﻿244 
  Lord 
  Rayleigh 
  : 
  Acoustical 
  Notes. 
  

  

  Pitch 
  of 
  Sibilants. 
  

   In 
  connexion 
  with 
  the 
  audibility 
  of 
  sibilants 
  it 
  is 
  desirable 
  

   to 
  have 
  some 
  idea 
  o£ 
  their 
  character 
  in 
  respect 
  of 
  pitch. 
  

   Doubtless 
  this 
  may 
  vary 
  over 
  a 
  considerable 
  range. 
  In 
  my 
  

   experiments 
  the 
  method 
  was 
  that 
  of 
  nodes 
  and 
  loops 
  *, 
  executed 
  

   with 
  a 
  sensitive 
  flame 
  and 
  sliding 
  reflector. 
  A 
  hiss 
  given 
  

   by 
  Mr. 
  Enock, 
  which 
  to 
  me 
  seemed 
  very 
  high 
  and 
  not 
  over 
  

   audible, 
  gave 
  a 
  wave-length 
  (X) 
  equal 
  to 
  25 
  mm. 
  with 
  good 
  

   agreement 
  on 
  repetition. 
  A 
  hiss 
  which 
  I 
  gave 
  was 
  graver 
  

   and 
  less 
  definite, 
  corresponding 
  to 
  X 
  = 
  32 
  mm. 
  The 
  frequency 
  

   of 
  vibration 
  would 
  be 
  of 
  the 
  order 
  10,000 
  per 
  second, 
  more 
  

   than 
  5 
  octaves 
  above 
  middle 
  c 
  f 
  . 
  

  

  Telephones. 
  

   Some 
  miscellaneous 
  observations 
  upon 
  telephones 
  may 
  here 
  

   be 
  recorded. 
  From 
  the 
  fact 
  that 
  an 
  improved 
  articulation 
  

   of 
  the 
  sibilants 
  and 
  some 
  other 
  consonants 
  accompanies 
  a 
  

   thickening 
  of 
  the 
  telephone 
  plate, 
  although 
  at 
  considerable 
  

   cost 
  in 
  other 
  respects, 
  it 
  was 
  thought 
  that 
  a 
  similar 
  advantage 
  

   might 
  be 
  attained 
  by 
  the 
  introduction 
  of 
  a 
  condenser 
  into 
  

   the 
  electrical 
  circuit. 
  This 
  entails 
  no 
  further 
  complication 
  if 
  

   the 
  transmitter, 
  as 
  well 
  as 
  the 
  receiver, 
  be 
  a 
  Bell 
  instrument 
  ;. 
  

   but 
  if 
  a 
  microphone 
  be 
  employed 
  as 
  transmitter, 
  a 
  small 
  

   transformer 
  must 
  also 
  be 
  introduced, 
  whose 
  ratio 
  of 
  trans- 
  

   formation 
  may, 
  if 
  desired, 
  be 
  1:1. 
  The 
  line, 
  receiver, 
  and 
  

   condenser 
  then 
  constitute 
  electrically 
  a 
  secondary 
  circuit, 
  

   and 
  by 
  choice 
  of 
  a 
  suitable 
  capacity 
  the 
  proper 
  tone 
  of 
  this 
  

   circuit 
  may 
  be 
  tuned 
  to 
  any 
  desired 
  pitch. 
  The 
  earliest 
  con- 
  

   sideration 
  of 
  resonance 
  in 
  an 
  electrical 
  circuit 
  in 
  response 
  to 
  

   a 
  periodic 
  force 
  was 
  probably 
  by 
  Maxwell 
  % 
  in 
  connexion 
  

   with 
  Grove's 
  " 
  Experiment 
  in 
  Magneto-Electric 
  Induction." 
  

   If 
  L, 
  R 
  be 
  respectively 
  the 
  self-induction 
  and 
  resistance 
  of 
  a 
  

   circuit, 
  C 
  the 
  capacity 
  of 
  the 
  interposed 
  condenser, 
  the- 
  

   current 
  (dx/dt), 
  elicited 
  by 
  the 
  imposed 
  electromotive 
  force- 
  

   E<? 
  2 
  "*, 
  is 
  given 
  by 
  

  

  (—Ln 
  2 
  + 
  i 
  Un 
  + 
  ^ 
  J 
  x 
  = 
  

  

  E 
  

  

  * 
  Phil. 
  Mag. 
  vii. 
  p. 
  149 
  (1879) 
  ; 
  Scientific 
  Papers, 
  i. 
  p. 
  406. 
  

  

  f 
  Compare 
  Wiersch, 
  Drade 
  Ann. 
  xvii. 
  p. 
  1001 
  (1905). 
  "Sieht 
  man 
  von 
  

   ihren 
  tiefsten 
  Partialtonen 
  ab, 
  welche 
  lediglich 
  infolge 
  Resonanz 
  der 
  

   Mundhohle 
  beigemischt 
  sind, 
  so 
  entstehen 
  die 
  eigentlichen 
  Reibelaute 
  

   durch 
  eine 
  Schwingungszahl, 
  welche 
  minimal 
  derjenigen 
  des 
  Grnndtones 
  

   der 
  Lul'tsaule 
  einer 
  einseitig 
  gedeckten 
  Pfeife 
  von 
  ca. 
  14 
  mm. 
  Lange 
  

   entspricht, 
  maximal 
  aber 
  im 
  Bereiche 
  der 
  Unhorbarkeit 
  liegt." 
  This 
  

   paper 
  contains 
  some 
  interesting 
  observations 
  upon 
  the 
  influence 
  of 
  the 
  

   proper 
  tone 
  of 
  a 
  telephone 
  plate 
  upon 
  the 
  articulation. 
  

  

  % 
  Phil. 
  Mag. 
  May 
  1868: 
  Maxwell's 
  Scientific 
  Papers, 
  ii. 
  p. 
  121. 
  

  

  