Timeline for Meaning of frequency and bandwidth of a signal, despite the fact that we do not know the signal
Current License: CC BY-SA 4.0
7 events
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| May 12, 2021 at 14:39 | comment | added | MBaz | There's no need to measure until infinity. You measure in a time range, and find the energy in the same time range. After sufficient measurements you declare that no energy will be found outside the range. It's the same process that scientists follow when they declare gravity is a universal law. I mean, gravity could flip direction at any time, right? Experience tells us that there is no need to worry about it (which is not the same as saying it is categorically impossible). | |
| May 12, 2021 at 14:32 | comment | added | Anastassis Kapetanakis | Do we measure the energy till current time? If yes, isn't there the chance that as we let a person speak in a microphone for a long period of time, the frequencies that were negligible might now show up in the spectrum? | |
| May 12, 2021 at 14:26 | comment | added | Anastassis Kapetanakis | How do we measure the energy of a signal? Again, as far as I know, to measure the energy of a signal you have to know how it behaves till $\infty$. | |
| May 12, 2021 at 14:13 | comment | added | MBaz | Also: when you hear DSP practitioners talk about a signal's frequency content, they are not referring to a pure tone (unless specified). When it is said that the human voice contains frequencies in a certain range, there is no implication that those frequencies are discrete. This claim should be interpreted as "human voice contains energy that is concentrated in this range of frequencies, with none to very little energy outside the range". | |
| May 12, 2021 at 14:10 | comment | added | MBaz | As Hilmar says: experiments and physics. When people talk into a microphone connected to a spectrum analyzer, no energy is detected outside that range. This is so consistent that scientists and engineers apply the deductive method and declare that range as the bandwidth of human voice. Researchers have also created mathematical models of the vocal tract and have a good understanding of what frequencies it is capable of creating. | |
| May 12, 2021 at 13:56 | comment | added | Anastassis Kapetanakis | You said that human vocal tract can generate signals netween 50Hz and 10000Hz. But speech is not just a tone with specific frequency. It's a sequence of tones with different frequencies each. So, when we create a bandpass filter(or whatever) that allows only those frequencies to pass, how do we know that the signal produced by me speaking has a bandwidth between those two frequencies, in order to create the impulse response of the filter? How do I know that the frequencies that are present in the Fourier Transform of the speech signal are connected with the tones I produced during speech? | |
| May 12, 2021 at 13:48 | history | answered | MBaz | CC BY-SA 4.0 |