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Natural Science Forum / Physics / Acoustics / July 2006frequency resolution of an acoustic signal
I ran an experiment which involved sending a 2ms broad bandwidth signal and recording the reflected signal, but I'm curious as to what the frequency resolution is. The signal has a bandwidth of 18kHz, with a center frequency of 18kHz and a start and stop frequency of 9kHz and 27kHz, respectively. I'm a little confused as to what would be limiting the frequency resolution though. I've heard of this time-bandwidth product, although I'm not sure how to interpret it. Would it be this that is limiting the resolution or is it the sampling frequency of the function generator that I'm using? Thanks, -Josiah > I ran an experiment which involved sending a 2ms broad bandwidth signal > and recording the reflected signal, but I'm curious as to what the [quoted text clipped - 10 lines] > Thanks, > -Josiah Frequency resolution is established by the duration of your signal. The bandwidth of your signal dosen't matter. If your signal is 2msec in duration, you will not be able to resolve (identify) spectral components in your signal that are separated in frequency by less than 1/(0.002)sec or 500Hz. This is the standard definition of frequency resolution. If you mean something different, you need to clarify what you mean by frequency resolution. Another way of looking at frequency resolution is to consider how long you have to look at a multi-frequency signal to establish that there are two components separated by 100Hz (eg 10.0KHz + 10.1KHz). The answer is 100mSec. >> I ran an experiment which involved sending a 2ms broad bandwidth >> signal and recording the reflected signal, but I'm curious as to what [quoted text clipped - 23 lines] > are two components separated by 100Hz (eg 10.0KHz + 10.1KHz). The > answer is 100mSec. The answer is 10mSec (1/100Hz). HI, The frequency resolution is determined by the length of the signal pulse you send out. If you have a 2msec pulse going out then you don't have more than 2 msec of data to analyze. Look at doing an FFT or whatever with this signal of duration 2 ms and you'll see that the resolution is independent of the center, start and stop frequencies for the most part. You'll get the most bandwidth out of a square pulse of 2 ms duration, but that shouldn't be your only consideration. Regards, Jerry > I ran an experiment which involved sending a 2ms broad bandwidth signal > and recording the reflected signal, but I'm curious as to what the [quoted text clipped - 10 lines] > Thanks, > -Josiah |
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