Chalmers Division of Applied Acoustics researchers conducted a laboratory investigation in which test subjects were subjected to concentration tests while exposed to background traffic noise. Individuals were asked to stare at a computer screen and respond to specific letters before rating their perceived workload. According to the study, the individuals performed much worse on the performance test and felt that it was more difficult to complete the task with street noise in the background.
“What is unique about our study is that we were able to demonstrate a decline in performance at noise levels as low as 40 dB, which corresponds to regular noise levels in an office environment or kitchen, says doctoral student Leon Müller. Department of Applied Acoustics in the Department of Architecture and Civil Engineering. The background noise consisted of two audio sequences simulating passing trucks from a distance of ten and fifty meters. Both sequences were normalized to the same total indoor level of 40 dB.
“The audio sequence simulating the nearest route, where the sound changes significantly as the vehicle passes, was generally the one that bothered the test subjects the most,” says Müller. “This may be because traffic that is further away is perceived as more stable by drones.”
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Housing is now built close to roads. The new results emphasize an already problematic situation of negative effects on health and job performance due to traffic noise. In recent years, Swedish cities have been allowed to reduce the distance between roads and newly built housing – a trend that can also be seen internationally.
Put simply, where construction is permitted, Swedish regulations are based on the average outdoor noise level over a 24-hour period – meaning they do not take individual pass-bys into account. Furthermore, existing regulations do not cover low-frequency noise peaks inside the home, which are harder to avoid and, according to research, are more disruptive and therefore have a greater impact on human health.
In a study modeling low-frequency noise, Jens Forsen, professor of applied acoustics at Chalmers, showed that such noise is mainly generated by heavy traffic at low speeds, and also by well-insulated windows and buildings closing It is difficult to make those that comply with all construction norms and guidelines for sound insulation.
Low vehicle speed can increase the exposure to noise indoors. “Calculations of different types of façades show that it is difficult to achieve an ideal indoor sound environment near heavily trafficked roads,” says Forsen. “Reducing the speed is not a solution, as our calculations show that indoor noise exposure can increase even at low speeds.”
Furthermore, Forsson says that the noise and sound environment is a factor that is often considered too late in the planning process and benefits can be gained if adjustments are made to make better use of the space in terms of noise pollution.
The researchers also agree that the most effective solution would be to avoid urban agglomeration in areas where traffic noise would have the greatest impact on health and well-being.