328 
Mr. T. J. Bowlker on tlie Factors serving 
long and ^ inch in diameter, -was inserted ; the area of this 
tube was about J-- of the area of the ear-tube and it pro- 
jected ^ inch beyond the disk. The outer ~l\ inches of the 
tube was very loosely plugged with cotton-wool to suppress 
resonance. 
A series of experiments was made, In one set the ear 
tube without the perforated disk was used, in the other the 
tube was used with the disk attached. 
The tube was placed over the one ear, the other ear being 
free : the head faced the source of sound, and the apparent 
angular displacement of the image was noted. 
The results are given in the following Table : — 
Length of tube 
applied to 
the ear. 
Tube applied to the Eight ear.i Tube applied to the Left ear. 
Angular dis- Angular dis- 
placement placement 
without per- with per- 
forated disk, forated disk. 
Inches. 
4 1 12° I. 
6 24°1. 
9 45^1. 
12 60° 1. &50°r. 
32° r. 
28 c r. 
10° r. 
0° 
16° 1. 
15 
18 
21 
— a 
26 
30° 1. 
36° 1. 
60° 1. & 45° r. 
24° r. 
20° r. 
14° r. 
0° 
10=1. 
40° 1. 
Angular dis- Angular dis- 
placement i placement 
without per- j with per- 
forated disk. ! forated disk. 
16 3 r. 
22° r. 
32° r. 
34° r. 
45° r. & 50° 1. 
40° 1. 
26° 1. 
0°1. 
10° r. 
14 = r. 
30° r. 
18° r. 
12° 1. 
36° 1, 
30° 1. 
0° 
From this it is evident that intensity plays an important 
part in fixing the position of the sound-image when there is 
a great difference of intensity at the two ears. 
Another experiment which shows the part played by 
intensity, and yet how largely the apparent position is affected 
by phase at the same time, was tried. In this case the 
observer's left ear was towards the source of sound, the 
vertical plane through the ears passing through the source. 
Ear-tubes of various lengths were applied to the right ear, 
and the head was kept fixed, the angle of displacement being 
noted. 
The results are as follow :- ■ 
The source is considered zero — the point in front of the 
