ARCHIVES OF ACOUSTICS Vol. 44, No. 4, pp. 783–792 (2019) DOI: 10.24425/aoa.2019.129733

Developing Assumptions for the Noise Attenuation Passive System Using the Noise Maps Analysis Method

Tomasz NOWAKOWSKI∗, Bartosz FIRLIK, Tomasz STAŚKIEWICZ

Poznan University of Technology Piotrowo 3, 61-138 Poznan, e-mail: bartosz.fi[email protected], [email protected] ∗Corresponding Author e-mail: [email protected]

(received January 21, 2019; accepted September 11, 2019)

The paper presents experimental research carried out to determine the possible actions to reduce the noise generated by in a highly urbanised area. A few design strategies affecting tram ride quality have been presented – especially in the aspect of the acoustic phenomena. Main sources of the noise in trams were characterised. The paper includes selected results of comprehensive studies of tram noise in the pass-by test based on the authors’ research methodology. The tests were carried out on various types of trams to recognise the acoustic phenomena characteristic for the rolling stock in a selected tram system. The results of the measurements were analysed both in the field of amplitudes based on noise maps and in respect to frequencies based on noise spectra. The results indicated the rolling noise as important issue demanding taking some actions in order to reduce its level. In this area, elements for the application of individual attenuation solutions, i.e. at the source and during propagation, were presented. The results of the measurements were used as input data to the assumptions of the noise attenuation passive system, which was the final outcome of the study. Dedicated external dampers were used in the case of wheel and rail pairs, where the dominant power of the noise is emitted. The acoustic properties of the area and the bogie side covers were redeveloped to hamper the noise propagation, which is a novel application. The presented results indicate measurable benefits from the applied solutions on the tram noise reduction. Keywords: tramway; noise; rolling noise; bogie covers; noise maps.

1. Introduction tive impact on the environment, regarding noise and vibration. Attention to these phenomena also results The main concept of the tram should refer to a reli- from the regulation of Polish environmental law and able implementation of the transport process, also pro- European Commission White Paper (European Com- viding positive vibroacoustic features of the vehicle. mission, 2011). The discussed phenomenon – traffic The strategy should assume the emphasise on noise noise, is classified as a kind of air pollution and is and vibration reduction – at the early stage of project the main source of noise in the cities (Miedema, Van evaluation (Niziński, Żółtowski, 2002). This par- der Berg, 1988; Engel, 2001; Mandula et al., 2002; ticularly applies to specifying the product definition Leśnikowska-Matusiak, 2014). This contamination (Hubka, 1991), in particular with regard to legal char- has a number of negative effects, which may manifest acteristics, i.e. in compliance with the requirements of themselves in the form of sleep disorders, anxiety dis- legal acts and standards. In Poland, the only condi- orders, general irritability, hearing impairments, and tion related to acoustics currently permitting a tram problems with the circulatory system caused by stress to ride, is the equivalent sound level measured during (Berglund et al., 2000; European Parliament, 2002; pass-by test (Polish Minister of Infrastructure, 2011). Pawlas, 2015; Cik et al., 2016). The noise of trams However, the positive vibroacoustic features should be is widely considered in terms of annoyance, which is characterised not only by meeting the requirements particularly important in urban areas (Kaczmarek of the regulation, but also by minimising the nega- et al., 2006; Popescu, Moholea, 2010; Hume et al., 784 Archives of Acoustics – Volume 44, Number 4, 2019

Fig. 1. Acoustic signatures up to frequency 25.6 kHz at constant speed 25 km/h; from the left: Düwag GT8, Solaris Tramino, Moderus Tatra.

Fig. 2. View of the microphones array with the layout diagram on the measurement stand: PM1–9 – measurements points.

2012; Pawlas, 2015). The reduction of noise emis- Electroacoustic sources are visible in the middle sion, which may contribute in total to lowering the and right side drawing (Fig. 2) as the parallel com- daily equivalent sound level in the city (Fidell et al., ponents in the form of elongated artifacts, parallel 1991; Berglund et al., 2000), is an important issue to the time axis, which results from strong modula- for the quality of residents’ life, definition in (Róg, tion of signals. These analyses are also presented in 1992). The problem of the noise in the cities is so im- more detail in (Czechyra, Tomaszewski, 2009). In portant that real time noise monitoring networks in the analysis of vibroacoustic phenomena, special atten- cities are also being used (Sanchez-Sanchez et al., tion should be paid to boundary conditions depend- 2018). ing, among other things, on the vibroactivity of track Regardless of the type of tram and its operational types (Targosz, Adamczyk, 2010; Nowakowski, characteristics, the wheel and rail noise is the dom- Tomaszewski, 2017). inating sound source of the rolling stock (Madej, 2001; Hemsworth, 2008; Thompson, 2008; Lakušić 2. Research methodology et al., 2011; Czechyra, 2012, 2013; Panulino- va et al., 2016). It depends inter alia on the design of Due to the highlighted problem areas related to the running gear, be it its motor or trailer bogie. An noise generation, research related to their minimisation important issue is also the dynamic wheel loads result- at the stage of the tram design was undertaken. The ing from the external excitations and vehicle design. areas of minimisation were focused on the issues of Traction motors located close to wheels make another rolling noise, which in contrast to electromechanical important source of the noise. Taking into account of- sources is possible to model, interfering with the basic ten contradictory technical requirements set for the structure of the tram. drive system, in this area, in the first stage of product Results of the experimental tests carried out on rep- development, it is usually power demands that come resentative types of trams were used as input data for as a priority. Also inverter assemblies used in mod- changes in their structures. The tests included sound ern trams constitute a group of electroacoustic sources. measuring arrays located in highest possible proxim- Differences in acoustic effects can be read directly from ity to the wheel and rail contact (Fig. 2). Analysis of time-frequency spectrum constituting acoustic signa- the obtained data was carried out in the time domain tures of trams (Fig. 1) (Golay, 2008; Czechyra, (noise maps), and in the frequency domain (noise spec- Tomaszewski, 2009). tra). T. Nowakowski et al. – Developing Assumptions for the Tram Noise Attenuation Passive System. . . 785

The first part of the research was the measurement sources. For 20 km/h, the main sources relate to power of the sound levels on a selected tramway track in Poz- supply equipment, and for 50 km/h to rolling noise nań (Poland), which constitutes a straight, separated, (Hemsworth, 2008). Figure 3 shows that among low ballasted track on concrete sleepers without additional floor trams passing at a speed of 20 km/h, Solaris noise-damping elements. The sound was recorded dur- Tramino S100, (the prototype version of the S105p ing the pass-by test of three different low floor trams model) results in many areas in navy blue color that – Siemens Combino, Solaris Tramino S105p, and So- means lower sound levels, ca. 65 dB(A). Sounds of laris Tramino S100 (the prototype version of the S105p a slightly higher level were generated by the Siemens model). Such a comparison was aimed at comparing Combino tram, which is a design from 2003–2004. So- the properties of typical low floor trams used by the laris Tramino S105p, as a construction from 2011 in local operator – “MPK Poznan”. Each tram performed this combination looks the least favorable and gener- three passes for each constant speed: 20 km/h and ates the highest level of sound. 50 km/h. The results obtained were averaged for each In the case of the Combino model, sound level of speed. First microphone of the array was placed on the 85 dB(A) was already achieved in segments without top of rail level. The spacing between the microphones and behind the last bogie. Model S105p reached was 100 mm each, so the last one was located 900 mm level 85 dB(A) on the entire length, and in addition it above the top of the rail. This allowed to cover the is interlaced with bands at the level of 90 dB(A). Bo- whole height of the bogie area, which is supposed to gies are the main sound generators, among the three be one of the main sources of sound. Acquisition of sig- vehicles, at the speed of 20 km/h, S100 model achieved nals was carried out through a PULSE○R multichannel the lowest sound level, i.e. 90–95 dB(A). S105p model system from Brüel & Kjær. achieved the highest sound level, up to 100 dB(A). The next part of the research was the development In the case of Combino maximum sound level is of a tram noise attenuation passive system based on 100 dB(A) in the last and middle bogie, and for the the conclusions from track-side measurements and ded- first bogie it is up to 95 dB(A). In the case of trams icated analysis of damping issues. In the last stage of S100 and S105p, the areas of sound with a higher and the research, validation measurements were done to as- constant level are clearly visible on the entire measur- sess the effectiveness of the developed system. ing height (in the form of stripes). In the case of Com- bino, they are more disrupted, especially in the first 3. Results and analysis bogie. Moreover, only the S105p model clearly shows sound levels as high as 85–90 dB(A) outside the area 3.1. Analysis in the amplitude domain of bogies. For Combino, the areas outside the bogie are at the level between 80–85 dB(A). The most homoge- Noise maps for the tested trams were obtained, neous level below 75 dB(A) in this area was observed which were imposed on the contours of vehicles for for the S100 tram. clear visualisation of the results. Signals were recorded Figure 4 shows noise maps for the ride speed of and adjusted by the A frequency-weightings. The ana- 50 km/h of the three trams. The sound level gener- lyses were carried out for two speeds: 20 km/h and ated by the Combino tram at the speed of 50 km/h 50 km/h, which differ in terms of the main noise increased significantly. In the case of the wheel and

Fig. 3. Noise maps of Siemens Combino, Solaris Tramino S100 and Solaris Tramino S105p (speed 20 km/h). 786 Archives of Acoustics – Volume 44, Number 4, 2019

Fig. 4. Noise maps of Siemens Combino, Solaris Tramino S100 and Solaris Tramino S105p – speed 50 km/h. rail contact, the sound level was around 100 dB(A), the implemented project (existing plans for further de- and at some points the tram reached even 110 dB(A). velopment of this platform by Solaris), were analysed. Beyond the bogies, the vehicle reaches the level of The following speed of 50 km/h was taken into con- 85–95 dB(A). In addition, it has an elevated sound sideration and two configurations were included: with level over 95 dB(A) over the entire area of the last and without bogie covers. The results obtained dur- bogie. This bogie definitely stands out from the oth- ing the experimental research have a matrix form. The ers. The S100 maintains good acoustic characteristics ordinate axis is made up of frequencies – from 20 Hz at the speed of 50 km/h. The maximum achieved sound to 20 kHz. The abscissa is the time, measured every level was equal to 103 dB(A), for the wheel and rail 125 ms. The sound levels are presented with colours. contact. However, still the major part of the bogie ar- The data were processed using the previously described eas generate sounds lower than 95 dB(A). Areas be- methods of visualising the sound. Due to the high num- tween bogies reach the level of even 75 dB(A), which ber of data, only signals from the selected microphones was not the case in other trams. A large part of the (first: PM1 and last: PM9) were presented. noise map for the S100 tram is around 80 dB(A) level, Figures 5, 6, and 7 present the results obtained at while in other vehicles these are small areas. In the the speed of 50 km/h without and with bogie cov- S100 model, the sound level of 90 dB(A) was mainly ers. In all cases, the characteristic areas where the observed for the bogies, while in the S105p and Com- sound level is the greatest (red colour), were areas cor- bino models it is present in the entire vehicle. responding to bogies. In addition, the darkest areas In the case of the S105p model, it is easy to see the corresponding to the highest levels are more extensive influence of speed on the change of sound levels which for passages with bogie covers. In lower frequencies, increased significantly at 50 km/h. For the S105p vehi- the values are very similar. Visualisation of the sig- cle, the sound level was 85 dB(A) or more, although it nal for the speed 50 km/h for microphone 1 (Fig. 5) reached lower values at several points. The bogies gen- for both cases is mostly a homogeneous, darker area erated maximum sound level of 108 dB(A). The areas in the range of 200–8000 Hz. In particular, this ap- outside of bogies were characterised by noise at a simi- plies to a vehicle without covers, where the sound level lar level as in the Combino vehicle. On the rolling bo- above 60 dB(A) has already been obtained at 50 Hz. gie of the S105p tram the sound level increased in the At 160 Hz it has exceeded 70 dB(A), and from 1500 Hz middle part, 92 dB(A). it already extends over the entire length of the tram. For a vehicle with covers sound level above 70 dB(A) 3.2. Analysis in the frequency domain creates three intense areas recorded at 630 Hz. Par- ticularly visible are the parts depicting the extreme The acoustic signals obtained from the tests were bogies. In the areas behind the first and before the analysed in the frequency domain using the Fast third bogie, approx. 60 dB(A) are achieved already at Fourier Transform (FFT) algorithm and presented in 125 Hz. In other areas, both left and right, the sound the form of tertiary-time-spectrum maps. In this case, remains between 30 and 40 dB(A), only at the lowest only the Solaris Tramino S105p trams, which is a serial frequencies the front of the vehicle gets quieter, up to construction and is important from the point of view of 20 dB(A). T. Nowakowski et al. – Developing Assumptions for the Tram Noise Attenuation Passive System. . . 787

Fig. 5. Microphone No. 1, speed 50 km/h.

Fig. 6. Microphone No. 9, speed 50 km/h.

Fig. 7. Average results for all microphones, speed 50 km/h. 788 Archives of Acoustics – Volume 44, Number 4, 2019

For the signal from the last microphone, the visu- damped due to the embedding between the wheel disc alisation is very similar for both options (Fig. 6). The and its rim with susceptible elements. Separation of the loudest points occupy a similar area, hence they form rim from the web with a rubber insert at a damping a similar shape. However, on the left, the phenomenon frequency below 1200 Hz reduces the rolling sound and is a bit more extensive, mainly for lower frequencies. minimises all the vibrations of the wheel web (Bouvet Differences in this area are the most visible. Only for et al., 2000). Increasing the frequency of damping will the image on the left, the sound level reduction in the gradually increase the sound emitted by the rail, un- middle of the vehicle remains within a slightly wider dermining the limitation of the sound emitted by the time range. wheel (Suarez et al., 2011). Similar conclusions also In addition, sound levels between 50 and 60 dB(A) arise from other studies (Esteban et al., 2006; Bet- are achieved at slightly higher frequencies. For the ima- gen et al., 2012). ge on the right, the level of 25 dB(A) occurs for ever Depending on its design, the wheels may also be higher frequency bands, reaching 40 Hz. The darker equipped with external damping, i.e. vibration damp- spot around the second bogie loses on clarity and ing systems arranged on the circumference of the depth. The middle bogie slightly stands out. On the wheel. Numerous studies on the impact of external left, the level of 20–30 dB(A) appears only in the front damping indicate a clear reduction of sound emitted part of the vehicle, while on the right it extends over by the wheel, especially in the case of high frequency its entire length. The level of 0–10 dB(A) on the left sounds when passing curves (Lopez et al., 2000; Vi- was recorded in a greater number of points, at the nolas et al., 2007). lowest of frequencies. On the right there are several The authors indicate that even though the reduc- such readings located only in the first measurement tion of the total sound power is not very large, when element, even though for a wider frequency range. In- analysing the graphs for the emission of the wheel it- variably, for both runs, at 20 kHz, the sound remains self, it is easy to notice a significant reduction in the at 25 dB(A). The average sound level from all micro- sound power of up to 15 dB(A) for the wheel with phones (Fig. 7) gives a fairly fuzzy colour area for the damping plates and 25 dB(A) for the wheel with layer vehicle without covers, but with the selection of mo- silencers relative to the wheel without damping, espe- tor bogie. When the covers are mounted, a wide, dark cially when passing curves, as shown in (Merideno strip located in the middle of the examined frequency et al., 2014). The wheels on the test tram were equip- band is a visualisation of the elevated sound level. In ped with internal circumferential damping elements. In this case, it is also possible to indicate the elements order to improve the sound minimising effect, external of the running gear. In both options, similar values of damping has been additionally applied in the form of the sound signal occur at 20 kHz. In the lowest band specially developed, screw-in anti-resonance silencers. on the right, these are mostly readings with levels be- Guidelines for desirable characteristics of structural vi- tween 35 and 40 dB(A), while on the left this range is bration dampers of the wheel web, taking into account wider. damping in the range from 500 Hz to 5 kHz, have been met by the wheel supplier. An exemplary view of the 4. Developing the sound attenuation passive wheel with the vibration damper installed is shown in system for tram Fig. 8.

The conducted research allows to develop a passive system based on the following assumptions: 1) adequate tuning of wheel vibration dampers used in the tram in close cooperation with the wheel supplier and development engineers of the running gear, 2) taking into account the need to meet the require- ments of vehicle gauge, and to avoid direct, un- wanted contact of absorbing/reflecting materials with the parts of the bogie, 3) utilisation of the tram structure to achieve good acoustic performance.

4.1. Damping in the wheels Fig. 8. Wheel dampers. Currently, resilient wheels are commonly used in tram engineering, which damp (to some extent) the vi- The effectiveness of the wheel dampers for the brations due to a dedicated design. The vibrations are squeaking in the curve due to micro slip, was evaluated T. Nowakowski et al. – Developing Assumptions for the Tram Noise Attenuation Passive System. . . 789

Table 1. Efficiency of wheel vibration dampers. Motor bogie Trailer bogie Left wheel [dB] Right wheel [dB] Left wheel [dB] Right wheel [dB] Without dampers 92.6 ± 0.4 88.1 ± 0.4 76.3 ± 0.4 76.5 ± 0.4 With dampers 85.2 ± 0.4 84.5 ± 0.4 72.4 ± 0.4 72.8 ± 0.4 Results −7.4 ± 0.4 −3.6 ± 0.4 −3.9 ± 0.4 −3.7 ± 0.4

during the tests in real conditions. Measurements of the primary material of the cover was a composite sound during driving were taken directly at the wheels. made of a steel frame and a laminate. The tests were conducted on a representative track in The standard (laminate) cover has been enriched the left curve under constant driving conditions. The with acoustic functions through the application of measurements were taken from the first (motor) and a polymer damping material with mineral fillers second (trailer) bogie of new Solaris Tramino S111o (Fig. 10). Fixing with a flexible glue of previously pre- tram, the results are presented in Table 1. pared 10 mm thick acoustic panel to the inside of the As it can be seen from Table 1, the sound reduction cover was applied. efficiency for the most adverse conditions (motor bogie, curve) is significant, and the reduction of the equiva- lent sound level was from 3.6 dB(A) to 7.4 dB(A).

4.2. Bogie covers

In the modern rail vehicles, in order to reduce the sound emission, running gears are protected by exter- nal bogie covers. Currently in Poland more than half of almost 4000 trams in total are operated without bogie covers – this mainly applies to old Konstal 105Na tram and its derivatives. About 26% of the bogie covers are mounted directly to the bogie, and about 19% of them make an integral part of the body. Bogie covers of- ten do not have proper characteristics to attenuate the sound. The only function that is partially fulfilled by them is reflection of sound propagating into the envi- ronment back to the vehicle (Fig. 9). This functionality Fig. 10. Laminate bogie cover. can be justifiably questioned in the case of using lami- nate covers. Due to their structure in the extreme case, they themselves can be a source of secondary acoustic Tests on the new bogie cover were carried out in signals, resulting from vibrations caused by passages the same way as for the tests in Subsec. 3.2. Improved on unevenness and vibrations of the bogie frame. covers were mounted on the first motor bogie and com- pared with the next motor bogie (last one) equipped with standard covers. The results of the measurements are shown in Fig. 11. The use of an improved bogie cover allowed sig- nificant sound attenuation at the level of 5–15 dB(A) depending on the frequency range (mainly in the range of 630–1600 Hz).

4.3. Bogie areas

As part of preventive activities aimed at minimis- ing the penetration of sound into the vehicle interior Fig. 9. Selected designs of bogie cover. it is a common practice to cover the floor from the underside with bitumen materials. The structure of In the test tram, the structural and functional con- this coating may have secondary functions of sound ditions made the covers attached to the bogie. Addi- scattering through diffraction on its surface, but this tionally, due to technological and economic reasons, phenomenon is considerably limited. In some modern 790 Archives of Acoustics – Volume 44, Number 4, 2019

Fig. 11. Results for microphone No. 1 and No. 9 and average results of all microphones, speed 50 km/h. constructions, there are other expositions of area above up to 3 dB. The “P” material shows no attenuation in the body. the 80–100 Hz and 500 Hz bands, giving the gain from Laboratory tests of two materials were carried out, 4.4 dB(A) to 8 dB(A). whose physico-chemical properties enabled their appli- In the low frequency bands 20–63 Hz and 160 Hz, cation on a rail vehicle. The tests were carried out using the attenuation is relatively low up to 3 dB(A). the author’s own testing method in a divided acous- Significant attenuation occurs in higher frequency tic tunnel. The tunnel was divided by a barrier in the bands above 5000 Hz and ranges from 15.2 dB(A)to form of tested damping material forming two parts of 60.6 dB(A). the tunnel. Signals were recorded in a part of the tun- Taking into account the obtained results, material nel with the sound source (white noise, LAeq = 100 dB, “P” with the structure of pressed plates is used. An t = 32 s) and in a part of the tunnel behind the barrier. example of such a solution is presented in Fig. 12. The main purpose of the research was to assess sound The used material has ribs which have acoustic fea- attenuation using damping material. The analysis of tures other than the reflection of the sound wave. In sound attenuation of tested materials was based on the analysed area, closed cell polyethylene foam was difference in sound levels in individual CPB spectrum used. As for the method of installing this material, it bands of acoustic signals recorded by microphones. The was decided to mechanically connect it with the load test results for material “M” (melamine foam) and ma- bearing elements of the body structure. This material terial “P” (closed cell polyethylene foam) are presented is spot mounted, allowing the creation of local airbags in Fig. 12. between the front of the material and the walls of the In the case of the material “M”, the highest val- vehicle. This action allowed to cause and use multi- ues of attenuations exceed the value of 11 dB(A) and ple reflections of the sound wave: falling on the front occur in the 200 Hz and 20000 Hz bands. In addi- part of the bogie area, passing through it, reenter- tion, there is a sound attenuation of up to 5 dB(A) ing the free space (air cushion), and falling on the wall, in the 31.5–125 Hz and 500 Hz bands. For the 3150– the wave is reflected and directed in the opposite di- 10 000 Hz frequency range, the attenuation level was rection.

Fig. 12. Sound attenuation of materials in CPB spectra. T. Nowakowski et al. – Developing Assumptions for the Tram Noise Attenuation Passive System. . . 791

tem for tram was developed as a standard procedure for managing the vibroacoustic activity of the tram and subsequently was implemented for production.

Acknowledgment

All work was realised as a part of the research project “Innovative package of subsystems improving the functional and operational properties of vehicles” (POIG.01.04.00-30-336/13), financed from the European Regional Development Fund under the Innovative Economy Operational Program. Fig. 13. View of area under bogie. References

5. Conclusions 1. Berglund B., Lindvall T., Schwela D.H. (2000), Guidelines for community noise, World Health Or- The results of the experimental research clearly ganization, Geneva, https://apps.who.int/iris/handle/ show that from the acoustic point of view the most 10665/66217. demanding area is that of the tram bogie, where the 2. Betgen B., Bouvet P., Thompson D., Demilly F., highest sound levels are generated. The research indi- Gerlach T. (2012), Assessment of the efficiency of cated that the S100 and S105p models differed signifi- railway wheel dampers using laboratory methods within cantly in terms of noise maps for all tested speeds de- the STARDAMP project, Proceedings of the Acoustics spite their closely related design. For 20 km/h, the low- 2012 Nantes Conference, Nantes, pp. 3733–3738. est levels of 90–95 dB(A) were observed for S100 and 3. Bouvet P., Vincent N., Coblentz A., Demilly F. the highest one was for S105p – 100 dB(A). The S100 (2000), Optimization of resilient wheels for rolling tram appeared to be less noisy, by around 5 dB(A) in noise control, Journal of Sound and Vibration, 231, the bogies sections and by around 10 dB(A) for the 3, 765–777, doi: 10.1006/jsvi.1999.2561. remaining areas of the vehicle. Frequency studies indi- 4. Cik M., Lienhart M., Lercher, P. (2016), Analy- cate that the critical frequency range regarding sound sis of psychoacoustic and vibration-related parameters levels falls within the range of 500–5000 Hz. This is to track the reasons for health complaints after the in- the frequency range that should be considered first to troduction of new Tramways, Applied Sciences, 6, 12, minimise the generated sound energy. 1–17, doi: 10.3390/app6120398. Due to technical limitations regarding sound ab- 5. Czechyra B. (2012), Noise and vibration activity of sorbing systems design and a very complex spectrum trams as a development of a tram acoustic signature, of the generated sound, there is no possibility to apply Proceedings of 19th International Congress on Sound active sound reduction appliances influencing sound and Vibration. Vilnus: International Institute of Acous- propagation. For this reason, the authors focused on tics and Vibration, Vilnus. the passive noise attenuation solutions. Possible activ- 6. Czechyra B. (2013), Vibroacoustic properties and in- ities may focus on the design of bogie covers enhanced teractions of an urban tram, [in:] Vibrations in physical with acoustic attenuation properties, e.g. through ap- systems, Cempel C. [Ed.], vol. 25, pp. 117–122, Poznan plication of damping materials. Actions should also University of Technology, Poznan–Bedlewo. be directed towards increasing the acoustic absorption 7. Czechyra B., Tomaszewski F. (2009), Acoustic of the car body surface facing the bogie by introduc- signature of trams, Proceedings of 16th International ing sound absorbing covers with internal attenuation Congress on Sound and Vibration, pp. 1401–1407, properties. The improved bogies covers, suggested in Krakow. this paper, allowed for a significant noise reduction by 8. Engel Z. (2001), Environmental protection against vi- 5–15 dB(A) in the band of 630–1600 Hz. Noise reduc- brations and noise [in Polish], PWN, Warsaw. tion at higher frequencies may be achieved by using 9. Esteban B., Serrano B., Rodríguez P., Blan- sound attenuating material in the area of the bogie. quer F. (2006), Comparison of vibration and rolling The attenuating material used in this study resulted noise emission of resilient and solid monobloc railway in noise reduction for frequencies above 5000 Hz by up wheels in underground lines, Proceedings of the 7th to 61 dB(A). World Congress on Railway Research, Montreal. The presented and applied technological solutions 10. European Commision (2011), White Paper – Roadmap allowed to realise the double goal of the research to a single european transport area. Towards a compet- project in the aspect of minimising the sound gener- itive and resource efficient transport system, Luxem- ated by the tram. The passive sound attenuation sys- burg. 792 Archives of Acoustics – Volume 44, Number 4, 2019

11. European Parliment (2002), The assessment and squeal noise in trams, Shock and Vibration, 3, 1–11, management of environmental noise – 2002/49/EC, doi: 10.1155/2014/473720. L189/12, Brussel. 25. Miedema H., Van der Berg R. (1988), Commu- 12. Fidell S., Barber D.S., Schultz T.J. (1991), Up- nity response to tramway nosie, Journal of Sound dating a dosage-effect relationship for the prevalence and Vibration, 120, 2, 341–346, doi: 10.1016/0022- of annoyance due to general transportation noise, The 460X(88)90444-0. Journal of the Acoustical Society of America, 89, 1, 26. Niziński S., Żółtowski B. (2002), Management of 221–233, doi: 10.1121/1.400504. exploitation of technical facilities by means of cost ac- 13. Fritschi L., Brown A., Kim R., Schwela D., counting [in Polish], Makat-B.Ż., Olsztyn-Bydgoszcz. Kephalopoulos S. (2011), Burden of disease form 27. Nowakowski T., Tomaszewski F. (2017), Analysis enviromental noise – Quantification of healthy life of dynamic tram-track interactions based on paraseis- years lost in Europe, World Health Organization, mic vibration, 24th International Congress on Sound Copenhagen, https://www.who.int/quantifying_ehim- and Vibration, pp. 3936–3944, London. pacts/publications/e94888.pdf?ua=1. 28. Panulinova E., Harabinová S., Argalášová L. 14. Golay F. (2008), Acoustic emission of trams. Mod- (2016), Tram squealing noise and its impact on hu- eling extended vehicles by point sound sources, Ph.D. man health, Noise & Health – A Bimonthly Inter- Thesis, University of Maine. disciplinary Interantional Journal, 18, 329–337. 15. Hemsworth B. (2008), Environmental noise direc- 29. Pawlas K. (2015), Noise as environment al pollution tive development of action plans for railways, UIC – medical aspects [in Polish], Environmental Medicine, Noise Expert Network: International Union of Rail- 18, 49–56. ways (UIC), https://uic.org/IMG/pdf/action_plan- ning_paper_final-2.pdf 30. Polish Minister of Infrastructure (2011), The technical conditions of trams and trolleybuses and the scope of 16. Hubka V. (1991), Construct property-appropriate. De- their necessary equipment, Journal of Laws, No. 65, sign for Propertie, International Conference on Engi- item 344. neering Design, Zurich. 31. Popescu D., Moholea I. (2010), Monitoring the re- 17. Hume K., Brink M., Basner M. (2012), Effects of action and response of people to urban noise, Archives environmental noise on sleep, Noise Health, 14, 61, of Acoustics, 35, 2, 237–244. 297–302, doi: 10.4103/1463-1741.104897. 32. Róg S. (1992), Quality of life and living conditions [in 18. Kaczmarek T., Hafke H., Preis A., Sandrock S., Polish], PWN, Warszawa. Griefahn B., Gjestland T. (2006), The tram bonus, 33. Sanchez-Sanchez R., Fortes-Garrido J., Boli- Archives of Acoustics, 31, 4, 405–412. var J. (2018), Noise Monitoring Networks as Tools 19. Lakušić S., Dragcevic V., Ahac M., Ahac S. for Smart City Decision-Making, Archives of Acous- (2011), Noise protection on railway stations [in Croa- tics, 43, 1, 103–112, doi: 10.24425/118085. tian], [in:] Designing of transport infrastructure [in 34. Suarez B., Chover J., Rodriguez P., Gonza- Croatian], Lakušić S. [Ed.], pp. 105–131, Faculty of lez F. (2011), Effectiveness of resilient wheels in re- Civil Engineering, University of Zagreb, Zagreb. ducing noise and vibrations, Proceedings of the Insti- 20. Leśnikowska-Matusiak I. (2014), Impact of traffic tution of Mechanical Engineers, 225, 545–565. noise on the state of human acoustic environment [in 35. Swedish Testing and Research Institute (1999), Vibra- Polish], Motor Transport, 3, 37–62. tions from railway traffic - Comparison of two methods 21. Lopez I., Vinolas J., Busturia J., Castanares A. of measurement and different guideline values – report (2000), Railway wheel ring dampers, Proceedings Inter- 1991:44 [in Swedish], Boras [Göransson C.]. Noise 2000, Paris. 36. Targosz J., Adamczyk J. (2010), Research and 22. Madej H. (2001), A gearbox housing modifications for evalution vibroactiviti construction of tram tracks in minimizing noise radiation, Scientific Journal of Sile- Poland [in Polish], Logistyka, 3, 2267–2276. sian University of Technology – Series Transport, 43, 37. Thompson D. (2008), Railway noise and vibration: 131–136. mechanism, modeling and means of control, Elsevier, 23. Mandula J., Salaiova B., Kovalakowva M. Oxford. (2002), Prediction of noise from trams, Applied Acous- 38. Vinolas J., Nieto F., Lopez Arteaga I., Egana J. tics, 63, 4, 57–68, doi: 10.1016/S0003-682X(01)00047-0. (2007), The effect of damping the wheels and varying 24. Merideno J., Nieto J., Gil-Negrete N., Landa- wheel/rail friction coefficient on railway noise, 19th berea A., Iartza J. (2014), Constrained layer damper International Congress on Acousitcs, pp. 1635–1641, modelling and performance evaluation for eliminating Madrit.