Marion Burgess m.burgess@adfa.edu.au
Brett Molesworth b.molesworth@unsw.edu.au
University of New South Wales, Australia
Popular version of paper
Presented June 28, 2017, in session 4aNSa, Measuring, Modeling, and Managing Transportation Noise I. 8:00 AM – 12:20 PM
173rd ASA Meeting, Boston
There are well established limits for workplace noise based on the risk of hearing damage. For example, an 8-hour noise exposure level is limited to 85 decibels (when the sound is this loud you need to shout to talk to someone near you). There are also guidelines for acceptable noise levels in workplaces that aim to ensure the noise will not be intrusive or affect the ability of the worker to do the tasks. For example, a design level for a general office may be 40 to 45 decibels (dBA), while for a ticket sales area, 45 to 50 dBA. In this range, noise should not have an adverse affect on your ability to complete a task.
However, there are many work environments, particularly in the transportation industry, in which the noise levels are above 50 dBA but the employees are required to perform tasks that require a high level of concentration and attention. For pilots and bus, truck and train drivers, the noise levels in the area they are working can be 65 to more than 75 dBA at times.
These workers all need to make safety-critical decisions and operate technical equipment in the presence of continuous noise generated from their vehicle’s engine. Transport check-in staff need to communicate and process passengers in noisy check-in halls where there is both vehicle and equipment noise as well as the noise from personnel around, such as “babble.”
In this paper, we discuss findings from a number of studies investigating the effect of constant noise at 65 dBA on various cognitive and memory skills. Two noise sources were used: One, a wideband noise like constant mechanical noise from an engine, and the other a babble noise of multiple persons’ incomprehensible speech. Language background is another factor that can increase cognitive load for those workers who are communicating in a language that is not native.
The cognitive tasks aimed to test working memory with an alphabet span test and recognition memory using a cued recall task. The signal to noise ratio used was 0, -5 and -10 dBA. Wideband noise was found to have a greater effect on working memory and recognition memory than babble noise.
Those who were not native English speakers were also more affected by the wideband noise than the babble noise. The subjective assessment, when the subjects were asked their opinion of the effect of the noise and the annoyance, was also greater for broadband noise.
These findings reinforce the limitations of basing acceptability on a simple overall dBA value alone. The reduction in performance demonstrates the importance of reducing the noise levels within transportation workplaces.