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## Main Question or Discussion Point

Ok, so in the interest of full disclosure at the outset, I'm a 69 y.o. retired epidemiologist who has an interest in HRV signal analysis specifically, and physics as a whole--always have. Am not an EE, physicist or mathematician so be kind, if you will. This is my first post.

In signal analysis (let's assume EM signal), I do have (I believe) a basic understanding of the use of Fourier analysis to decompose the signal/function into its oscillatory components via sine and cosine functions. And, if desired, to use Fourier synthesis to reverse the process to obtain the original signal. Where I am "lost" is that these "component" sine and cosine signals obviously don't represent the actual contributory signals which sum to produce the signal being examined. E.g., we have a given acoustic EM signal consisting of various overlaying frequencies and amplitudes.

Think a musical composition. How does one "dissect" the actual contributing component signal frequencies and amplitudes (I realize there are other qualities such as tonality and timbre in music which I'm not concerned about here) that are resulting in the final observed/listened-to signal. Seemingly, just because one can decompose a signal into sine/cosine functions does not indicate that those functions actually exist within the studied signal.

I hope I am getting my question across and apologize to those readers who are more well-versed in this topic than I am. I will leave this be before even professing more than I presume to understand at this point. Thank you kindly.

In signal analysis (let's assume EM signal), I do have (I believe) a basic understanding of the use of Fourier analysis to decompose the signal/function into its oscillatory components via sine and cosine functions. And, if desired, to use Fourier synthesis to reverse the process to obtain the original signal. Where I am "lost" is that these "component" sine and cosine signals obviously don't represent the actual contributory signals which sum to produce the signal being examined. E.g., we have a given acoustic EM signal consisting of various overlaying frequencies and amplitudes.

Think a musical composition. How does one "dissect" the actual contributing component signal frequencies and amplitudes (I realize there are other qualities such as tonality and timbre in music which I'm not concerned about here) that are resulting in the final observed/listened-to signal. Seemingly, just because one can decompose a signal into sine/cosine functions does not indicate that those functions actually exist within the studied signal.

I hope I am getting my question across and apologize to those readers who are more well-versed in this topic than I am. I will leave this be before even professing more than I presume to understand at this point. Thank you kindly.

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