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For general audio programming or playback, 96kHz or 192hHz is simply useless. Indeed, the Nyquist theorem tells you that a signal can be exactly reproduced given that the sample rate is greater than the highest frequency contained in the original signal. The "excuse" of the slope of analog filter required after digital to analog conversion is no longer ...

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because the higher the sampling rate is the sloppier the (annalogue) filtering preceding the sampler can be to reduce the aliased noise/interference

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The intensity of your signal at every moment is given indeed by |x(t)|^2, s.t. the total intensity of the signal during the time is the integration of |x(t)|^2 over time. About the connection with the frequency, see below. You can describe the signal by its behavior in time x(t). But you can decompose it in sine and cosine functions, i.e. (1) $x(t)$ = ...

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If $x(t)$ is the current through a resistor $R$, then the voltage is $Rx(t)$ and then the instantaneous power dissipated is $Rx(t)\bar{x}(t)$ and the dissipated energy over all times is $E_s=\int R\vert {x(t)}\vert ^2 dt$. Because of Parseval's theorem you can write mean square in time as the mean square of the frequency spectrum, ie., Fourier transform ...

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Hobbs answer is accurate. I just want to point out that "phase-coherent" is a confusing term because what should be said is they are phase-continuous at the symbol rate. This means that as one tone is switched to the other there are no phase jumps and the wave form is continuous like in this example. You can see your two different rates 1800 and 1200 ...

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They're phase-coherent with respect to the symbol rate. Suppose you're doing conventional coherent FSK with 1200Hz and 1800Hz tones, and 600 symbols per second. A switch can instantaneously connect either tone to the output, and the tones are continuous (they keep their phase even when they're not being output). Start a symbol at an instant when the 1200Hz ...

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You do know that your phone will transmit only enough power to reach the nearest tower right? Most of the time that is much less than the max it is capable of. But when there are buildings between you and the tower or you are on the open road you'll be happy not to be dropping so many calls... So there are two things to notice here. First - every 3 dB ...

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