Board Told Of Noise Tests Near Airport

Press, Volume XCVIII, Issue 28869, 14 April 1959, Page 10

Board Told Of Noise Tests Near Airport

The noise of aircraft flying in and out of Christchurch Airport could not be considered separately, but only in relation to other noises in the area, an acoustics consultant told the Town and Country Planning Appeal Board yesterday. He was giving evidence during the hearing of appeals by 11 landowners against a ban by the Christchurch City Council on subdivision of land close to the airport. A total of 528 sections is involved. The appeal board comprises Messis F. F. Reid, S.M., (chairman), G. Tremain (Municipal Association), W. F. McArthur (Counties Association) and C. H. Taylor (Government member). Making the appeals are Lionel Denis Cotterill and William John McMillan, trustees of trie C. A. L. Boag Trust (Mr E. E. England), Lance Selwyn Jewell, Gordon William Fairweather, and Arthur William Johnson (Mr A. C. Perry); Raymond Augustus Witbrock, Leonard Arthur Cox, and Lillian Cox (Mr E. P. Wills); Charles Richardson Witty and Rita Corfield (Mr G. C. P. Beadel); and Avice Hill and Ethel Ellen Perry Francis (Mr P. H. T. Alpers). • Opposing the appeals is the Christchurch City Council, represented by Mr J. G. Leggat. with him Mr A. Hearn. The hearing began last Thursday. It is expected to finish today. Measurements Idris Julian Hugh Kelly, an acoustics consultant, sad that using a sound-level-meter, he measured noise levels at and about the airport. Some readings were taken of specific aircraft noises. “However, aircraft noises cannot be considered separately, but must be considered only in relation to other noises more or less constantly present,” he said. Kelly said traffic density on Memorial avenue was of great importance because it was the chief contributor to the background noise in the area where the blocks of land would be situated. Noise from day-time traffic on the road masked to a large degree the average noise from operations at the airport, he said. Quoting a United States handbook of acoustic noise control. Kelly said that for a given noise, annoyance would increase with loudness and intensity, but it was not possible to measure a “general threshold of annoyance.” “Generally it has been found overseas that the piston type of aircraft has a higher nuisance value because of the low-fre-quency beating or throbbing. “Jets and turbo-props, generally speaking, have an equally high noise level, but the noise is of a more even nature, without any sharp peaks,” he said. Kelly said the attitude of the listener to a noise was of the utmost importance. “Purchasers of the proposed residental section would knowingly come into the vicinity of the airport with all its noises.” He said it was quite different from aircraft noises being thrust upon people who had lived in the area for years. None of his noise level readings had been taken indoors, but walls in an ordinary home reduced noise levels by 10 to 20 decibles. Furniture in a house and buildings, hedges and shrubs, outside, would further lessen noise. At night aircraft noises would seem louder, but would be less frequent and people would adapt themselves as they would to the noise of trains passing through residential areas, he said. Reducing the noise of routine aircraft testing and servicing was not an insurmountable problem. Successful test pits and mufflers had been developed in the United Kingdom and United States for ground test “run-ups” with the engine still in the airframe. “Noise levels generally indicated for this area in the future can readily be found in other areas of heavy traffic density in and about the city; both by day and night,” he said.

Cross-examined by Mr A. Hearn, for the City Council, Kelly said the area of greatest noise was on the runways and this applied also to the subsidiary runway. People had become accustomed to the noise of DC3 aircraft using the airport and the noise of Viscounts or jets produced no greater psychological effect, he said. Esmond Allan Gibson, a Wellington aeronautical expert, said there had been established a standard known as a “calculated acceptable risk” and this was used in airport planning. This “calculated acceptable risk” applied to people on the ground not to people in an aircraft, he said. Gibson said the risk of a crash in a runway approach fan was “about one in every four million aircraft movements.” “There is more risk of a man being kicked to death by a pony at an agricultural show than being killed by an aircraft crash in an approach fan,” he said. Mr P. H. T. Alpers said the estates he represented were about 17 acres. “Both have held this land since 1939 and 1934 respectively. Since July, 1953, they have been pursuing, through their solicitors, plans for subdivision. “They are not late-comers trying to crash in on the proximity of the airport and are the most remote from the airport.” Mr Alpers said it should be assumed that the City Council would do all it could to reduce noise “if only for the airport population and others close at hand.” “House builders going into the area will seek to reduce noise by using certain furniture and linings,” he said. Mr Alpers said that the situation at Harewood was quite different from that around certain airports in England and the United States. The hearing will be continued today.