Audio on 16mm projector at DVinfo.net

Mitch Buss · August 28th, 2006, 11:36 PM

I recently acquired a 16mm Bell and Howell projector that plays sound as well. It reads the audio print with the exciter lamp. I was wondering if anyone can tell me how this works. I have no idea and am extremely curious. Thanks.

Richard Alvarez · August 29th, 2006, 09:17 AM

Look closely at the filmstock. You will see a portion of the filmstock that appears to be black, with a clear wiggly line running through it. This is the sound track. The exciter lamp projects a light through this track and strikes a photo receptor on the other side. Because the wiggly line alters the ammount of light that reaches the receptor, the voltage is regulated. This is translated into sound.

A physical parrallel can be drawn between the wavy grooves in a record and the wavy lines of the optical sound track.

Mitch Buss · August 30th, 2006, 01:12 AM

So that is how the different sounds are made, just by the amount of light that is let through? That is amazing. Thanks for the info!

Richard Alvarez · August 30th, 2006, 08:10 AM

Mitch.

Not so amazing when you think about it. Analogue processes all use a wave form for emulating their information stream. Amplitude and frequency information are both contained in a wave. The wave can be a physical representation... again, like the grooves in a record OR the wavy lines on the sound track. One uses the vibration of a needle, the other the vibration of the light source. Even your speakers are simply 'vibrating' to transmit sound. The reverse of that process in the old telephone speakers is the carbon particles underneath the plastic diaphragm in the mouthpiece.

Digital information, when you get down to it, is a SAMPLING of those waves, broken down into tiny bits and transmitted in a stream.

Remember my friends, we LIVE IN AN ANALOGUE WORLD.

August 28th, 2006, 11:36 PM	#1
Mitch Buss Regular Crew Join Date: May 2004 Location: Chicago, IL Posts: 184	Audio on 16mm projector I recently acquired a 16mm Bell and Howell projector that plays sound as well. It reads the audio print with the exciter lamp. I was wondering if anyone can tell me how this works. I have no idea and am extremely curious. Thanks.

August 29th, 2006, 09:17 AM	#2
Richard Alvarez Inner Circle Join Date: Sep 2002 Location: San Mateo, CA Posts: 3,840	Look closely at the filmstock. You will see a portion of the filmstock that appears to be black, with a clear wiggly line running through it. This is the sound track. The exciter lamp projects a light through this track and strikes a photo receptor on the other side. Because the wiggly line alters the ammount of light that reaches the receptor, the voltage is regulated. This is translated into sound. A physical parrallel can be drawn between the wavy grooves in a record and the wavy lines of the optical sound track.

August 30th, 2006, 01:12 AM	#3
Mitch Buss Regular Crew Join Date: May 2004 Location: Chicago, IL Posts: 184	So that is how the different sounds are made, just by the amount of light that is let through? That is amazing. Thanks for the info!

August 30th, 2006, 08:10 AM	#4
Richard Alvarez Inner Circle Join Date: Sep 2002 Location: San Mateo, CA Posts: 3,840	Mitch. Not so amazing when you think about it. Analogue processes all use a wave form for emulating their information stream. Amplitude and frequency information are both contained in a wave. The wave can be a physical representation... again, like the grooves in a record OR the wavy lines on the sound track. One uses the vibration of a needle, the other the vibration of the light source. Even your speakers are simply 'vibrating' to transmit sound. The reverse of that process in the old telephone speakers is the carbon particles underneath the plastic diaphragm in the mouthpiece. Digital information, when you get down to it, is a SAMPLING of those waves, broken down into tiny bits and transmitted in a stream. Remember my friends, we LIVE IN AN ANALOGUE WORLD.