Spectrograms are usually created in one of two ways: approximated as a filterbank that results from a series of bandpass filters (this was the only way before the advent of modern digital signal processing), or calculated from the time signal using the short-time Fourier transform (STFT). These two methods actually form two different quadratic Time-Frequency Distributions, but are equivalent under some conditions.
The bandpass filters method usually uses analog processing to divide the input signal into frequency bands; the magnitude of each filter's output controls a transducer that records the spectrogram as an image on paper.
Creating a spectrogram using the STFT is usually a digital process. Digitally sampled data, in the time domain, is broken up into chunks, which usually overlap, and Fourier transformed to calculate the magnitude of the frequency spectrum for each chunk. Each chunk then corresponds to a vertical line in the image; a measurement of magnitude versus frequency for a specific moment in time. The spectrums or time plots are then "laid side by side" to form the image or a three-dimensional surface.
The spectrogram of a signal s(t) can be estimated by computing the squared magnitude of the STFT of the signal s(t), as follows:
Read more about this topic: Spectrogram
Other articles related to "generation, generations":
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Famous quotes containing the word generation:
“Society in America means all the honest, kindly-mannered, pleasant- voiced women, and all the good, brave, unassuming men, between the Atlantic and the Pacific. Each of these has a free pass in every city and village, good for this generation only, and it depends on each to make use of this pass or not as it may happen to suit his or her fancy.”
—Henry Brooks Adams (18381918)
“We need to encourage members of this next generation to become all that they can become, not try to force them to become what we want them to become. . . . You and I cant even begin to dream the dreams this next generation is going to dream, or answer the questions that will be put to them.”
—Barbara Coloroso (20th century)
“There is hardly an American male of my generation who has not at one time or another tried to master the victory cry of the great ape as it issued from the androgynous chest of Johnny Weissmuller, to the accompaniment of thousands of arms and legs snapping during attempts to swing from tree to tree in the backyards of the Republic.”
—Gore Vidal (b. 1925)