As more people live closer together, and as they use machines
to produce leisure, they find that their leisure, and even their working hours,
become spoilt by a by- product of their machines--namely, noise. Noise is
nowadays in the news; it has acquired political status, and public opinions are
demanding, more and more insistently, that something must be done about
it. 46) To control noise is to demand much self-discipline
(annoyance arises often from lack of common courtesy) a sense of proportion
(there is usually a conflict of interest if a noise is to be stopped), the
expenditure of money (and it is far more economical to do this early rather than
late), and, finally, technical knowledge. Technical
difficulties often arise from the subjective-objective nature of the problem.
You can define the excessive speed of a motor-car in terms of a pointer reading
on a speedometer. But can you define excessive noise in the same way 47) You
find that with any existing simple "noise-meter", vehicles which are judged to
be equally noisy may show considerable difference on the meter.
Though the ideal cure for noise is to stop it at its source, this may in
many cases be impossible. The next remedy is to absorb it on the way to the
ear. 48) Domestic noises may perhaps be controlled by
forethought and courtesy, and industrial noises by good planning and technical
improvement. But if we are going to allow fast motor-cycles and heavy diesel
lorries to pass continuously through residential and business districts, the
community must decide on the control it needs to exercise, for in the long run
it has got to pay for it. 49) And if a nation is to take part in modern air
trans port, it must enter into international agreements on the noise control
measures it will impose at its airports-and here the cost of any real control is
to be measured in millions of dollars. Jet engines may be modified to reduce
their noise level, or insulation from air traffic noise may be provided by the
purchase of land around airports or the insulation of buildings. 50) One
estimate is that ＄5.7 billion would be required to equip all existing jet
engines with noise control devices; however,, considering the current state of
the art, even taking this step will not reduce noise levels at all points to
acceptable values. Some combination of methods is probably necessary.