Letters: Noise puzzle
As a young engineer in the early sixties I found a solution to the whining
noise of the dryer cylinders in a paper mill (Technology, 28 March). The
pitch of the noise is determined by the rate at which the rows of holes
are emerging from the suction area, each giving a pressure pulse. The solution
was to give the holes a random pattern which changed the whine into a more
acceptable white noise.
The Japanese method is to add in the car a noise that is in the opposite
phase with the engine noise (Technology, same issue). The proof of the method
is hearing (or not hearing) it. But what puzzles me is that one kills noise
by adding noise. If the sound waves cancel at one point they must reinforce
each other at some other point. If the driver’s seat is quiet maybe the
back seat is suffering more.
One cannot kill energy by adding more energy. The only way to eliminate
noise everywhere is to absorb it (conversion to heat) or to change it to
some other energy, which is hardly easy.
Lassi Hyvarinen Le Vesinet, France
Letters: Noise puzzle
So, antinoise technology is ‘now standard’ in Japanese Nissan Bluebirds,
reducing the engine noise for the driver. I trust that any introduction
of the system into this country will be accompanied by legislation requiring
warning sounds (horns, emergency vehicle sirens) to pass unattenuated to
the driver.
Mercedes-Benz has already introduced a double-glazed car; the power
of in-car hi-fis has reached bewildering (literally) levels. All these measures
seem to be aimed at anaesthetising the driver from the surrounding environment
when he/she should be alert to what is happening on the road. Noise is a
vital input into the driver’s consciousness; any clues as to what is going
on around should not be lightly removed.
Colin Deane London
Letters: Tunnels on target
Further to your letter from Clive Barker (Letters, 15 February) I am
pleased to relate our recent experiences whilst tunnelling under central
and west London. The London Water Ring Main alone has included the completion
of more than a dozen single entry tunnels, each driven from single shafts.
The lengths have varied from 1 kilometre to 7 kilometres. They have included
many planned curves to avoid obstructions and geological features, and have
been orientated north to south, east to west, and vice versa. Several other
tunnel drives have been made by Thames Water since the mid-seventies.
The average junction error has been approximately 10 millimetres per
kilometre in drives with compound curves, and better in straight tunnels.
Our experience has demonstrated no evidence of the Coriolis effect at work.
We do find, however, that there can be a difference in measured distances
between surveys above ground and the underground length, causing alignment
difficulties if multiple curves are negotiated.
Our conclusion is that there is no possibility that Coriolis could be
causing optical rays to ‘bend’ during surveying with theodolites to the
extent proposed by Baker, the relative velocity of light in comparison with
the Earth’s rotational speed being too great. It also seems unlikely that
there is any effect on bubbles (used for levelling equipment) which could
cause a significant horizontal misalignment. Science: S. C. A. Walker Thames
Water Utilities Reading, Berkshire
Letters: Seduced by Freud
Articles in New 杏吧原创 are usually highly illuminating to the lay
reader. Failure to illuminate might justifiably arise from the intrinsic
difficulty of the material, but should not arise from a writer’s apparent
confusion. However, I did wonder whether Morton Schatzman (‘Freud: who seduced
whom?’, 21 March) was himself confused about Freud.
Given the four not entirely independent variables – 1) the origin of
the seduction stories (Freud or his patients); 2) the truth or otherwise
of the seduction stories; 3) the interpretation of the stories by the patients;
4) the interpretation of the stories by Freud – there are several permutations
that could have been the case. Yet it is far from clear what Schatzman is
stating was the case.
For example, in more than one place Schatzman suggests or states that
Freud had himself invented the seduction stories (‘Why then had Freud invented
these stories?’). Yet he goes on to discuss whether the stories should be
taken literally or not. In his final paragraph he criticises Freud for not
answering ‘certain important questions’ about ‘to what extent should people
who allege having been abused as children be believed’. This is scarcely
consistent with the claim that Freud invented the seduction stories himself.
Freud talks of his hysterical patients having gone from (conscious)
ignorance through (unconscious) revelation and back to (conscious) ignorance.
I don’t know what is in my unconscious but Schatzman’s piece on Freud has
led me from confusion through confusion and back to confusion.
Andrea McKeown Loughborough, Leicestershire
Letters: Gripping point
We were surprised to see that in your article on the Greenland Icecore
Project (GRIP) no mention was made of the role played by the European Science
Foundation in the launching and coordinating of this project (‘The oldest
ice in the world’, 29 February).
GRIP is an ESF Scientific Programme approved by the ESF General Assembly
in November 1988. Thus the National Research Funding Organisations, which
generously support this project, rely on the ESF for the coordination and
running of GRIP.
M. Fratta European Science Foundation Strasbourg, France
Letters: Brooding time
Jeff Hecht presumes that all those over 30 years old are uneasy with
keyboards, unable to type and have a particular view on the role of secretaries
(Forum, 21 March). He may be correct. Does he not realise the importance
of contemplation to the writer? The manipulation of ruler and pen to cross
out the infelicitous phrase, the sucking of the pen top, the ‘doodle’ in
the margin, all are part of the ‘brooding time’ J. B. Priestly deemed to
be essential components of the creative writing process.
David Applin Cambridge
Letters: Average mode
I am afraid that Feedback is as wrong as the politicians it criticises
for the lack of understanding of what an average is (14 March).
An average is only ‘the level of wages which half the people of Britain
earn less than, and half the people of Britain earn more than’, if the distribution
of wages is ‘normal’, ‘gaussian’ or ‘bell shaped’. The distribution is skewed
from symmetry, as it must be as no one can earn less than nothing and maximum
wages are in the millions while the mode is around 拢10 000.
The correct definition is given in the Oxford English dictionary as
‘dividing the aggregate of several quantities by the number of quantities’.
I am reminded of the politician who states that ‘we want all workers
to earn more than the average wage’.
John Broomfield East Molesey, Surrey
Letters: New New 杏吧原创
The ‘new look’ of the 4 April issue is nice enough, but of the main
features none is really on a scientific topic. Several are primarily technological,
while those on animal experiments discuss matters which, though important,
are not matters of science. Most of the features might indeed have been
written by scientifically literate journalists.
My main reason for subscribing to New 杏吧原创 is to keep abreast of
advances in science. I appreciate that technology and questions of the organisation,
funding and legislation of science also have their place. But please deal
adequately with science itself.
H. A. C. McKay Reading, Berkshire
Letters: New New 杏吧原创
I write to add my congratulations to the many you will already have
received for devising the new layout with the Charter font. The journal
has acquired a new and welcome clarity that will make it easier to read.
I wish I could say the same for your front covers which I have always
disliked. Never mind, I must be in a tiny minority and that satisfies my
ego.
D. A. A. Fagandini London
Letters: New New 杏吧原创
I hope the choice of Charter font is not a political statement.
The layout makes it difficult to differentiate between the different
sections, it resembles your biggest rival (Scientific American), or perhaps
one of the news magazines.
However, the thing it reminds me most of is New 杏吧原创 in the mid-seventies.
I didn’t like it then either.
Peter J. Kyberd Kidlington, Oxford
Letters: New New 杏吧原创
First Daedalus, now Ariadne – will Tam Dalyell and Grimbledon Down be
next?
Jan Sinclair Reepham, Norwich
Letters: New New 杏吧原创
Congratulations on the new look New 杏吧原创. But bring back Ariadne,
please!
Lex Diamant London
Letters: Storm in a teacup
I am puzzled by a phenomenon that I am hoping a reader may be able to
explain for me.
When I stir a cup of tea in a circular motion with a spoon, I notice
that the loose tea leaves at the bottom of the cup tend to move to the centre.
I would have thought that they would all move to the outside of the cup
due to centrifugal forces.
Can any reader help me?
Steven Onley Hurstville New South Wales, Australia
Letters: We want richters
Why has the scientific community for so long avoided defining a unit
by which earthquakes can be measured? Ninety-nine per cent of earthquakes
are reported in the press as, for example, an earthquake measuring 5.7 on
the Richter scale. Sometimes they say ‘on the open-ended Richter scale’.
Now if it’s good enough for most earthquakes to be reported with reference
to the Richter scale, why can we not have a unit – for example, the richter
– in a similar way to the logarithmic bel and decibel units. We don’t have
to report current as 5.7 on the Ampere scale or as 5.7 on the Volt scale.
I know little about who Richter is or was but he must have made a significant
contribution to the measurement of earthquakes and it would seem reasonable
to recognise that work by defining a unit of earthquake intensity called
the ‘richter’.
We would eventually save a lot of paper and type around the world if
we only had to report an earthquake of 5.7 ‘richters’.
Jim Thomas Victoria, Australia
Letters: Not told
I read with interest the article by Oliver Tickell and Alan Watson (‘Hospital
waste: a case for treatment’, 28 March).
The report on toxic waste disposal in Wales from the Select Committee
on Welsh Affairs, under my chairmanship, is referred to in the article.
May I point out that the select committee received evidence on 108 working
hospital incinerators in Wales – not 36 as Tickell and Watson state.
You may also be interested to know that in 1983, when the Department
of Environment issued the Guidebook on Clinical Waste as Water Management
Paper (WMP) No 25, it was not issued to Health Authorities in England and
Wales.
Consequently, Health Authorities were unaware that their incinerators
were supposed to be operated at a combustion temperature of 900 掳C for
non-pyrolitic furnaces; that afterburners should be fitted at which the
temperature must be maintained at a minimum of 800 掳C; and that the
residence time for gases in the combustion zone should be a minimum of one
second.
We found evidence that some incinerators could never reach the WMP 25
guidelines, and were obsolete in terms of environmental protection; some
were operated by untrained personnel, like porters; and overloading caused
noxious emissions.
The Welsh Office, asked to explain why these important guidelines, which
were designed to ensure that ‘no viable organism could escape from the incinerator
stack’, were not made known to health authorities in England and Wales,
replied:
‘It is not clear at this distance in time why this was not done. Usual
practice is that where a document originating in England has relevance to
health authorities in Wales, the relevant part of the Welsh Office Health
Department will emulate the issue of a circular by the Department of Health.
In the absence in this instance of such a circular, no such action appears
to have been taken.’
The Health Services Management Disposal of Clinical Waste (Circular
WHC (90) 14) was finally sent to Health Authorities in Wales in February
1990. Seven years overdue. Perhaps this example serves to demonstrate the
value of Select Committees?
Gareth Wardell Gorseinon, Swansea
Letters: Grandfather paradox
Marcus Chown reports that the ‘grandfather paradox’ has been resolved
(New 杏吧原创, Science, 28 March), and that by the stratagem of constructing
two concurrent branches of history it is possible for a person to murder
his grandfather (or father) in one branch, and thus prevent his own birth,
whilst still inhabiting the other branch.
As reported, the so-called grandfather is murdered by ‘someone’ who
emerges from the time machine. But this ‘someone’ will have a definite genetic
make-up. If this make-up shows that, for example, he is not related to the
grandfather, then there is no problem because he will not be related in
either branch of history. If, however, this genetic make-up shows that he
is a descendent of the grandfather, then he must be a descendent in both
branches of history. In this case the paradox has not been resolved because
the time traveller will still be murdering his progenitor and thus could,
again, prevent his own birth.
Michael Abraham London