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Re: ?

At what level would an FM signal be so masked by noise that it would be theoretically impossible for a radio tuner to capture it and detect it? Looks like I've got to go hunting down some old textbooks and pour through them. I'm sure the phenomenon of s/n ratios and the point beyond which no usable informaton can be retrieved has been well studied both theoretically and practically. Somehow I thought it was defined as 0db.

One thing should be kept in mind about assessing noise in sound fields as opposed to electrical analogs and that is that sound fields are vectors while the electrical signals are scalars. This means that sound fields with very low S/N ratios only a fraction of a db above the ambient noise threshold can be collected and summed to enhance S/N ratio making it highly audible. I think there are a couple of spots under the Capitol dome where you and another person can stand and whisper to each other and clearly hear each other despite very high ambient noise levels. This is due to the dome acting somewhat like a parabolic reflector focusing sound the way a reflector telescope mirror focuses light. The famous "Big Ear" was a parabolic dish you could buy with a microphone mounted at the dish's focal point connected to an amplifier and earphones. This would allow you to focus sounds too soft for human hearing but above ambient noise...like your neighbors fighting behind closed doors and windows :-)


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  • Re: ? - Soundmind 13:01:44 06/17/06 (1)
    • Re: ? - Ted Smith 13:08:24 06/17/06 (0)


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