Noise levels inside the coaches of Greater Cairo tunnel metro, line 3 tunnel
|نوع نگارش مقاله||
scopus – master journals – JCR
۴٫۲۷۶ در سال ۲۰۲۰
۲۶ در سال ۲۰۲۱
۰٫۹۰۱ در سال ۲۰۲۰
|شاخص Quartile (چارک)||
Q1 در سال ۲۰۲۰
خرید محصول توسط کلیه کارت های شتاب امکان پذیر است و بلافاصله پس از خرید، لینک دانلود محصول در اختیار شما قرار خواهد گرفت و هر گونه فروش در سایت های دیگر قابل پیگیری خواهد بود.
فهرست مطالب مقاله:
This paper investigates the noise inside a metro coach running through the most recent tunnel of Cairo. The study focuses on the effects of alignment profiles on the A- weighted noise level. Although the latest line has not been studied yet, noise levels inside the old lines attracted the attention of researchers due to their importance as the first mass transit system in Africa. Given that windows are usually kept open, measurements were con- ducted inside the empty cabin at the end of the train with open windows according to ISO
3381:2005. Results showed that noise emissions inside the running coaches are high and do not follow either international or general national legislation, which presents health hazards for drivers and commuters. Speech intelligibility is required for train radio units and driver con- soles for voice communications, which provides a safe working environment for the train crew. The present study reveals that tight curves mainly contribute to high noise. The noise levels are further raised by the reflective surface of the tunnel with a circular cross-section and the unballasted track. Moreover, the noise level is affected by the location of the coach and window conditions (open/close) to some extent.
|بخشی از متن مقاله:|
Railway noise represents a daily environmental concern in developed and developing countries (Fields and Walker,
1982) and affects the safety and health of employees and passengers (Eade, 1999). The World Health Organization (WHO) indicates that environmental noise in western Eu- ropean countries, which is estimated at approximately one million healthy life years per year due to traffic noise, significantly impacts the disability adjusted life years (DALYs) (WHO, 2011). Hearing loss is the most common ef- fect caused by exposure to excessive noise according to the
2010 occupational illnesses report. Noise resulting from transportation, including vehicles, railway, and aircraft, represents approximately ۶۰% of noise in Africa (UN- Habitat, 2014) and the main cause of noise in Greater Cairo (Egyptian Environmental Affairs Agency, 2008). Excessive noise exposure, viruses, and conditions caused by normal aging are the main reasons for sensorineural hearing loss, which is defined as an impairment that is associated with irreversible deterioration to the inner ear and mostly cannot be healed (OSHA, 2019). Noise-induced hearing loss (NIHL) represents one of the common occupational diseases in different cities of the United States (Bauer et al., 2001). In addition, a recent study showed that exposure to freight train noise together with its vibration affects the heart rate during sleep, which may influence cardiovascular func- tioning (Croy et al., ۲۰۱۳). Moreover, excessive noise exposure influences human health in several ways, such as headache, insomnia, fatigue, high blood pressure, arrhythmia, annoyance, problems with performance and communications, lowered morale, poor signal intelligibility, and poor concentration (OSHA, 2019).
Underground train noise can be classified into airborne and structure-borne noise. Airborne noise originates from different sources, such as steel wheel/rail action, train siren/whistle, aerodynamic noise, power and auxiliary equipment (such as HVAC systems), power units, and en- gines (Croy et al., 2013).
Structure-borne noise is derived from vibro-acoustic sources radiated by vibration transmission into the train envelope from bogies and mounted equipment, in which the predominant frequencies are mostly below 200 Hz (Choi et al., 2004). The emission of wheel/rail noise increases with the train speed and the surface roughness of wheel/ rail contact. Instead of cast-iron treaded brake stocks, applying disc brakes for rolling stocks results in reduced noise by 8 dB(A) at speeds of 160 km/h (Eade, 1999). Noise barriers can be an effective countermeasure for mitigating wayside noise but does not decrease the noise inside the coaches and the driver cabin (Eade, 1999).
Noise emission from trains arising between the wheels and rails is influenced by rail alignment, lack of mainte- nance, and rigidity of track supports (ARUP, 2015). How- ever, any alignment usually runs along narrow corridors, which comprises numerous horizontal curves and vertical slope gradients. Such curves lead to the excessive wear of rails because of the abrasive action of the rolling wheels.
Greater Cairo, which is the first of Africa’s megacities and the second by 2025, has approximately 17 million residents. Northern African cities, including Egypt, experience pollu- tion and congestion because of the high numbers of private motor cars (UN-Habitat, 2014). Mass public transport sys- tems, particularly railway transportation, have been applied to address the needs of overpopulation. Fig. 1 shows that the Great Cairo Metro network links three governorates with three lines in operation. As of 2020, the network comprises
68 stations with a total length of 81.6 km. The underground section extends approximately 36 km (roughly ۴۴% of the total length) and mainly comprises two different cross- sections, namely cut & cover and circular sections.
Line 3 is the latest in operation despite the inauguration of only three of its five phases. Upon completion, Line 3 will form the east-west corridor of the city, which connects Alf Maskin (east) to Boulak and/or Rod El Farag suburbs (west). The overall length of Line 3 will be approximately 34.5 km and comprise 34 stations. The current routing, which is fully located underground, is ۱۶ km long and includes 13 un- derground stations (National Authority for tunnel, 2012a). The tunnel lots connecting these stations have a circular cross-section.
The literature on railway noise in Egypt, particularly inside tunnels, includes some reports on this particular problem despite the presence of many tunnels in the Cairo mass transit network, which is currently continuously extended. Thus, studying the noise levels along the existing tunnels is crucial to examine the daily exposure for the train crew and passengers and determine the influential factors. Based on field measurements, this paper in- vestigates the airborne noise caused by rapid transit trains inside the typical circular tunnel of the newest line of Cairo’s Metro network.
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