# Three memory systems, what transforms are needed to synchronize them?

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In a mechanical memory system, such as a tape recorder or gramophone, the input movements of sound waves are constrained by the mechanism to motions back and forth along a single line. A separate mechanism(s) adds motion along a different line to stretch the needle marks far enough that they don't overlap at frequencies within the design range.

The question is, how can the speed and direction of the added movement(s) be calculated from the recording needle track?

With a needle bouncing perpendicular to the length of a recording tape, if the tape moves in a straight line past the moving needle there are only two directions to choose from. Can we tell if the tape speed changes at some point?

With a gramophone, the needle bounces perpendicular to the arm it is mounted on. The spin of the disc and the slide of the needle toward or away from the disc center combine to make a spiral track. Can the length of the arm which slides the needle along an arc be determined from the track on the disc? How can the speed of the spin be determined? Near the outer edge of the disc, the speed of the needle relative to the disc surface is faster. What is a method for mathematical transformation of the recorded sound pattern at the faster speed to the same sound pattern at the slower speed near the disc center?

When the needle mount is moved in a straight line at an angle not perpendicular to the bouncing, how would you calculate the difference in shapes of the sound waves vs that recorded on a perpendicular?

This puzzle is presented for the entertainment of better educated mathematicians than me.

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14 minutes ago, OptimisticCynic said:

In a mechanical memory system, such as a tape recorder or gramophone, the input movements of sound waves are constrained by the mechanism to motions back and forth along a single line. A separate mechanism(s) adds motion along a different line to stretch the needle marks far enough that they don't overlap at frequencies within the design range.

Sound waves are indeed longitudinal, but aren't the mechanical copies impressed on the medium transverse ?

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1 minute ago, studiot said:

Sound waves are indeed longitudinal, but aren't the mechanical copies impressed on the medium transverse ?

Sound waves are not just longitudinal. They move out spherically from the source. Plus, when you have multiple sound sources, they get really mixed up in three dimensions.

In the simplest mechanism, a circular diaphragm has a needle mounted at its center. This center mounting on a diaphragm fixed around the circumference constrains the needle to move (almost, some very limited material flexing) only perpendicular to the plane of the diaphragm.

For a gramophone, the precursor to the spinning disc record player you're probably familiar with, the diaphragm was mounted edge vertical. The needle had a bend so the tip, bouncing transverse to the spin, would touch the disc.

Edison's original phonograph made indentations of varying depth in a foil. Many different configurations of mounting the diaphragm, bending the needle, and moving the recording surface are possible. The gramophone design was more practical.

The same song could be recorded simultaneously on multiple configurations and at multiple speeds. As long as the direction and speed were repeated correctly for each, the playback would be effectively identical. If you didn't already know the correct direction and speed to play the record, is there a way to calculate it from examining the track?

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1 hour ago, OptimisticCynic said:

Sound waves are not just longitudinal. They move out spherically from the source. Plus, when you have multiple sound sources, they get really mixed up in three dimensions.

In the simplest mechanism, a circular diaphragm has a needle mounted at its center. This center mounting on a diaphragm fixed around the circumference constrains the needle to move (almost, some very limited material flexing) only perpendicular to the plane of the diaphragm.

For a gramophone, the precursor to the spinning disc record player you're probably familiar with, the diaphragm was mounted edge vertical. The needle had a bend so the tip, bouncing transverse to the spin, would touch the disc.

Edison's original phonograph made indentations of varying depth in a foil. Many different configurations of mounting the diaphragm, bending the needle, and moving the recording surface are possible. The gramophone design was more practical.

The same song could be recorded simultaneously on multiple configurations and at multiple speeds. As long as the direction and speed were repeated correctly for each, the playback would be effectively identical. If you didn't already know the correct direction and speed to play the record, is there a way to calculate it from examining the track?

Thank you, I know how sound systems work.

Until the advent of digitisation, all the recording systems I know of have been transverse to the direction of travel of the recording medium, from soot on glass plates through impressions in wax cylinders to linear tracks on long pieces of paper to spiral tracks on disks.

What I am trying to understand is what your question is.

Do I understand that you wish to analyse this track to determine playing speed ?

If the track was a piece of music, a musician would be able to determine the number of beats per minute for the piece.

So if you played and timed it at any old speed, correcting it to the beat would do it for you.

I am not a musician so would not be able to tell you if Fourier analysis would do this for you instead, however I have done FA for engine analysis achieving the same purpose.

Effectively you need a Rosetta length embedded in the sound track that you can calibrate.

By the way I once read a very amusing science fiction short story about aliens who did this, not for sound but for a film strip they found in the ruins of an old dead civilisation. They worked out that running the film through a suitable projector they created,  would produce a 'movie'.

But they didn't know how fast to run the film.  That was when the fun started.

?

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9 hours ago, studiot said:

By the way I once read a very amusing science fiction short story about aliens who did this, not for sound but for a film strip they found in the ruins of an old dead civilisation. They worked out that running the film through a suitable projector they created,  would produce a 'movie'.

But they didn't know how fast to run the film.  That was when the fun started.

Would differing flicker fusion rates cause issues?

Edited by Endy0816
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17 hours ago, Endy0816 said:

Would differing flicker fusion rates cause issues?

Sorry I don't understand the question.

Nor do I understand why the OP, who I see has been back several times since I posted, has not responded.

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5 hours ago, studiot said:

Sorry I don't understand the question.

Probably overanalyzing this, but a different species might not see it playing correctly at the original rate.

The equivalent of a dog watching an early human film.

They randomly might be okay too though.

Edited by Endy0816
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You obviously know more about flicker frequencies than I do.

But yes, that is why I said a rosetta stone is needed.

Something to tie distance along the sound track to time, such as a musical beat or in my case the engine rpm.

The  OP was wanting to analyse a sound track, but I can tell you more about the sf short story if you like.
It has a very funny punchline, which you flicker frequency would be relevant to.

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5 hours ago, studiot said:

You obviously know more about flicker frequencies than I do.

But yes, that is why I said a rosetta stone is needed.

Something to tie distance along the sound track to time, such as a musical beat or in my case the engine rpm.

The  OP was wanting to analyse a sound track, but I can tell you more about the sf short story if you like.
It has a very funny punchline, which you flicker frequency would be relevant to.

Sure, sounds interesting.

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OK it was in the Gollanz Christmas SF annual circe mid 1960s, I can't remember the title or author though.

The gist of the story was that a manned space probe was investgating solar systems and came across one where there was a planet that had been inhabited by a technologically advanced race.

But the planet had been devasted in a great disaster, which appeared to be the result of a mighty war wiping out the race entirely.

In digging over the ruins to find out more about the long dead race,  the scientists came across a reel of clear material containing pictures in sequence.

They worked out that the strip could be run through a viewer, combining the individual pictures revealing a moving image.

When they did this they saw a creature rushing about chasing another smaller creature about the landscape and being constantly knocked  over ( and then geting up again) by large hurtling objects.

They wondered what sort of a world it was that life made life so frenetic and pondered if that was what caused the final conflagration.

Then they came to the last picture, apparantly disconnected from the rest which had a strange design they could not decipher  "Walt Disney Productions -  The End"

The author tried his best to make it seem as though the investigators were human until that last punchline.

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