﻿30 
  C. 
  K. 
  Wead 
  — 
  Intensity 
  of 
  Sound. 
  

  

  were 
  correct 
  in 
  their 
  judgments 
  about 
  the 
  loudness 
  of 
  sound 
  of 
  

   a 
  watch 
  when 
  held 
  at 
  different 
  distances 
  in 
  only 
  55 
  per 
  cent 
  of 
  

   their 
  trials 
  if 
  the 
  ratio 
  of 
  loudness 
  in 
  the 
  two 
  cases 
  (computed 
  

   from 
  the 
  law 
  of 
  inverse 
  squares) 
  was 
  100:92. 
  In 
  the 
  light 
  of 
  

   such 
  experiments 
  the 
  numbers 
  headed 
  per 
  cent 
  of 
  difference 
  

   in 
  our 
  tables 
  are 
  strikingly 
  small 
  in 
  nearly 
  every 
  case 
  — 
  partly 
  

   of 
  course 
  because 
  of 
  the 
  method 
  of 
  averages 
  we 
  have 
  followed, 
  

   a 
  number 
  of 
  pipes 
  sounding 
  at 
  once 
  in 
  most 
  cases. 
  

  

  It 
  is 
  interesting 
  to 
  compare 
  the 
  energy 
  used 
  here 
  with 
  that 
  

   of 
  a 
  tuning 
  fork. 
  From 
  table 
  IV 
  of 
  my 
  former 
  paper 
  (p. 
  186) 
  

   it 
  appears 
  that 
  the 
  maximum 
  energy 
  I 
  could 
  give 
  by 
  bowing 
  

   to 
  Konig's 
  forks 
  of 
  the 
  middle 
  octave 
  mounted 
  on 
  their 
  cases 
  

   was 
  considerably 
  less 
  than 
  0*5 
  Xl0 
  6 
  ergs. 
  ; 
  and 
  the 
  maximum 
  

   rate 
  at 
  which 
  energy 
  was 
  lost 
  was 
  about 
  0*1 
  XlO 
  6 
  ergs, 
  per 
  sec. 
  

   But 
  the 
  Open 
  Diapason 
  pipes 
  of 
  this 
  range 
  (c 
  / 
  — 
  c") 
  used 
  each 
  

   from 
  18 
  to 
  30 
  XlO 
  6 
  ergs, 
  per 
  sec, 
  some 
  250 
  times 
  as 
  much 
  as 
  

   the 
  fork 
  giving 
  its 
  maximum 
  sound, 
  or 
  from 
  1,000 
  to 
  6,000 
  

   times 
  as 
  much 
  as 
  the 
  fork 
  when 
  giving 
  an 
  ordinary 
  sound. 
  

   About 
  one-millionth 
  of 
  one 
  horse-power 
  would 
  maintain 
  in 
  

   ordinary 
  vibration 
  one 
  of 
  the>e 
  forks 
  ; 
  and 
  a 
  tenth 
  of 
  this 
  

   amount 
  gave 
  a 
  sound 
  loud 
  enough 
  to 
  be 
  heard 
  200 
  feet 
  in 
  the 
  

   open 
  air. 
  

  

  There 
  remains 
  one 
  question 
  of 
  some 
  interest 
  : 
  Do 
  all 
  parts 
  

   of 
  the 
  scale 
  seem 
  to 
  the 
  ear 
  to 
  be 
  of 
  equal 
  loudness, 
  especially 
  

   the 
  scale 
  of 
  an 
  organ 
  for 
  which 
  we 
  have 
  found 
  the 
  relative 
  

   intensity 
  of 
  vibration. 
  I 
  find 
  few 
  musicians 
  who 
  have 
  any 
  

   definite 
  impression 
  on 
  the 
  subject 
  ; 
  the 
  question 
  is 
  certainly 
  

   difficult, 
  and 
  is 
  perhaps 
  indefinite. 
  If, 
  for 
  example, 
  we 
  call 
  

   that 
  sound 
  the 
  louder 
  which 
  can 
  be 
  heard 
  at 
  t*he 
  greater 
  dis- 
  

   tance 
  and 
  then 
  compute 
  the 
  energy 
  passing 
  through 
  the 
  unit 
  

   of 
  surface 
  at 
  the 
  limit 
  of 
  hearing, 
  we 
  make 
  the 
  violent 
  assump- 
  

   tion 
  that 
  the 
  efficiency 
  of 
  the 
  two 
  sound-producers 
  is 
  the 
  same. 
  

   If 
  we 
  place 
  the 
  two 
  bodies 
  at 
  the 
  same 
  distance 
  Mayer* 
  has 
  

   shown 
  that 
  the 
  sensation 
  of 
  one 
  sound 
  may 
  be 
  obliterated 
  by 
  

   a 
  lower 
  one 
  that 
  could 
  not 
  be 
  heard 
  as 
  far 
  off 
  as 
  the 
  first. 
  And 
  

   there 
  are 
  other 
  physiological 
  difficulties. 
  In 
  fact 
  the 
  problem 
  

   before 
  us 
  is 
  analogous 
  to 
  the 
  long-standing 
  one 
  of 
  the 
  compari- 
  

   son 
  of 
  two 
  lights 
  of 
  different 
  colors. 
  The 
  problem 
  must, 
  

   therefore, 
  be 
  left 
  as 
  insoluble 
  with 
  our 
  present 
  knowledge 
  ; 
  but 
  

   two 
  statements 
  of 
  musicians 
  are 
  of 
  interest 
  in 
  this 
  connection. 
  

   One 
  organist 
  points 
  out 
  that 
  if 
  a 
  piece 
  of 
  music 
  is 
  played 
  on 
  a 
  

   two 
  or 
  three 
  manual 
  organ, 
  the 
  left 
  hand 
  on 
  the 
  swell 
  key- 
  

   board, 
  while 
  the 
  melody 
  is 
  played 
  by 
  the 
  right 
  hand 
  on 
  the 
  

   great, 
  and 
  the 
  swell-boards 
  are 
  opened 
  to 
  give 
  a 
  proper 
  balance 
  

  

  * 
  Phil. 
  Mag., 
  ii, 
  500. 
  

  

  