424 
DR. W. S. TUCKER AND MR. E. T. PARIS ON 
somewhat differently owing to their positions in the room. That the sensation of 
suppression of a note is not obvious is no doubt due in some measure to the distance 
between the two ears. 
Experiments on Refection. —A large sheet of uralite was set up out of doors with its 
plane vertical. An electrically driven tuning-fork served as the source of sound, and was 
mounted opposite the centre of the uralite at a distance of 30 feet from. it. The sound 
was thus incident normal to the surface and capable of producing stationary waves. 
The curve connecting deflection of the galvanometer and distance from the reflector 
is shown in fig. 17 and indicates clearly the position of nodes and antinodes. The 
Fig. 17. 
distance between the nodes agrees well with that obtained front a wave-length of 43 
inches, except for that nearest to the mirror. All observations taken with various surfaces 
showed that the first antinode was nearer the mirror surface than was anticipated, 
which may be due to the lack of rigidity of the reflecting surface. The effect at the 
reflecting surface varies very largely with itsjnature; thus, when a wooden door is employed, 
the effect is greatest at the centre of the door midway between the four panels and least 
at the panels where there is minimum rigidity. 
The reflecting qualities of different surfaces for sound can thus be compared. It is 
also obviously a simple matter to test the transmitting properties of various media— 
taking care to confine the sound transmitted to the material under test. 
Experiments with Trumpets. —A trumpet has certain magnifying and directional pro¬ 
perties, which depend on its dimensions and the wave-length of the sound employed; 
and another important factor in magnification is the material of which the trumpet is 
made. In the experiments described below the tru m pet employed was conical, having 
a mouth 18 inches in diameter, a throat J inch in diameter and a slant side of 
25| inches. It was made of 1-inch wood in 16 segments. 
The trumpet was mounted on a stand with its axis horizontal, and was capable of 
rotating about a vertical axis, its bearing being indicated by a pointer travelling over 
a horizontal circle graduated in degrees. The narrow end of the trumpet received the 
