480 



BELL SYSTEM TECHNICAL JOURXAL 



in time of sunset and of sunrise, are shown in I'"ig. 17. Eacli curve is 

 the average of all the measurements taken during that particular 

 month in 1023 and 1924. The diurnal variations are generally similar 

 for the different months in respect to the high night-time values 

 which are limited to the period between the times of sunset and sun- 



ri({. 17 -Monthly avuraRcs of diurnal variation of noise, New .Soiithj;ate, England- 

 57,000 cycles— 1923-1924 



