The motion picture projectionist (Nov 1929-Oct 1930)

42 The Motion Picture Projectionist January, 1 930 List Common Sound Faults IN order to establish a criterion as to "noises" caused by faulty projection of sound films, Douglas Shearer, recording engineer for Metro-Goldwyn-Mayer, recently made an exhaustive demonstration for the members of the Academy of M. P. Arts and Sciences sound classes. Single reels of two recent pictures were printed up with the deliberate idea that they were to be maltreated in every possible way. Further, the projection machine through which they were to be run was loosened in every manner which might cause extraneous sounds. The result was an amazing series of unpleasant noises and other acoustic flaws which very well illustrated what can happen to a perfectly recorded picture if the projection is not equally perfect. Following the experiments, Mr. Shearer prepared the following chart of the noises due solely to bad projection. Sprocket Noise — Caused when the film pulls over to the left in the projector, allowing the exciter lamp of the light-ray reproducing system to play through the sprocket holes of the film as well as the sound track. The noise is a rather high-pitched buzz, somewhat like a busy door-bell. Flutter — This is a pulsation in the recorded tones. It sounds as if the speaker is gagging a bit over a mouthful of mush. It is caused by too long or too short loops in the projection machine, or loose pads on the track guiding the film. These things cause both picture and sound track to move in and out of focus. Frame Noise — The opposite of sprocket trouble. Caused when the film is pulled in the machine too far to the right, running off the soundtrack onto the picture itself, playing, so to speak, the picture and the dark spaces between the frames. Sounds like a motorboat at high speed. Motorboating — Same as Frame Noise. Overspeed — When the speed is suddenly increased beyond the normal of 90 ft. per min. (33 1-3 R.P.M. for discs), the high frequency sounds are emphasized at the expense of the lower ranges. In other words, the great basso, Chaliapin, would sound like a soprano under excessive overspeeding. Underspeed — When the projector is suddenly slowed down the reverse of the above occurs. The lower frequencies are emphasized, and GalliCurci would sound like Chaliapin. Dirt Noise — Film should always be carefully cleaned after each running, but sometimes an operator is careless. When this happens, specks of dirt form on the sound track. These specks cause variations of sound which are manifested in many ways — ■ squeaks, whistles, fire-cracker noises, etc. Loose Exciter Lamp — When the exciting lamp of the light-ray sound reproducing system becomes loose there is a distortion of sound, making it hard to keep the attention concentrated. Gear Noise — Noise recurring at regular intervals, dum-de-dum, etc., can usually be traced to loosened gears in the projector. Blooping — This is a sudden "plop," usually caused by a bad splice between sections of the film. This can always be avoided by correct splicing, and properly blocking out the spliced patch in the sound track. Insulation Noise — Some theatres have not yet installed the heavier tripods and insulation pads required for sound reproduction. The amplifying tubes and the photo-electric cell are very sensitive to jar. Sudden "whack" noises from the screen are generally traceable to trouble caused by vibrations when the projectionist walks across a booth in which the insulation has been badly done. There are other noises which can be caused by accidents and by faulty handling of the equipment, but these are the major extraneous sounds which annoy theatre-goers. All of these sounds can be eradicated. BELTONE REPRODUCER ON SIMPLEX PROJECTOR BELTONE SOUND REPRODUCER MECHANICAL SYSTEM. Cell house drum and guide rollers are made of nitralloy, which is twice as hard as tool steel, giving maximum life. Threading extremely simple. QPTICAL SYSTEM is very small and compact, V has no mechanical slit nor mirrors and produces about four times as much light as can be had with other systems. TPXCITER LIGHT. Due to the sensitivity of ■*-i the Burt supercell and the efficiency of our optical system no special tubes nor lamps are required, but an ordinary six-volt automobile headlight bulb is used which has a life of from 1,000 to 2,000 hours. UUPER CELLS used are non-microphonic, have k-' very low impedence, and are guaranteed for one year. Their output is such that only five stages of amplification are required including the Power Stages. Developed by Dr. R. C. Burt of the Burt Scientific Laboratories, Pasadena, California, recognized as one of ihe foremost authorities on Photo Electricity. SOUND-HEAD AMPLIFIERS and fader mounted in one cabinet which is placed on the floor between the projectors. A small six-volt storage battery and a 45-volt "B" battery are contained in lower part of cabinet. Special volume and quality control. 'PURNTABLES are mounted on pedestal at rear of projec A tor and are driven by a hollow steel shaft from the Movietone shaft of projector head. This type of mounting successfully eliminates all vibration, waver and tremolo. T NSTALLATION can be made on present bases of Powers, ^ Simplex, or Fulco projectors, without structural changes, in a few hours, eliminating necessity of shutdown. ■p RICES. Sound on film equipment, including head ampli"^ fier and fader, $1,500.00. Disc equipment $500.00 additional. Power amplifiers and speakers additional as required from $500.00 to $1,000.00. All prices f.o.b. Los Angeles. Write for Bulletin No. 200. BELTONE CORPORATION, Ltd. 9035 Venice Boulevard Los Angeles, Calif.