,500 waste tires per lane mile.

Diamond Grinding – ADOT is exploring another option for smoothing out the ride along Valley freeways where the RA has aged and is wearing down. Diamond Grinding is a technique for preserving and rehabilitating the concrete pavement surface of a highway. This technique has the potential to reduce costs of rehabilitating our aging infrastructure, while still providing travelers with a smooth, quiet ride.

Although rubberized asphalt has been successful at reducing freeway noise levels, it wears down over time and must be replaced every 10 to 15 years. Costs associated with replacing rubberized asphalt are projected to increase by nearly 300 percent in the coming years

In addition to saving money, diamond grinding could result in less highway maintenance. For example, rubberized asphalt has a service life of 10 to 15 years. Over time, it wears out because of traffic and the elements. Diamond grinding is a longer-lasting solution.

Drivers on a surface treated with diamond grinding will enjoy a smooth ride, much like a new rubberized asphalt surface. Also, as rubberized asphalt ages and wears down, noise levels associated with highway traffic increase. However, noise levels have not been shown to increase over time on freeways treated with diamond grinding.

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BARRIER INSERTION LOSS

Unmitigated 70 dBA

Mitigated 63 dBA

Insertion Loss = 7 dBA

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NOISE BARRIER LENGTH

Use 4:1 ratio as a starting point, use modeling tools to refine the design

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