AIRCRAFT (NOISE) (Hansard, 31 October 1946)

§ Mr. Symonds (Cambridge)
In drawing the attention of the House to the question of reducing the noise of aircraft, I am raising a matter which particularly affects my own constituency. But Questions on the Order Paper during this past year have shown quite clearly that this is a matter affecting many other constituencies in many other parts of the country. In 916 all quarters there is a demand that the noise of aircraft, particularly those engaged in night flying training, should be reduced. 'In East Anglia, in the flat lands there, we have a network of aerodromes, and in my own constituency, we have an elementary flying training school situated close to a built-up area. However, I have no wish to treat this as a local matter. I want to raise the question as a general one, which is having its influence on the attitude of the public in general towards aviation.
I approach the subject as a layman. I can claim no technical knowledge of the problems involved. Perhaps that is a good thing in a sense, because it is easy to get bogged in technicalities. I wish to deal with it solely as a matter of public policy. No one denies that we owed our survival in the recent war very largely to our power in the air, to our aircraft; never forgetting, of course, the men who flew them, the men who kept them in the air and the men who built them. In the war, everything had to be subordinated to speed, power and efficiency, and the public put up with the noise quite cheerfully, because they realised it was all in a good cause. But the situation today is not quite the same. We have won the war; Service flying as such is being considerably reduced, and we are attempting to build up a system of civil aviation. I want to see that use of civil aviation increased; I think this country can have a great future in the air, but it can only have that future if aviation has the support of the citizens of this country. At the moment I fear the average man in the street has a great prejudice against the aircraft which fly over his head. At the moment the average man tends to regard the aeroplane as a curse rather than a blessing, because inevitably it disturbs his peace and quiet. As I say he put up with noise cheerfully during the war, but the war being over, he does look forward to enjoying a good night's rest.
Turning to the question of the noise itself, to me it seems a very curious situation in which this can happen: It is a punishable offence for a man to drive a 10 horsepower car past my door without a silencer, but it is perfectly legal, and is not a punishable offence for that same man, if I happen to live on the edge of an airfield, to take off just over my roof top in an aircraft trainer of perhaps 100 horsepower, or a medium plane of 1,000 917 horsepower or a multi-engined plane of 10,000 horsepower without any silencer at all. If the car has to be silenced, why not the plane? Here, aircraft technicians come in and raise objections, and say that such a thing is quite impossible. We are told that a silencer reduces the power of an engine; we are told that it is at the very moment of taking off that an aircraft needs most power, and, therefore, if we silence the engine the result would be, either to make the take off more dangerous because there would be less resultant power, or else, because of lightening the load, the whole business would become uneconomical.
There is also now the further complication of the use of jet aircraft. We are reminded also that the noise involved does not come merely from the engine, but from the plane itself and the propeller. Without understanding all the technicalities involved, I do appreciate that these are difficulties. But I would suggest that our wartime experience of achieving the apparently impossible should give us hope that even these technical problems can be solved if they are tackled drastically.
I should like my hon. Friend who is to reply to say what is being done and what has been done in research into this problem. I found it very difficult indeed to obtain information of any work going on. I have heard that there was a period of experiment in the late 'twenties and early 'thirties. I have heard of experiments at Heston with a German Klemm, using a long exhaust pipe and a Burgess silencer. I was also told that in the early 'thirties, at the Hendon air display, a Fairey 3F was tried out, which was very impressive. I believe that before the war the Air Ministry made certain experiments with training planes—for instance, fitting exhaust pipes pointing upwards over the top of the aircraft instead of downwards, so that the plane itself acted as a sort of buffer between the noise and the ground. Cambridge University Air Squadron had a Tiger Moth on which they fitted some sort of exhaust pipe. I drew the attention of the Air Ministry to this in April this year and I received eventually a letter in these terms: Flying Training Command have been carrying out comparative trials over their own headquarters, sending up Tiger Moths with and without exhaust tail pipes. Unfortunately, however, they have reached the conclusion that there is no appreciable diminution of the noise, whether or not the aircraft is fitted with 918 these pipes, and they have gone so far as to say that the ear simply cannot distinguish the difference. They have, therefore, decided not to pursue the matter, bearing in mind the extra cost which would be involved to no purpose. In other words, after what was perhaps a limited kind of experiment they simply washed their hands of the whole problem and gave it up. Aeroplanes were sent up with and without exhaust pipes. The listeners on the ground said to one another, "Can you hear any difference?" "No." "Let's go and have a drink." And that was the end of it. I do not think that that indicates that the problem has been tackled really seriously.
I should like to know what kind of research is going on at the moment. I rather suspect that research into this problem is really the Cinderella of aeronautical research, and that the concentration is on speed and power, with no thought for the civilian on the ground suffering from the noise. But the feeling of the general public must be taken into account. There is, at the moment, still a feeling in many people's minds that civil aviation is the rich man's hobby which the ordinary man in the street cannot afford; and so we get the feeling that the airborne plutocrat gaily flies into the air, ignoring the discomfort of the less affluent and grounded man in the street. I do not think this is fully true, or need be true, particularly when we remember the prewar flying clubs, such as the Civil Aviation Service Corps, which, I was told, consisted very largely of London busmen and motor mechanics, and so on, and did invaluable work in the days just before the war, in producing the very men who saved our bacon in 1940.
I should like to see aircraft, and civil aircraft, used much more by the ordinary people of this country, but unless and until their prejudice against this form of travel is overcome, we shall not see that development. The people directly concerned with the industry are very much involved in this problem. The Aerodrome Owners' Association, for instance, which represents all commercial and municipal airports, I understand, has made frequent appeals to the Air Ministry that this problem should be tackled. The general public dislike having airports inside towns and close to centres of population, but from the airport owners' point of view, they would naturally like to be close in to the towns to prevent the 919 present waste of time spent travelling from the centre of a town or city to an airport. Logically, for quick travelling, the air terminals should be in the centres of population, but unless this noise problem is tackled, the general public will object to that.
How should research into this matter be undertaken, and by whom? We might say that after a certain date all aircraft would be grounded unless they achieved a certain standard of silencing, but obviously that is impossible. Individuals cannot afford it, and groups of people cannot afford it. No firm could take on a job of this kind; only the Government, with their powers of setting research going, could do it. It will, I think, involve large scale research, but I am not put off by that consideration. During the war we wanted a floating harbour, and eventually we were given the Mulberry. Similarly, a real drive into this problem could produce a more silent plane. I am not asking for the moon; I do not expect a completely silent plane. That may well be impossible, but 1 do think that if our researchers were given their head, they could produce a much more silent plane than we have now, with the result that we might eventually be able to pass a law saying that after a certain date, all types of aircraft produced would have to comply with certain standards of silencing and that all existing types would have to be modified according to those standards within a period of years.
One word about the international aspect of this matter. It may be objected that if we alone concentrated upon this problem, particularly if it involved any reduction in power through using silencers, it might be a handicap to us in the world aspect of civil aviation. We might find ourselves handicapped as against other countries who are more prepared than ourselves to put up with noise. I do not necessarily accept that if this problem is really tackled thoroughly, it will involve a reduction of power; it may be so or it may not. I do not think it is possible to answer that question yet. Nor do I say that it necessarily follows that other countries are completely indifferent to noise. I would like to quote from a paper called "American Aviation," of 1st August this year. Under the heading: "Call for research to reduce aircraft noise," it says: 920 Mr. T. P. Wright, C.A.A. administrator, has invited the National Advisory Committee on Aeronautics Air Transport Association and the Aircraft Industries Association to participate in a joint attack on the problem of aircraft noise. In his call for an integrated research programme he pointed to a rising tide of public complaint 'which threatens to undermine aviation progress.' That is the situation in America. I suggest that that is the situation here now— a rising tide of public complaint which threatens to undermine aviation progress. Therefore, I ask the hon. Gentleman to say that the Government will tackle this problem drastically as only the Government can. We want this country to be air-minded, but unless and until the hostility and prejudice of the man in the street are overcome, we cannot expect him to welcome the extension and development of this form of travel.

§ Mr. Keeling (Twickenham)
I am all for reducing noise, but I remember that when I was at the Air Ministry a year or so before the war, I introduced a deputation from the Noise Abatement League on this subject, and we were told that the main cause of aircraft noise was the propellers, which it was impossible to silence, and that the additional noise caused by the engines made very little difference. As the noise of the propellers is greater than the noise of the engines a reduction in engine noise would have very little effect on the whole volume of noise. Two pigs squealing under a gate do not make twice as much noise as one pig, but only a small percentage more. I should be interested to hear from the Minister whether this is still the case or whether there has been further research which gives hope of reducing the noise made by aircraft.

§ Mr. Stubbs (Cambridgeshire)
I wish to support the case put forward by the hon. Member for Cambridge (Mr. Symonds). For my part, I do not think that any airports should be permitted near a built-up area. One airport in my constituency is close to a built-up area, where a large number of railwaymen and other workers are employed. When the aircraft leave the airport, the noise they make when they roar over the roofs means that the workers cannot get their proper rest, and because of that, they are not fit for their work. I would call atten- 921 tion also to the effect on nervous women and children, and on those who are ill, when these aircraft roar overhead. It happens just as much on a Sunday as on any other day and something should be done about it, with particular regard to the question of the building of airports close to built-up areas. Local authorities feel that the airport should be stationed at least ten miles from the town. I have been fined for riding a motor-bicycle with a noisy silencer, and if that can be applied to a motor bicycle, why not to aircraft? The suggestion seems to be that in a university town one must not disturb the undergraduates at their studies, but that when it comes to the case of the workers, it is a different thing. I hope we shall hear from the Minister that it is the Government's intention to attend to this matter.

§ The Joint Parliamentary Secretary to the Ministry of Supply (Mr. Woodburn)
I think the House will have been interested in this rather novel question. The prevalence of noise is a matter that has disturbed the community very much in the past, but this time we are dealing with a new noise, a noise that is different. We live in a world of noise, and it is curious that while it is railway workers who are objecting to the noise of aircraft, they themselves do not hear the engines, the whistles, and the other railway noises and claim that they work quite unheeding of them. It is a physical thing, I think, this capacity for ignoring noises to which one has grown accustomed. The first time you listen to a gramophone record with a crack in it it is a terrible scraping sound which you feel you are unable to stand, but after two or three repetitions you get used to it. Then there are people who turn on a wireless set, and then start a conversation to drown the wireless, or who talk with the wireless going on, as a background. The noise that is objected to is the new noise, the one we do not like, and the one we are not expecting to hear. I sympathise very much with the hon. Member who raised this matter and with the railway workers. I am certain indeed that the people in East Anglia will be very glad if they never hear the noise of aircraft again, after the very trying experiences they had during the war. Noise has a psychological effect on people who have been subjected to heavy aeroplane raids, which one does not find to the same 922 extent in an area where an aircraft is a comparative novelty, an object of the same interest to children as railway engines used to be.
This problem has been under continual observation, but I regret I cannot give a satisfactory answer to the plea put up by my hon. Friends. They used the analogy of a car on the ground, but the car on the ground gives its noise from the exhaust, and if the main noise of an aeroplane came from the exhaust, it might be possible, by the experiments to which the hon. Member referred, to eliminate it. Experiments have been made to take the exhaust up over the wing, and lift it upwards and so direct it away from the ground, but this has only eliminated the lesser not the greater noise. That is the reason why experiments in eliminating the noise of exhausts have had no effect whatever in lessening the general disturbance, because in aircraft the main noise comes from the tip of the propeller blade which is breaking up the air. One cannot have propellers that give safe speeds without having the sound waves which cause this considerable disturbance. The question is: Can the noise of propellers be eliminated? So far, science has found no way of eliminating the noise of propeller blades. In regard to civil aircraft, a law has been laid down limiting the speed of propellers to something under 700 feet per second in the cruising position, with a view to lessening the noise. That has been done more with a view to make travel in aircraft comfortable, than from the point of view of people living in the vicinity of the noise.
The noise of an aircraft rising from the ground is much greater than it is in the air for the simple reason that the engines are "revved up" and "boosted" very considerably in order to lift the aircraft off the ground. Some experiments have been carried out to see whether the noise that does come from the propellers, and in the case of the jet aircraft, from the jet, can be diverted away from houses by directing it upwards. In the case of jet engines on test beds, we have been making experiments to see whether we cannot divert the noise upwards away from the houses, so that the noise will be less disturbing. I cannot claim that they have been terribly successful so far, but there is a considerable prospect, I think, of development along that line. 923 With regard to aircraft starting up on an airfield and "revving up" their engines, this does cause a terrible noise, and the only way I have suggested in which the noise might be lessened in the case of the aircraft "revving up" is by putting them in such a position that there are baffle walls to prevent the noise waves from reaching the public of the surrounding area with the same intensity as they would from an open field. In some such way it might be possible to arrange "revving up" so that a silencer is imposed from outside, and not from the inside of the aircraft. Experiments will be carried out in regard to that. Professor Cave-Browne-Cave has been doing a lot of experiment in measurement of noise, and something may result from his researches which will help to solve the problem. The main hope is in the diversion, rather than in the suppression of noise. The first element in aircraft must be safety and, as the hon. Member has said, we cannot subordinate safety to silence. The main danger in aircraft is during the take-off. At that moment it is necessary to have the maximum of power, and we cannot take the risk of suppressing any power, until such time as there is a sufficient margin.
We come now to the jet. The noise of the jet is a different kind of noise—a whine—and there is a possibility that we might raise the frequency of the whine to such an extent that people would not hear it. But that introduces the danger 924 of physical repercussions more serious than just a noise in the head. It might set up vibrations of which one would be unconscious at the time. It has not always been possible to eliminate noise. It is a hundred years now since the railways were developed and nobody has found a way of silencing them, and it may be that we shall get used to the aeroplane noise, as we have got used to that of the railway. I assure both my hon. Friends and the hon. Gentlemen opposite, that experiments are going ahead as hard as we can, but science knows no general way in which the noise can be suppressed. As to the calculation made by the hon. Gentleman opposite in regard to the multiplication of noises I think it is probably true that if you put one noise on top of another noise—

§ Mr. Keeling
But cannot you measure noise?

§ Mr. Woodburn
Professor Cave-Browne-Cave is trying to measure noise and ascertain the direction and radiation of noise and it might be that by finding what direction noise takes, we should be more successful than we have been in trying to eliminate the noise itself. It may be that noise upon noise does not multiply noise. It may indeed be that it will be possible to produce a musical noise which will be quite pleasant to hear.