What attribute of electricity holds the information, i.e. the positive and negative movement of the speaker cone? How does that signal stay intact when going through things like capacitors etc.
I really don’t understand electronics.
Thanks!
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There are three ways.
1. Amplitude Modulation (AM) – you start with a carrier wave of some frequency much higher than the sound frequencies you want to transmit, typically around 1 MHz while sounds are something like 10 Hz – 10 kHz. (k = 1000, M = 1000,000). You then change the amplitude – i.e. wave height or signal strength – in time with the sound waves you want to transmit. This change in amplitude can be picked up at the other end of your circuit and transmitted to the speaker coils. This is done by using diodes to turn the AC into DC, and the DC can then be used to move the speaker cone – as the current in the speaker coils changes, the magnetic field changes and the speaker is moved around.
2. Frequency Modulation (FM) – you start with a carrier wave of some frequency, typically around 100 MHz, and change that frequency a small amount in time with the sound waves you want to transmit. To receive the signal, you can couple your receiver circuit to one which is tuned to be just off-resonance, meaning that its response will change amplitude according the the exact frequency of the incoming signal, and you’ve converted the FM into AM.
3. Digital: you encode the sound into a binary string (i.e. a set of 1s and 0s), and transmit high frequency pulses conveying 1 as high amplitude and 0 as low amplitude. You then decode this at the other end back into the sound. There’s less of a direct relationship between the transmitted information and the sound, and it can be encoded (i.e. represented) in lots of different ways – you just need the encoder and decoder to be doing the same thing, or you’ll end up with nonsense.
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