Rail transport or train transport is one of the main transportation modes these days, both for transferring passengers and goods. Every day people commute to work and back home using trains in a form of subway systems, light rail transits and other types of rail transport. These types of system can create noise both to the passengers inside of the train as well as to the environment. In this article, we will discuss about noise source components that we hear daily both inside and outside of the train.
If we pay attention to the noise when we are on board of a train, there are more than one noise source that we can hear. The main sources for interior noise in a train are turbulent boundary layer, air conditioning noise, engine/auxiliary equipment, rolling noise and aerodynamic noise from bogie, as illustrated in the following figure.
By the way, we wrote and recorded the sound of Jakarta MRT. You can see the link below to help you imagine the train situation better.
Rolling noise is caused by wheel and rail vibrations induced at the wheel/rain contact and is one of the most important components in railway noise. This type of noise depends on both wheel and rail’s roughness. The rougher the surface of both components will create higher noise level both inside and outside of the train. To be able to estimate the airborne component from the rolling noise, we must consider wheel and track characteristics and roughness.
Another noise component that contributes a lot to railway noise is aerodynamic noise which can be caused by more than one sources. These types of sources may contribute differently to internal noise and external noise. For example, aerodynamic noise contributes quite significantly at lower speeds to internal noise while for external noise, it doesn’t contribute as much if the train speed is relatively low. For example, on the report written by Federal Railroad Administration (US Department of Transportation), it is stated that aerodynamic sources start to generate significant noise at speeds of approximately 180 mph (around 290 km/h). Below that speed, only rolling noise and propulsion/machinery noise is taken into consideration for external noise calculation. In addition to external noise, machinery noise also contributes to the interior noise levels. This category includes engines, electric motors, air-conditioning equipment, and so on.
To perform the measurements of railway noise, there are several procedures that are commonly followed. For measurement of train pass-by noise, ISO 3095 Acoustics – Railway applications – measurement of noise emitted by rail bound vehicles,is commonly used. This standard has 3 editions with the first published in 1975, and then modified and approved in 2005 and again in 2013. The commonly used measures for train pass-by are Maximum Level (LAmax), Sound Exposure Level (SEL) and Transit Exposure Level (TEL).
For interior noise, the commonly used test procedure is specified in ISO 3381 Railway applications – Acoustics – Measurement of noise inside rail bound vehicles. This procedure specifies measurements in few different conditions such as measurement on trains with constant speed, accelerating trains from standstill, decelerating vehicles, and stationary vehicles.
Written by:
Hizkia Natanael
Acoustical Design Engineer
Geonoise Indonesia
hizkia@geonoise.asia
Reference:
D. J. Thompson. Railway noise and vibration: mechanisms, modelling and means of control. Elsevier, Amsterdam, 2008
Federal Railroad Administration – U.S. Department of Transportation, High-Speed Ground Transportation Noise and Vibration Impact Assessment. DOT/FRA/ORD-12/15. 2012
Jakarta, the capital city of Indonesia, is home to 10 millions of Indonesia population. Recently the Indonesian government is being sued by a group of activists and environmentalists due to the unhealthy air quality in Jakarta. The plaintiff hopes that through the lawsuit, the Indonesian government can improve existing policies to address the air pollution issues.
On 18 Jul, according to the Switzerland-based pollution mapping service AirVisual, the Air Quality Index (AQI) of Jakarta is 153, categorized as unhealthy and may cause increased aggravation of the heart and lungs. The recommendation upon this condition is to wear a pollution mask and use air purifiers inside the room. The AQI Measures five criteria air pollutants (particulate matter, sulphur, dioxide, carbon monoxide, nitrogen dioxide, and ozone), and converts the measured pollutant concentration in a community’s air to a number on a scale of 0 to 500.
Air Quality Index – AirVisual
Jakarta is one of the largest urban agglomerations in the world. The uncontrolled increase in urban population is proportional to the number of the vehicle in Jakarta. According to Badan Pusat Statistik (Statistics Indonesia), the growth of motorized vehicle in Jakarta is 5,35% every year, on the other hand, this growth will increase the number of pollution in Jakarta. This statement is supported by the acting head of Jakarta Environment Agency, Andono Warih, the fuel residue of motorized vehicles was the main contributor to severe air pollution as 80 per cent of vehicles powered by diesel fuel operated from Jakarta Greater Area (Jabodetabek) to the capital.
Jakartan can contribute directly to overcome air pollution issues. Public transportation is an environmentally friendly mode of getting around. Because public transportation carries many passengers on a single-vehicle, thus it can reduce the number of vehicles as well as reducing the number of emissions from transportation in a dense urban area. Further, public transportation can help Jakarta to reduce the smog, to meet air quality standards and to decrease the health risk of unhealthy air quality.
The urban transportation system in Indonesia consists of buses, trams, light rail, metro, rapid transit and ferries. Particularly in Jakarta, urban rail-based transportation, such as Commuter Line Train, Light Rail Transit (LRT) and Mass Rapid Transit (MRT), provides mobility and access to the urban area.
MRT Jakarta Phase 1 – MRT Jakarta
The first phase of MRT Jakarta (MRT-J) has been operating since March 2019. In daily operation, the train runs from Lebak Bulus Grab Station to the Bundaran HI Station. There are 13 stations along the railway; the underground stations are Bundaran HI, Dukuh Atas BNI, Setiabudi Astra, Bendungan Hilir, Istora Mandiri, and Senayan Station. Meanwhile, the overground stations are ASEAN, Blok M, Blok A, Haji Nawi, Cipete Raya, Fatmawati, and Lebak Bulus Grab Station. The MRT-J only needs 30 minutes to travel along the 16 kilometres railway, starting from Lebak Bulus Grab Station in South Jakarta to the Bundaran HI Station in Central Jakarta.
There are 16 train lines available to take the passengers getting around. Based on the MRT-J website, In weekdays operation, the trains operate at 05.00 WIB to 24.00 WIB with a total of 285 trips. Meanwhile, in weekend operation, the trains run at the same hour with a total of 219 trips.
During the promo operation (1 April – 12 May), the average number of daily passengers reached 82,643, whereas after the full tariff was applied, the average per day was 81,459.
The following pictures will show you the scenes of MRT Jakarta.
So what do you think? Have you tried getting around using MRT Jakarta? If you have never, try immediately and feel the different sensation of Public Transportation in Indonesia.
Further, through this article, I would like to invite you, explore the MRT Jakarta through a different perspective, that may be for a group of people this method is still rarely used, a sound.
Do you realize that sound can tell us about character, place, and time? Sometimes, it informs us in ways visuals can’t, and that is the idea of what we are going to do right now. Later you will hear, a file of recorded sound of MRT-J in its daily operation.
The sound was recorded by the soundwalk method, any excursion whose primary purpose is listening to the environment. It is exposing our ears to every sound around us no matter where we are. We may be at home, walking across a downtown street, or even at the office. Meanwhile, in this case, our environment is inside the line of MRT Jakarta. The goal is to capture any sound sources that exist during the operation of MRT-J, including the activity of the passengers.
The sound was recorded by using a mounted microphone on the iPhone X at a level of 1.2 m above the ground. The following sound is a recorded environment while the MRT-J was travelling from Bundaran HI Station to Setiabudi Astra Station, the duration of recording sound is 4 minutes and 40 seconds. Please use an earphone or any similar devices to listen to the audio for a better experience.
Caution: please set the volume around 50 – 70 % of the maximum volume.
After listening to the sound, can you identify what sound sources are presented in the recording? Here are the sound sources that I have identified:
Now we have identified the sound sources that are presented in the recording. But, do you know how many decibels that I have to endure while travelling using the MRT-J? In this article, manual measurements of noise levels were performed with a sound level meter in the MRT Jakarta with passengers on its usual route. A-weighted sound level measurements were recorded directly from one station to the next during the time between 08:00 and 09:00, using a calibrated microphone on a stand at a level of 1.2 m above the ground. The results of equivalent continuous A-weighted noise levels Leq (LAEq) in the MRT-J with passengers on its usual route from one station to the next is shown in Chart 1.
Leq is the A-weighted energy means of the noise level averaged over the measurement period. The results from the measurements show that the A-weighted noise level is varied between 77 dB to 82 dB. Further, if we look closely into the Chart, the noise level is fluctuating. It can be caused by a lot of factors, such as:
The position of MRTJ (When MRT-J inside the tunnel, the noise can be levelled up due to the reflection phenomenon).
Speed (The machine indicates producing a higher noise when in the maximum speed).
Path Crossing.
The Public Address System Volume.
Moreover, the level of continuous noise in Chart 1 represents a quite noisy environment. According to The National Institute on Deafness and Other Communication Disorders, states that Long or repeated exposure to sound at or above 85 dB can cause hearing loss. Thus, according to the measurement results, I suggested you wear ear protection during commuting by MRT-J. The earplug is one of the equipment that we can use to protect our hearing; you only need to spend a few thousand rupiahs for this. Wearing earplugs can help you to reduce the noise by 18 – 34 dB, it depends on the models/brand. For more accurate results, we need to do a complex measurement, such as:
Add measurement point (In this article, the measurement was done only in a measurement point, at the second car of the line).
Add a velocity as a measured parameter.
Add the measurement time; the measurement can be done during the operation hour, non-stop. (05:00 – 24:00 WIB).
Nonetheless, the idea of showing the measurement results is spreading noise awareness. Noise sticks with you around, even common sounds you hear at work or home can contribute to long term hearing loss and other health risks, they are everywhere, but only a few people are aware of it. Noise pollution is a health threat nobody is talking about. Here are some parameters to help you determine acceptable — and dangerous — noise levels:
45 dB: nightly noise ordinance threshold set by many municipalities concerned with industrial noise exposure for residents
65 db+: exposure for prolonged periods can cause physical and mental fatigue
85 dB+: can cause permanent hearing loss if exposed for extended periods
85-120 dB: dangerous over 30 minutes of exposure
120-130 dB: can cause permanent hearing loss for exposure over 30 seconds
130 dB+: not only are these noises painful, but hearing protection should always be used if avoidance is not possible.
Everyone needs to take care of their ears and hearing, as damage to the auditory system could be irreparable. The loss because of the noise exposure is gradual; you might not notice the signs, or you ignore them until they become more apparent. Please do protect your ears.
NAHA, OKINAWA PREF. – The Okinawa branch of the Naha District Court ordered the government on Thursday to pay some ¥754 million in damages to residents near the Futenma air base because of aircraft noise.
Some 2,200 plaintiffs who live close to the controversial U.S. base in Ginowan complained of mental distress, poor sleep and disruption to their daily lives.
In seeking about ¥1 billion in damages from the central government, they also said they feared aircraft crashes, according to lawyers representing the plaintiffs and their lawsuit.
“The noise damage suffered by the plaintiffs is serious and widespread,” presiding Judge Satoshi Hikage said in the ruling, adding that the court found that the damage reached an unacceptable level.
The judge acknowledged that the base serves the interest of the people in the country, and that it can only be served with the sacrifice of a minority of people. But he said that does not mean they should accept the damage. The use of the air base by the U.S. military therefore “violates the rights of the plaintiffs.”
The ruling comes as Japan and the United States are seeking to move Futenma to a less densely populated area further north on Okinawa Island and return the land at Ginowan to Japanese control. Local opposition is running high, however, and many people in Okinawa want the base moved outside the prefecture altogether.
“I’m relieved that damages were awarded,” said Sogi Ganaha, a plaintiff in the suit who lives about 300 meters from the base. “Whenever I hear the roaring of a helicopter circling above my head, I remember the war 70 years ago. I’ve wanted to get compensated for my daily suffering.”
Okinawa Gov. Takeshi Onaga, an opponent of the plan to relocate Futenma within the prefecture, hailed the ruling as “meaningful.”
Chief Cabinet Secretary Yoshihide Suga argued the government had failed to fully explain its arguments to the court.
“We will adequately deal with this after coordination among the ministries and agencies concerned,” he said at a news conference.
The suit follows a similar one filed by local residents in October 2002. In that case, the Fukuoka High Court ordered the government in July 2010 to pay about ¥369 million in damages to the plaintiffs. But it rejected their plea to suspend early morning and evening flights.
The latest suit was filed in 2012 by individuals who were not plaintiffs in the earlier case.
During the trial, the government sought an exemption and to reduce the sum of compensation, arguing that some of the plaintiffs had moved to the area knowing that an air base existed there, and that the government had taken measures to reduce noise, such as funding noise abatement work on homes.
The plaintiffs’ damages were reduced as the court recognized that the government’s noise abatement measures had been effective, to some extent.
The court also dismissed the claims of around 80 plaintiffs who lived in areas where the noise level is below 75 on the Weighted Equivalent Continuous Perceived Noise Level, or WECPNL, an internationally recognized index for aircraft noise.
The decision was in line with the 2010 Fukuoka High Court ruling, in which the WECPNL of 75 or above formed the benchmark for ordering government compensation.
The court did not acknowledge the suffering the plaintiffs said was caused by low-frequency sounds from helicopters, citing a lack of evidence.
