1 / 17

Calculation of a constant Q spectral transform

Calculation of a constant Q spectral transform. Judith C. Brown. Journal of the Acoustical Society of America,1991. Jain-De,Lee. Outline. INTRODUCTION CALCULATION RESULTS SUMMARY. INTRODUCTION. The work is based on the property that, for sounds made up of harmonic frequency components.

ace
Download Presentation

Calculation of a constant Q spectral transform

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Calculation of a constant Q spectral transform Judith C. Brown Journal of the Acoustical Society of America,1991 Jain-De,Lee

  2. Outline • INTRODUCTION • CALCULATION • RESULTS • SUMMARY

  3. INTRODUCTION • The work is based on the property that, for sounds made up of harmonic frequency components

  4. INTRODUCTION • The positions of these frequency components relative to each other are the same independent of fundamental frequency

  5. INTRODUCTION • The conventional linear frequency representation • Rise to a constant separation • Harmonic components vary with fundamental frequency • The result is that it is more difficult to pick out differences in other features • Timbre • Attack • Decay

  6. INTRODUCTION • The log frequency representation • Constant pattern for the spectral components • Recognizing a previously determined pattern becomes a straightforward problem • The idea has theoretical appeal for its similarity to modern theories • The perception of the pitch–Missing fundamental

  7. INTRODUCTION • To demonstrate the constant pattern for musical sound • The mapping of these data from the linear to the logarithmic domain • Too little information at low frequencies and too much information at high frequencies • For example • Window of 1024 samples and sampling rate of 32000 samples/s and the resolution is 31.3 Hz(32000/1024=31.25) • The violin low end of the range is G3(196Hz) and the adjacent note is G#3(207.65 Hz),the resolution is much greater than the frequency separation for two adjacent notes tuned

  8. INTRODUCTION • The frequencies sampled by the discrete Fourier transform should be exponentially spaced • If we require quartertone spacing • The variable resolution of at most ( 21/24 -1)= 0.03 times the frequency • A constant ratio of frequency to resolution f/δf = Q • Here Q =f /0.029f= 34

  9. CALCULATION • Quarter-tone spacing of the equal tempered scale ,the frequency of the k th spectral component is • The resolution f/δf for the DFT, then the window size must varied fk = (21/24)kfmin Where f an upper frequency chosen to be below the Nyquist frequency fmincan be chosen to be the lowest frequency about which Information is desired

  10. CALCULATION • For quarter-tone resolution • Calculate the length of the window in frequency fk Q = f / δf = f / 0.029f = 34 Where the quality factor Q is defined as f / δf bandwidth δf = f / Q Sampling rate S = 1/T N[k]= S / δfk = (S / fk)Q

  11. CALCULATION • We obtain an expression for the k th spectral component for the constant Q transform • Hamming window that has the form W[k,n]=α + (1-α)cos(2πn/N[k]) Where α= 25/46 and 0 ≤ n ≤ N[k]-1

  12. CALCULATION

  13. CALCULATION

  14. RESULTS

  15. RESULTS

  16. RESULTS Constant Q transform of piano playing diatonic scale from C4 (262 Hz) to C5(523 Hz) The attack on D5(587 Hz) is also visible Constant Q transform of violin playing diatonic scale pizzicato from G3 (196 Hz) to G5(784 Hz) Constant Q transform of violin playing D5(587 Hz) with vibrato Constant Q transform of violin glissando from D5 (587 Hz) to A5 (880Hz) Constant Q transform of flute playing diatonic scale from C4 (262 Hz) to C5 (523 Hz) with increasing amplitude

  17. SUMMARY • Straightforward method of calculating a constant Q transform designed for musical representations • Waterfall plots of these data make it possible to visualize information present in digitized musical waveform

More Related