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The Department of the Environmental (as was) funded a study by the UK's Building Research Establishment [BRE] to study how best to measure clay target shooting
noise and to establish the correlation between such measurements and
community response. The Chartered Institute of Environmental Health [CIEH] has
incorporated the results of this research into a consultation draft for
Clay Target Shooting Noise, dated Nov 1997 [REFERENCE 1]; it is intended
that this document would be adopted under Section 71 of The Control of
Pollution Act 1974. The BRE research is the only study of its kind ever
to have been conducted in the UK or elsewhere. Some of the research
findings are surprising and all have important implications for the
assessment of clay target shooting.
Initially it had been hoped that agreement could be
reached between the
CIEH and the
sport's governing body the
CPSA
to produce a joint document; however, the CIEH have decided to "go it
alone" and their document can be seen on their website
here.
This paper examines the main findings of the BRE
research, compares it with the two most commonly used standards for
assessing clay target shooting noise, by reference to measurements made
at a typical shooting ground, and finally draws conclusions.
THE RESEARCH
The BRE research report has
still not been published,
but some details have emerged
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With the possible exception of high background
noise levels, the level of background noise, or the excess of the
shooting noise over the background is not important.
-
The research did not find that Sunday shooting was generally more disturbing
that shooting on other days of the week.
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The research did not find that the
frequency (oftenness) of shooting and the rates of fire were
important in deciding the degree of disturbance.
-
It was an opinion of the
researchers that measurements should be made using a graphic level
recorder and sound level meter or a short-Leq meter with source
coding buttons.
-
It was an opinion of the
researchers that the most reliable descriptor of shooting noise is
the logarithmic average of the 25 loudest shots in a 30 minute
period using LAFmax - termed the "Shooting Noise
Level" or "SNL"
-
Widespread annoyance is unlikely below around 55
dB(A) [as measured in 5. above], but likely above around 65 dB(A).
Thus a level of, say, 60 dB(A) may be deemed acceptable at one site,
but not at another.
The conclusions as how best to measure this noise are
based on measurements around 20 shooting grounds. The analysis of
community response to shooting noise impact was based on a subset
of 8 shooting grounds. All noise measurements were made with a positive
wind component, e.g. at locations to the southwest of a shooting ground
measurements were always made with a light northeasterly wind.
COMPARISON WITH OTHER ASSESSMENT METHODS
The two main standards for assessing noise to date,
have been produced by the Clay Pigeon Shooting Association [CPSA] -
reference 2 and CIEH - reference 3 [but based on Ref.4]. Both documents are very detailed. Only a brief summary is given
below.
CIEH [3]
This document requires the noise of individual
gunshots to be measured, and then compares the logarithmic average level
of all measurable gunshots against a limit value that depends upon the
preexisting background level of noise in the area:
This code says that "It is recommended that
unless by virtue of planning consent, accepted existing use, or mutual
agreement between the shoot organiser(s) and the local community,
shooting should not normally take place on any Sunday, Bank or Public
Holiday, or evening period." Also "The hours of
shooting on weekdays (inclusive of Saturday) should be confined to be
between 9.30 am and 6.00 pm subject to a single organised event taking
place over a maximum duration of one four-hour consecutive period."
CPSA [2]
This Code of Practice attempts to weigh the factors
of noise level, character of noise, duration of exposure, time of day
and so on by recommending inter alia that:-
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The logarithmic average level of all measurable
gunshots should not exceed 60 dBA 'Fast' at any noise sensitive
premises.
-
That unless there is specific local agreement,
shooting hours should be restricted to:-
Mondays to Saturdays 0930 - 1830 hrs.
Sundays 1000 - 1700 hrs. [shooting < 4 hrs.]
Summary
Both the existing assessment methods consider that
Sundays are more sensitive than other days of the week, and permit the
measurements to be made by writing down the results from the
display of a standard sound level meter; also, both derive the
logarithmic average of all measurable gunshots. The CIEH draft
Professional Practice Note [ref.3] also considers that the excess of shooting
noise over background level is important.
ASSESSMENT OF A SHOOTING GROUND
Figure 1 shows a real shooting ground "somewhere
in the south of England". The shoot lies to the northeast of the
measurement position, and a busy bypass lies to the southwest of
measurement position, when the wind is from the northeast the shoot
noise is relatively high and the background relatively low, and the
situation is reversed when the wind is from the southwest.
On a particular day the weather conditions were
constant with a light northeast wind. It can be seen that there is no
screening by barriers and little variation in separation distance or
firing direction from stand to stand; however, even at this ground,
there was a 30 dB(A) variation between the loudest and quietest shots. Over the course of 2½ hours, some 850 individual shots
were measured; therefore, 170 shots represent approximately 30 minutes
worth of data. It is possible to compare the "rolling"
logarithmic average of 170 shots (30 minutes), against the
"rolling" average of the loudest 25 of the same 170 shots,
i.e. to compare the "BRE" assessment method against that of
the CPSA (and CIEH). The background noise level at the measurement
location was 42 LA90.
The second figure shows the results of the comparison. It can
be seen that on this day, the assessment methods were relatively stable;
both varied within a 3.5 dBA band. The BRE method was around 76.5 dBA
and the CPSA/CIEH around 71 dBA; the mean difference between the two
methods was 5.5 dBA, again for this shoot on this day.
By contrast, on days when the wind was from the
southwest, the CPSA/CIEH method would produce a rating of 55 dBA
compared with a BRE rating of 56 dBA. The background noise levels were
50 LA90. The different wind direction produced lower shooting noise
levels, and higher background noise levels; hence, the range of
measurable gunshots was compressed. Such a variation in noise impact for
different weather conditions is not unusual.
DISCUSSION
Comparison with CPSA and CIEH Recommendations
Looking at the results from the real shoot, it seems
likely that for most shoots, the BRE method will be between 1 and 6 dBA
above the CPSA/CIEH method.
The CPSA code of practice seeks to avoid ratings in
excess of 61 to 65 dBA (using BRE method), which ties in reasonably well
with the BRE’s conclusions that widespread annoyance is likely above
around 65 dB(A) (using BRE method).
If we now compare the BRE assessment method with that
of CIEH, for many shooting locations the daytime background noise levels
are between 35 and 45 LA90. Accordingly the CIEH Code of Practice seeks
to avoid ratings in excess of 56 to 66 (using BRE method), depending on
the background level of noise and the variability of shooting noise.
If we now assess the real shoot results using all
three methods; noise levels on the first occasion exceeded the
recommended limits of both the CPSA and CIEH, and the BRE research would
indicate that widespread annoyance is likely. On the second occasion
noise levels were within the recommended limits of the CPSA and CIEH,
and the BRE research would indicate that widespread annoyance is
unlikely. None of the assessment methods give guidance on the
implications of variation in noise impact from day to day.
Finally the 30 dB(A) spread between the loudest and
quietest shots has another important consequence (see Figure 3 below);
the BRE method is based on the loudest 25 shots in a 30 minute period;
therefore, the higher the firing rate the more likely it is that the
loudest 25 shots will be lie towards the upper end of the spread of
results, i.e. the higher the firing rate the higher the rating level; an
increase from 3 shots/minute to 33 shots per minute would increase the
SNL by 4.5 dB(A). By contrast the research did not find
that firing rate affected annoyance.
REFERENCES
[1] "Clay target shooting, guidance on the
management and control of noise, public consultation draft, November
1997", Chartered Institute of Environmental Health, British
Shooting Sports Council, Clay Pigeon Shooting Association.
[2] "Draft Code of Practice on Noise from Clay
Pigeon Shooting 1989" Clay Pigeon Shooting Association.
[3] "Noise from Clay Target Shooting -
Professional Practice Note, draft for consultation June 1993"
Chartered Institute of Environmental Health
[4] "Code of Practice on Noise from Clay Target
Shooting" Midland Joint Advisory Council for Environmental
Protection - Fourth Revision August 1994.
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