776 NOISE
well-documented. And, we can estimate the effect of intru-
sive noise on speech intelligibility and masking of warn-
ing signals. Equivalent sound levels and day-night sound
levels based on hearing protection, activity interference, and
annoyance are given in Table 9. The United States Census
Bureau identified noise as the top complaint about neighbor-
hoods, and the major reason for wanting to move. In a typi-
cal city, about 70% of citizen complaints relate to noise. The
most common complaints are aircraft noise, highway noise,
machinery and equipment, and amplified music.
Noise tolerance varies widely among individuals. It is
difficult to relate noise levels to psychological and non-
auditory physiological problems. But there is anecdotal evi-
dence that violent behavior can be triggered by noise. In a
New York case, one man cut off another man’s hand in a
dispute over noise. In another noise-related incident, a New
Jersey man operated his motorcycle engine inside his apart-
ment, leading a neighbor to shoot him.
Chronic noise exposure has been related to children’s
health and cognitive performance. In a study of British
schools, Stansfield and Haines (2000) compared reading
skills of students at four schools with 16-hour equivalent
sound levels less than 57 dBA and four schools with levels
greater than 66 dBA. After adjustment for socioeconomic
factors, lower average reading scores were found at the nois-
ier schools. The difference was equivalent to six months of
learning over four years.
A study by Zimmer et al. (2001) examined aircraft noise
exposure and student proficiency test results at three grade
levels. Communities with comparable socioeconomic status
were selected for the study. Noise-impacted communities
with a day-night sound level greater than 60 dBA and com-
munities with a level of less than 45 dBA were compared.
If proficiency test results are extrapolated to educational attain-
ment and salary level, one could predict a 3% salary level dis-
advantage for students from the impacted communities.COMMUNITY NOISEContributors to community noise include aircraft, highway
vehicles, off-road vehicles, powered garden equipment,
construction activities, commercial and industrial activities,
public address systems and loud radios and television sets.
The major effects of community noise include sleep interfer-
ence, speech interference, and annoyance.
Highway noise. Noise levels due to highway vehicles
may be estimated from the Federal Highway Administration
(FHWA) model summarized by the sound level vs. speed
relationships in Table 7. These values make it possible to pre-
dict the impact of a proposed highway or highway improve-
ment on a community.
The contribution that a given class of vehicles makes to
hourly equivalent sound level is given by(^)
LL DVSAAAA
AS
eqHo lg o B D F G
10
25
[]
(10.1)
where D o 15 m, V volume (vehicles/hr), S speed
(km/hr). A B, D, F, G and S are adjustments for barriers, distance,
finite highway segments, grade and shielding due to buildings,
respectively. Each term is applied to a given class of vehicles
and traffic lane. For acoustically absorptive sites, the distance
adjustment is
ADDDo15 lg[]⁄ (10.2)
where D distance from the traffic lane (m). Hourly equiva-
lent sound level at any location is predicted by combining the
contributions from all vehicle classes and traffic lanes. The
result is
L
i
eqH COMBINED
N
( )
⁄
∑
10 10 10
1
lg LHieq.
(10.3)
Design noise levels for highways. Design noise levels
specified by the Federal Highway Administration (1976) are
summarized in Table 8. Noise predictions based on projected
traffic on proposed highways are compared with the design
levels. These data aid in selecting a highway design and
routing alternative including the “no-build” alternative.
Aircraft noise. Noise contour maps are available for
most major airports. These enable one to make rough predic-
tions of the impact of aircraft noise on nearby communities.
Federal Aviation Administration publications (1985a and b)
outline aircraft noise certification procedures and aircraft
noise compatibility planning. Many of the existing airport
noise contour maps are based on the descriptor Noise expo-
sure forecast (NEF). An approximate conversion from NEF
to L DN is given by
LDNNEF 35 (10.4)
where L DN day-night sound level ( about 3 dBA).
Community noise criteria. There are thousands of dif-
ferent community noise ordinances, with a wide range of
permitted sound levels. Their effectiveness depends largely
on the degree of enforcement in a particular community. The
Environmental Protection Agency has identified the noise
TABLE 7
Energy mean emission levels for vehicles
Vehicle
class
Sound level
L 0 dBA
Speed S
km/hr
Autos 31.8 lg S 2.4 50
Autos 62 50
Med. trucks 33.9 lg S 16.4 50
Med. trucks 74 50
Heavy trucks 24.6 lg S 38.5 50
Heavy trucks 87 50
Sound levels at 15 meters. Source: Barry and Reagan
(1978).
C014_003_r03.indd 776C014_003_r03.indd 776 11/18/2005 10:46:11 AM11/18/2005 10:46:11 AM