SECTIONAL TRANSACTIONS.—G. 433 
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Dr. W. Rosenuarn, #.R.S.—Metals and Alloys in relation to Engineering 
Progress. 
Prof. F. C. Lea.—The Effect of Temperature on some of the Physical 
Properties of Metals. 
The creep or flow of metals and other materials under stress at ordinary and high 
temperatures is a well-known phenomenon, The arts of drawing and forging metals 
have been long practised. Lead flows easily at ordinary temperatures, but at the 
temperature of liquid air resists considerable stresses. The quantitative determination 
of creep under stress and its importance in industry is a modern development. Some 
methods of determining creep under direct, torsional and repeated stresses. Positive 
and negative creep. The ‘ Limiting Creep Stress.’ Inter-crystalline effects of stress 
and temperature and the embrittling effects of stress and temperature. 
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Prof. E. Witson.—On the Origin of Tron in Corrosion. Products due to 
London Atmosphere. 
The corrosion products on metal exposed to the atmosphere of London are known 
to contain iron which is wind-borne. Analysis of the soot collected from chimneys 
in the neighbourhood of certain conductors exposed on the roof of King’s College 
showed an appreciable percentage of ferrous sulphide but no metalliciron. Determina- 
tions of the magnetic susceptibility of the soot and corrosion products have led to 
the conclusion that the iron present in the corrosion is due to the mineral iron pyrites 
originally in the coal. 
Friday, September 25. 
Mr. Nort Asuprivcr.—Acoustical Problems of Broadcasting Studios. 
The first section of the paper deals with the development of studio acoustics, 
_ beginning with the conditions existing when broadcasting first became a public 
service in 1922. At first the study of acoustical conditions in studios was hampered 
_ by severe distortion in both the transmitting and receiving apparatus. The micro- 
_ phone and the loud-speaker were probably the most imperfect units, and introduced 
_ distortion to such an extent that it is not remarkable that the scientific treatment of 
studios did not receive immediate serious consideration. The earliest microphones 
_ were originally intended for the reproduction of commercial speech, with the result 
that little or no response was given to frequencies below 250 p.p.s. or above about 
3,000 p.p.s. However, it was at once realised that when a broadcast was carried 
out from an ordinary room where a large proportion of the wall and ceiling surfaces 
consisted of hard plaster, the reverberation period was too great. The imperfections 
of the electrical apparatus accentuated this effect, owing to the existence of electrical 
resonances, and in the case of the microphones and loud-speakers, mechanical 
resonances in addition. For these reasons there was a tendency to go to extremes, 
and all early studios were very heavily ‘damped’ with sound absorbing material. 
_ With the rapid development of microphones and other apparatus, the lack of normal 
reverberation became obvious and objectionable. 
Since it was considered that the amount of reverberation allowable for different 
types of musical programme must be variable, and because in many cases the same 
‘Studio was of necessity used for widely different purposes, the difficulty was at first 
overcome by the introduction of ‘ artificial echo’; a device by which the apparent 
verberation time of a studio can be increased to an adjustable degree by a com- 
bination of mechanical and electrical means. It became evident, however, some 
years ago, that this method did not give results comparable to those obtained when 
using a studio which possessed good natural acoustic properties. Consequently, the 
roblem of designing studios which themselves possessed such properties had to be 
faced. 
_ The next section of the paper deals with the conditions which obtain both from the 
scientific and practical points of view. ‘There is the difficulty that it is impossible to 
forecast accurately the conditions under which the music will be reproduced in the 
1931 FF 
