Show LEARNING to HEAR With the EYES EAF mutes if they are arc not suffering from froma D DEAF a structural defect of or the organs of speech may be taught to speak but their instruction instruction instruction tion is difficult and its progress slow It has been facilitated by the invention of Prof Lindner in instructor instructor instructor in- in of deaf dear mutes in Leipzig who assisted by the Institute of Physics of Leipzig University has evolved two instruments of visualizing the sound of human speech One called a Do vocal ocal as described in Popular Science Monthly has a circular frame over which a thin membrane is stretched A metal plate attached to the membrane b bears ars a pointed pin or thorn Against this pin rests a small plate of brass The apparatus can be used only in a dark room Words spoken en into the funnel cause the membrane to vibrate The vibrations are transmitted transmitted transmitted trans trans- by the pointed pin to the brass plate resting resting resting rest rest- ing against it This plate has a tiny mirror minor at attached attached attached at- at to it upon which a n ray of light is As the mirror is moved b by t the tho vibrations of the membrane the ray of light reflected by it draws designs on a a i screen The same sound of the same volume produces always the same design Deaf mute pupils soon lc learn to recognize sounds by the tho designs Another the drum apparatus does not require a dark room for or its successful employment A small drum is suspended from rom two vertical supports support B By means of a delicate electrical contact the vibrations of or the membrane of the drum arc U transmitted to a small incandescent incandescent incandescent cent lamp fed ed by a battery The variations in the intensity and in the I-h I rhythm of the glow arc are interpreted interpreted interpreted in in- by the pupils and arc are used by comparison comparison com com- parison as a means of correcting their own sound production They soon become expert in producing producing producing ing similar variations |