PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Another Halving of Rail Freight Traffic Noise by Wheel AbsorberMartin FEHNDRICH
Bochumer Verein Verkehrstechnik GmbH, Germany

ABSTRACT
By 2020 the freight traffic noise in Germany and Switzerland should be halved by changing cast iron brake
blocks wheels to composite brake blocks. This means, by this time levels of 93 dB(A) should become
83 dB(A), which is the limit defined in the TSI Noise. A further reduction by half would lead to 73 dB(A),which is a part of the SBB Cargo vision for its future fleet.
The fact that this reduction is possible is shown by first results of the SBB Cargo’s 5L project, where large
number of suppliers helped to build a train with 16 freight wagons with a series of different noise-reducing
measures (e.g. disc brakes instead of block brakes) and is currently being tested in regular traffic. Since thewheel is still the predominant source of sound emission in railway traffic, the biggest impact is reducing thewheel noise. With BVV wheel absorbers sound levels of 73 to 75 dB(A) could be achieved.
Keywords: Rail Traffic, Wheel Absorber, Reduction, Damped Wheel, 5L

1. INTRODUCTION
Wheel absorbers not only reduce the noise emissions in high-speed traffic, they also greatly reducenoise emissions in freight traffic (1).
Even if freight wagons do not fulfill the conditions of TSI Noise (2) and may no longer be used inGermany and Switzerland after 2020, there remains a demand for a further reduction of emissions. For
example, SBB Cargo's vision is to use vehicles with emission levels of less than 73 dB as of 2021 (3).
This 10 dB reduction to the 83 dB TSI level would decrease the noise by half. With the use ofblock-braked freight wagons, such a goal can hardly be achieved even with the conversion of thesevehicles to K or LL brake blocks. On the other hand, the acoustically unfavorable wheel contours ofblock-braked wheels and the difficult mounting options for wheel sound absorbers speak in favor of
the use of disc-braked and absorber-damped wheels. Application of disc brakes instead of block brakes
can also benefit lifetime costs. As a result, AAE AG increased its usage of vehicles with disc brakes toreduce operating costs compared to vehicles braked with K- or LL blocks (4).
The wheels of disc-braked wheelsets can be dampened in freight traffic in a similar way as inpassenger traffic. Therefore, four of sixteen vehicles of the demonstrator train of the 5L project
initiated by SBB Cargo, were equipped with absorber dampened wheels from BVV (5, 6).

2. WHEEL
The wheel used is a solid freight wagon wheel with a straight web and radial wheel absorbers bolted
under the running gear wheel tread. The wheel shape follows the design principles of stress balanced
wheels used in high speed traffic (e.g., ICE). This leads to lower stress levels in the wheel and has also
proven to be acoustically favorable. The higher load requirements compared to an ICE wheel require alittle different dimensions and a higher mass.
The radial wheel absorbers are comparable to absorbers used in high speed traffic or the wheel
absorbers used for Wuppertal Suspension Railway. Special hammerhead screws attached in a dovetailgroove under the wheel rim connect the absorbers to the wheel.
The design and production of wheels is carried out according to the current standards (EN 13979 -1,EN 13262). The wheel material is “Exzellent”, a material development of BVV in terms of improved
tread properties and increased mileage compared to the standard material ER8. This material is also
included in the current revision of EN 13262 under the material designation ERS8 with the description

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that it is intended for non-clogged solid wheels and provides increased resistance to rolling contact
fatigue.

Figure 1 – This is a BVV-wheelset with wheel absorber in a vehicle of the 5L project

2.1 Wheel Absorber
Radial wheel absorbers are state of the art in passenger transport and have been used for many years
in high-speed traffic (7). They are not only used for ICE vehicles in Germany, but also for vehicles in
Spain (AVE) and in China.

Figure 2 – This is a wheel absorber for radial damping

The absorbers are mounted below the wheel rim with special hammerhead screws in a dovetailgroove. The geometry is designed to attenuate radial vibration modes which dominate the runningnoise. However, there is also a significant damping of axial vibration modes, such that good results canbe expected even while running through switches and curves.
The absorbers have a sandwich structure comprising steel and elastomeric material. Absorbers
designed specifically for the shape and the natural frequencies of the associated wheel type. The
natural vibration of the wheel is transferred to the absorber, which absorbs the vibration energy.
The absorbers can be used without any problems in a temperature range of (minus) -50 °C to+ 200 °C. There is a fire protection certificate according to EN45545-2: 2013-08. Requirement set R9
is met for the highest hazard level HL3.

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2.2

Damping / Measurement of the Transfer Function

The damping can be shown by measuring the transfer function. The wheel is excited to vibrate andthe resulting vibration acceleration is measured. The ratio of vibration acceleration to excitation force
is shown frequency-dependent. Therefore a logarithmic dB scale is selected.
By measuring excitation and acceleration on the wheel tread, one can depict the radial vibration
modes that dominate the rolling noise when driving straight ahead. If axial excitation and oscillation
are measured on the wheel face, the behaviour of axial modes of vibration can be observed. Axial
modes dominate curve squeal sound.
The absorber effect is shown by comparing the measurement on the undamped wheel and theabsorber damped wheel. The wheel was suspended at the axle. The wheel was stimulated on the tread(radial) or on the front side (axial) with an impact hammer.

Figure 3 – Wheel with absorber, (Photo H. Neumann, IFS, RWTH Aachen)

The vibration modes can be recognized as oscillation maxima in the transfer functions. The
frequency of the two-knot radial mode of vibration (R2 mode) dominating the wheel’s running noise is1560 Hz, the frequency of the R3 mode is 2325 Hz.
The heights or width of the peaks provide a measure of the damping. The reduction of these peaklevels indicates the absorber effect. The measurement of the transfer function is therefore also an
important step in the development of absorbers for a given wheel.
The axial and radial transfer functions of the damped and undamped wheels are shown in Figure 4.

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Axial excitation, wheel without absorber

Axial excitation, wheel with absorber

Radial excitation, wheel without absorber

Radial excitation, wheel with absorber

Figure 4 – Transfer functions of the BVV-5L wheel measured with impact hammer and acceleration sensor.
It can be seen that both with axial excitation and with radial excitation, the vibration modes of thewheel equipped with absorbers are significantly attenuated.
2.3 Acoustic Measurements
As a part of the 5L project, acoustic measurements were carried out while driving straight ahead
and in curves. These were carried out in accordance with EN ISO 3095:2013 at three speed levels.
The acoustic level measurements were carried out at three locations in Switzerland. The
pass-by-distance measurement was performed at a straight track in Kerzers, a measurement curve withradius 490 m is located in Willisau, and a curve with radius 290 m in Menznau (5, 6).
The train was assembled with 16 vehicles. Each vehicle is equipped with different components
from various manufacturers (bogie, wheelset, brake, pads, coupling). Four vehicles are equipped withwheelsets from BVV (car IDs 3, 4, 8 and 10). As a reference, the SBB vehicles are equipped with Y25
bogies, wheelsets SBB Db10SA, KS Klotz brakes with JU 816M brake pads and clutches fromFaiveley. Table 1 shows the components of the four vehicles in which BVV wheelsets were installed.
Table 1 – components of the vehicles with wheelsets

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ID

Vehicle no.#

Bogie

Brake

Brake Pads

clutches

3003-8ELH

DAKO-CZ

BE_SP 140FF

Voith

10010-3

Greenbrier

Knorr-Br.

JU707-11Faiveley

8008-7WBN

Faiveley

SWG36

Faiveley

4004-6

Tatr. poprad

Knorr-Br.

JU707-11

Faiveley

The acoustic levels are always determined for a transition between two vehicles from vehicle centerto vehicle center. Since different combinations of components have been installed in different vehicles,
there is no vehicle pair and thus no transition, which have only the same components. Only transitions
with only one type of wheels are considered.
2.4 Pass by measurement on straight track
The levels measured on the straight track can be found in Table 2. The two transitions ID 10/8 andID 8/4 have only BVV wheelsets. The reference are that Y25 bogies of the SBB vehicles 15 and 16, thevehicles at which no flat spots occurred during the test drives.

Table 2 – Pass By Levels LpA in dB, (*) influenced by flats, Y25 wheelsets 15/16 as reference
M#, no. ofDriving

measurement directionv

LpA (dB)

LpA (dB)

LpA (dB)

km/h

ID 10/8

ID 8/4

ID 15/16

M05

276.4

74.5

73.9

79.2

M07

276.9

74.5

74.7*

77.6

M09

277.3

74.6

74.8*

77.6M04

2

96.3

74.1

73.3

79.3

M11

2

98.0

74.0

74.2*

77.0

M08

1

98.1

74.2

74.4*

80.5

M132

98.6

74.0

74.1*

77.9

M02

299.9

74.4

73.5

80.3

M01

2

10.,5

74.0

73.0

80.8

M06

1

118.0

74.1

74.4*

81.0

M12

1

118.7

74.2

74.6*

82.2

M10

1

120.3

74.1

74.9*

82.0

M03

1

120.9

74.1

73.7

81.9

The levels have been converted to a speed of 80 km/h for comparability. A correction to apl/vehicle
length was not done in this compilation (6), since all vehicles are of the same type and length and thisis not necessary for a comparison of the level values with each other. From the M06 drive, em ergency
stops have caused flaps in the area of the DG 4/7 transition, which also led to faults in the DG 8/4
interval. In these cases, at the DG 8/4 transition greater LpA levels than 74 dB have been determined(*), while for the first rides, approximately 1 dB lower levels - all below 74.0 dB - have beendetermined.
The average levels of the three speed levels are shown in the following table:Table 3 – Pass By Levels LpA in dB, without apl correction
Levels, Levels of ID8/4 include influence of flatsv

LpA (dB)

LpA (dB)

LpA (dB)

km/h

ID 10/8

ID 8/4

ID 15/16

80

74.5

74.5

78.1

100

74.1

73.8

79.3

120

74.1

74.4

81.8

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In the TSI Noise (2), acoustic levels for freight wagons are now related to a reference APL value of0.225 m-1 . The previously applicable scale is no longer be used. According to TSI NOI 2014, themeasured level is changed by the correction term -10 log (APL_Wagon/APL_Ref).
The wagons used in the 5L project have a length of 20.05 m. This corresponds to an APL of0.1995 m-1 . For comparison with TSI levels, therefore, a correction term of +0.52 dB must be added.
Values to be used for assessing conformity are then:Table 4 – Pass By Levels LpA in dB, APL corrected,
Levels of ID8/4 include flat influencev

LpA (dB)

LpA (dB)

LpA (dB)

km/h

ID 10/8

ID 8/4

ID 15/16

80

75.0

75.0

78.6

100

74.6

74.3

79.8

120

74.6

74.9

82.3

The levels of BVV-wheeled vehicle transitions are rounded up to TSI levels of 75 dB. Looking atthe transition ID 4/8 and ignoring rides with the influence of flats of the adjacent transition, gives avalue of 74 dB, which would however be based on very few measurements.

3. Comparison with TSI Acceptance Measurements
To classify the determined level, it is compared with levels of other freight vehicles. This is basedon a report commissioned by the German Federal Environmental Agency (UBA) and written byMBBM, in which the noise emission from rail vehicles was recorded and compiled during TSI
noise-related certification during a survey (8).
Figure 5 shows a representation of all registration levels of freight wagons from this report, inwhich the 5L levels have been added, extending the field of measured points downwards.

Figure 5 – Overview of TSI levels from the UBA report (8) supplemented by one point for the level of the 5L
project (75 dB / APL 0.2).

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This shows that it is possible to reduce the passing levels of freight wagons well below the TSIvalues. It makes sense to encourage the use of such low-emission technologies with a noise-related
train path pricing system, in which particularly quiet cars have to pay significantly less (9).

4. CONCLUSIONSIn SBB Cargo’s 5L project, an innovative freight train was put together. Wheelsets from Bochumer
Verein Verkehrstechnik GmbH were used in four wagons, which are equipped with absorber-damped
wheels. The lowest pass-by levels LpA were measured from 73 dB to 75 dB at the vehicle interchanges
with BVV wheelsets corresponding to TSI levels of 74 dB to 75 dB. The results show, that a further
reduction of freight traffic by half, from 83 dB to 73 dB, is possible, when using disc-braked andabsorber-damped wheelsets.

REFERENCES
1. Engel, B. et al: Bedämpfung von Rollgeräuschen mit Absorbern bei niedrigen Geschwindigkeiten,
DAGA 2007, Stuttgart
2. TSI NOI 2014, VO (EU) 1304/2014
3. S. C. Hofstetter, Asset Management SBB Cargo. Ergebnisse und Ausblick 5L-Güterwagen, VPI
Technische Informationsveranstaltung, Hamburg, 21. Juni 20185.
4. Stevenson, M. et al: Scheibenbremse und Güterwagen, Internationales Verkehrswesen (66) 3, 2014, S.
102.
5. Zwischenbericht Akustisches Verhalten SBB, Monitoring_TIS-5L, Akustische Verhalten, 2017, SBB
Cargo AG, PJ Messtechnik GmbH
6. Fehndrich, M. 73-75 DB(A) mit scheibengebremsten und absorbergedämpften Güterwagenrädern
7. Fehndrich, M., Murawa, F. Dämpfung der Laufgeräusche bei Eisenbahnrädern, Der Eisenbahningenieur
10/2011
8. Lutzenberger, S., Gutmann, C.: Ermittlungen des Standes der Technik der Geräuschemissionen
europäischer Schienenfahrzeuge und deren Lärmminderungspotenziale mit Darstellung vonBest-Practice-Beispielen, UBA-Bericht, 2013
9. Fehndrich, M., Köhler, G.: Differenzierung des lärmabhängigen Trassenpreissystems nach Emissionen,
DAGA 2015, Nürnberg

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