Exhaust Noise Control Locomotive 2815
Redesigning the coffin muffler to address low
frequency noise problems
1/8/2013
ARTC’s EPL 3142:
“Almost a third of all rail noise complaints received
by the Environment Protection Authority (EPA)
between 2007 and 2011 were generated by pass
by noise from locomotives. For this reason the
EPA considers the ongoing monitoring and
management of locomotive noise to be a critical
component of environmental regulation on the
NSW rail network.”
EPA Noise Limits for Locomotives
new to the NSW Network
Operating Condition Speed and Location of
Measurement
Noise Limit at 1.5 m
above ground level
Idle with compressor radiator fans
and air conditioning operating at
maximum load occurring at idle
Stationary 15 m contour 70 dB(A) Max
All other throttle settings under self
load with compressor radiator fans
and air conditioning operating
Stationary 15 m contour 87 dB(A) Max
95 dB Linear Max
All service conditions As per Australian
Standard AS2377-2002
87 dB(A) Max
95 dB Linear Max
Back in 2006…
Notch Setting Level @ 15m Noise Limit
Notch 4 & 5 83 dB(A) Max
104 dB Linear Max
87 dB(A) Max
95 dB Linear Max
Notch 8 85 dB(A) Max
102 dB Linear Max
87 dB(A) Max
95 dB Linear Max
In 2012, with modified transition muffler…
Notch Setting Level @ 15m Noise Limit
Notch 8 87 dB(A) Max
99 dB Linear Max
87 dB(A) Max
95 dB Linear Max
Locomotive Passby Noise
• Four examples of passby noise - different
locomotive classes
• All recorded at 7.5 m from the track, same
direction of travel, same location
• Uncontrolled test – varying speeds and number
of locomotives
Starting Point – Loco 2815
• A-weighted noise compliant with EPA limits
• Linear noise levels up to 4 dB above EPA
limits (in Notch 8)
• Linear levels dominated by 50 Hz
component – low frequency emissions of
particular concern to the EPA
• Overall, noise emissions similar to many
locomotives operating in NSW
Contents
• Sound intensity testing
• Transmission loss measurements
• Coffin muffler design
• Scale model prototypes
• Full scale cold testing
• Hot testing
• Repeat of stationary type testing
Sound Intensity Testing
• Scan locomotive to identify source of noise
emissions in different frequency bands
Sound Intensity Contours 50 Hz
Transmission Loss
• Aim to establish performance of existing
muffler – both the coffin muffler and the
previously modified transition muffler
• Measure at exhaust height, 3m from outlet
– Original transition muffler, original coffin muffler
– Modified transition muffler, original coffin muffler
– Transition muffler removed (ie, no transition or
coffin muffler)
Transmission Loss Measurements
Transmission Loss Results
• With original transition – particularly poor performance below 100 Hz
– noise emissions in several frequency bands (including
50 Hz) amplified rather than attenuated.
• With modified transition – performance remained poor at low frequencies.
– overall linear attenuation of 7 dB
– attenuation of 0 dB at 50 Hz
Coffin Muffler Design Inputs
• Drawings of original muffler
• Information on muffler internals
• Exhaust flow rates
• Exhaust temperatures
Resources available
• 1 x spare muffler
• 1 x spare original transition
• 1 x modified transition
• 1 x locomotive (2815)
• Support from Aurizon
Design Approach
• Decision made not to use FE software
• Theoretical design (calculations)
• Scale model testing for design optimisation
(scaled for size and temperature)
• Cold testing with adjustable components
(results scaled for temperature)
• Hot prototype testing
Full scale cold testing
Scale model testing
Cold testing – Tuning
Full Scale Prototype
Final Prototype Design
• Volume increased by 60% – increased height of muffler body – take advantage of
available space
– width and length maintained
• Double expansion chamber
• Tuned quarter wave chambers targeting 50
Hz frequency component
Prototype Hot Testing
• Initial hot testing took place on 11 March
using identical 3m microphone positioning
to that employed for the transmission loss
tests of the original muffler.
Hot Testing Results
Hot Testing Results
Parameter Original
Level @ 3m
New Level
@ 3m
Increase in
Attenuation
A-Weighted
Overall LAeq 96 dBA 96 dBA 0.0 dB
Linear
Overall Leq 107 dB 101 dB 5.4 dB
25 Hz
1/3 Oct Band Leq 101 dB 84 dB 16.1 dB
50 Hz
1/3 Oct Band Leq 101 dB 83 dB 18.1 dB
Hot Testing Results
• Overall linear noise levels reduced by 5 dB
• No change in A-weighted levels
• Major reductions in tonal noise in Notch 8:
– 18 dB reduction in the 50 Hz band
– 16 dB reduction in the 25 Hz band
Before and after –
recordings at 3m from
exhaust outlet
In 2013, with redesigned coffin muffler…
Notch Setting Level @ 15m Noise Limit
Notch 8 86 dB(A) Max
94 dB Linear Max
87 dB(A) Max
95 dB Linear Max
Conclusion
• The EPA has subsequently approved this
locomotive class (re-badged as the 3200
class) for use in NSW:
“Based on the information provided, the EPA
considers that the noise performance of the
3200 class locomotive is consistent with
current best practice in NSW.”
Thanks
• Steve Brown – design lead
• Evan Brown – prototyping assistance
• Aurizon – Matt Pearce and Ray McCabe