We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
VOLUME I, No. 45
NOV. 10, 1928
The Movietone Sound Track
This picture shows the sound track magnified to thirty of sound track are shown the corresponding percentage transmissions of total light.
N explanation of the movietone
system of recording and projecting quickly dispels the mystery of the sound track. The pressure of sound waves impinging on the diaphragm of a condenser microphone, (as distinguished from a carbon microphone), causes the diaphragm to vibrate. The amount of the displacement of the diaphragm is proportional to the intensity or loudness of the sound. This movement varies the capacity of the condenser microphone, thus altering the charge on the grid of a vacuum tube which is connected in series with the microphone. The
resulting alternating current is proportional and in phase with the movement of the diaphragm.
If a carbon microphone is used, the displacement of the diaphragm varies the resistance of the microphone and causes a varying or modulated direct current. This current may be considered as made up of a direct and alternating component.
After several stages of amplification in which the voltage is increased approximately 100,000 times, it is impressed on an Aeo light. The Aeo light is a gas tube excited by direct current and so
times its original size.
Beneath the strip
designed that its intensity or brightness is proportional to the applied voltage. The light shines through a narrow slit on a moving negative film in the camera and the variations of the light are recorded upon it. The exposure of the film is in phase and proportional to the alternating voltage applied to the Aeo light. Thus the sound track is a record of the exposure due to the variations in brightness of the Aeo light.
In reproducing, the printed sound track is passed through a narrow light beam, (.001” x .08”), of constant intensity and the transmitted