EAR-TRUMPET. A contrivance for improv the hearing of the partially deaf, and, as its name implies, a trumpet-shaped tube. whose action depends on the principles of reflection. The waves of sound strike the hell of the trum pet and are reflected into the narrower portion of the tube. As the proceed. the wave front narrows in bread lb. but increases in in tensity and the sound reaches the inner ear mag nified. In a great number of cases of impaired hearing, there can be no doubt that much assist ance is obtained from the use of the ear-trumpet: still it must not be used indiscriminately, for in unsuitable eases it may do much mischief, both in increasing the deafness and aggravating the noises in the head front which deaf persons often suffer so much. It also possesses the great dis• advantage of magnifying certain sounds at the expense of others. The ear-trum pet. on account of its shape, acts as a resonator, and will strengthen and increase the vibrations of cer tain frequencies. while others will he almost de stroyed. Ear-trumpets aro of most use. per
haps. in advanced cases of nervous deafness, though injurious in the early stages of this com plaint; they are hurtful also in all acute dis eases of the ear. and of little or no use in those cases of great thickening of the contents of the middle ear, where the adapting power of the organ has been lost. Alost of the small and so-called invisible ear-trumpets are eonsidered practically useless. All of the useful instru ments have good-sized bowls, which in some eases rest against the temple when inserted in the ear. thus aiding the hearing by bone conduc tion. Another variety, applicable to the more severe eases of deafness, consists of an elastic tube, one end of which is tipped with ivory and is placed in the ear of the patient ; the other is held in the hand of the speaker, who applies his mouth to the open extremity. Ear-trumpets are generally made of some thin metallic sub stance. such as tin. Gutta-percha and other sub stances are also frequently used. See ArmeitoNE.