Ventilation Noise as an Environmental Problem


Ventilation Noise as an Environmental Problem Ventilation Noise as an Environmental ProblemNoise generated from ventilation systems can constitute a big problem, partic­ularly in environments where other ambient noise is low. For this reason, ven­tilation noise has attracted particular attention in environments such as offices, schools, and public areas. The effects which occur there are due prima­rily to ventilation noise levels that are below the level at which there is a risk of hearing damage. The most common effects are a feeling of annoyance and disturbance of work due to fatigue or disturbed concentration. Ventilation noise also occurs, of course, in other environments with special demands on air quality and air change. In some environments, such as workshops, ware­houses, machine rooms, garages, etc., the great need for air changing may lead to relatively high ventilation noise levels. The noise from large fans may In

Ventilation Noise as an Environmental Problem

Ventilation Noise as an Environmental Problem

FIGURE 5.59 Schematic view of a typical centraJ scation ventilation system, including a far., ducts, and diffusers.

Such cases sometimes reach levels around the threshold for hearing damage. A risk for hearing damage appears in cases of repeated daily exposure above 70 dB(A). Another problem which may arise at high levels of ventilation noise is masking of speech or of other sound signals. In most cases, the sound from ventilation noise is dominated by low-frequency components, which means that the speech-masking effect is not always pronounced. The biggest speech — masking effect occurs if the background noise coincides with the speech fre­quency range, 500-4000 Hz.

Ventilation noise and the annoyance effects which may result have been a recurring question in recent years for researchers, occupational health ser­vices, and various authorities. In spite of this, there are still major shortcom­ings in our knowledge about the links between human effects and exposure to ventilation noise. Current regulations and recommendations are thus based on uncertain principles in certain respects.

Today there is a pronounced need to take more effective measures against this type of noise. The problem is complicated, however, by the fact that these measures in many instances are unilaterally targeted at achieving a lowering of the dB(A) level, which in many cases has resulted in only a marginal restric­tion of the inconvenience, or even none at all.

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