Examination of Witnesses (Questions 7140
- 7159)
7140. Finally, we can note in the Foreword,
that "...there will be a relationship between the incidence
of complaints and the level of general community annoyance, quantitative
assessment of the later is beyond the scope of this standard,
as is the assessment of nuisance." So this standard is not
concerned, is it, to look at the level of general community annoyance?
(Mr Thornely-Taylor) No.
7141. Can we go on in the document to page 6
of the standard, paragraph 9 (page 107 of 125 in the document
provided to the Committee).[83]
It is this paragraph, is it not, where one gets the reference
made to a difference of plus 55 dB?
(Mr Thornely-Taylor) Yes.
7142. It is this paragraph which tells us what
it is that should be attached to that, in the context of the consideration
of complaints, not a consideration of general community annoyance,
and it is here saying that " . . . +5 dB is of marginal significance".
(Mr Thornely-Taylor) Yes.
7143. So this document is not suggesting, is
it, that 5db plus is of no significance?
(Mr Thornely-Taylor) It says: "A difference
of around +5 dB is of marginal significance".
7144. Yes, not of no significance. And it is
looking at it not in the context of community annoyance but simply
in relation to the question of complaints.
(Mr Thornely-Taylor) Yes.
7145. Am I right in supposing that, perhaps
influenced by the length of time in your career and otherwise,
acoustics as a science has made progression over the past 20 or
30 years?
(Mr Thornely-Taylor) The laws of physics have
not changed. There has been progression in awareness and understanding.
It would have been very difficult to have dealt with the complex
numbers we have dealt with before this Committee 30 years ago,
because it would have been such a strange subject—I am sure
you will say it is strange enough as it is, but awareness has
greatly improved—but the engineering underlying it is in
many respects much the same as it was 30 or 40 years ago.
7146. Policies, of course, have advanced during
the past 25 or 30 years, have they not?
(Mr Thornely-Taylor) Yes.
7147. And concern over noise has in fact become
greater.
(Mr Thornely-Taylor) Very much greater.
7148. That has found expression in some of the
policy documents to which reference was made earlier today.
(Mr Thornely-Taylor) Yes.
7149. You have relied upon, amongst other things,
the Jubilee Line Extension.
(Mr Thornely-Taylor) Yes.
7150. That was before Parliament in the late
1980s?
(Mr Thornely-Taylor) No, in the early 1990s.
7151. There was no debate or challenge within
that, was there, to the approach which you are now putting forward.
(Mr Thornely-Taylor) Yes, there was. Westminster
led the same argument as we are having today.
7152. At Camden, you have relied upon the inquiry.
It is right, is it not, that the London Borough of Camden did
not call any technical evidence?
(Mr Thornely-Taylor) No, it was all agreed
before we got into the inquiry.
7153. There is no discussion in the inspector's
report, is there, as to the validity or otherwise of an approach
of plus 5?
(Mr Thornely-Taylor) It was not necessary because
both Camden and Transport for London agreed on a condition.
7154. Am I right in supposing that, if one introduces
a new plant into an existing situation where obviously there is
noise, the background noise must increase by virtue of the introduction
of the new plant?
(Mr Thornely-Taylor) No. Before the break in
my evidence I did explain that, as far as the tunnel vent fans
are concerned, which are the sources that will be principally
affected by this policy, there is no effect at all on the background
as determined by BS4142 by a subsequent developer.
7155. Forgive me, the question was posed in
relation to an existing situation, where there is a background
noise and one introduces something into that background noise
which is going to have a noise of its own.
(Mr Thornely-Taylor) No, the tunnel vent fans
will not normally run, so when a subsequent assessment is made
of some other source, and background is determined, according
to BS4142, which is what we are talking about at present, there
is no change in the background for the next development.
7156. Forgive me, let us look at it without
reference to how one might go about a subsequent assessment. I
am simply concerned to establish what the facts are. If a noise
source is introduced to a situation where there is already noise,
then the background noise, by virtue of that introduction, must
be increased, must it not?
(Mr Thornely-Taylor) No, because the background
noise is defined in section 7 of BS4142, and, because the tunnel
vent fans will not normally run, they will not be running when
the background is measured and there will be absolutely no change
in the background.
7157. The situation posed by the terms of the
Crossrail works with which we are concerned—if we move it
slightly beyond ventilation for the moment—is that there
will be continuous noise.
(Mr Thornely-Taylor) If we move out to outer
areas where we have line-side equipment, traction, signalling
equipment, there will be some items of plant which run continuously
up to a point—the demand on them will change throughout
the day—but those are sites where the provision in the draft
information paper (to do much better than the L90+5) will bite
and lower noise levels will be achieved.
7158. Can we take that step again, please, Mr
Thornely-Taylor. The fact of the matter is that the equipment
provided by Crossrail will generate noise into an already existing
noise climate, will it not?
(Mr Thornely-Taylor) Some will not, normally.
Some will, but it is likely to benefit from a greater amount of
noise control engineering.
7159. If one does introduce as a general concept
noise into an already existing noise climate, the background noise
must go up, must it not?
(Mr Thornely-Taylor) Not as defined in section
7. As long as we are concerned with BS4142—which we are—the
answer has to be no.
83 Crossrail Ref: P75, British Standard 4142:1997
Method for rating industrial noise affecting mixed residential
and industrial areas, Assessment Method (HAVGLB-14704-107). Back
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