Railroad Noise Associated with the
Canadian National Railway Use of the EJ&E Railroad
6/8/12
Prepared for the:
Village of Hoffman Estates
Prepared by:
Thomas Thunder, AuD, FAAA, INCE
Audiologist and Acoustical Consultant
Acoustic Associates, Ltd
Palatine, Illinois
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Executive Summary
The Canadian National Railway acquired control of the EJ&E and has projected that the number of trains
will increase from 10 to about 25 per day. As part of the regulatory process, an environmental impact
statement was prepared that identified noise impacts to property near the tracks. The portion of track
relevant to Hoffman Estates residents is the section running from Golf Road to Shoe Factory Road.
The primary source of railroad noise in this case is locomotive and rolling noise. Locomotive engines
produce high levels of low frequency noise. But this noise is short-lived compared to the longer
exposure of the rolling noise generated by the interaction of numerous wheels on the long rails. Rolling
noise has an extra impact because the frequencies it generates fall within the range of frequencies
necessary for speech communication.
The noise from one train was measured on the deck of a home 140 feet from the tracks. It peaked at 78
dB when the locomotives passed. The average level of the rolling noise from this 120 car train moving at
about 15 mph was 69 dB. This level is twice the loudness of conversation.
The impact of train noise is evaluated by determining the average daily sound level (called the day-night
level or Ldn). In this case, the primary factor for increasing the noise impact is the number of trains.
From a strict acoustical perspective, increasing the number of trains by 2½ times would increase the Ldn
by 4 dB. This increase falls between a just noticeable difference (3 dB) and a significant difference (5 dB).
Wheel and rail roughness is directly correlated with the noise from trains. Limiting roughness has a
direct benefit for the entire community. Since measuring rail roughness is not the jurisdiction of any
town, Hoffman Estates will need to trust that CN also recognizes this relationship and that it will exceed
the Federal Railroad Administration (FRA) and American Railway Engineering and Maintenance-of-Way
Association (AREMA) standards with respect to roughness.
To mitigate the noise, CN has proposed tall masonry walls. It anticipates a noise reduction of about 5-9
dB. This reduction would be significant and would cut the loudness by nearly 50% for the closest
locations. But those in the 2nd and 3rd row of homes away from the tracks would experience much less
mitigation (although these homes are less impacted anyway simply because they are farther from the
tracks). Making the walls shorter would reduce their effectiveness. Landscaping would not reduce the
noise, but there would be a psycho-acoustical benefit by adding more green space.
Constructing the proposed walls has been called into question for several reasons:
1) Because of their intermittent and transient nature, communities as a whole are more tolerant of
railroad noise than other sources that have equal daily average sound levels (e.g., aircraft,
factories, and road traffic).
2) The proposed wall would offer little benefit to 2nd floor elevations,
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3) Trains are not a novel source to this community and, as such, a number of residents may have
acclimated to this type of noise,
4) While doubling the number of trains would seem like it ought to double the impact, in the field
of psycho-acoustics, it represents only a noticeable, not significant, increase in impact, and
5) The walls would block the view of the forest preserve; this would remove the green landscape
view that residents currently enjoy, value, and hope to have for many years.
In addition to, or in lieu of, the tall CN walls, residents could employ their own controls. One control
would be to build short and partially transparent walls around their decks or patios. They could also
replace windows on the east side, especially the 2nd floor bedroom windows, with acoustically rated
windows to lower the noise inside the home.
Background
The Canadian National Railway Company (CN) acquired control of the EJ&E Railway in 2009. Currently,
about 10 trains per day operate along the tracks that lie along the eastern border of the residential
areas in Hoffman Estates between Golf Road and Shoe Factory Road. Figure 1 shows an aerial view of
the residential community on the west side of this section of the railroad tracks
CN has projected that the number of trains would increase to about 25 per day. The Section of
Environmental Analysis (SEA) of the Surface Transportation Board (STB) conducted an Environmental
Impact Study (EIS) that included a noise impact evaluation. Based on
computer modeling, the SEA determined that the Day-Night Level (Ldn)
of noise on the adjacent residential property would increase by more
Day-Night Level (Ldn) is
than 3 dB and to a level greater than an Ldn of 65 dB. To mitigate this
the time-averaged
impact, noise barrier walls have been proposed. These walls would be
sound level over a 24constructed of precast masonry blocks and would reduce railroad noise
hour period with 10 dB
on the closest properties by an estimated 5-10 dB.
added to the noise
This paper discusses railroad noise relative to the residential areas in
Hoffman Estates in a greater depth than presented in the EIS. It also
characterizes the current and future impact of this noise on the
adjacent residents, reviews barrier walls as a basic noise mitigation
approach, and offers conceptual approaches not covered in the EIS.
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between 10 PM and 7
AM to account for the
greater sensitivity to
noise during this period.
Ldn is the descriptor
CNRR
IL 59
Forest Preserve
Figure 1 - Aerial view of railroad running from Golf Road to Shoe Factory Road that
borders the eastern edge of Hoffman Estates residential areas.
Field Measurements of Existing Railroad Noise
The EIS did not base its analysis and findings on actual measurements of the noise from the current
operations along the subject segment of the railroad. While it was not the intent of the EIS to conduct
such a survey, we felt it was important to measure at least one train pass-by event to characterize the
noise from the perspective of residents. This assessment also served as a basis for evaluating the validity
of the EIS modeling.
On February 15, 2012, we set up a sound level meter and digital recorder about 140 feet from the tracks
at a home on Nicholson Drive in the Estates of Deer Crossing subdivision. Figure 2 shows this equipment
set up on the deck with a view of the railroad tracks just beyond the white fence. Popular Creek Forset
Preserve is in the background. At 9:43 AM, a northbound train passed this area. The train was about
120 cars long and was reportedly traveling at a speed of about 15-25 mph.
A time-history analysis was conducted that resulted in the trace shown in Figure 3. This trace shows the
sound level generated by the train over time. Before the train arrived, the level was about 47 dB. This is
called the ambient noise of the neighborhood. As the locomotives approached, the sound level
increased reaching a maximum level of 78 dB as the locomotives passed directly in front of the
measuring station.
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Figure 2 - Sound measuring equipment set up on the deck of a home adjacent to the railroad tracks.
Figure 3 – Sound level time-history of a train passing near the background of a home.
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Once the locomotives passed, the sound level dropped about 10 dB and remained at that level until the
last railcar passed. This last part of the noise event is called rolling noise, which, as seen by the trace,
fluctuates because of the interaction of the wheels and rails. The time-averaged level of the rolling noise
(often called the equivalent level or Leq) was 69 dB.
A spectral analysis was also conducted to examine which frequencies contribute the most to the overall
noise level. The left-hand portion of Figure 4 shows the total (unweighted) and A-weighted sound levels.
The lowest ambient noise recorded was 43 dB. This is the noise
with no trains and due to the all-encompassing sounds of distant A-weighted sound level is the
overall sound level after the low
sources - such as the traffic along Shoe Factory Road.
frequencies are diminished to
The right-hand portion of Figure 4 shows the train noise broken account for the reduced sensitivity
down into the full audible spectrum between 20 and 20,000 Hz.
that humans have for low-pitched
The locomotive noise spectrum reveals a prominent frequency at
sound. The A-weighted level is
63 Hz. This is the low-pitched rumble heard as the engines pass.
used so commonly that this filter is
assumed unless otherwise
For the rolling noise spectrum, a prominent frequency at 80 Hz is
stipulated.
seen, which may be from the low speed wheel-rail interaction.
Rolling noise in general is related to the degree of roughness of the wheel and/or track and the speed of
the train. Rolling noise also produces a wideband noise in the 160-5,000 Hz range. This range is
important because noise in the critical speech range (i.e., the frequencies between 500 and 4,000 Hz)
will greatly impair speech communication.
Figure 4 - Spectral plot showing the overall level and the frequency components of locomotive
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and rolling noise.
In summary, locomotive noise is characterized by an intense, low-frequency sound that is transient. On
the other hand, rolling noise is characterized by a lower sound level, but much longer in duration and
predominately in the mid-frequencies.
A sound exposure analysis was conducted to determine whether locomotive or rolling noise has the
greatest impact on people. The Sound Exposure Level (SEL) is a metric based on the product of the
intensity of the noise and its duration. Although the results were comparable for the specific train we
measured, rolling noise has the greater impact for three reasons:
1) With freight trains, the duration of rolling stock noise is substantially greater than passenger
trains.
2) Humans are more sensitive to mid-frequency noise, which is where rolling railcars generate a
substantial amount of noise.
3) Rolling stock produces a substantial amount of noise in the speech frequencies, which has a
great impact on listening to the TV, hearing over the phone, and understanding people in
conversation.
Sources of Railroad Noise
Noise is a byproduct of the power generated by the engines and the interaction of the railcars and the
tracks. With the massive and large loads of most freight trains, it is not surprising how much noise a
train generates. There are a number of sources of railroad noise. Aerodynamic noise is one source; but
this only applies to high-speed trains. Rail squeal is another source, but this only applies to curved
sections of tracks. Train horns are another source, but in this case, horn soundings are distant because
Shoe Factory Road is designated as a Quiet Zone.
The only relevant sources in this case are the locomotives and the wheel-rail interaction of the railcars.
Locomotives generate noise from the air intake, engine casing, traction, and exhaust. Because of their
low rotational movement, the locomotive engines normally generate low-pitched noise. Locomotive
noise in this case is transient because the locomotives usually pass relatively quickly. In other words,
they are not expected to idle or perform back-and-forth movements on a regular basis.
Railcars generate “rolling noise,” which is the sound associated with: a) the vibration of the wheels, b)
the undercarriage (bogie), c) the body of the railcars, and d) the interaction of the wheels with the rails
and ties (sleepers) on the roadbed. Research has shown that rolling noise is a significant source of
railroad noise and originates mostly from the wheels - not the undercarriages or the railcar bodies.
The sound level of freight trains generally increases about 10 dB per doubling of speed. Conversely, a
train traveling at half the speed will generate 10 dB less noise – which sounds half as loud. This means
that a train moving at 22 mph is half as loud as one moving at 44 mph.
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The character of railroad noise is a low frequency bass sound as the locomotives pass. The rolling noise,
however, is largely a mid-frequency spectrum where the ear is more sensitive. Because the duration of
rolling noise is typically much longer than locomotive noise, the rolling noise is the dominant impact
As indicated above, wheel and rail noise are the dominate sources of rolling noise. Wheel noise is
primarily a higher frequency noise. Rail noise is primarily a wideband noise, but can be lower in
frequency if the rail supports are “soft.” The most significant effect on the noise emissions from wheels
and wheels are their roughness. Since noise is a product of vibration, the rounder and smoother the
wheel and the rail are, the lower the vibration and the lower the noise. In some cases, a regular pattern
of roughness can occur which creates a “corrugation” in the rail. This causes a howling sound known as
“rail roar” whose frequency is related to the speed of the train; the greater the speed, the louder and
more high-pitched the sound.
The propagation of wheel and rail noise to residents in Hoffman Estates is significant because of several
factors.
1) The back patios and decks are in close proximity to the train tracks. With a distance of only 100200 feet, there is little land to buffer the residents from the noise.
2) Because trains are made up of a multitude of wheels (sources), the reduction in noise with
distance is only 3-4 dB per doubling of distance - not the usual 6 dB per doubling of distance
observed for single, stationary sources like a neighbor’s air conditioning unit. This means that
comparatively more residents are affected by train noise.
3) The existing natural vegetation is insufficient in density and depth to noticeably reduce the
noise. In addition, the amount of total existing vegetation varies along the length of the
subdivision.
The annoyance of any type of noise depends primarily on the average daily level of the noise – as
reflected by the Day-Night Level (Ldn) metric. Other factors also play a role such as ambient noise, time
of day and year, tonal content, range of noise intrusion, novelty of the exposure, and the nature of the
noise itself (e.g., aircraft vs. railroad vs. road traffic).
New methods of relating the proportion of people in a community annoyed by a noise have resulted in a
metric called the Community Tolerance Level (CTL). This metric is defined as the Ldn where half the
community is highly annoyed by the noise. It is worthy to note that the CTL for freight trains, as in this
case, was 87.8 dB in contrast to the CTL for aircraft which was 73.3 dB. Other sources such as high-speed
trains, high vibration trains, passenger trains, and road traffic fell in between. What this means is that
communities are generally more tolerant of freight railroad noise than other sources. Stated differently,
given the same Ldn, there would be far fewer people annoyed by train noise than other sources.
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Frequently Asked Questions
The following section answers many of the questions that homeowners and Village officials have asked
about railroad noise, the EIS, and the walls that CN has proposed to mitigate the noise.
1. How loud is train noise and what does it compare to?
Based on our measurements at 140 feet from the track for a train travelling at around 15-25 mph,
we found that the locomotive engine reaches a maximum, A-weighted, sound level of 78 dB. But the
longest and most significant noise is the rolling noise from the railcars. The time-averaged level of
this noise was 69 dB. Based on normal conversational speech at 60 dB, this train was about twice as
loud as conversation.
2. Would lower train speeds equate to less noise?
Yes. Each time you cut the speed in half, you lower the level by 9 dB. For example, if a train measured
80 dB while moving at 48 mph, it would be 71 dB moving at 24 mph and 62 dB moving at 12 mph. In
acoustics, a drop of 10 dB represents a loudness reduction of one-half. Hence, each time the train
speed is cut in half, its loudness is cut in half as well. The sound exposure level (SEL) of an event is a
metric that correlates with the impact of that even. The SEL is based on the intensity and duration of
the event. Although a train moving at half speed will take twice as long to pass, calculations reveal
that the net SEL of a slower moving train is significantly less than the same train moving at a higher
speed.
3. Considering that the number of trains will increase from 10 to 25 per day, what is the general
increase in impact?
The metric used most often to assess long term impact of noise is the Day-Night Level (Ldn). This is a
time-averaged level computed over a full 24-hour day and includes a 10-dB penalty applied between
10 PM and 7 AM to account for the increased sensitivity that people have during nighttime hours. If
the increase in train traffic is during the night, the Ldn would increase substantially because of this
penalty. But If the increase were limited to daytime hours, the Ldn would increase only a small
amount. The Ldn is not an arithmetic average. Instead, it uses logarithmic averaging which weights
the louder sounds more than the soft sounds. The time-averaged level of the entire 6-minute train
event we observed was 71 dB at 140 feet. Based on an ambient sound level of 47 dB, the timeaveraged level for 10 trains during the day would be 59 dB. For 25 trains during the day, it would
increase to 63 dB, an increase of 4 dB. An increase of this amount would represent only a slight
increase in impact compared to the impact the residents now experience with 10 trains per day.
4. Where is an appropriate measurement reference, e.g., middle of yard vs. in the home; 1st floor vs.
second floor; patio vs. kitchen, etc.
Outdoors is the conventional place to take noise readings. This gives less variance to the
measurement. Also, the levels inside a home can be predicted based on the construction of a home.
The reference distance that CN used appears to be about 75 feet from the tracks. Although a more
common reference distance is 50 feet, this distance represents the middle of most backyards and is
closer to the tracks than the back decks or patios of the homes. The ground location is acceptable
since the noise level (at least without a barrier wall) would not differ much between a 1st or 2nd floor
location.
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5. Does the Parsons’ analysis meet and conform to best practice and current standards?
Yes. Based on a review of portions of the EIS, the analysis was performed using the methods of the
Federal Transportation Administration.
6. Are their findings valid and substantiated?
Yes. Based on extrapolating the train event we assessed, we estimate a daytime time-average level
of 63 dB at 140 feet for 25 trains in a day. If this is corrected for trains at 30 mph, for CN’s reference
distance of 75 feet, and assuming a nominal number of trains occurring at night, then CN’s projected
Ldn of 69 dB as given in the EIS is reasonable.
7. What if any changes to the study should be made?
There was no evaluation of existing train noise to show that the computational model used was
indeed representative and valid. In addition, even though wheel and rail roughness are major factors
in the generation of railroad noise, there was no discussion of this or of existing wheel and rail
conditions.
8. Is there anything different that should have been recommended?
Although the STB decision references AREMA standards (which contain rail condition criteria),
knowing how critical wheel and rail conditions are in generating rolling noise, the EIS should have
explicitly addressed these factors and stated what rail condition was assumed to generate the noise
contours. Since the EIS did not address wheel and rail roughness, it is not surprising that it did not
also outline how roughness would be monitored and corrected in the future. However, a condition of
the STB approval does require that CN maintain the track and its equipment in a manner that meets
the AREMA standard.
9. How is wall effectiveness evaluated?
The effectiveness of a wall is measured by how many decibels the noise drops at a specific location
when the wall in introduced. This is called “insertion loss.” How well a wall works is related to how
much farther the noise must travel over the top of the wall compared a direct path without the
barrier.
10. How does wall proximity change the wall’s effectiveness?
Barriers work by ensuring that the path over the top of the wall is longer than a direct (but blocked)
path through the wall. When either the source or the receiver is close to the wall, the path length
difference is large and the barrier is very effective. Although not practical in this case, a short wall
just a bit higher than the top of the wheels would be effective, but only if it was very close to the
wheels. A short wall on a receiver’s patio could also be effective, as long as it is close to the listener.
When the wall is far from the source, its height must be increased to maintain the same path length
difference and, therefore, its effectiveness. Also, residents in the 2nd and 3rd row of homes would be
far enough from the wall that they would hear little difference with or without the wall (although
they would experience less impact anyways simply because they are farther from the tracks).
11. We question the effectiveness of the stated noise reduction of 5 to 10 dB as being significant.
A 3-dB decrease would not be noticeable. However, a 5-dB decrease is considered significant. A 10
dB decrease represents a substantial noise reduction since it sounds ½ as loud. Accordingly, the
stated noise reduction would, in fact, be significant.
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12. Will the proposed wall design achieve the noise reductions represented in the analysis?
Yes. As a rule, if a barrier is tall enough to block the line-of-sight of a source, you can expect a 5-dB
decrease. Every foot above this yields ½ to 1 dB more reduction depending on the noise spectrum
and the type of noise source (e.g., trains vs. a transformer). Using this rule-of-thumb, CNs stated
performance of 5-9 dB appears valid.
13. What are the effects of different material types, e.g., reflecting vs. absorptive?
For a barrier to work well, the only noise heard on the receiving side should be the sound that “spills”
over the top. To ensure this, heavy and solid materials like steel, brick, masonry blocks, and timber
are used to block the sound from transmitting through the wall. In cases where the source is large,
like a railcar, sound bounces off the source itself and back over the top of the wall. This diminishes
the wall’s effectiveness. In these cases, it is helpful to use sound absorption material. This is often in
the form of slotted concrete blocks that contain sound absorptive fill in their hollow cores or as
perforated steel panels that cover sound absorptive blankets. Sound absorption can make a 2-3 dB
difference.
14. Why does the wall have to be so high?
To be effective, the height of a wall must exceed the height of the sound source. Locomotives and
railcars are tall, so the wall must also be tall. Also, as discussed above, the farther a wall is located
from the source (or receiver), the less effective it is. To compensate for this, the wall must be made
taller. Another factor is the frequency of the noise source. Walls are less effective at blocking low
frequency sound. So if low frequency sound is the major contributor to the overall noise, then the
wall is made taller to reduce “spill-over.”
15. How does the effectiveness of a wall change where the wall ends and the tracks are high relative
to homes?
At the ends of the barrier, some of the train noise will travel around the side. This is called flanking
noise and reduces the effectiveness of the wall for those homes near the ends of the wall. Also, if
there are points where the tracks are high, the wall height might need to change a corresponding
amount to maintain wall effectiveness.
16. Would landscaping work in lieu of the walls?
No. Unless the trees were tall, dense, and deep, there would be little effect. Landscaping does,
however, have a psychological effect in reducing the annoyance of the noise when trees and bushes
block the view of the noise source. This perceptual effect is roughly equivalent to a 5-dB reduction.
17. What is the general effectiveness of windows, doors, and home insulation?
While most modern homes are designed with enhanced thermal insulation, this does not necessarily
improve its sound insulation performance. Homes can be built for reduced noise transmission, but
this is best done when the home is constructed. Retrofitting a home for noise reduction can be
expensive. However, because windows are usually the weakest element in a building facade, indoor
noise levels can be lowered by replacing these windows with acoustically rated windows. Acoustically
rated windows are designed and tested for a high sound transmission class (STC) rating. Depending
on a number of factors, this may amount to a 4-8 dB noise reduction.
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Options for Railroad Noise Reduction
1. Control at the Source
Control of noise at the source is generally more cost-effective than controls in the path (like a wall or
earth berm) or at the receiver (such as sound proofing a home). In addition, controls at the source
benefit everyone in the community, not just a select few that are immediately adjacent to the source.
Unfortunately, since the demise of the Office of Noise Abatement and Control, there has been no
Federal directive encouraging the reduction of train noise emissions. Instead, the focus has been on
path controls such as barrier walls, despite their high cost and visual intrusion.
Reductions in wheel and rail roughness will lead to reduced noise in direct proportion to the reduction
in roughness. Maintaining wheels and tracks in good condition by periodic rail grinding and wheel truing
is the most effective and important means for controlling the noise from wheel/rail interaction.
Although the roughness of the worst component (wheel or rail) must be lowered first, the range of
roughness is much greater on rails than on wheels.
According to CN officials, “geometry cars” will be used to measure rail roughness. If necessary, a grinder
is sent out to restore the original shape. Along the Hoffman Estates section of track, surfacing and
grinding were completed in the later part of 2011 and a geometry car checked roughness in February of
2012. These operations have been reported by CN to meet or exceed both AREMA and FRA standards.
As for wheels, certain types of brakes reduce the development of roughness, which, on a good track, can
reduce the noise by 10 dB. No matter what type of brake is on a wheel, according to CN, “Wheel Impact
Load Detectors” have been installed at several locations on the EJ&E to pick up wheel irregularities. If
wheel roughness is detected, this device notifies the crew so that they can set off the car for repair.
2. Controls in the Path
Noise barriers are the most commonly used strategy to mitigate railroad noise despite the fact that
retrofitting for source controls has better cost-effectiveness. But without national incentives, it is easier
to install barriers. There are several arguments against walls in this location:
1) There is a general aversion to the walls because of their proposed height. Even at the proposed
height, their effectiveness is greatly diminished for 2nd floor locations because at this elevation,
the line-of-site is not effectively blocked.
2) Trains are not a new source to this community. While introducing trains for the first time would
substantially impact residents, residents have acclimated to a certain degree to the existing train
noise. In addition, increasing the existing train traffic two- or three-fold has a far less
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incremental impact than introducing a new source to the community.
3) The noise source is transient and intermittent with long intervals. Compared with sources that
generate noise all the time (like a manufacturing plant or trucking depot), the noise in this case
is only “on” for short periods with relatively long intervals in between.
4) The noise from the railroad is predictable. The noise level and character experienced by
residents is the same. And while residents don’t have control over the time and length of the
trains, they do know that the noise will end in a few minutes.
5) The walls would block the view of the forest preserve. If these walls blocked the view of a
manufacturing plant, a trucking facility, or an expressway, there would be a psychological
benefit of a wall. But in this case, the wall would remove “green landscape” from their view.
According to residents, this green landscape is a critical component of their desire to live where
they live. Furthermore, as a forest preserve, they know that this land will not be developed,
which is a notion that adds value to their properties.
3. Controls at the Receiver
There are receiver controls that residents could consider to help mitigate train noise. One option would
be to build a short wall around parts of their patio or deck. The lower portion could be masonry or wood
and the upper part could be Plexiglas or glass to allow a view of the forest preserve. As discussed above,
if close enough, a wall near the listeners could be effective. A test project would help quantify the actual
benefit of such a barrier and guide residents in their construction if they wished to pursue this approach.
Figure 5 – An example
of a transparent wall
that would mitigate the
train noise but allow
residents to view the
Forest Preserve and
observe their children
playing in the backyard.
The height would be
about 8 feet tall.
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Another control would be to replace the windows on the east side of the homes with windows that have
a higher acoustical rating. To evaluate this approach, a representative window should be examined and
tested at Riverbank Acoustical Labs in Geneva to determine its sound transmission class (STC) rating. An
acoustical study should then be conducted to evaluate the potential benefit of retrofitting windows with
acoustical windows. A test project would help quantify the benefit of such windows and help residents
make an informed decision about retrofitting. This test project would be especially useful for 2nd floor
bedroom because: 1) 2nd floor elevations will receive little benefit from the wall proposed by CN, and 2)
bedrooms are a critical receiving location because of issues relating to sleep quality.
A final option relates to enhanced landscaping. As indicated above, conventional landscaping will have
negligible effect on train noise. However, to the degree that landscaping can visually shield the train,
there will be a beneficial psycho-acoustical effect.
Conclusions
The Canadian National Railway has estimated that the number of trains will increase from about 10 to
25 per day. Since the calculated Ldn exceeds the Federal criteria for impact, CN has proposed tall,
masonry walls to shield the noise. Concerns have been expressed by residents about the construction of
these walls. While the estimated reduction of 5-9 dB is reasonable and significant, they understand it is
not substantial. The residents also feel the walls will block their view of the forest preserve to the east,
a view they currently enjoy and value and hope to for many years.
There are also concerns about the need for the proposed wall from an acoustical perspective.
Communities as a whole are more tolerant of railroad noise than other sources such as aircraft,
factories, and road traffic. In addition, train noise is not a new source to this community. Hence the real
measure of impact is the increase in noise, not so much the absolute level of noise. Based on increasing
the number of trains from 10 to 25 per day, the incremental impact is 4 dB. This represents a noticeable,
but not a significant change. Furthermore, the walls would offer little to no benefit for 2nd floor
elevations.
With the direct correlation between wheel/rail roughness and noise, it is surprising that the EIS did not
acknowledge the critical role that this factor plays in railroad noise. Without this acknowledgment, it is
not surprising that the EIS did not outline a program to ensure that wheels and rails would be checked
and treated to limit roughness.
In lieu of (or In addition to) the tall walls that CN has proposed, residents could employ their own
controls. This could include partially transparent walls around decks and patios that would shield the
noise and make it easier to communicate. Residents could also replace windows on the east side with
acoustically rated windows to lower the noise inside their homes. This would be especially beneficial for
2nd floor bedrooms where sleep quality is important.
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