Rail Transit Noise Vibration

8/3/2019 Rail Transit Noise Vibration

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RAIL TRANSIT NOISE AND VIBRATION

DAVID A. TOWERS, P.E.

PRINCIPAL ENGINEER

HARRIS MILLER MILLER & HANSON INC.



Outline of Rail Transit Noise and Vibration Topics

Descriptors

Sources

Criteria

Assessment

Mitigation



Noise

How do we describe noise?

Amplitude (loudness)

Frequency (pitch)

Time pattern



Descriptors of Transportation Noise

A-Weighted Sound Level, dBA

Instantaneous sound level

Maximum Sound Level, Lmax

Used to characterize specific events, e.g., train horn

Equivalent Sound Level, Leq “Average” noise over a period of time

Found to be a good indicator of community response to

different types of noise

Day-Night Sound Level, Ldn (DNL for airports)

The most common measure of noise “climate”



Combining Decibels





Instantaneous sound level

Maximum Noise Level, Lmax









Maximum Noise Level (Lmax)

Single-event noise descriptor

Commonly used in transit vehicle noise specifications

Definition:



Typical A-Weighted Maximum Sound Levels





Instantaneous sound level Maximum Noise Level, Lmax









Day-Night Sound Level (Ldn)

Descriptor for cumulative 24-hour exposure

Defined as 24-hour Leq with 10 decibel nighttimepenalty (10 P.M. to 7 A.M.)

Correlates well with residential annoyance

Adopted by Federal Agencies: EPA, HUD, FAA, FTA,FRA

Can be computed from hourly Leq’s



Calculation of Ldn



Typical Ldn’s



Overview: Descriptors of Transportation Noise

A-Weighted Sound Level, dBA “Instantaneous” sound level

Maximum Noise Level, Lmax

“Highest” noise level from an event

Equivalent Sound Level, Leq

“Average” noise over a period of time

Day-Night Sound Level, Ldn

The measure of noise “climate”



Typical Rail Transit Noise Sources

Line Segments

Train horns, whistles & bells

Vehicle electric motors and

auxiliary equipment

Diesel engine noise

Wheel/Rail Noise

– Rolling

– Impacts

– Wheel Squeal

Grade crossing bells

Maintenance

Transit Stations

Buses & cars (moving/idling)

PA systems

Maintenance Facilities

Idling vehicles

– Prime Mover Engine

– Auxiliaries

Horns, whistles & bells

Train movements

Vehicle maintenance and

testing

PA systems



Types of Wheel/Rail Noise

Rolling Noise Interaction of steel wheels rolling on steel rails

Source of most environmental impact

Impact Noise Wheel impacts at joint gaps

Wheel impacts at crossovers and turnouts

Squeal Noise Although a localized source, often a major source of noise

complaints

Generally only caused on short radius curves



Rolling Noise: Smooth vs. Rough Wheels

Rough Wheels

Smooth Wheels



Rolling Noise: Rail Roughness - Corrugations



Sources of Impact Noise

Crossover FrogRail Joints

Wheel Flats



Wheel Squeal Generation



Grade Crossing Noise Sources

Train Horns (FRA rules)

Warning Bells

Idling Traffic



Typical Noise vs. Speed



Regulations, Standards and Guidelines Applied to

Railroad and Transit Projects

EPA RR Noise Emission

Standards

FRA RR Noise Emission

Compliance Regulations

FRA RR Horn Use Rule

Surface Transportation Board(STB) Procedures

Local Regulations

US Department of

Transportation

FRA

FTA



FRA Horn Use Rule

49 CFR Parts 222 and 229

“Use of Locomotive Horns at Highway-Rail Grade Crossings:

Final Rule”

Regulates horn noise emission levels

Noise limits on horns, 31m (100 ft) in front of locomotive

Maximum 110 dBA; Minimum 96 dBA

Front- or low-mounted horns

– Measured at 1.2 m (4 ft) above ground level

Mid-cab horns

– Measured at 4.5 m (15 ft) above ground level



FTA Environmental Noise Guidelines

Federal Transit Administration, “Transit Noise and

Vibration Impact Assessment,” FTA-VA-90-1003-06,

May 2006



Land Use Categories and Metrics for

FTA Noise Impact Criteria (May 2006)

* Leq

for the noisiest hour of transit-related activity during hours of noise sensitivity.

Institutional land uses with primarily daytime and evening use.

This category includes schools, libraries, theaters, and churches

where it is important to avoid interference with such activities as

speech, meditation and concentration on reading material.

Places for meditation or study associated with cemeteries,

monuments, museums, campgrounds and recreational facilities

can also be considered to be in this category. Certain historical

sites and parks are also included.

Outdoor Leq(h)*

3

Residences and buildings where people normally sleep. This

category includes homes, hospitals and hotels where a nighttimesensitivity to noise is assumed to be of utmost importance.

Outdoor Ldn2

Tracts of land where quiet is an essential element in their

intended purpose. This category includes lands set aside for

serenity and quiet, and such land uses as outdoor amphitheaters

and concert pavilions, as well as National Historic Landmarks

with significant outdoor use. Also included are recording studios

and concert halls.

Outdoor Leq(h)*1

Description of Land Use Category

Noise Metric

(dBA)

Land Use

Category



FTA Environmental Noise Impact Criteria

New noise caused by project compared to existing noise



FTA Noise Impact Criteria

Increase in total noise exposure caused by project



FTA Noise Criteria Impact Levels

Severe Impact:

A significant percentage of population will be highly annoyed.

Noise mitigation will normally be specified unless there are trulyextenuation circumstances that prevent it.

Moderate Impact:

The change in cumulative noise level will be noticeable, but may notbe sufficient to cause strong adverse community reaction.

In this transitional area, other project-specific factors must beconsidered to determine the magnitude of the impact and the needfor mitigation. Such factors include the following:

– The existing noise level

– The predicted level of increase over existing noise levels

– The types and numbers of noise-sensitive land uses affected – The noise sensitivity of the properties

– The effectiveness of the mitigation measures

– Community views

– The cost of mitigating noise to more acceptable levels



Noise Impact Assessment Procedure

Measure/Predict Existing Noise Levels

Predict Project Noise Levels

Compare Project and Existing Noise Levels

Determine Level of Impact Using FTA Criteria



Long-Term (24-hour) Ambient Noise Monitoring



Short-Term (1-hour) Ambient Noise Monitoring



Noise Exposure vs. Distance



Noise Mitigation Measures



Vehicle Skirts –Houston METRO LRT



Vehicle Skirts – KCRC (Hong Kong)



Vehicle Skirt with Sound Absorption (KCRC)



Undercar Sound Absorption (KCRC)



Maintenance for Minimum Noise

Rolling noise

Keep wheel and rail surfaces smooth

Prevent the occurrence of rail or wheel corrugations Treat before corrugations grow

Impact noise

Use continuously welded rail

Align joint and frog surfaces to minimize impacts Adjust frog surfaces to make for smooth load transfer between

different load bearing surfaces

Squeal noise

Lubricate wheels and/or rails Optimize track and wheel profiles to minimize flanging and riding on

restraining rail

Install resilient or damped wheels



Sound Wall (train side)



Sound Wall (residence side)



Absorptive Sound Walls



Crossover/Turnout Mitigation Options



Horn Noise Mitigation Options

Limiting the Lmax of train horns

Changing the location of train horns Changing the horn blowing practice

Changing the directivity of train horns

Establishing Quiet Zones

Wayside Horns



Requirements for Creating Quiet Zones

All crossings must have automatic warning deviceswith both flashing lights and gates

Safety improvements are required to compensate for the loss of the train horn as a warning device, or to atleast reduce the average risk to below the NationwideSignificant Risk Threshold (NSRT)

Supplementary Safety Measures (SSMs) approved for use include:

Temporary (i.e. nighttime) closure of grade crossing

Four-quadrant gate systems Gates with medians or traffic separators

Conversion of a two-way street into a one-way street withgates



Wayside Horns

Alternative to locomotive-mounted horns

Mounted at the crossing, and focus noise toward

approaching vehicles and nearby pedestrians

Limit the amount of noise exposure for noise-sensitive

receptors adjacent to the tracks in the vicinity of

crossings



Grade Crossing with Wayside Horn System



Wayside Horn Verification Signal

Wayside vs. Locomotive Horn Noise Levels



(at 100 feet from both Track and Roadway)

50

60

70

80

90

100

110

Time (s)

S o u n d

L e v e l ( d B A )

Wayside Horn Locomotive Horn



Locomotive Horn Noise Contours

W id H N i C t



Wayside Horn Noise Contours

H N i Diff (L ti W id )



Horn Noise Difference (Locomotive – Wayside)



Ground-Borne Vibration

Propagation of Ground Borne Vibration into Buildings



Propagation of Ground-Borne Vibration into Buildings

Descriptors of Rail Vibration



Descriptors of Rail Vibration

For Vibration Damage: Peak Particle Velocity, PPV (in./sec)

For Vibration Annoyance: Root Mean Square (rms) Vibration Velocity Level

Expressed in Vibration Decibels (VdB) re 1 micro-inch/sec.

Typical Levels of Ground Borne Vibration



Typical Levels of Ground-Borne Vibration

Factors That Affect Ground-Borne

Vibration and Noise



Vibration and Noise

Source

Vehicle suspension

Wheel type and condition Track/roadways surface

Track support system

Speed

Transit structure Depth of vibration source

Path

Soil type

Rock layers Soil layering

Depth of water table

Frost depth

Receiver

Foundation type

Building construction Interior acoustical absorption

Location in building

Position of receiver in room

Vehicle Suspension Dynamics



Vehicle Suspension Dynamics

Vibrations Caused by Wheel Defects



Vibrations Caused by Wheel Defects



Ground-Borne Vibration and Noise Impact Criteria for General Assessments (FTA)



General Assessments (FTA)

Notes:1. "Frequent Events" is defined as more than 70 vibration events of the same source per day. Most rapid transit projects fall into this category.

2. “Occasional Events” is defined as between 30 and 70 vibration events of the same source per day. Most commuter trunk lines have this many operations.

3. "Infrequent Events" is defined as fewer than 30 vibration events of the same kind per day. This category includes most commuter rail systems

4. This criterion limit is based on levels that are acceptable for most moderately sensitive equipment such as optical microscopes. Vibration sensitive manufacturing or research will require detailed evaluation to define the acceptable vibration levels. Ensuring lower vibration levels in a building often requires special design of the HVACsystems and stiffened floors.

5. Vibration-sensitive equipment is generally not sensitive to ground-borne noise.

48 dBA43 dBA40 dBA83 VdB78 VdB75 VdBCategory 3: Institutional land uses with

primarily daytime use.

43 dBA38 dBA35 dBA80 VdB75 VdB72 VdBCategory 2: Residences and buildings

where people normally sleep.

N/A4N/A4N/A465 VdB465 VdB465 VdB4Category 1: Buildings where vibrations

would interfere with interior

operations.

InfrequentEvents3

OccasionalEvents2

FrequentEvents

1

InfrequentEvents3

OccasionalEvents2

FrequentEvents1

GBN Impact Levels(dB re 20 micro Pascals)

GBV Impact Levels(VdB re 1 micro-inch /sec)

Land Use Category

Ground-Borne Vibration and Noise Impact Criteria for Special Buildings in General Assessments (FTA)



Special Buildings in General Assessments (FTA)

Notes:1."Frequent Events" is defined as more than 70 vibration events per day. Most rapid transit projects fall into this category.

2."Occasional or Infrequent Events" is defined as fewer than 70 vibration events per day. This category includes most commuter rail systems.

3.If the building will rarely be occupied when the trains are operating, there is no need to consider impact. As an example, consider locating a commuter rail line next to a concert hall. If

no commuter trains will operate after 7 pm, it should be rare that the trains interfere with the use of the hall.

25 dBA25 dBA

25 dBA

38 dBA

43 dBA

25 dBA25 dBA

25 dBA

30 dBA

35 dBA

65 VdB65 VdB

65 VdB

80 VdB

80 VdB

65 VdB65 VdB

65 VdB

72 VdB

72 VdB

Concert HallsTV Studios

Recording Studios

Auditoriums

Theaters

Occasional or Infrequent

2

Events

Frequent1

Events

Occasional or Infrequent2

Events

Frequent 1

Events

Ground-Borne Noise ImpactLevels

(dB re 20 micro-Pascals)

Ground-Borne Vibration ImpactLevels

(VdB re 1 micro-inch/sec)

Type of Building or Room

New GBV Criteria for Detailed Analysis (FTA)



y ( )

Prediction of Ground-Borne Vibration



Ground-Borne Vibration Propagation Testing at TTC



g g

Ground-Borne Vibration Mitigation Measures



Maintenance

Special track work

Vehicle specifications

Track support systems

Resilient track fasteners Ballast mats

Resiliently supported

ties Floating slabs

Building modifications

Trenches

Operational changes

Buffer zones

Vibration Mitigation: Resilient Track Fasteners



Vibration Mitigation: Ballast Mats



Vibration Mitigation: Floating Slabs



Crossover/Turnout Mitigation Options



Cost for Vibration Mitigation (installed in Year 2000)



$200Standard DF track

$600Track on floating slab

$400LVT track

$145

$230

Track on ballast & concrete tie

….with ballast mat

$250Booted track

$230

$260

Resilient rail fasteners

Premium resilient…..

Approximate Cost per Track Foot (mid-range $)

Treatment

Finally, what to do when mitigation is impractical!

Rail Transit Noise Vibration

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