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Assessments of low frequency noise complaints among the local
Environmental Health Authorities and
a follow-up study 14 years later
Johanna Bengtsson,
Kerstin Persson Waye
2
Department of Environmental Medicine, Göteborg University, Sweden.
johanna.bengtsson@envmed.gu.se
2.
Presently at the Department of Acoustics, Fredrik Bajers Vej 7 B5, DK-9220 Aalborg Ø,
Denmark, kpw@acoustics.dk
Corresponding author:
Johanna Bengtsson
Department of Environmental Medicine
Medicinaregatan 16, 41390 Göteborg, Sweden
johanna.bengtsson@envmed.gu.se
ABSTRACT
Interviews among a selection of 37 of the 289 Swedish local Environmental Health
Authorities (EHA) were undertaken in order to assess the occurrence of complaints on low
frequency noise. The study also aimed to evaluate whether the specific guideline on low
frequency noise, adopted in 1996, was used and how it performed when assessing low
frequency noise. The results showed that most complains on low frequency noise were due to
noise from fan- and ventilation installations, amplified music, compressors and laundry-
rooms. According to 46% of the EHA, complaints due to low frequency noise had increased
during the last two years, while the same percentage reported no change. When assessing low
frequency noise, 62% of the EHA reported that the specific guideline on low frequency noise
based on third octave band analysis performed better or much better compared to previous A-
weighted guideline, and only one EHA thought it performed worse.
Key words: Low frequency noise, complaints, guidelines, Environmental Health Authorities.
INTRODUCTION
In estimating the importance of low frequency noise as an environmental health problem a
fundamental question is: How large is the problem or more specifically how many people are
negatively affected by low frequency noise? For transportation noise the number of exposed
people are rather easy to assess based on standardised calculations that take into account e.g.
the number of vehicles, their average speed, distance from the road to the dwellings. For low
frequency noise it is more difficult to estimate the number of people exposed as no records
exists on the number of low frequency sources that people may be exposed to and also as
some sources may be generating a low frequency noise due to inaccurate installations. One
way to estimate the effect is to use indirect estimations such as prevalence of complaints to
the authorities that are responsible for nuisance due to noise in the general environment.
Complaints directed to the local Health Authorities have been studied previously. Tempest
[1989] carried out a questionnaire survey among 50% of the local Health Authorities in the
United Kingdom. Complaints were prompted by a variety of sources, the most common being
factories (35%), music (13%), traffic and other vehicles (11%) and commercial premises
(9%). No estimation of the proportion of low frequency noise complaints in relation to other
noise complaints was made. A questionnaire study among all local Environmental Health
Authorities (EHA) in Sweden, gave the result that the three low frequency noise sources: fan-
and ventilation noise, heavy vehicles and heat pumps comprised 71% of the total number of
complaints on noise during a six month period in 1985 [Persson and Rylander 1988]. In that
study was found that 32% of the EHA reported that complaints on low frequency noise had
increased during 1985 as compared to 1984, while 9% reported a decrease and 58% no
change. The main reasons given for the increase were heat pumps, followed by fan- and
ventilation installations and road traffic.
When evaluating the importance of complaints one has to bear in mind that although
complaints are an important tool for the Environmental Health Authorities to prioritise the
resources, the reasons for a complaint depend on several factors related to the authority, the
individual and the noise source. Hence the number of complaints does not automatically
reflect how many that is actually disturbed, but can be seen as an indicator of disturbance.
As the referred studies were undertaken more than 10 years ago it would be of interest to
investigate the situation today. Furthermore, in 1996, Sweden adopted a specific guideline on
low frequency noise in the general environment [SOSFS 1996:7/E]. In short, the guideline
states that low frequency noise should be assessed based on third octave band measurements
in the frequency range of 31.5 to 200 Hz and the sound pressure levels given in Table 1
should not be exceeded in any third octave band. The measurement procedure is given in SP-
Report 1996:10. For intermittent sounds such as amplified music, the guideline also states that
an A-weighted level of 25 dB may be used. It was thus also of interest to investigate whether
the specific guideline on low frequency noise was used in assessing low frequency noise and
whether it had lead to an impaired or improved situation.
Table 1. Guideline on low frequency noise (SOSFS 1996:7/E)
Third octave
band (Hz )
Equivalent sound
pressure levels (dB)
31.5 55
40 49
50 43
63 42
80 41.5
100 38
125 36
160 34
200 32
AIMS
The aim of this study was to evaluate the occurrence of complaints related to low frequency
noise directed to the EHA and to see if the introduction of the specific Swedish guideline on
low frequency noise had influenced the EHA assessment of low frequency noise. A secondary
aim was to compare the results with a similar study carried out 14 years ago.
METHODS
In Sweden the EHA are the authorities responsible for the environmental and health aspects
including noise disturbance in the municipalities. The contact with the public is mainly
complaint orientated. A complaint is a well-defined and recognized expression and it is
registered at the EHA. Complaints are also one of the more important tools for the EHA to
prioritise resources. We therefore considered the EHA to be the most reliable source of
information as regards noise complaints in the general environment.
Among the 289 EHA in Sweden, 41 EHA were randomly selected. Of those, 37 (90.2%)
participated. The selection of the EHA was based on the number of inhabitants and
geographical distribution of the municipalities. The selected sample comprised all eleven
EHA in municipalities with more than 100 000 inhabitants, ten EHA in municipalities with 51
000 to 99 000 inhabitants and 20 EHA in municipalities with less than 50 000 inhabitants.
The number of inhabitants of the participating municipalities ranged from 6 000 to 740 000,
with a median value of 57 500.
A questionnaire was distributed by mail together with an introductory letter describing the
purpose of the investigation. It was stated that we wanted to ask about the prevalence of
complaints on noise and low frequency noise in particular. A low frequency noise was defined
as a noise with dominant sound pressure levels in the frequency range of 20 to 200 Hz and to
further clarify, some examples of sources of low frequency noise, such as some ventilation
systems, compressors, pumps, attenuated electronic music, heavy artillery shooting and
explosions were given. Finally we asked to get in contact with the officer that was most
knowledgeable in these matters. Approximately one week later, telephone interviews were
carried out with one environmental health officer per municipality.
The questionnaire comprised 35 questions divided into different sections: administrative
matters, registered complaints on noise and low frequency noise, assessment of and actions
undertaken against low frequency noise. Section I comprised questions on how the authorities
perceived their competence of noise in general, the perceived possibility to prevent noise,
routines to follow up complaints and legal processes. Section II comprised questions on the
total number of complaints directed to the EHA during the last year (1999), complaints on
noise and complaints on low frequency noise. In section III and IV, specific questions were
posted on the most common sources that caused the complaints on low frequency noise, how
the EHA handled complaints due to low frequency noise, if they performed third octave band
analysis and had access to relevant equipment. Finally, in section V the EHA answered
whether the number of complaints due to low frequency noise had increased, decreased or
been the same during 1996-1997 as compared to 1998-1999.
STATISTICAL TREATMENT
Data was analysed for all municipalities and divided into three groups based on the number of
inhabitants. Median values and percentiles are given for data with skewed distribution, while
mean values and 95% confidence intervals of proportions are given for data showing normal
distribution.
RESULTS
The results from the interviews showed that the total number of complaints directed to the
EHA during 1999 varied from 23 to 1 040, with a median value of 140. The total number of
complaints on noise was 1578 and varied from 0 to 330, with a median value of 19. The
number of complaints on noise in general comprised 15% (95% CI; 11.3%-18.1%) of the total
number of complaints.
The number of complaints on low frequency noise directed to the EHA varied from 0 to 215,
with a median value of 7.
The number of complaints on low frequency noise per EHA is shown in Figure 1.
FIGURE 1 IN ABOUT HERE
The proportions of low frequency noise complaints in relation to complaints on noise in
general varied from 0 (8 EHA) to 100% (2 EHA). The mean value of the proportions was
35% (95% CI; 18.5 % – 51.5%). Overall the total sum of low frequency noise complaints in
relation to the total sum of complaints on noise comprised 44%.
Another factor of interest was the incidence rate, i.e. the number of complaints per
inhabitants. The incidence rate was calculated as complaints per 10 000 inhabitants to avoid
very small numbers. For all municipalities the median value of incidence rate for complaints
on low frequency noise per 10 000 inhabitants was 1.1 (25
th
perc – 75
th
perc; 0.25-2.4). The
corresponding rate for noise in general was 3.3 (25
th
perc – 75
th
perc; 2.5-6.6).
Table 2 gives the incidence rate for municipalities divided into the three categories: number of
inhabitants less than 50 000, between 50 000-99 000 and more than 99 000 inhabitants.
Table 2. The incidence rate related to municipality size
Municipality size Median value of
incidence rate per
10 000 inhabitants
25
th
percentile 75
th
percentile
<50 000 0.78 0 1.6
50 000-99 000 0.93 0.38 3.8
>99 000 1.6 0.86 3.0
The table indicates a somewhat higher incidence rate for the largest municipalities, however
the differences between municipality categories were not statistically significant (Chi
2
=2.709,
df=2, p=0.258, Kruskal Wallis test).
EHA with more than 5 complaints on low frequency noise (18 EHA altogether) were more
closely analysed to see which noise sources was responsible for the largest proportion of
complaints.
The relative proportion of the different noise sources emitting low frequency noise is shown
in Figure 2.
FIGURE 2 IN ABOUT HERE
The analyses showed that complaints regarding fan- and ventilation installations comprised
the largest part (21%), followed by amplified music (18%), compressors (17%), and laundry-
rooms (16%). Less frequent were complaints on noise from heavy vehicles (9%), sea
transports and aircraft (6%) and heat pumps (5%). The occurrence of complaints on low
frequency noise due to installations placed inside a building was similar to complaints due to
installations placed outside a building. The sector named “others” includes different sources
such as quarries, heavy artillery shooting, trains and road traffic.
To assess low frequency noise, most EHA used a combination of measuring third octave band
sound pressure levels, dBC and the dBC-dBA difference, as well as listening to the noise. One
third of the EHA (30%) reported that they did not have enough access to relevant equipment.
On the question on how the EHA considered the specific guideline [SOSFS 1996:7/E],
involving third octave band analysis, to perform when assessing low frequency noise
complaints as compared to the previous guideline in A-weighted noise levels, 62% reported
that it performed better or much better, 35% did not know and only one EHA considered it to
perform less well (Figure 3).
FIGURE 3 IN ABOUT HERE
Finally, 46% of the EHA estimated that complaints on low frequency noise had increased, 3%
that they had decreased and 46% that the number of complaints had been stable during the last
two years. Reasons given for an increased number of complaints were an increasing number
of restaurants with music, fan- and ventilation installations and also, an increased awareness
among the inhabitants and among the EHA regarding the problems with low frequency noise.
DISCUSSION
Methods
The investigated sample of EHA comprised 13% of the EHA in Sweden. With this rather
small proportion it cannot be excluded that the results are not representative for all EHA.
The sample in this study was chosen to be representative of both population size and
geographical distribution and as the main aim was to get a deepened knowledge, an
investigation of all EHA was not possible. In this study and the previous [Persson and
Rylander 1988] there were also no clear relationships between size of municipality and
number of complaints on noise or low frequency noise per inhabitants, and it can thus be
concluded that there are no strong indications that the results would have been different if the
number of EHA had been greater.
The investigation of the occurrence and type of complaints in this study, was based on a
comprehensive questionnaire sent out in advance and a subsequent interview. This was done
as some of the questions required the EHA to go through their records of registered
complaints in beforehand. We have however not been able to check the validity of the
answers, i. e. how well the answers were in agreement with the actual registered complaints in
each authority. This could have been done by going through the registered number of
complaints in a randomly chosen sample, but was unfortunately not within the scope of this
study. Furthermore there were no indications during the interviews that the numbers given
would be incorrect. If present, this type of error would probably apply to both complaints in
general, complaints to noise and low frequency noise, and it would hence not affect the
relative distribution of these complaints. It would however affect the certainty of the numbers
given and also the information on which sources that caused complaints. The error is
estimated to be rather similar between this study and the previous.
A third factor that should be considered is how well the data on complaints reflect the
occurrence of noise disturbance in the general environment. As mentioned in the introduction,
the reasons for a complaint depend on several factors such as the accessibility of the authority,
the individuals´ earlier experience, education level and attitude to the noise source, the
presence of local opinion and possibilities (perceived and otherwise) of influencing the noise
source [Miller 1978]. It has also previously been found, based on experience in England and
USA, that only a small number of people who are annoyed will actually formalise their
distress into a complaint [Miller 1978, Daryl 1978, U.S. EPA 1974]. Taken together it can be
concluded that if a complaint is present it can be taken as an indicator of the presence of
annoyance, while no indication is given of the extent of annoyance. There are no indications
that the factors influencing the reasons for whether a complaint is put forward or not in
Sweden have changed considerably between 1985 and today.
Results
The results indicate that the proportion of low frequency noise complaints in relation to noise
in general was lower in this investigation compared to the study carried out in 1985 [Persson
and Rylander 1988]. The proportion of low frequency complaints of the total complaints on
noise was in this study 44% compared to 71% found in the previous study. As this study
comprised a selection of EHA, it may be more relevant to compare the mean value of the
relationship between the total number of complaints and low frequency noise for each EHA.
The mean value was 35%.
There are several possible reasons for the different results between this study and the one
carried out in 1985. One reason could be that the number of complaints on noise in general
has increased. In the previous study, the total number of complaints on noise to 284 EHA
registered during a six months period, was 1 026 and of those 728 were categorised as low
frequency noise complaints. Assuming that the 6 month period was representative for the
whole year this totals 2 052 complaints on noise in general and 1 456 complaints on low
frequency noise during a year. In this study the total number of complaints on noise in general
was 1 578 from a sample of 37 EHA and of those 692 were categorised as low frequency. In
the previous study, the medians values of complaints on noise in general were 4, and for low
frequency noise 2. In this study the median values of complaints on noise in general were 17
and for low frequency noise 7. Although, the comparison is hampered by the different sample
selection, and a somewhat different method, the data indicate that the different results may be
due to a relatively greater number of complaints on noise in general being directed to the
EHA today. Another factor that would give the same results would be if noise sources in the
previous study incorrectly were classified as low frequency. This is not unlikely as the
knowledge of low frequency noise in 1985 was less widespread. Furthermore, the
classification in 1985 was in most cases based mainly on the C-weighted levels and possible
octave band measurements, which made classification less precise. Since then, the knowledge
of low frequency noise among the EHA has increased to a great extent, mainly due to the
introduction of specific guideline on low frequency noise.
In this study the dominant sources of low frequency noise complaints were fan- and
ventilation installations, followed by music, compressors and laundry-rooms. In the previous
study, fan- and ventilation installations were also the largest source of complaints followed by
heavy vehicles and heat pumps. The relative proportion of complaints between the sources
asked for in the previous study and this study is strikingly similar. Fan- and ventilation noise
complaints are/were reported about twice as often as heavy vehicles and heavy vehicles
are/were reported about twice as often as heat pumps.
In the study by Tempest [1989], factory noise was the dominant source followed by music,
traffic and other vehicles and commercial premises. Music was not specifically asked for in
the study carried out in 1985, but from the results in the present study it can be concluded that
it is an important source for low frequency noise complaints today.
As regarding changes over time compared to a previous reference period, the results from the
previous study showed that 32% reported an increase, 9% a decrease and 58% an unchanged
number. This study found that 46% reported an increase, 3% a decrease and 46% an
unchanged number. These results indicate that low frequency complaints are an important
issue that still seem to grow.
In the previous study ten EHA stated in an open question that present regulations for
controlling low frequency noise were not adequate. The data from the present study show that
nearly two third of the EHA stated that the specific guideline on low frequency noise based on
third octave band analysis was much better or better compared to the previous A-weighted
guidelines when assessing low frequency noise. This is worth observing as the specific
guideline on low frequency noise is more time-consuming, requires a higher degree of
competence and more sophisticated equipment. It is also worth noting that 35% did not know
if the specific guideline was better or worse and most of those did not have access to
equipment that could measure third octave band sound pressure levels. The lack of relevant
equipment may thus be an impediment for appropriate and equal assessments of complaints
between municipalities.
CONCLUSIONS
The interview among a selection of the EHA in Sweden indicates that the proportion of low
frequency noise comprised 35% of the total complaints on noise. The study also shows that
complaints on low frequency noise are still an important and probably growing issue.
Most of the EHA preferred the specific guideline on low frequency noise based on third
octave band analysis to previous A-weighted guidelines when assessing low frequency noise,
even thought it is more time-consuming and require more competence and advanced
equipment.
REFERENCES
Daryl N M. Basic subjective response to noise. In: Handbook of Noise assessment (N M
Daryl ed.), New York, Van Nostrand Reinhold. Pp 3-38, 1978.
Miller J D. Effects of noise on people. In: Handbook of Perception (E C Carterette and P F
Morton, eds.) Academic press. Vol IV, pp 609-640, 1978.
U. S. Environmental Protection Agency, EPA report No 550/9-74004. Information on
levels of environmental noise requisite to protect public health and welfare with an adequate
margin of safety. 1974.
Persson K and Rylander R. Disturbance from low frequency noise in the environment: A
study among the local environmental health authorities in Sweden. J. Sound. Vib.1988; 12:
339-345.
SOSFS 1996:7/E. Indoor Noise and High Sound-Levels. General Guidelines issued by the
Swedish national Board of Health and Welfare, 1996.
SP-REPORT 1996:10. Measurement of low frequency sound in rooms. Swedish National
Testing and Research Institute, Borås, Sweden.
Tempest W. A survey of low frequency noise complaints received by local authorities in the
United Kingdom. J Low Freq Noise Vibr. 1989; 8:45-49.
Legends to figures
Figure 1. Number of complaints of low frequency noise per EHA.
Figure 2. The relative distribution of noise sources causing complaints on low frequency
noise.
Figure 3. The proportion of EHA reporting on how the specific guideline on low
frequency noise (SOSFS 1996:7/E) performed relative to the earlier used A-weighted
guidelines.
Number of complaints on LFN
215
160
55
35
30
25
20
18
15
14
10
8
6
3
2
1
0
Number of EHA
10
8
6
4
2
0
Compressors
Fan/ventilation
Heatpumps
Laundry
See/air transport
Heavy vehicles
Music
Others
17%
8%
18%
9%
6%
15%
5%
21%
Much better
Do not know
Worse
Better
38%
24%
35%
3%
