December 20, 1907] 



SCIENCE 



879 



debted for permission to publish the present 

 description.^ 



Tlie room is located on the top story of the 

 laboratory building devoted to physiology. 

 This floor of the building is little used, except 

 for the sound room, and there are, conse- 

 quently, few footsteps and other noises in tha 

 immediate neighborhood of the room. The 

 location of the room at a distance from the 

 street prevents to some extent the transmission 

 of vibrations and jars of the street traffic. 



A vertical section of the room from north to 

 south is given in the accompanying figure. It 

 will be seen that in the construction a small 

 room has been formed to the south of the 

 sound room. The ceiling of the small room 

 is the roof of the building. The roof has 

 been cut to form a window which admits light 

 and air. The small room has been con- 

 structed with walls nearly as sound-proof as 

 the larger room, and for some work may be 

 used as an additional place for sound experi- 



FiG. 1 



Moreover, the room is an inside one, sepa- 

 rated from the building walls by other rooms 

 or a corridor, although in its construction, as 

 will be noted below, provision is made for 

 thorough ventilation and the entrance of sun- 

 light. The other rooms of the laboratory on 

 the same floor are comparatively little used, 

 and by surrounding the sound room they help 

 to isolate it. 



' At the International Physiological Congress, 

 Heidelberg, August, 1907, Professor Zwaarde- 

 maker read a description of the room and showed 

 lantern slides of the plans of construction. Later, 

 the writer had an opportunity of examining the 

 room in the laboratory at Utrecht. A full de- 

 scription of the construction is to be published in 

 the Zeitschrift f. Ohrenheilkunde. The proof of 

 this article was in the writer's hands at the time 

 of writing the present account. 



ments. When closed, it also serves to act as 

 a dead air space between the larger room and 

 the building wall and roof. 



The inside measurements of the sound room 

 are as follows: Length, 228 em.; width, 220 

 cm.; height, 228 cm. 



The sides of the room are built of six layers. 

 From the inside outwards the layers are as 

 follow: (1) Tricliopiese, about 5 cm. thick. 

 This is a felt-like material made of horse hair, 

 and from experiments it has been found to 

 have very low coefiicients of conduction and 

 reflection of sound. This layer is covered with 

 a net on the inner side (to keep the hair from 

 falling) and then fastened with nails to the 

 second layer, which is more stable. (2) Porous 

 stone, 7.5 cm. thick. This part of the wall 

 does not rest directly on the floor, but is iso- 

 lated from the floor by a layer of sheet lead. 



