Loud networking with 2-AFSK
I wonder how far one could transmit using only sound waves in open air? I am considering something that would not be intrusive, so it needs to emit below the regulated acceptable ambient sound pressure limits (about 30-40dB here). I only intend to operate it intermittently, maybe for a few seconds in every hour - depending on attainable bandwidth. My ultimate goal is to be able to transfer about an SMS in a run, but I would be more than happy to make trade-offs that could result in quieter operation.
Higher frequency carriers could both provide more bandwidth easily and be inaudible at the same time, but there's a catch. They say, sound waves below about 1kHz usually penetrate air much better than ultrasounds. I need to test this specifically, but about at most 500Hz-1000Hz looks like a hard upper limit for long range transmission according to the graphs. Another drawback of larger wavelengths is the enormous sized dish that would be needed to concentrate the beam of sound. By the way, I need to do further research to find the most economical materials to build a dish.
This is of course just an experiment, and the system would benefit vastly from better modulation techniques, like those used in newer modems.
Higher frequency carriers could both provide more bandwidth easily and be inaudible at the same time, but there's a catch. They say, sound waves below about 1kHz usually penetrate air much better than ultrasounds. I need to test this specifically, but about at most 500Hz-1000Hz looks like a hard upper limit for long range transmission according to the graphs. Another drawback of larger wavelengths is the enormous sized dish that would be needed to concentrate the beam of sound. By the way, I need to do further research to find the most economical materials to build a dish.
This is of course just an experiment, and the system would benefit vastly from better modulation techniques, like those used in newer modems.
Comments
Post a Comment