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4.3. Specific Environments
Noise measures based solely on LAeq values do not adequately characterize most noise environments and do not adequately assess the health impacts of noise on human well-being. It is also important to measure the maximum noise level and the number of noise events when deriving guideline values. If the noise includes a large proportion of low-frequency components, values even lower than the guideline values will be needed, because low-frequency components in noise may increase the adverse effects considerably. When prominent low-frequency components are present, measures based on A-weighting are inappropriate. However, the difference between dBC (or dBlin) and dBA will give crude information about the presence of low-frequency components in noise. If the difference is more than 10 dB, it is recommended that a frequency analysis of the noise be performed.

4.4. WHO Guideline Values

The time base for LAeq for “daytime” and “night-time” is 16 h and 8 h, respectively. No separate time base is given for evenings alone, but typically, guideline value should be 5 –10 dB lower than for a 12 h daytime period. Other time bases are recommended for schools, preschools and playgrounds, depending on activity.

Annoyance to community noise varies with the type of activity producing the noise. Speech communication, relaxation, listening to radio and TV are all examples of noise-producing activities. During the daytime, few people are seriously annoyed by activities with LAeq levels below 55 dB; or moderately annoyed with LAeq levels below 50 dB.
Guidelines or noise abatement measures should also take into account residential outdoor activities.

Table 4.1: Guideline values for community noise in specific environments

Specific environment

Critical health effect(s)

LAeq [dB]

Time base [hours]

LAmax , fast [dB]

Outdoor living area

Serious annoyance, daytime and evening

Moderate annoyance, daytime and evening

55

50

16

16

-

-

Dwelling, indoors

Inside bedrooms

Speech intelligibility and moderate annoyance, daytime and evening

Sleep disturbance, night-time

35

30

16

8

 

45

Outside bedrooms

Sleep disturbance, window open (outdoor values)

45

8

60

School class rooms and pre-schools, indoors

Speech intelligibility, disturbance of information extraction, message communication

35

during class

-

Pre-school bedrooms, indoors

Sleep disturbance

30

sleeping-time

45

School, playground outdoor

Annoyance (external source)

55

during play

-

Hospital, ward rooms, indoors

Sleep disturbance, night-time

Sleep disturbance, daytime and evenings

30

30

8

16

40

-

Hospitals, treatment rooms, indoors

Interference with rest and recovery

#1

 

 

Industrial, commercial shopping and traffic areas, indoors and outdoors

Hearing impairment

70

24

110

Ceremonies, festivals and entertainment events

Hearing impairment (patrons:<5 times/year)

100

4

110

Public addresses, indoors and outdoors

Hearing impairment

85

1

110

Music through headphones / earphones

Hearing impairment (free-field value)

85 #4

1

110

Impulse sounds from toys, fireworks and firearms

Hearing impairment (adults)

Hearing impairment (children)

-

-

-

-

140 #2

120 #2

Outdoors in parkland and conservation areas

Disruption of tranquillity

#3

 

 

#1: as low as possible;
#2: peak sound pressure (not LAmax, fast), measured 100 mm from the ear;
#3: existing quiet outdoor areas should be preserved and the ratio of intruding noise to natural background sound should be kept low;
#4: under headphones, adapted to free-field values