310 iriEORY or bar xavMPETS, 



XIII. 



Ohsercdtwns on tht Theory of Ear trumpets, with a View t» 

 their Improvement ; A3/J0HV Gouch, K^q, 



Sir, Middfeshau\ *iOtk Nov. 1807'. 



Animpro^red ^JTNE of your correspondents, who appears at pas,e 51 o£ 

 requested. >^ur XlHth volunae, under the signature of A. B. has lately 

 *' addressed me in the same anonymous character on the subject 



of ear ti umpets. He requests to learn my sentiments res- 

 pecting these instruments, and hints leading to their improv** 

 ment through the medium of your Journal, 



•ni^subject hi- j^ believe but liltlc attention has been hitherto bestowed OQ 



therto reglect- 



cd by philoso- this part of acoustics, though the inquiry is intimately con- 



P*^^*** nected with the ease and happiness of the partially deaf ol 



all ranks and ages. This negligence in experimental philo- 



phers, who have done so much for the improvement ot optics, 



obi ges me to begin with a fundamental and essental point 



' of my subject; for we are in uncertainty at present in what 



Two theories manner an ear trumpet acts on the auditory organs. We 



trumpeTpro- ^^*y Conceive the sonoriterous pulses to be collected in the 



posed. cavity of the vessel, and to pass thence into the meatus au- 



ditorius in a state of increased condensation. 



On the other hand, we ma^ suppose, that the same pulses 

 strike the sides of the trumpet, and excite similar vibration* 

 in this metallic s..c'}, vliich imparts them to the orifice of the 

 The latter the- iiud it ory duct. The latur supposition is rendered plausible 

 ry p u I . ^^ ^ simple experiment ; if the porches of the ears be se- 

 curely stuffed with wet paper, you may convey the clicking of 

 a watch along a rod of wood or metal to the seat of bearing 

 by simply. touching the watch with one end of the rod, and 

 pressing the other against the'forehead, your teeth, or the wet 

 paper in your ears. The preceding fact, in conjunction with 

 other circumstances and arguments, induced me at first to 

 prefer the second theory of ear trumpets, and to conclude, 

 that the vibrations of the metal ccmstitute the real cause of 

 augmented sound rather th;in the condensation offlcnoriferou? 

 pulses. 



After 



