Importance of Noise Dosimetry

The incidence of hearing loss has been growing steadily. While this condition was once mainly confined to elderly subjects, it has become common in younger people, even affecting teenagers and pre-teens. Deafness can have various causes. Until the mid-twentieth century, infections and, perversely, some of the antibiotics used to treat them were common culprits, along with congenital causes. However, today, noise dosimetry, a technique for measuring ambient sound intensity, confirms that the most common cause is prolonged and repeated exposure to deafening noises.

Quite possibly, this trend began soon after the dawn of the industrial revolution and the move to machine-based manufacturing. That said, the condition remained largely unnoticed by physicians until the end of the First World War. Large numbers of returning troops complained of deafness following continuous exposure to gunfire and other explosive detonations. This mass hearing loss prompted the birth of audiometry. Later, concerns for factory workers’ hearing led to the development of noise dosimetry.

As civilisation has advanced, the inhabited areas of the planet have become progressively noisier. Legislation to limit the sound levels produced by vehicle exhausts and jet aircraft during takeoff ensued. Regular exposure to loud machinery has long been identified as a significant health hazard on the factory floor. Employers are required by law to take whatever steps are necessary to protect their workers from the risk of NIHL or noise-induced hearing loss. NIHL is the most frequent cause of permanent hearing loss and the most common source of claims for industrial compensation. Noise dosimetry can provide employers with a means to identify workers at risk of developing premature hearing loss.

The Occupational Health and Safety Act 85 of 1993 was a landmark in South African history. Previous legislation addressed working conditions in selected occupations, such as mining. However, the new act made provision for all workers. It also provided facilities for training specialists to investigate the workplace and identify any physical, chemical, or biological hazards to which workers might be exposed. One of the necessary skills for an occupational health specialist is a working knowledge of noise dosimetry.

The first step when evaluating the risk of NIHL is to obtain an accurate measurement of the ambient sound levels. These levels are measured in decibels using a suitable sound meter. The decibel scale is logarithmic. Although a normal conversation registers about 60 dBA, an increase of only three dBA represents a tenfold increase in sound intensity. Eight hours’ exposure to 80 dBA will cause some permanent hearing loss, which worsens with subsequent exposures. When ambient levels appear hazardous, noise dosimetry should be the next step.

This step assesses the risk of NIHL in individual workers employed in those areas that have been identified as potentially hazardous. The measuring device is known as a dosimeter and can be attached to the worker’s clothing, where it provides a cumulative reading of each individual’s exposure during a shift. Before that reading reaches the safety threshold, the worker can depart from the danger zone.

Individual noise dosimetry offers a means to mitigate the threat of NIHL by indicating where protection, such as ear defenders, may be required. For more information and a comprehensive range of occupational health services, contact the experts at IOH Solutions.