Night noise guidelines for Europe - WHO/Europe - World Health ...

1.3 CONSIDERATIONS WITH REGARD
TO NIGHT-TIME NOISE INDICATORS
METHODS AND CRITERIA 7
Briefly, the fundamental choices of night-time noise indicators with respect to length
of night, use of single event descriptors and long-term average are commented on to
assist the reader in understanding the relations presented in later chapters.
1.3.1 LENGTH OF NIGHT
Time use studies (Centre for Time Use Research, 2006) show that the average time
adult people are in bed is around 7.5 hours, so the real average sleeping time is somewhat
shorter. Due to personal factors such as age and genetic factors there is considerable
variation in sleeping time and in beginning and end times. For these reasons,
a fixed interval of 8 hours is a minimal choice for night-time protection. From Fig.
1.4 it can be noted that around 50% of the population is protected with an interval
of 8 hours and it would take a period of 10 hours to protect 80%. On Sundays,
sleeping time is consistently one hour longer, probably due to people recovering from
sleep debt incurred during the week. Data for other countries are readily available
but this is the only study covering a long period in a consistent way. Fig. 1.5 (from
a time use study in Portugal) shows that the stable pattern found in the Netherlands
(Fig. 1.4) is not only typical for northern Europe, but also for the southern part. The
pattern, however, seems to have shifted slightly. These figures stress that sleep times
might be biologically fixed in humans, and culture has almost no influence.
P er centage of population in be d
100
90
80
70
60
50
40
30
100%
80%
60%
40%
20%
20
0%
10
0
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
18.00
20.00
22.00
24.00
0
2
4
6
8
10
12
14
16
18
20
22
24
Sunday 2005 Tuesday 1980 Tuesday 2005 Sunday 1980
Source SCP (TB='80-'50)
Watch television Read Household occupation Work and study
Personal care Eating Sleep
Fig. 1.4
Sleep pattern of Dutch population on weekdays
and Sundays, 1980–2005
.
Fig. 1.5
Percentage of time that the Portuguese population
spend asleep or in different activities
Source: http://www.ine.pt/prodserv/destaque/arquivo.asp, based on
a study by the Instituto Nacional de Estatistica Portugal, 1999
1.3.2 EVENT OR LONG-TERM DESCRIPTOR
Much attention has been paid to the use of single event descriptors such as L Amax
(maximum outdoor sound pressure level) and SEL (sound exposure level). As the
Position Paper on EU noise indicators (European Commission, 2000) points out,
this is an important laboratory tool to describe instantaneous reactions to noise. But
when it comes to long-term protection, the number of events is equally important.
The possibility of predicting after-effects like sleepiness, reaction time, sleeping pill
NIGHT NOISE GUIDELINES FOR EUROPE