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  2. Combination tone - Wikipedia

    en.wikipedia.org/wiki/Combination_tone

    The result is a pitch at a common subharmonic of the pitches played (one octave below the first pitch when the second is the fifth, 3:2, two octaves below when the second is the major third, 5:4). This effect is useful especially in the lowest ranks of the pipe organ where cost or space could prohibit having a rank of such low pitch.

  3. Frequency (statistics) - Wikipedia

    en.wikipedia.org/wiki/Frequency_(statistics)

    A frequency distribution shows a summarized grouping of data divided into mutually exclusive classes and the number of occurrences in a class. It is a way of showing unorganized data notably to show results of an election, income of people for a certain region, sales of a product within a certain period, student loan amounts of graduates, etc.

  4. Two-tone testing - Wikipedia

    en.wikipedia.org/wiki/Two-tone_testing

    Two signal generators, set to two different frequencies F1 and F2, are fed into a power combiner through circulators. The combiner needs to have good isolation to prevent the signal from one generator being sent to the output of the other. If this happens, intermodulation can occur in the non-linear parts of the generator internal circuit.

  5. Grouped data - Wikipedia

    en.wikipedia.org/wiki/Grouped_data

    Another method of grouping the data is to use some qualitative characteristics instead of numerical intervals. For example, suppose in the above example, there are three types of students: 1) Below normal, if the response time is 5 to 14 seconds, 2) normal if it is between 15 and 24 seconds, and 3) above normal if it is 25 seconds or more, then the grouped data looks like:

  6. Least-squares spectral analysis - Wikipedia

    en.wikipedia.org/wiki/Least-squares_spectral...

    The result of fitting a set of data points with a quadratic function. Least-squares spectral analysis (LSSA) is a method of estimating a frequency spectrum based on a least-squares fit of sinusoids to data samples, similar to Fourier analysis.

  7. Mixed-data sampling - Wikipedia

    en.wikipedia.org/wiki/Mixed-data_sampling

    A MIDAS regression is a direct forecasting tool which can relate future low-frequency data with current and lagged high-frequency indicators, and yield different forecasting models for each forecast horizon. It can flexibly deal with data sampled at different frequencies and provide a direct forecast of the low-frequency variable.

  8. Fast Fourier transform - Wikipedia

    en.wikipedia.org/wiki/Fast_Fourier_transform

    For cases where frequency information varies over time, alternative transforms like the wavelet transform can be more suitable. The wavelet transform allows for a localized frequency analysis, capturing both frequency and time-based information. This makes it better suited for applications where critical information appears briefly in the signal.

  9. Spectral density estimation - Wikipedia

    en.wikipedia.org/wiki/Spectral_density_estimation

    For instance, only non-linear or time-variant operations can create new frequencies in the frequency spectrum. In practice, nearly all software and electronic devices that generate frequency spectra utilize a discrete Fourier transform (DFT), which operates on samples of the signal, and which provides a mathematical approximation to the full ...