VI 
PREFACE 
a melancholy fact that these papers were either never written or else 
were destroyed by their author; no trace of them can be found. The 
extent of the labors of which no adequate record remains may best be 
judged from the following extracts taken from the notes on the Paris 
lectures just mentioned. 
“ On the one hand we have the problem (Reverberation) which we 
have been discussing up to the present moment, and on the other 
the whole question of the transmission of sound from one room to 
another, through the walls, the doors, the ceiling and the floors; and 
the telephonic transmission, if I may so call it, through the length of 
the structure. It is five years.ago since this second problem was first 
attacked and though the research is certainly not complete, some 
ground has been covered. A quantitatively exact method has been 
established and the transmission of sound through about twenty 
different kinds of partitions has been determined. 
“ For example: Transmission of sound through four kinds of doors 
has been studied; two of oak, two of pine, one of each kind was 
paneled and was relatively thin and light ; one of each kind was very 
heavy, nearly four centimetres thick; through four kinds of windows, 
one of plate glass, one with common panes, one double with an air 
space of two centimetres between, one with small panes set in lead 
such as one sees in churches ; through brick walls with plaster on both 
sides; through walls of tile similarly plastered; through walls of a 
character not common in France and which we call gypsum block; 
through plaster on lath; through about ten different kinds of sound 
insulators, patented, and sold in quantities representing hundreds of 
thousands of dollars each year, yet practically without value, since 
one can easily converse through six thicknesses of these substances 
and talk in a low tone through three, while a single thickness is that 
ordinarily employed. The behavior of an air space has been studied, 
the effect of the thickness of this air space, and the result of filling 
the space with sand, saw-dust and asbestos. In spite of all this, the 
research is far from complete and many other forms of construction 
must be investigated before it will be possible to publish the results ; 
these determinations must be made with the greatest exactness as 
very important interests are involved. . . .