﻿of 
  the 
  Direction 
  of 
  Sounds. 
  311 
  

  

  sound 
  on 
  the 
  outside 
  and 
  were 
  struck 
  with 
  a 
  constant 
  force 
  

   by 
  a 
  soft 
  hammer 
  operated 
  by 
  a 
  lever 
  outside 
  the 
  box. 
  A 
  

   glass 
  funnel, 
  with 
  its 
  shank 
  protruding 
  through 
  the 
  side 
  of 
  

   the 
  box, 
  collected 
  the 
  sound 
  which 
  then 
  entered 
  the 
  slider 
  

   tube 
  by 
  a 
  rubber 
  tube 
  connected 
  to 
  the 
  shank 
  of 
  the 
  funnel 
  

   and 
  to 
  the 
  T-piece. 
  

  

  If 
  rubber 
  stoppers 
  were 
  inserted 
  in 
  the 
  orifices 
  of 
  the 
  

   tubes 
  at 
  the 
  ear-caps, 
  and 
  the 
  latter 
  placed 
  over 
  the 
  ears, 
  no 
  

   sound 
  from 
  the 
  fork 
  could 
  be 
  heard, 
  but 
  with 
  the 
  tubes 
  free 
  

   it 
  could 
  be 
  heard 
  clearly 
  and 
  the 
  intensity 
  was 
  sufficient 
  to 
  

   locate 
  its 
  direction 
  accurately. 
  I 
  found 
  this 
  arrangement 
  

   to 
  be 
  much 
  better 
  than 
  to 
  have 
  both 
  listener 
  and 
  the 
  fork 
  

   in 
  the 
  same 
  room, 
  for 
  two 
  reasons. 
  In 
  the 
  latter 
  case 
  

   the 
  sound 
  passing 
  through 
  the 
  outside 
  air 
  directly 
  to 
  the 
  

   listener 
  caused 
  confusion 
  with 
  the 
  sound 
  passing 
  through 
  

   the 
  apparatus, 
  when 
  decisions 
  were 
  made. 
  Also 
  the 
  listener 
  

   involuntarily 
  tried 
  to 
  guess 
  the 
  position 
  of 
  the 
  slider 
  

   independently 
  of 
  the 
  sound 
  heard, 
  even 
  though 
  a 
  large 
  

   screen 
  concealed 
  it 
  entirely 
  from 
  sight. 
  The 
  desire 
  of 
  the 
  

   listener 
  to 
  guess 
  the 
  position 
  of 
  the 
  slider 
  was 
  also 
  lessened 
  

   by 
  seating 
  him 
  so 
  that 
  the 
  line 
  through 
  his 
  ears 
  was 
  at 
  right 
  

   angles 
  to 
  the 
  sliding 
  tube. 
  

  

  Unmounted 
  Koenig 
  tuning-forks 
  were 
  used 
  as 
  sources, 
  

   and 
  by 
  sliding 
  the 
  T-piece 
  back 
  and 
  forth, 
  any 
  difference 
  of 
  

   phase 
  was 
  obtainable 
  at 
  the 
  two 
  ears. 
  In 
  the 
  series 
  of 
  

   observations 
  which 
  follow, 
  I 
  noted 
  the 
  apparent 
  direction 
  

   of 
  the 
  sound 
  and, 
  after 
  recording 
  it, 
  my 
  assistant, 
  Mr. 
  P. 
  

   B. 
  Evens, 
  who 
  managed 
  the 
  forks 
  and 
  slider, 
  told 
  me 
  the 
  

   position 
  of 
  the 
  latter 
  by 
  the 
  scale. 
  The 
  sequence 
  of 
  the 
  

   positions 
  was 
  quite 
  irregular 
  and 
  not 
  known 
  to 
  me 
  previously. 
  

   The 
  apparent 
  direction 
  of 
  the 
  sound 
  was 
  recorded 
  as: 
  middle, 
  

   when 
  the 
  sound 
  seemed 
  to 
  lie 
  in 
  the 
  medial 
  plane 
  of 
  the 
  

   head 
  ; 
  right 
  or 
  left 
  when 
  directly 
  from 
  either 
  side 
  ; 
  and 
  a 
  

   fourth, 
  half, 
  or 
  three-fourths 
  right 
  or 
  left 
  as 
  the 
  angle 
  

   increased 
  by 
  22 
  J° 
  from 
  the 
  middle 
  to 
  the 
  sides. 
  

  

  Figs. 
  2 
  to 
  11 
  (p. 
  312) 
  show 
  the 
  results 
  of 
  such 
  a 
  set 
  of 
  

   observations. 
  They 
  have 
  been 
  plotted 
  in 
  the 
  convenient 
  

   manner 
  adopted 
  by 
  Myers 
  and 
  Wilson. 
  The 
  abscissae 
  represent 
  

   the 
  position 
  of 
  the 
  T-piece 
  in 
  centimetres 
  and 
  the 
  ordinates 
  

   the 
  apparent 
  direction 
  of 
  the 
  sound, 
  above 
  the 
  axis 
  to 
  indicate 
  

   from 
  the 
  right, 
  and 
  below 
  it, 
  the 
  left. 
  The 
  points 
  plotted 
  are 
  

   not 
  means 
  of 
  several 
  readings 
  taken 
  for 
  the 
  same 
  position 
  of 
  

   the 
  slider, 
  but 
  separate 
  judgements. 
  The 
  dotted 
  lines 
  show 
  the 
  

   theoretical 
  positions 
  of 
  the 
  points. 
  

  

  Y2 
  

  

  