For no good reason...

On the way home today I was thinking about an experiment. I shall present it here in an A-Level physics practical style:

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Objective
To determine whether audio language or visual language attenuates more quickly with distance.

Equipment Required:
1. A blind person (A) with perfect hearing
2. A deaf person (B) with perfect sight
3. A person (C) who can speak and do sign language (sight and hearing optional)
4. A trolley
5. Ticker tape
6. A piece of lined paper
7. A sharp pencil

Method
1. Place the person, C, in the trolley facing towards persons A and B.
2. Attach the ticker tape to the trolley.
3. Get C to start talking and signing as normal. It doesn't matter what they say, as long as it is not totally predictable.
4. Ensure A can hear C's voice and B can see C's signs.
5. Raise A's right arm in the air.
6. Raise B's left arm in the air.
7. Pull the trolley away from A and B slowly. Ensure that the ticker tape is ticking whilst this is happening.
8. Ensure that A and B know the following things: (a) that B should lower his raised arm as soon as he can no longer understand C's signs and (b) that A should lower his raised hand as soon as he can no longer understand C's voice.
9. Probably best to do stage 8 before stage 3.
10 Wait until A or B does the thing from stage 8.
11. If neither person lowers their arm before the ticker tape runs out, politely re-explain the requirements to A and B. It may be necessary to enlist C's help to communicate with B. Restart the experiment from stage 2.
12. Record whose arm fell first on a piece of lined paper using a sharp pencil.

Results
???

Conclusion
???

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Sadly I am unable to complete the final two sections because I have not carried out the experiment. The reason I haven't done this is because I do not have any of the required equipment apart from the piece of lined paper. Not even a sharp pencil!

I tried doing it as a thought experiment but all the people I thought about (A, B and C) kept getting bored and wondering off halfway through. Idiots. And the trolley had a broken wheel.

So I'm a bit stuck. Can anyone help? Which is the best means of communication over longer distances - sign language or speaking? And is C allowed to shout and/or make really big gestures?