INGENIOUS INVENTION.

New Zealand Herald, Volume LXVIII, Issue 20969, 4 September 1931, Page 12

INGENIOUS INVENTION.

"SEEING" BROADCAST MUSIC. VIBRATIONS OF FINE WIRE. An ingenious instrument which allows broadcast music to be "seen" as it is picked up and issued by a radio loudspeaker has just been constructed by Mr. W. M. Dawson, chief engineer of Philips Lamps (New Zealand), Limited. The device allows detailed study and analysis of radio reception, as wave-forms are readily measured for amplitude, frequency and harmonic content. The instrument consists of an exceedingly fine tungsten wire stretched between the poles of a powerful magnet, and the various loud-speaker currents are made to pass along this wire, causing it to vibrato in accord with the speech or music. By means of an intense light and an optical system, the shadow of the moving wire is projected through a narrow slit on to a ground-glass screen. At this stage the effect is only a blurred shadow moving too rapidly for the eye to follow, as the vibrations may reach 5000 a second. ' Behind the ground-glass screen is a four-sided mirror which is rotated by an electric motor, and by looking down on this mirror a black line is seen on a brightly-lit ground. The line is straight until speech or music issues from tho radio set, when it is contorted into a variety of shapes. Each subtle change in tone or volume is simultaneously visible on the screen as a variation in the shape of the line, while a sustained note produces a symmetrical series of curves, which by a proper adjustment of the mirror speed may be made to appear stationary, so that their exact shape may be studied. Permanent photographic records of this "visual" speech and music are provided for by replacing the rotating mirror with a specially-designed camera using cinematograph film, which is developed and printed in the usual way. The instrument is equally valuable in studying the nature of radio interference, the functioning of various appliances and variations in illumination, while it is expected to have other scientific applications.