350 SECTIONAL TRANSACTIONS.—G. 
is not wholly rigorous. Nevertheless there are ways of overcoming the 
more serious of the difficulties, and objective meters have been used suc- 
cessfully for measuring moderate and loud sounds of very varied char- 
acter. ‘The meters are often more reliable than individual observers in 
assessing the average judgment. The difficulties are minimised and the 
apparatus is simplified if the sounds concerned are of similar character 
’ and of the same order of loudness. A test within these limits will determine 
whether noise of a given kind or from a given type of machine exceeds the 
loudness specified as the maximum permissible, and appears to be within 
the scope of objective noise meters, subject possibly—in present conditions 
—to preliminary test and adjustment of the meter for the type of noise 
concerned. 
Mr. E. O. TurNER.—Motor horns—effective and offensive (11.50). 
It is endeavoured to examine by what means motor horns may be rendered 
less offensive to road users without reducing their effectiveness. 
The chief types of horns which have been in wide use are reviewed. 
Non-electric types are first mentioned. Electric horns and oscillograms of 
their sounds are then considered. ‘They are shown to be most effective 
when resonance is obtained between the fundamental or a harmonic of the 
sound source (generally a vibrating diaphragm) and an additional vibrator, 
resonance chamber, or air column. 
A tentative conclusion is drawn that the least offensive signal should be 
strictly periodic and complex in wave shape, avoiding both pure tone on 
the one hand and an undue number and amplitude of non-harmonic over- 
tones on the other.. 
The advantage gained by care in the choice of position and method of 
mounting on the car is referred to, and other means of reducing offensive- 
ness are considered : the use of staccato signals and the elimination of horns 
having comparatively long starting and stopping periods, and optional soft 
and loud signals for town and country use. 
Reference is made to regulations and by-laws regarding warning signals 
in force in other countries, and to other traffic regulations likely to affect the 
use of horns. 
AFTERNOON. 
Excursion to Bridge of Dee for demonstration of noise reduction. 
Tuesday, September 11. 
Prof. Sir James B. HENDERSON.—Development of invention as a stimulus to 
economic recovery (10.0). 
The history of industrial progress shows that it has been due in large 
measure to a combination of inventors with scientific vision, with promoters 
having capital and economic vision. Since the war this type of combination 
has been greatly reduced, and the only type of invention which has been in 
demand has been one which will further reduce employment by saving 
costs of production. 
Industrial research, which has been greatly stimulated, is looking after 
the industry of ten or more years ahead, whereas quick recovery is to be 
found in the development of inventions lying dormant in our patent records. 
This important branch of our industry requires urgent stimulus. At 
