IMPROVED TYPE OF MICROPHONE

Radio Record, Volume VII, Issue 4, 4 August 1933, Page 44

IMPROVED TYPE OF MICROPHONE

Man Makes "Velocity" Instrument LTHOUGH he chooses to remain anonymous, a Christchurch radio engineer who has been intimately connected with broadcasting in New Zealand since its inception, has constructed a microphone that is the first of its type to be made in the Dominion, says the Christchurch "Sun." From all points of view it is a definite improvement on the "mikes" now in general use, and it has peculiar advantages that make it particularly suitable for talkie recording. _ This new "velocity" microphone is gaining favour in America, and it pro- | mises to bring about great changes in the quality and technique of radio broadeasting. It is actuated by the velocity of the minute air particles set in motion by sound waves, which are reproduced with a fidelity never before

possible; ordinary diaphragm microphones have been cramped by their limited tonal range, which could not reproduce all tones without some distor-tion-the rattling of a bunch of keys would sound like the jangling of tin cans, There is no diaphragm in the new microphone, but instead a sensitive ribbon of duralumin, the heart of the |instrument, which vibrates with the

— ------- variations of the air particles; it responds uniformly to the entire audible range of sound from zero to 14,000 cycles or over, Which means that all the subtle tonings that give light and shade-and therefore reality-to recording are faithfully mirrored. Diaphragms offer a relatively large and impeding surface to sound waves, but in the new instrument the metal ribbonwhich is enly one three-thousandth of an inch in thickness-is suspended on a magnetic field, thus enabling -the sound waves to pass through freely. Another important feature is that the instrument is bi-directional, sounds coming form two directions being reproduced. This is an important step forward in studio and talkie work, for the director can stand on the "blind" side of the instrument and give his instructions. No longer is it necessary to crowd performers on one side, as entertainers can say their lines facing each other, and orchestra in large ensemble effects can be placed more advantageously. The "mike" has a sighting screen similar to that on a’ camera, the sounds from all speakers, singers, or instruments within the range being recorded. In movie studios, the grind of the camera can be eliminated, and wherever the microphone is placed the recorded or broadcast sound js free from echo effects.