o 



300 Mr. R. II. M. Bosanquet en the Present 



The organ is much used in the description, as by reference to 

 it magnitudes can be described in a way that is intelligible to 

 a large number of persons. Stops of average voicing are to 

 be understood, not in the swell-box unless stated. The sound 

 is supposed to be heard in a church or hall of moderate size. 



The estimate is to be formed purely as to loudness; and for 

 this purpose it is advisable to compare unmusical noises. 



Sound- 

 magnitudes. 



f 1. Steam whistle. Camion close Toy Church bells in the chamber. 

 j 2. Tromba (tuba mirabilis). Sounds of (1) at a little distance. 

 Loud bells at foot of tower. 

 "3 J 3. Full organ without tromba. 



4 Trumpet with diapasons. Singing or public speaking at the top 

 of the voice. 



5. Modern loud diapasons (German). Loud singing or intoning. 

 Ordinary public speaking. 



6. Soft diapasons (old English). Soft singing or intoning. Loudest 

 ordinary conversation. 



7. 4 choir 8-foot stops. Ordinary speech. 



8. Stopped diapason alone. Soft speech. 



9. Dulciana, Strong whisper. Tick of watch close to ear. 

 ^ I 10. Dulciana or salicional (in swell-box closed). Faintest whisper. 



[_ Tick of watch at arm's length. 



Great precision is not attempted ; but it is generally easy 

 to say whereabouts in the scale a given sound lies. Precision 

 will come in time. 



Several problems then lie before us: — 



(1) What is the common ratio of the mechanical intensity 

 in two successive magnitudes ? 



(2) What is the absolute value of the mechanical intensity 

 corresponding to one definite magnitude ? 



(3) What is the law of the dependence of the magnitude of 

 sound of given mechanical intensity on variation of pitch. 



As to the first two I have made some rough determinations; 

 but the apparatus at my disposal is too imperfect to enable 

 me to quote the results as being of any value. With a better 

 bellows I see no difficulty in the way of answering these two 

 questions*. 



* Since the above was written I have made a determination of the ratio 

 by observations of " Tom/' Christ Church, Oxford, when the 101 strokes 

 are rung, after 9 t.m. At the foot of the tower, say SO yards off the source, 

 it was of 2nd magnitude; at the distance of If mile, of 10th magnitude. 

 This gives for the common ratio of the mechanical energy for two conse- 

 cutive magnitudes, 1 : 3-2 nearly. The experiment with a resonator above 

 referred to, gave 1 : 2'3 for the common ratio, from an estimated difference 

 of two magnitudes, the estimate being of course very uncertain. The 



