SCIENCE OF COMMON THINGS. 127 



Construction of the speaking trumpet. Ear trumpet. 



that the rays of sound (proceeding from the mouth 

 when applied to it), instead of diverging, and being 

 scattered through the surrounding atmosphere, are 

 reflected from the sides, and conducted forward in 

 straight lines, thus giving great additional strength to 

 i the voice. The course of the rajs of sound proceeding 



Fig. 33. 



from the mouth through this instrument, may be shown 

 by Fig. 33. The trumpet being directed to any point* 

 a collection of parallel rays of sound moves towards 

 such point, and they reach the ear in much greater 

 number than would the diverging rays which would 

 proceed from a speaker without such an instrument. 



8O3 What is an ear trumpet f 



An ear trumpet, Fig. 34, is in form and application 

 the reverse of a speaking trumpet, but 

 in principle the same. The, rays of 

 sound proceeding from a speaker, more 

 or less distant, enter the hearing trum- 

 pet, and are reflected in such a manner 

 as to concentrate the sound upon the 

 opening of the ear. Fig. 34 repre- 

 sents the form of the ear trumpet generally used by 

 deaf pei-sons. The aperture A is placed within the ear, 

 and the sound which enters at B is, by a series of 

 reflections from the interior of the instrument, concen- 

 trated at A. 



SO Why do persons hold the hand concave behind the ear, in order to 

 hear more distinctly ? 



Because the concave hand acts in some respects as 

 an ear trumpet, and reflects -the sound into the ear. 



