Reducing urban noise
Englishman Maurice Western lives practically underneath one of Birmingham’s most notorious traffic interchanges. Experts say that long-term exposure to levels of 80 decibels (which was measured outside Maurice Western’s house during a quieter period of the day) can be harmful. After 35 years, Maurice Western says he barely notices the noise, that he is “conditioned to it” and has “come to accept it”. However, although people can adjust to road traffic noise, it doesn’t mean that the long term health effects will go unnoticed.
Stephen Stansfeld, professor of psychiatry at Queen Mary University’s School of Medicine and Dentistry in London, explains that, aside from annoyance, noise can cause sleep disturbance (i.e. difficulty falling asleep, waking during the night). Other symptoms can include those of a psychological nature: tension, headaches, etc. It also seems that urban noise can affect children’s learning capabilities. Studies suggest that high levels of noise can have an adverse effect on complex tasks (for example, learning to read).
In 2004 European researchers began the second phase of a European research programme, called CALM II. The aims include assessing urban transportation noise from cars, lorries, trains, ships and planes and coming up with further recommendations for research and to support European policy.
One participant in CALM II is the Birmingham City Council. The environmental department, under the direction of John Hinton, has developed a useful tool called noise maps. Such maps can be used to build a picture of noise within a city environment. John Hinton lists some possibilities for road traffic noise reduction in Birmingham as speed limit reductions on some roads, introduction of low-noise road surfaces and some noise barriers in certain locations.
CALM scientists’ work includes assessing where in the automobile the most noise is produced. AVL is one of the leading developers of engines and power transmission systems. Some of their scientists work at a test track in Graz, Austria as part of a project called SILENCE. One goal is to identify noise patterns of cars at different speeds. The primary noise sources at lower speeds are the motor and the transmission. However the tyres can become the loudest source at high speeds; the higher the speed, the louder the tyres become. Additional noise sources include the effects of the wind and the noise from the exhaust system and air intake.
More precise tests can be made in AVL’s sound laboratory. Manufacturers can then use the results to redesign certain car components. For example, foamed aluminium, a material developed during the SILENCE project, can be used in the creation of some engine parts. It possesses exceptional sound damping qualities - and is very lightweight.
The impact of noise levels in the work place is also being considered in the CALM II project. It is already known that noise levels have a direct effect on one’s hearing and, in extreme cases, can cause deafness, But recent studies have been looking at other effects on the human body, like high blood pressure and changes in stress hormones.
The rapid growth rate of cities world-wide is a factor leading to concern over the urban transport noise. With the research achieved during the CALM II project, plans can be put in place to reduce urban transport noise to acceptable levels. European researchers see a 10-decibel urban noise reduction as a realistic goal for 2020, meaning, to our ears, that the noise will be halved.