Page 390 - Industrial Ventilation Design Guidebook

5,4 VENTILATION NOISE—CHARACTERISTICS, EFFECTS, AND SUGGESTED COUNTER-MEASURES 34S

5.4 VENTILATION NOISE—CHARACTERISTICS, EFFECTS,
AND SUGGESTED COUNTER-MEASURES

5.4.1 Occurrence
Ventilation is encountered today in practically all types of indoor environ-
ments, e.g., in dwellings, leisure facilities, service facilities, schools, hospitals,
factories, machine rooms, workshops, stores, offices, vehicles, meeting rooms,
teaching areas, restrooms, arid control rooms. The problem affects a very
large number of people, both at work and during their leisure time. Com-
plaints about ventilation noise have increased in recent years, at the same time
as very limited efforts have been made to deal with the problem. The recom-
mendations applicable to ventilation noise usually indicate a maximum ac-
ceptable level of 35-40 dB(A). The highest recommended levels are exceeded,
however, in many environments.
A schematic view of a typical central station ventilation system, including
a fan, ducts, and diffusers, is given in Fig. 5.59.

5.4.2 Ventilation Noise as an Environmental Problem
Noise generated from ventilation systems can constitute a big problem, partic-
ularly in environments where other ambient noise is low. For this reason, ven-
tilation noise has attracted particular attention in environments such as
offices, schools, and public areas. The effects which occur there are due prima-
rily 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, ware-
houses, 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

FIGURE 5.59 Schematic view of a typical central station ventilation system, including a fan, ducts,
and diffusers.'