288 SPEAKING TRUMPETS, 



The intenfity of One decifive experiment remained to be made with thefc in- 



kffencrbVde-"' ^rumenfs, this was to deftroy and to reftore the adion of the 



Uroying the re- refle6lion in a rpeaking trumpet, fuppofing it to take place, 



rcfleftionby and to compare the intenfity of the found obtained in thefe 

 means of an . ' ^ 



internal woollen two circumftances, in order to determine the proportion of the 

 •ovcnng. effed produced by this refle6lion. I confequently procured a 



fpeaking trumpet of woollen Huff, which I placed within one 

 of tin, and I obferved tiiat the intenfity of the found obtained 

 with or witliout the fluff in the infide, w^as fenfibly the fame; 

 whence it follow<} that the refleflion has 'no appreciable influ- 

 ence on the augmentation of found in a fpeaking trumpet. 

 Except inaf- I have faid that the intenfity of the found was fenfibly the 



mbiihes the" ^^'"^' nevertheleffs I muft obfervfe that it was diminifhed; for 

 diameter of the the beating of my watch, placed in th6 mouth of the bare 

 mftrument. ; fpeaking trumpet was heard at a diflartce of 3". 94, mean of 

 five experiments (b), while when placed in the mouth of the 

 fame inftrument covered in the infide with the fluff, it was not 

 heard beyond 2". 48. This difference, which at the moment 

 might be fuppofed to arife from the refledion of the found tak- 

 ing place in the one cafe, and not in the other, feems to de- 

 pend folely on the diminution of the diameter of the cylinder 

 of the fpeaking trumpet and of the Enlarged parts occafioned 

 by the fluff placed within them: I fatisfied myfelf that the 

 fpeaking-trumpet which I made ufe of (h), preferring all its 

 dimenfions and experiencing no difference except in the diam- 

 ettr of the tube, produced a diminution in the intenfity of 

 the found, whenever a fmaller diameter was made ufe of; 

 thus, in the fpeaking trumpet already mentioned (h)^ the beat- 

 ing of my watch was heard at adiflance of 3*. 94, when the 

 -diameter of the tube was 0". 035 ; it was not heard beyond 

 3"". OS, when the tube was only'0™.OS2; finally, it was not 

 ■heard beyond 2'". 34, when the tube was 0*". 028. It is evi- 

 -dent, therefore from thefe experiments, that the diminution in 

 the intenfity of the found by covering the interior of a fpeak- 

 ing trumpet with fluffs, arifes from the diminution of the di- 

 ameter of its tube. 

 The diminution- I fiiould obferve that if the internal flufl^ occafions an incon- 

 *" ^'y^ '"^^"5^7 fiderable diminution in the intenfity of the found, it, on the 



of the found is i i 



compenfated by' Other hand, produces a great advantage by rendering the arti- 

 its clearnefs. . culaled founds clearer and lefs confufed. 



Gcncp^lcon- It follows from all which has been fliewn on the auricles of 



^lufions, animals, on horns, and acouflic tubes, and on fpeaking trum- 



pets. 



