Acoustic comfort at Kyiv metro stations Illia Melnyk 1 Evheny Fridlib Artem Maksymenko Hanna Kliushnichenko Acoustic Consulting LLC (Acoustic Group member) Ukraine, Kyiv, Kurenivska str., 18

ABSTRACT Kyiv Metro was opened in 1960 and became the first metro system in Ukraine. From then until the beginning of the 21st century it was developing without considering the acoustic com- fort of its passengers and employees. Increased levels of noise and vibration in public transport are mostly ignored, although they are certainly recognized as the reasons for increasing the harmfulness of work for metro employees. The present report analyzes noise levels at metro stations depending on their design features.

There are several main types of stations in the Kyiv metro: deep-lying, shallow-lying, as well as above-ground stations. For all types of underground stations, there are options both with and without sound-absorbing finishes. Also, during the construction of the newest stations of the Kyiv metro, vibration isolation systems were used for the construction of the permanent way were used. Within this study, sound pressure levels were measured on the platform at sta- tions of various types.

These measurements made it possible to establish a significant influence of the shape of the station vestibule, the presence of sound-absorbing finishes in it, as well as the vibration isolation of the permanent way, on the objective and subjective parameters of acoustic comfort for pas- sengers and employees of the subway.

1. INTRODUCTION

Train movement sounds in underground public transport are a constant and well-known problem to the citizens of the different metropolises. which can endanger human health, employees and pas- sengers could be exposed to excessive noise. The main sound sources in the metro are intersections (junctions, pins, switches), wheels rotating on tracks, electric motors, electrical equipment, signals, locomotives, brakes, stops, and the train’s aerodynamic sound. Quite a bit of attention is paid to the sound influence to which passengers and employees at stations are exposed. According to statements released by the World Health Organization (WHO), noise exposure to 85 dB A-weighted over 45 min will lead to noise-induced hearing loss (NIHL) [3].

As part of the study of the impact of the architectural design of subway stations on the acoustic comfort and legibility of loudspeaker notifications, a series of field measurements of sound pressure level during the movement of subway trains at the station, as well as background noise. The most typical types of Kyiv metro stations were selected for analysis (classified by type):

1) illia.melnyk90@gmail.com

inter.noise 21-24 AUGUST SCOTTISH EVENT Cais

 shallow-lying stations with flat ceiling • Pochayna – a station with sound-absorbing ceiling

Fig. 1: Pochayna station • Tarasa Shevchenka – a station without sound-absorbing finish

Fig. 2: Tarasa Shevchenka station  shallow-lying vaulted station • Minska – a station without vibration insulation

Fig. 3: Minska station

• Vasylkivska – a station with vibration insulation under sleepers

Fig. 4: Vasylkivska station  deep-lying column stations • Palats Sportu – a station with sound-absorbing finishes

Fig. 5: Palats Sportu station • Olympiyska – a station without sound-absorbing finish

Fig. 6: Olympiyska station

 Hydropark – an above-ground station without a closed volume of the platform.

Fig. 7: Hydropark station

2. NOISE MEASUREMENTS AT METRO STATIONS

Measurements of the noise level were carried out in the period from August 16 to 31, 2021 during rush hours by the certified noise meter-analyzer of the spectrum "ECOPHYSICA". Measurement time ∆t = 25 sec for each point (average train travel time before / after the stop). Noise level meas- urement points were selected at characteristic points – at a distance of 2 m from the edge of the platform in the head, middle and tail of the train. The noise level was measured both during train arrival and departure. The background noise level at the station while waiting for the train was also measured separately. The general method of measurements was chosen in accordance with [1]. The points of the measurements are marked on the Figure 8.

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Fig. 8: Principled situational map of the location of measuring points on the platform of the station.

1. The tail of the train. 2. Mid platform. 3. The head of the train. 4. Measurement of background noise in the center of the platform

At least 3 measurements were performed at each point for both arrival and approach of the train. Because the measurements were recorded from different trains, the noise level of which was not constant, the measurement results were averaged. Table 1 below shows the noise levels in the octave bands and the equivalent level in comparison at all characteristic points.

Table 1: Results of the noise measurements at metro stations

Sound pressure levels L (equivalent sound pressure

Equivalent

levels Leq) in dB in octave frequency bands with

sound

Measurement points

geometric mean frequencies in Hz

levels

31,5 63 125 250 500 1000 2000 4000 8000 L А eq, dBA

Pochayna station 1. Arrival of the train. Head 74 70 67 69 68 62 59 56 52 77

2. Departure of the train. Head 85 85 82 86 90 84 80 75 72 90

3. Arrival of the train. Middle 80 81 77 84 84 79 75 71 66 85

4. Departure of the train. Middle 78 81 76 85 85 79 75 72 69 86

5. Arrival of the train. Tail 85 83 81 88 87 82 79 73 67 88

6. Departure of the train. Tail 78 78 77 84 82 76 73 72 68 83

7. Background noise level 69 63 56 52 51 47 45 42 38 53

Tarasa Shevchenka station 1. Arrival of the train. Head 80 84 79 85 83 77 71 62 54 83

2. Departure of the train. Head 88 90 85 93 93 87 82 76 69 93

3. Arrival of the train. Middle 81 87 80 89 87 81 76 69 63 87

4. Departure of the train. Middle 84 89 85 94 93 88 83 78 71 94

5. Arrival of the train. Tail 85 91 82 90 89 85 79 72 67 90

6. Departure of the train. Tail 85 87 83 91 91 84 79 73 67 90

7. Background noise level 78 76 72 68 63 58 52 47 41 65

Minska station 1. Arrival of the train. Head 76 78 75 86 85 79 73 66 59 85

2. Departure of the train. Head 81 82 79 91 92 86 81 74 67 92

3. Arrival of the train. Middle 79 81 78 90 89 83 77 70 63 89

4. Departure of the train. Middle 83 86 80 92 93 87 80 74 68 92

5. Arrival of the train. Tail 87 84 81 91 91 85 80 74 67 91

6. Departure of the train. Tail 83 82 79 88 87 81 76 69 63 87

7. Background noise level 77 73 64 63 64 58 53 48 40 64

Vasylkivska station 1. Arrival of the train. Head 73 77 77 83 82 78 72 66 58 83

2. Departure of the train. Head 77 79 78 85 84 79 74 69 62 85

3. Arrival of the train. Middle 77 78 78 86 85 81 76 69 62 86

4. Departure of the train. Middle 74 77 77 81 81 77 72 67 60 82

5. Arrival of the train. Tail 78 80 79 89 87 83 78 70 63 88

6. Departure of the train. Tail 74 79 77 82 82 77 72 68 60 82

7. Background noise level 67 66 66 64 63 57 51 45 37 63

Palats Sportu station 1. Arrival of the train. Head 82 79 75 79 76 69 65 62 57 77

2. Departure of the train. Head 85 86 81 89 89 83 78 73 69 89

3. Arrival of the train. Middle 85 81 79 84 83 76 71 66 62 83

4. Departure of the train. Middle 81 78 78 86 84 77 72 69 66 84

5. Arrival of the train. Tail 93 90 86 90 87 81 75 70 65 88

6. Departure of the train. Tail 84 81 81 84 82 74 68 64 61 82

7. Background noise level 79 72 70 69 59 52 47 41 35 62

Olympiyska station 1. Arrival of the train. Head 85 87 88 94 95 91 86 81 78 96

2. Departure of the train. Head 77 81 79 85 84 78 73 66 59 84

3. Arrival of the train. Middle 82 84 84 93 92 86 82 75 69 92

4. Departure of the train. Middle 81 83 85 90 90 84 79 73 68 90

5. Arrival of the train. Tail 85 86 85 92 91 87 81 75 71 92

6. Departure of the train. Tail 83 85 83 89 89 83 78 73 68 89

7. Background noise level 74 73 68 66 61 55 49 42 34 62

Hydropark station 1. Arrival of the train. Head 74 74 68 71 70 69 63 57 49 73

2. Departure of the train. Head 81 78 74 80 80 77 72 67 59 81

3. Arrival of the train. Middle 78 76 73 81 78 74 68 63 58 79

4. Departure of the train. Middle 82 78 74 84 82 77 72 65 60 83

5. Arrival of the train. Tail 78 81 74 82 80 78 73 67 60 83

6. Departure of the train. Tail 77 81 74 75 73 70 65 60 56 75

7. Background noise level 69 81 71 67 63 66 62 53 45 69

The recommended maximum allowable constant noise level that does not affect the

deterioration of health according to [2]. Leq 79 71 64 58 54 51 49 48 47 60 Lmax 92 84 77 72 68 66 64 63 62 75

Notes: • The noise level recorded when trains pass through the station depends very much on the intensity

of braking or acceleration applied by the driver – the more abruptly the speed of the train changes, the more noise it produces. These differences were leveled by repeated measurements for each point.

3. ANALYSIS OF MEASUREMENT RESULTS

It should be noted that the standard requirement for equivalent sound pressure level should only apply to background noise levels at stations. Noise during train movement can be compared with the permissible maximum noise levels at the station.

Thus, the level of background noise does not exceed the recommended permissible level only at the Pochayna station, where there is a sound-absorbing ceiling and there are no escalators. At other stations there are excesses that were due to the background noise level at the station was affected by the presence of escalators (Palats Sportu and Olimpiyska), and in the case of the Hydropark station - by external noise. The background noise level was also affected by the fixtures. Characteristic buzz- ing was recorded at stations with old fluorescent lamps (Minska and Tarasa Shevchenka stations).

Also, attention should be paid to significant excesses of the recommended permissible maximum noise level during the movement of trains at stations without the use of any acoustic solutions (sound- absorbing finishes or vibro-insulated upper track structure).

Next, we consider some individual cases in more detail and compare the results of measurements at similar stations with different acoustic solutions.

3.1. Background noise level

dB

9032631252505001000200040008000ПочайнаПалац СпортуТараса ШевченкаМінськаОлімпійськаВасильківська

80

70

60

50

40

30

32 63 125 250 500 1000 2000 4000 8000 Gz

Гідропар к

Fig. 9: Comparative graphs of background noise levels at stations

The graphs of the background noise level at the stations illustrate that the lowest background noise level in the most fundamental from the acoustic point of view range 500…2000 Hz is the lowest at the stations with acoustic finish: Pochayna and Palats Sportu. At the same time, the highest level of background noise was recorded at the Hydropark station from external sources. Increased noise level in the frequency bands 125… 250 Hz at deep embedding stations was formed by the influence of constant noise from escalators.

3.2. Train noise

To compare the results of the measured values of the noise level at the underground stations with and without finishing, we choose the Hydropark station, which has no closed volume and, accord- ingly, has a minimum of echoes and expected lowest noise levels from the train passage.

dB

95

90

85

80

75

70

65

60

55

Gz

32 63 125 250 500 1000 2000 4000 8000

Pochayna Palats Sportu Tarasa Shevchenka Minska

Olimpiyska Vasylkivska Hydropark

Fig. 10: Comparative graphs of noise during train passage

Thus, the highest noise levels at stations during train passage were recorded at Olimpiyska, Minska and Tarasa Shevchenka stations. They are distinguished by the lack of sound-absorbing finish. It should be noted that at the Vasylkivska station the noise level is actually the same as the level at stations with sound-absorbing cladding, namely 5-7 dB lower. This is due to the use of vibration- insulated sleepers at this station. In addition, the presence of vibration isolation under the sleepers gives a characteristic reduction in the noise level in the frequency band of 31.5 Hz. At the same time, the noise level at the Hydropark station during the passage of trains is still 3-5 dB lower, which shows the approximate "target" noise level, which can be achieved by using highly efficient solutions for the correction of acoustics at stations.

3.3. Comparison of the efficiency of sound-absorbing finishes at stations under the condition of close spatial planning solutions

As an example, consider the pairs of stations Pochayna - Tarasa Shevchenka and the Palats Sportu - Olimpiyska.

dB

95

90

85

80

75

70

65

60

55

Gz

32 63 125 250 500 1000 2000 4000 8000

Pochayna Tarasa Shevchenka

Fig. 11. Comparative graphs of noise during train passage at Pochayna and Tarasa Shevchenka stations

dB

95

90

85

80

75

70

65

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55

Gz

32 63 125 250 500 1000 2000 4000 8000

Palats Sportu Olimpiyska

Fig. 12: Comparative graphs of noise during train passage at Palats Sportu and Olimpiyska stations

The graphs show that the noise level at stations of similar volume with sound-absorbing finish is significantly lower than at stations without it. And in the fundamental frequency range of 250 - 1000 Hz, the difference between noise levels is up to 5-8 dB.

3.4. The effectiveness of solutions for vibration isolation of the upper structure of the track in reducing the noise level at the station

To assess the impact of vibration insulation of the upper track structure on the acoustic comfort at the station, it was chosen to compare Minskа and Vasylkivska stations, which have a vaulted shape of the main vestibule and approximately the same volume.

dB

95

90

85

80

75

70

65

60

55

32 63 125 250 500 1000 2000 4000 8000

Gz

Minska Vasylkivska

Fig. 13: Comparative graphs of noise during train passage at Vasylkivska and Minska stations

The graphs show that the noise level at stations of similar volume with vibro-insulated upper track structure is significantly lower than at stations without vibration isolation. And in the fundamental frequency range of 250 - 1000 Hz, the difference between noise levels is up to 5-6 dB. It should be noted that this observation suggests that the main source of high noise levels at stations is the rumble, which is excited in the upper structure of the track with rigidly monolithic half-sleepers.

4. CONCLUSIONS

This study describes the impact of sound-absorbing finishes at Kyiv metro stations, as well as the vibro-insulated upper track structure on the noise level, as an indicator of acoustic comfort.

The measurement results show that with the simultaneous installation of a sound-absorbing fin- ishing and vibration isolation of the upper track structure, there is a prospect of reducing the noise level at stations by 10-15 dB. This will lead to achievment a high level of acoustic comfort at the station both during the movement of trains and while waiting on the platform. This will reduce the fatigue of passengers and metro employees and increase the legibility of announcements. Thus, it is recommended to provide for both sound-absorbing finishing of stations and vibration isolation of the railway track when designing new metro stations.

Specific methods and materials should be considered in the sections on noise and vibration pro- tection as part of the general design documentation for construction.

5. REFERENCES

1. ГОСТ 23337-2014 (ISO 3166) «Шум. Методы измерения шума на селитебной территории

и в помещениях жилых и общественных зданий» (Noise. Methods of measuring noise in res- idential areas and in residential and public buildings). 2. Державні санітарні норми допустимих рівнів шуму в приміщеннях житлових та громадсь-

ких будинків і на території житлової забудови від 22.02.2019 р. Наказ МОЗ України №463. (State sanitary norms of admissible noise levels in premises of inhabited and public houses and in the territory of inhabited building). 3. R. Guski, D. Schreckenberg, and R. Schuemer, “WHO environmental noise guidelines for the

European region: a systematic review on environmental noise and annoyance,” International Journal of Environmental Research and Public Health, Vol. 14, No. 12, Dec. 2017. 4. W. Passchier-Vermeer and W. F. Passchier, “Noise exposure and public health.,” Environmental

Health Perspectives, Vol. 108, No. suppl 1, Mar. 2000.