﻿of 
  the 
  Direction 
  of 
  Sounds. 
  

   Fig. 
  9. 
  {n 
  = 
  640). 
  

  

  T 
  

  

  313 
  

  

  Fig. 
  10. 
  (w 
  = 
  768). 
  

  

  If 
  the 
  phase 
  does 
  influence 
  the 
  location 
  of 
  the 
  sound 
  then 
  

   no 
  difference 
  of 
  phase 
  or 
  a 
  difference 
  of 
  any 
  whole 
  number 
  

   of 
  half 
  wave-lengths 
  should 
  cause 
  the 
  sound 
  to 
  come 
  from 
  

   the 
  front 
  or 
  back 
  and 
  as 
  the 
  difference 
  of 
  phase 
  increases 
  to 
  

   one 
  fourth 
  a 
  wave-length, 
  the 
  sound 
  should 
  swing 
  around 
  

   to 
  the 
  side, 
  and 
  then 
  go 
  back 
  to 
  the 
  middle 
  as 
  the 
  difference 
  

   increases 
  further 
  to 
  a 
  half 
  wave-length. 
  From 
  a 
  half 
  to 
  a 
  

   whole 
  wave-length 
  the 
  cycle 
  is 
  the 
  same, 
  but 
  from 
  the 
  

   opposite 
  side, 
  and 
  so 
  on 
  to 
  any 
  number 
  of 
  wave-lengths. 
  

   The 
  curves 
  show 
  this 
  clearly, 
  the 
  sound 
  apparently 
  coming 
  

   from 
  the 
  side 
  whose 
  phase 
  is 
  in 
  advance. 
  Since 
  the 
  shifting 
  

   of 
  the 
  slider 
  doubles 
  the 
  phase-difference, 
  the 
  wave-lengths 
  

   have 
  been 
  divided 
  by 
  two, 
  so 
  that 
  they 
  would 
  agree 
  when 
  

   the 
  scale-readings 
  were 
  plotted 
  instead 
  of 
  phase-differences. 
  

  

  In 
  the 
  series 
  of 
  observations 
  given, 
  it 
  is 
  unnecessary 
  to 
  

   record 
  them 
  in 
  tables 
  as 
  they 
  can 
  be 
  read 
  easily 
  from 
  the 
  

   curves, 
  which 
  are 
  plotted 
  from 
  individual 
  readings. 
  The 
  

   observations 
  on 
  the 
  direction 
  were 
  made 
  by 
  myself 
  in 
  all 
  of 
  

   them 
  and 
  the 
  close 
  agreement 
  to 
  the 
  theoretical 
  curves 
  

   which 
  are 
  shown 
  dotted, 
  I 
  attribute, 
  not 
  to 
  any 
  keenness 
  of 
  

   hearing 
  on 
  my 
  part, 
  but 
  to 
  the 
  precaution 
  of 
  having 
  the 
  

   sounds 
  made 
  in 
  a 
  different 
  room 
  and 
  muffled 
  by 
  striking 
  

   the 
  forks 
  in 
  a 
  padded 
  box, 
  thus 
  entirely 
  eliminating 
  the 
  

   distraction 
  caused 
  by 
  hearing 
  the 
  sound 
  otherwise 
  than 
  

   through 
  the 
  tubes. 
  

  

  We 
  may 
  conveniently 
  divide 
  the 
  curves 
  into 
  two 
  groups. 
  

   Figures 
  2 
  to 
  7 
  inclusive, 
  showing 
  records 
  of 
  forks 
  C, 
  

   (n 
  = 
  64 
  dble. 
  vib.) 
  to 
  g' 
  (n 
  = 
  384 
  d. 
  v.), 
  give 
  almost 
  perfect 
  

  

  