Sound motion pictures : from the laboratory to their presentation (1929)

Record Details:

Something wrong or inaccurate about this page? Let us Know!

Thanks for helping us continually improve the quality of the Lantern search engine for all of our users! We have millions of scanned pages, so user reports are incredibly helpful for us to identify places where we can improve and update the metadata.

Please describe the issue below, and click "Submit" to send your comments to our team! If you'd prefer, you can also send us an email to with your comments.

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.

44 SOUND MOTION PICTURES camera is motor driven and is connected by wire with the telephonic apparatus, there is little difference between the recording of picture and voice by this method and the or- dinary picture recording in a studio. This is called the "flashing lamp" method of recording. The presentation of one of these sound pictures to an audience is in effect a reversal of this process. The stand- ard film, containing both picture and sound in a photo- graphic record, is run through a standard projection machine to which has been attached a sound reproducing unit. This unit includes a light that is reflected onto the sound record of the film. As the sound record on the film passes the light it interrupts the constant light shining through it and sets up light variations corresponding to those photographed. These variations then fall on a photo-electric cell which changes the light variations back to electrical vibrations. The latter variations, being too delicate to be heard directly, are accordingly amplified and carried by wire from the projection booth to the horns placed back of the screen, from which the sound emerges. A main amplifier raises the energy of the feeble electric currents to a level adequate to supply the loudspeakers with sufficient volume to serve the specific theatre. As a step to follow the amplifier, there is an output control panel which consists of an auto-transformer, with a large number of taps. Each of the sound projectors or loud- speakers is connected to a dial switch, and these dial switches in turn are connected to the taps, so that each sound projector can be fed from any tap desired. Through this panel it is possible to make the impedance of the am- plifier output suitable for the desired number of horns, in order to obtain the most efficient use of the power avail- able, and also to adjust the relative volume of the indi- vidual horn. It will therefore be seen that the only difference between