450 Tufts — Transmission of Sound through Solid Walls. 

 a T-tube at g. One arm of the T-tube is provided with an ear 



piece, 



A, which can be inserted in the ear of the observer. 



The iron pipes, a and b, were inserted in openings in an eight- 

 inch brick wall, and the observer could thus be placed in a 



room adjoining the one in which the sound was produced. 

 The materials, the transmission of sound through which was 

 to be investigated, were cut into discs about 10*5 cm in diameter, 

 and clamped in the unions at i and^', respectively. The appli- 

 cation of a little cement rendered the junction air tight. 



Yarious sources of sound were used in these experiments, 



