CIRCUIT PLANS FOR INEXPENSIVE AUDIOMETERS

Abstract

At this time, when mass production of radio parts has made small electric equipment so cheap, it is possible to assemble without great outlay practical audiometers giving perfect performance. A knowledge of the circuits is, of course, essential; but with the plans here set forth it should be possible for any otologist to make the instruments described or even to have them made. VARIETIES OF AUDIOMETERS A Buzzer Audiometer .—The principle of the buzzer audiometer has been in use for many years. The first of these instruments used a clockwork mechanism with a percussion hammer similar to the alarm clock; subsequent types used the electric bell announcer, dry batteries and binaural stethoscope tubes. Recently, as in the Western Electric 3- A audiometer, a vibrating reed similar to the announcer buzzer is still used, but is in circuit with a telephone. The apparatus works from dry cells, and has an intensity