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Shoreditch Town Hall on October l6th this year, when the inventor addressed' the
audience together with the Chief Public Health Inspector and myself and described
the progress, the research and investigations which had "been made to
date, together with an explanation of the function and construction of the
Noise Converter'
This meeting was followed by a practical demonstration of the noise
converter in Shoreditch, Octave band analysis together with a strike rate of
the hammers was carried out both on the 'naked' hammer, and the hammer equipped
with the noise converter. At the same time a ballot was taken from those
present and information was collated therefrom in order to be able to assess
the success or otherwise of the noise converter, as judged by the ear alone.
The octave band, analysis proved beyond doubt, that a dramatic reduction
had been achieved in the 'speech interference levels' of the sounds which go to
make up the noise, and the subjective tests proved almost unanimous in the
acceptance of the noise converter.
It is with the greatest of pleasure that I am able to report that all
the principal manufacturers (10) have now adopted the noise converter to their
breakers and by the end of the year orders have been placed in the London Area
alone of upwards of 1100 for these noise converters.
At the request of manufacturers, your Chief Public Health Inspector
has visited the works of three firms where hammers and compressors are made,to
advise them as to the best way of ridding their hammers of unnecessary and
irritating noise. In connection with this, visits have been made to Glasgow,
Gloucester and Bristol and arrangements are already being made for conferences
and demonstrations to be held both in Gloucester and Bristol early in the
coming year.
It also is interesting to note that several local authorities have
followed Shoreditch's example of inserting a clause in contracts to the effect
that no pneumatic road breaker shall be used within the Borough unless equipped
with an effective silencing arrangement, and also that the hours of operation
are limited except in cases of emergency. Many local authorities are following
the work being done by Shoreditch with interest.
The main object of research and investigation has not as yet been
achieved, but progress has been so marked during the year that it is confidently
hoped that in the near future the Department will be able to recommend a
standard of noise from pneumatic road breakers both acceptable to all the
makers and users of pneumatic hammers and to the local authorities.
It is with gratitude one must acknowledge the invaluable assistance
afforded to the department by both the Building Research Station and the
Scientific Branch of the London County Council and it is most encouraging to
know that the full blessing of both these establishments'has been given to the
policy of converting the annoying and high frequency sounds (those responsible
for annoyance and irritation) into the more acceptable low frequency, sounds,
and confirming, that it is upon 'Speech interferences levels' of sound that
standards should be based, as opposed to the overall decibel measurement of
noise.
One can never assess a Noise Nuisance by overall decibel measurements
alone. It is essential to employ octave band analysis if one is to be able to
discover and either eliminate or reduce those mid-frequency sounds, which are
usually responsible for noise nuisance.