62361Re: Transmitting Sound by the Tracks
- Jun 30, 2009I don't know any sites explaning this and a quick search only comes up with common DC and DCC components. I am wondering if this goes back to the AC rail days and Neil Young's (yes, that Neil Young) patent for Sound for Model Railroading.
To send it down the rails, the problem is isolating the motor's low impedance, essentially adsorbing the higher frequencies. Components can be used to reduce this effect but electrical contact variations would drive this design crazy in my opinion. The components for this are more practical in larger scales. The speaker itself will loo
Even with off the shelf DC and DCC decoders, as Alan says, the sound is limited to just the highest of frequencies. One scheme here is Surroundtrax using block detection and under layout speakers that provide better sound but also only for DCC. MRC's (K-E-Y, m-o-u . . . .) Synchro Sound for DC uses a single speaker under the layout:
SF Bay Area Z
In email@example.com, Alan Cox <alan@...> wrote:
> > "Another type of analog system is to have a sound unit located at the control panel and use the track rails as "wires" to send the filtered audio impulse to a speaker on board the loco."
> Using the rails as a carrier - basically "radio over rails". You mix the
> near DC of the rails with an audio signal modulated on a carrier high
> enough in frequency you can filter it from the motor ok.
> Doesn't really make much sense in Z because the biggest Z problem is
> speaker size anyway. If you want good sound in Z put speakers in the
> corner of the room and use surround sound. It's still a fair bit of work
> (track sensors and software to work out what to play but the hard bits of
> the audio work are all done by standard PC libraries like OpenAL)
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