Examination of Witnesses (Questions 5160
- 5179)
5160. Mr Kahn, you are not a civil engineer
and you are not a railway engineer, and you will forgive me for
saying that Crossrail contains many people who are used to designing
escalators; indeed, we have many escalators within this project.
(Mr Kahn) Absolutely.
5161. If you receive an assurance that it can
be built, have you any reason to doubt it? You do not have the
expertise to discuss it, but if you were looking for reassurance
why would you doubt that reassurance?
(Mr Kahn) For the reasons that I gave you before.
I would want to see the technical details that they have properly
considered the problems involved, rather than a sketch to say
it should not be a problem. You said earlier that the little bit
at the top and the little bit at the bottom were common to all
escalators, in which case they would be something that had been
done before. When I asked Crossrail if it had been done before
they said no, so you cannot rest on the precedent that Crossrail
have had lots of engineers who have done lots of things before.
5162. Mr Kahn, as before, you are confusing
things, with respect.
(Mr Kahn) Possibly.
5163. You are asking for a report about whether
these acoustic insulators have been used before—and you
are right in saying no. The load-bearing issue, which is the issue
you raised, is common to all escalators. This is not a technical
drawing. I have put it in, partly to amuse the Committee—
5164. Chairman: You have succeeded.
5165. Mr Elvin: —but also to inform
them at least as to where the insulating elements go, just to
illustrate the point. The fact is that the loading question is
common to all escalators, is it not?
(Mr Kahn) Normally the load would be distributed
along the length. I think that if there is some technical information
we would probably be very happy to accept it. We have always said
that. But, in the absence of technical information, I think it
is not a matter between an acoustician and a lawyer; it is probably
a matter for structural engineers.
5166. I will tell you what: talk to Mr Berryman
after you have finished giving evidence and then you can let us
know whether there is anything that remains. Can I ask you about
the theatre, the issue of the acoustic insulation, the lining.
You say 300 or 400 mm; Mr Thornley-Taylor, who has designed and
been involved in the insulation of an EMI studio in St John's
Wood in a Victorian building—which you can imagine poses
some problems in this respect—is satisfied that 200 mm is
achievable, possibly even down to 150 mm. As I understand your
evidence, you are not suggesting this is unachievable, you are
just concerned, is that right?
(Mr Kahn) I have very strong doubts that 150
mm, full thickness of the isolation shell and the internal acoustic
treatment that will be required—
5167. To achieve the thickness, you use metal
sheeting which increases the density of the shielding.
(Mr Kahn) Yes.
5168. That would mean that you could have a
thinner layer, would it not, because the metal would be more dense?
(Mr Kahn) Yes, it would, but you still need
to be sure ... The metal has a certain amount of structure, and
that would take up thickness as well. In addition, you would need
a void. It is not a simple equation between the amount of the
mass and the void. You would need—this is where there was
some ambiguity about the cocoon—some acoustic treatment
on the inside as well, in order that you had satisfactory acoustic
environment for the critical listening function that is required.
5169. I am going to let Mr Thornley-Taylor deal
with this side. Are you bringing forward any reason as to why
the screen could not be moved closer to the seats? Or is that
a matter that has to be covered by the BBFC witness?
(Mr Kahn) As I say, the positioning of the
screen and everything else is principally not an acoustic issue,
but my experience in designing and considering theatres, viewing
rooms and dubbing and mixing suites, and also generally in designing
rooms, is that, particularly in cinemas, where the film itself
is flammable and there is quite a significant risk of fire, there
is a requirement for a fire escape and so there needs to be a
clear corridor along the room.
5170. I am sorry, Mr Kahn, do not misunderstand
me. I am not suggesting interfering with the fire exit; I am talking
about moving the screen slightly a little bit that way.[40]
Are you able to point to any standards as to the minimum distance,
or is that a matter that I can only put to the BBFC witness?
(Mr Kahn) The minimum distance
as a standard is not an acoustic issue.
5171. In that case, I took that as far as I
could with the witness this morning.
(Mr Kahn) Yes.
5172. Mr Elvin: Thank you very much.
Re-examined by Mr Cameron
5173. Mr Kahn, you were asked about the British
Standard 8233. Do you remember those questions?
(Mr Kahn) I do, yes.
5174. And you were asked about the applicability
of that standard to cinemas. This was the standard which Mr Elvin
had on Mr Thornley-Taylor's computer but was not able to put it
on the screen at the time.
(Mr Kahn) Yes.
5175. Mr Elvin: I can now.
5176. Mr Cameron: That is extremely helpful.
(Mr Kahn) Could I suggest that I have a slide—
5177. No, I would like, if I can, to take it
this way. The pages I need, if Mr Elvin is volunteering, are pages
1 and 24.[41]
You were asked about 7.6.8.1. I think you referred
to the scope but then did not have the document to hand. It is
now going to come up on the screen. The British Standard gives
recommendations for controlling noise in and around buildings
and suggests appropriate criterion limits in different situations:
"These criteria and limits are primarily intended to guide
the design of new or refurbished buildings undergoing a change
of use, rather than to assess the effect of changes in the external
noise level." As far as the scope of this guidance is concerned,
what is its primary purpose?
(Mr Kahn) I think, as it says there, explicitly—and
I had this on my slide 9—"These criteria and limits
are primarily intended to guide the design of new or refurbished
buildings undergoing a change of use, rather than to assess the
. . . changes in the external noise level."
5178. So that it is read properly, ". .
. rather than to assess the effect of changes in the external
noise level."
(Mr Kahn) Sorry. It also says, if I may go
on a little bit longer: "It covers room acoustics for simple
situations, but not the design of buildings where the acoustics
are critical, such as auditoria." I would have said that
for the critical listening and examination of films in this case
for a statutory purpose, the acoustics are critical.
5179. Chairman: The document you have
just presented to us will be A62.
40 Committee Ref: A59, British Board of Film Classification,
Existing Floor Plans-Basement Plans (WESTCC-14805-114). Back
41
Committee Ref: A62, British Standard BS8233-Scope, p1 (SCN20060323-007). Back
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