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Is DNL appropriate for airport noise zoning
Article in The Journal of the Acoustical Society of America · June 2008
DOI: 10.1121/1.2933575 · Source: PubMed
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Acoustics 08 Paris
Is DNL appropriate for airport noise zoning?
J. G. Slamaa , F. A. C. Mora-Caminob and T. C. Revoredoa
a
UFRJ, Av. Horacio Macedo, 2030, Centro de Tecnologia, Bl. G, Sala 204, Cidade
Universitária, 21941-914 Rio de Janeiro, Brazil
b
Ecole Nationale de l’Aviation Civile, 7 avenue Edouard-Belin BP 54005, 31055 Toulouse,
France
julesslama@yahoo.com.br
1967
Acoustics 08 Paris
The use of the DNL metric in airport noise zoning is based in the works of Schultz, that were later
improved by Fidell. The basic idea is to use the percentage of highly annoyed people as a parameter
to organize the area around airports. In urban zoning it is recommended to use the equivalent sound
level LAEQ, which uses different criteria to day and night periods to define the land use. With regards
to airport noise one may use LAD and LAN metrics which are the equivalent sound levels determined
for day and night period, respectively. In this case, the maximum levels chosen to the establishment of
the zoning are based on the land use. It is possible, through a simple equation, to determine the DNL
level associated to a LAD, LAN pair. The inverse problem, however, has not a unique solution, once this
relation depends on the number of daily and night flights of the airport. Thus, the use of DNL in airport
noise zoning may lead to completely different results for different airports. Examples are presented and
discussed for two main brazilian airports: Recife and Congonhas.
1
Introduction
Thus, the airport zoning regulation in many countries
in the world are based in the DNL metric. In Brazil, for
example, residencies are authorized by the airport regulation to be placed in areas where the DNL ≤ 65dB(A).
The use of DNL (Day Night Sound Level) metric in airport zoning was based on the idea of controlling the
number of complains generated by the airport operation
in its surroundings. DNL is said to be the best single
system of noise measurement that can be uniformly applied in measuring noise in the communities and around
airports, and for which there is a highly reliable relationship between projected noise and surveyed reaction
of people to the noise. DNL takes into account the magnitude of the sound levels of all individual events that
occur during the 24-hour period, the number of events,
and an increased sensitivity to noise during typical sleeping hours. DNL is an average in that it accumulates all
the noise exposure over a 24-hour period and divides the
total by the number of seconds in a day [WYLE].
2
Zoning comparison
In addition to the annoyance sensation, the airport noise
has many adverse effects of which the most important
are the interference on communication during the diurnal period and the sleep disturbance during the nocturnal period.
Urban noise produces the same adverse effects, and based
on this characteristics the urban zoning regulation adopts
different criteria to evaluate diurnal and nocturnal noise.
The metric generally adopted is the equivalent sound
level, LAeq. In order to calculate a sound level in a
critical receiver using this metric it is necessary to define an evaluation period which will depend on the time
characteristics of the considered noise.
The relation between the DNL metric and the number
of highly annoyed people was studied by Schultz [1] as
shown in Figure 1.
In Brazil, the urban regulation for noise pollution control uses the criteria shown on 1 for the diurnal and
nocturnal periods:
Table 1: Noise levels according to NBR 10151
LAeqD LAeqN Area Type
40
35
A1
50
45
A2
55
50
A3
60
55
A4
65
55
A5
70
60
A6
Figure 1: Relation between DNL and highly annoyed
people
The area types shown on Table 1 are described below.
The same notation will be used on the next tables on
this paper.
The DNL metric is defined as follows:
DN L = 10 log10 {
• A1 - Farm
1
× α}
3600 × 24
• A2 - Strictly urban residential, hospitals or schools
(1)
• A3 - Mixed, predominantly residential
• A4 - Mixed, commercial and administrative vocation
on which:
α=
10pm
Z
10
7am
LA (t)
10
dt +
7am
Z
10
LA (t)+10
10
• A5 - Mixed, recreational vocation
dt
(2)
• A6 - Mainly industrial
10pm
Because of the non stationary characteristics of the airport noise, if one tries to use the urban regulation and
Later, Fidell [1] presented new results on these relation.
1968
Acoustics 08 Paris
the LAeq metric in regions close to an airport, the evaluation periods must be all diurnal period (from 7h to
22h) and all nocturnal period (from 22h to 7h on the
next day). We call LAeqD and LAeqN the equivalent
sound levels calculated at a critical receptor during the
diurnal and nocturnal periods, respectively, as shown on
Eq. 3 and 4.
between LAeqD and DNL in a certain airport surroundings depends on the relation between the number of diurnal and nocturnal movements on the airport.
If we consider the ”Acoustical Amplitude”, which is defined by Eq. 6, we can find new relationships between
DNL, LAeqD , LAeqN and ∆, as shown on Eq. 7 e 8 .
LAeqD − LAeqN = ∆
LAeqD = 10 log10
1
3600 × 15
LAeqN = 10 log10
10pm
Z
10
LA (t)
10
7am
1
3600 × 9
7am
Z
10pm
10
LA (t)
10
dt
dt
(6)
(3)
h
i
−∆
LAeqD = DN L − 10 log10 1 + 6 × 10 10 + 2
h ∆
i
LAeqN = DN L − 10 log10 10 10 + 6 + 2
(4)
(7)
(8)
Thus:
If ∆ = 10 then LAeqD = DN L , LAeqN = DN L − 10
3
Conversion between LAeqD , LAeqN
and DN L
It is important to note that a simple relation between
DNL, LAeqD and LAeqN in one point near the airport
exists. This relation is given by Eq. 5.
It is observed that on each airport the relation between
DNL, LAeqD e LAeqN depends on the number of aircraft
movements during the day and the night.
Example 1 Congonhas Airport
LAeqD
LAeqN
LAeqD
i
LAN
LAD
1 h
DN L = 10 log10 (
15 × 10 10 + 90 × 10 10 ) (5)
24
Thus, once LAD and LAeqN levels are known, it is possible to calculate the equivalent DNL level. Considering
values shown on Table 1 we are able to determine the
DNL level for each type of area.
= DN L − 0, 5dB(A)
= DN L − 19, 5dB(A)
−LAeqN = 19dB(A)
Thus, a DNL level of 58dB(A) corresponds to a LAeqD
of 57,5 dB(A) and a LAeqN of 38,5 dB(A). In this case
the diurnal condition LAeqD ≤ 55dB(A) is not verified.
Thus, in an airport vicinity, considering that the urban
regulation for noise pollution control is applicable, we
have the values shown on Table 2:
Table 2: Equivalent DNL level for
10151
LAeqD LAeqN DNL
40
35
42,57
50
45
52,57
55
50
57,57
60
55
62,57
65
55
65
70
60
70
If ∆ = 0 then LAeqD = LAeqN = DN L + 6, 4dB
Example 2 Recife Airport
the criteria of NBR
LAeqD
= DN L − 6, 6dB(A)
LAeqN
= DN L − 6, 3dB(A)
Thus, a DNL level of 58dB(A) corresponds to a LAeqD of
51,4 dB(A) and a LAeqN of 51,7 dB(A). In this case the
nocturnal condition LAeqD ≤ 50dB(A) is not verified.
Area Type
A1
A2
A3
A4
A5
A6
Thus, the use of the condition DNL ≤ 58dB(A) may
lead to different conditions in different airport.
The fact of punishing the nocturnal period noise in 10dB(A)
does not mean that the land use conditions are respected.
Thus, considering LAeqD = 55dB(A) and LAeqN = 50dB(A)
values, which is the criteria level for a mixed, predominantly residential area near an airport we find a correspondent DNL level of 58dB(A). Once that this type of
area is the most noisy residential area according to Table 1, one can see that this level is much lower than that
of the airport noise regulation (65dB(A)). It is verified
that one should use a lower value.
Thus, considering the criteria DNL≤58dB(A) to authorize the implantation of residencies, one may think that
the criteria LAeqD ≤ 55dB(A), LAeqN ≤ 50dB(A) are
verified. However this is not the case once the relation
From the examples shown above it can be verified that
the level DNL = 65dB(A) is not representative of the
limit from residential and non-residential areas. It is
important to reduce the current levels of Portaria 1141
GM5 in order to meke them compatible with the levels
used on NBR 10151. In accordance with the value shown
above, we suggest a reduction of initially 5 dB(A) over
the levels of 65 dB(A) and 75 dB(A), lowering them to
60 dB(A) and 75 dB(A), trespectively.
More specific strategies are shown below.
1969
Acoustics 08 Paris
4
Zoning based on LAeqD and LAeqN
according with ABNT NBR10151
Standard
Considering the NBR 10151 Standard and adopting the
LAeqD to represent the equivalent sound level during the
day and the LAeqN to represent the equivalent sound
level during the night, it is possible to develop a necessary logic condition for the interior of each area.
Table 3: Logic condition for the interior
LAeqD LAeqN Logic Condition
40
35
LAeqD ≤ 70dB(A)
∧ LAeqN ≤ 60dB(A)
50
45
LAeqD ≤ 65dB(A)
∧ LAeqN ≤ 55dB(A)
55
50
LAeqD ≤ 60dB(A)
∧ LAeqN ≤ 55dB(A)
60
55
LAeqD ≤ 55dB(A)
∧ LAeqN ≤ 50dB(A)
65
55
LAeqD ≤ 50dB(A)
∧ LAeqN ≤ 45dB(A)
70
60
LAeqD ≤ 40dB(A)
∧ LAeqN ≤ 35dB(A)
Table 5: Most and less noise sensitive areas
Area Type Diurnal Nocturnal
A3
55
50
A6
70
60
Table 6: Logic conditions for the most and less noise
sensitive areas
Area Logic Condition
Complementary Logic
Type (interior of the area) (exterior of the area)
A3
LAeqD ≤ 55dB(A)
LAeqD > 55dB(A)
∧LAeqN ≤ 50dB(A)
∨LAeqN > 50dB(A)
A6
LAeqD ≤ 70dB(A)
LAeqD > 70dB(A)
∧LAeqN ≤ 60dB(A)
∨LAeqN > 60dB(A)
of each area
Area Type
A1
A2
Area 3 definition (residential): LAeqD ≤ 55dB(A) ∧
LAeqN ≤ 50dB(A)
A3
A4
5
The case of LDEN
A5
Recently, Day-evening-night level has been adopted by
the Europe as a general descriptor for urban noise. Dayevening-night level. is a descriptor of noise level based
on energy equivalent noise level (Leq ) over a whole day
with a penalty of 10 dB(A) for night time noise (22.00The complementary logic condition describes the com7.00) and an additional penalty of 5 dB(A) for evening
plementary areas of the areas described on Table 3.
noise (i.e. 19.00-23.00). Similarly, for airport noise
we introduce LAeqD , LAeqE and LAeqN the equivalent
Table 4: Complementary logic conditions
sound levels calculated at a critical receptor during the
LAeqD LAeqN Logic Condition
Area Types
diurnal, evening and nocturnal periods, respectively, Then
LAeqD LAeqN Logic Condition
Near an Airport it is possible to write the conversion equation.
40
35
LAeqD > 70dB(A)
A1
1
∨LAeqN > 60dB(A)
LDEN = 10 log10 ( × β)
(9)
24
A2
50
45
LAeqD > 65dB(A)
∨LAeqN > 55dB(A)
55
50
LAeqD > 60dB(A)
A3
LAeqE
LAeqN
LAeqD
∨LAeqN > 55dB(A)
β = 12×10 10 +9.486×10 10 +90×10 10 (10)
60
55
LAeqD > 55dB(A)
A4
∨LAeqN > 50dB(A)
Let us introduce ∆E and ∆N
65
55
LAeqD > 50dB(A)
A5
∨LAeqN > 45dB(A)
70
60
LAeqD > 40dB(A)
A6
∆E = LAeqD − LAeqE
(11)
∨LAeqN > 35dB(A)
∆N = LAeqD − LAeqN
(12)
A6
Thus, we have the following relation:
We can write the equation:
A1 ⊂ A2 ⊂ A3 ⊂ A4 ⊂ A5 ⊂ A6
We adopted in the last paragraph the mixed, mainly
residential area as the residential area most sensitive to
noise and the mainly industrial area as the less sensitive
to noise. The diurnal and nocturnal levels are on Table
5.
LDEN = LAeqD + 10 log10 (
θ = 12 + 9.486 × 10
One may write the above table as logic condition and
complementary logic condition which would be the exterior of the area defined to the initial logic conditions.
6
Area 1 definition: LAeqD > 70dB(A)∨LAeqN > 60dB(A)
Area 2 definition: [LAeqD > 55dB(A)∨LAeqN > 55dB(A)]−
Area1
1970
−∆E
10
1
× θ)
24
+ 90 × 10
−∆N
10
(13)
(14)
Conclusion
The DNL metric is appropriate to develop environmental impact studies. However, the use of this metric on
airport zoning does not seem adequate, once it may lead
to distortions in the local noise situation.
Acoustics 08 Paris
It is recommended to use for zoning purposes, diurnal
and nocturnal metrics that will allow to consider different adverse effects such as sleep disturbance and disturbance on oral communication.
It is observed that, by the nature of the noise sources
involved, the use of DNL to evaluate the annoyance generated by land transport noise will lead to different relations between the levels of the metric and the number
of highly annoyed people.
We presented two propositions for the revision of Portaria 1141 GM5 based on the NBR 10151. From these
propositions, the second would be the most satisfactory,
which is based on the use of LAeqD and LAeqN in a
logic condition to define airport noise zoning. At first,
it is recommended to adopt the first proposition which
consist in continue to use the DNL metric and reduce
the levels for each of the noise curves, lowering from 75
dB(A) to 70 dB(A) for curve 1 and from 65 dB(A) to
58 dB(A) for curve 2.
Acknowledgments
We thank the cooperation of the GERA (Airport Noise
Study Group) / COPPE / UFRJ, and the support given
by CNPq (Scientific and Technologic Development National Council) and by CAPES (Coordination for the
Improvement of Higher Education Personnel).
References
[1] S. Fidell, ”Assessment of the effectiveness of aircraft noise regulation”, Noise & Health, 17-25
(1999)
[2] S. Fidell, L. Silvati ”Parsimonious alternative to regression analysis for characterizing prevalence rates
of aircraft noise annoyance”, Noise Control Eng.
J. 52(2), 56-68 (2004)
1971
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