Even weak traffic noise has a negative impact on work performance

Newswise — Scientists at Chalmers' Applied Acoustics Division performed an experimental analysis in which participants underwent concentration assessments while exposed to ambient traffic sounds. The participants were instructed to observe a computer monitor and respond to specific letters, then evaluate their perceived level of effort afterward. The investigation demonstrates a noticeable decline in performance outcomes among the participants, who also experienced heightened difficulty in executing the task due to the presence of traffic noise.

"The distinguishing aspect of our research lies in our ability to illustrate a decrease in performance even at noise levels as low as 40 dB, equivalent to the typical ambient noise found in an office or kitchen," explains Leon Müller, a doctoral candidate in the Department of Architecture and Civil Engineering's Division of Applied Acoustics.

The ambient noise comprised two simulated audio sequences resembling the sound of trucks passing at distances of ten and fifty meters. Both sequences were adjusted to have an identical overall indoor level of 40 dB.

"The audio sequence representing the closer passages, characterized by noticeable sound variations as the vehicle passes by, typically caused the greatest discomfort among the participants," states Müller. "This might be attributed to the perception that traffic from a greater distance is experienced as a more consistent humming noise."

Housing is built closer to roads now

The fresh findings accentuate an existing concerning scenario of detrimental effects on health and work productivity stemming from traffic noise. In recent times, there has been a trend, both in Sweden and internationally, of diminishing the distance between residential areas and roads during new housing construction.

In a somewhat simplified manner, the construction regulations in Sweden are determined based on the average outdoor noise level during a 24-hour timeframe. This approach overlooks the consideration of individual passing vehicles. Furthermore, the existing regulations fail to address the indoor peaks of low-frequency noise, which are challenging to mitigate and have been shown through research to be more disruptive and have a greater impact on human health.

In a study examining low-frequency noise, Jens Forssén, a Professor of Applied Acoustics at Chalmers, conducted research that demonstrated how this type of noise is predominantly produced by slow-moving heavy traffic. Furthermore, the study revealed that even with windows and buildings designed to meet construction standards and guidelines for sound insulation, it remains challenging to effectively block out low-frequency noise.

Reduced vehicle speed can increase the noise exposure indoors

"For various types of building facades, our calculations indicate that achieving optimal indoor sound conditions near heavily trafficked roads is a challenging task," explains Forssén. "Simply reducing vehicle speeds is not a viable solution either, as our calculations demonstrate that indoor noise exposure may actually increase at lower speeds."

Additionally, Forssén highlights that noise and the acoustic environment are often overlooked until later stages of the planning process. He suggests that there are potential benefits to be gained by making adjustments early on to optimize the utilization of space in terms of mitigating noise pollution. By considering noise issues earlier in the planning phase, it becomes possible to achieve more favorable outcomes and capitalize on the advantages associated with a well-managed sound environment.

The researchers concur that the most effective approach would be to prevent urban densification in regions where traffic noise would exert a significant adverse influence on health and well-being. By avoiding the construction of densely populated areas in such locations, the potential negative consequences associated with excessive traffic noise can be minimized.

More about the research

The laboratory setting at Chalmers where the research took place resembles a furnished living room, complete with furniture and textiles. However, concealed behind the ceiling panels and windows is a sophisticated speaker system that enables the researchers to simulate a wide range of sounds, including road traffic noise. This advanced setup provides a controlled environment for studying and analyzing the impact of different auditory stimuli on human subjects.

During the experiments, the 42 participants were engaged in a continuous performance test (CPT) while exposed to different sound sequences. They were situated in front of a computer monitor displaying a series of letters and were instructed to press a button for all letters except X. Concurrently, the subjects completed a questionnaire known as the NASA Task Load Index (NASA TLX), which is designed to gauge their subjective evaluation of the workload experienced while performing the task. The participants rated their perceived workload across six dimensions, including mental workload, physical workload, time pressure, effort, performance, and degree of frustration.