§ Mr. Hugh Jenkinsasked the President of the Board of Trade whether, in view of the inaccuracy of existing methods and indices of aircraft measurement, he will institute a comparative investigation of Noise and Number Index, I.C.N., and Level of Noise Pollution, with a view to adopting the most satisfactory measurement or of evolving a new measurement capable of producing an accurate measurement of noise nuisance which will take into account the degree of pollution and the number of persons suffering annoyance.
§ Mr. Goronwy RobertsThere are very many indices of aircraft noise exposure used or proposed for different purposes, and research continues in this country and abroad to improve the way disturbance to the public can be measured. The Noise and Number Index (N.N.I.), unlike many others, is firmly based on sociological investigations; and if further research shows the need to modify it, this will be done.