A sound source in a room usually produces a diffuse (i.e. non-directional) sound field. The sound pressure level of this field depends on the energy emitted by the source and the amount of absorption by the surfaces of the room. Most of this absorbed energy is lost as heat but a small part is transmitted through the walls or floor and radiated into adjoining rooms causing another diffuse sound field. Ihsically it is the difference between these two sound ficlds which is the airborne sound insulation of a wall or floor. H. J. Purkis
ALVAR LIDDELL : And now for a report about a recent Conference. In London last week the Institution of Structural Engineers held a 50th Anniversary Conference. Sir Alfred Pugsley, Professor of Civil Engineering in the University of Bristol, and until recently, President of the Institution, was at the meeting and tonight he tells us about some current developments in this important field of engineering.
PUBLIC opinion seems to have been educated to the urgency of the complete reconstruction of our arterial highways system, appreciating that the alternative is the effects of “arterio-sclerosis” in our industries, yet it is apparent that it still needs further demonstration of the even greater need for rapid transportation through and around those essential “organs of the national body,” the urban areas. Urban routes designed originally by chance, or the “rolling English drunkard,” have been improved in the past from the unpaved channels, fit only for cattle, to roads suitable in most cases for the horse drawn cart, and from that stage with few exceptions merely adapted to the needs of successive generations. Lieut.-Colonel G. W. Kirkland
PROFESSOR H. J. COWAN was interested to note the comment by Mr. J. Bak on the effect of concrete encasement on the torsional resistance of steel sections and Mr. Terrington’s reply.