Audio signal processing effects equalizer compressor, limiter noise gates flanger chorus phaser leslie pitch-shift - time scaling Acoustics II: time reversal signal restoration clicks audio signal processing tape speed variations hum noise examples back Kurt Heutschi 2013-01-18
Audio signal processing effects equalizer compressor, limiter noise gates flanger chorus phaser leslie pitch-shift - time scaling effects time reversal signal restoration clicks tape speed variations hum noise examples back
Audio signal effects: introduction processing effects equalizer compressor, limiter noise gates flanger chorus phaser ◮ effects: alteration of the original sound such as: leslie pitch-shift - time scaling time reversal ◮ adjustment of the frequency response signal restoration ◮ reduction of the audibility of unwanted signal clicks tape speed variations components hum ◮ .... noise examples ◮ creation of new sounds back
Audio signal processing effects equalizer compressor, limiter noise gates flanger chorus phaser leslie pitch-shift - time scaling equalizer time reversal signal restoration clicks tape speed variations hum noise examples back
Audio signal equalizer: function processing effects equalizer compressor, limiter ◮ function: noise gates flanger chorus ◮ manipulation of the amplitude response of a sound phaser leslie or a transmission system pitch-shift - time scaling time reversal ◮ applications: signal restoration ◮ flatten a non-ideal frequency response of a clicks tape speed variations loudspeaker hum noise ◮ loudness filtering examples ◮ attenuation of the low frequency end in PA back systems for speech ◮ equalization of headphones ◮ ....
Audio signal equalizer: realizations processing effects equalizer compressor, limiter noise gates flanger chorus phaser ◮ parametric equalizer: leslie pitch-shift - time scaling ◮ several bandpass/notch filters with variable time reversal ◮ center frequency signal restoration ◮ bandwidth clicks tape speed variations ◮ amplification/attenuation hum noise ◮ universal applicability, however not that intuitive examples back to reproduce a predefined amplitude response
Audio signal equalizer: realizations processing ◮ graphical equalizer: effects equalizer ◮ series of adjacent bandpass filters of constant compressor, limiter noise gates relative bandwidth flanger chorus ◮ third-octave filters (typ. 30 bands) phaser ◮ octave filters (typ. 10 bands) leslie pitch-shift - time scaling ◮ adjustable amplification/attenuation in each band time reversal (typ. +/- 15 dB) signal restoration clicks ◮ setting with linear controllers → graphical tape speed variations hum representation of the amplitude response noise examples back
Audio signal processing effects equalizer compressor, limiter noise gates flanger chorus phaser leslie pitch-shift - time scaling compressor/limiter time reversal signal restoration clicks tape speed variations hum noise examples back
Audio signal compressor/limiter: function processing effects equalizer compressor, limiter ◮ function: noise gates flanger chorus ◮ reduction of the signal dynamics phaser leslie ◮ applications for compressors: pitch-shift - time scaling time reversal ◮ increase of loudness with given maximal signal signal restoration amplitude clicks tape speed variations ◮ music production hum ◮ commercials noise examples ◮ radio stations (listeners are often in noisy back environment) ◮ applications for limiters: ◮ avoid clipping in digital recordings
Audio signal compressor/limiter: principle of operation processing effects equalizer compressor, limiter noise gates flanger chorus phaser leslie pitch-shift - time scaling time reversal signal restoration clicks tape speed variations hum noise examples ◮ VCA: Voltage Controlled Amplifier back ◮ steering voltage: smoothed input signal ◮ amplification is lowered above an adjustable threshold
Audio signal compressor/limiter: characteristics processing effects ◮ example (threshold = 0 dB) equalizer compressor, limiter ◮ input level → amplification noise gates flanger chorus phaser leslie pitch-shift - time scaling time reversal signal restoration clicks tape speed variations hum noise examples back
Audio signal compressor/limiter: characteristics processing effects ◮ example (threshold = 0 dB) equalizer compressor, limiter ◮ input level → output level noise gates flanger chorus phaser leslie pitch-shift - time scaling time reversal signal restoration clicks tape speed variations hum noise examples back
Audio signal compressor/limiter: time constants processing ◮ VCA is steered by the level of the audio signal effects ◮ determination of the level needs an average process equalizer compressor, limiter noise gates ◮ choice of the time constant is critical flanger chorus ◮ implementation of two constants: positive for signal phaser leslie increase and negative for signal decrease pitch-shift - time scaling time reversal ◮ positive slope time constant too small → signal restoration distortion of start transients of musical instruments clicks tape speed variations ◮ negative slope time constant too small → hum noise pumping: modulation of the signal by dominant examples components back ◮ positive/negative slope time constant too large → signal dynamics is not properly reduced due to delayed reaction ◮ typical values: ◮ positive slope: order of milliseconds ◮ negative slope: 10 to 3000 milliseconds
Audio signal compressor/limiter: example processing effects equalizer compressor, limiter noise gates flanger chorus phaser ◮ original sample leslie pitch-shift - time scaling ◮ → original time reversal signal restoration ◮ compression starting 25 dB below full-scale → clicks tape speed variations approx. 10 dB higher signal power at identical peak hum value noise examples ◮ → with compression back
Audio signal compressor/limiter: finalizer processing effects equalizer compressor, limiter noise gates flanger chorus phaser ◮ loudness war leslie pitch-shift - time scaling ◮ producers push perceived loudness to maximum time reversal signal restoration ◮ increasing concern regarding audio quality clicks ◮ loss in dynamic range tape speed variations hum ◮ unofficial dynamic range data base: noise examples http://www.dr.loudness-war.info/ back
Audio signal compressor/limiter: finalizer: loudness war processing effects equalizer compressor, limiter noise gates flanger chorus → Metallica: Death Magnetic: My Acopalypse, 2008 phaser leslie pitch-shift - time scaling time reversal signal restoration clicks tape speed variations hum noise examples back
Audio signal processing effects equalizer compressor, limiter noise gates flanger chorus phaser leslie pitch-shift - time scaling noise gates time reversal signal restoration clicks tape speed variations hum noise examples back
Audio signal noise gates: function processing effects equalizer compressor, limiter noise gates flanger chorus phaser leslie ◮ function: pitch-shift - time scaling time reversal ◮ attenuation of low level signals signal restoration clicks ◮ applications: tape speed variations hum ◮ suppression of noise during pauses of the signal noise examples back
Audio signal noise gates processing effects ◮ parameters: level and step equalizer compressor, limiter noise gates flanger chorus phaser leslie pitch-shift - time scaling time reversal signal restoration clicks tape speed variations hum noise examples back
Audio signal processing effects equalizer compressor, limiter noise gates flanger chorus phaser leslie pitch-shift - time scaling flanger time reversal signal restoration clicks tape speed variations hum noise examples back
Audio signal flanger: principle processing effects equalizer compressor, limiter noise gates ◮ summation of signal and a delayed copy flanger chorus ◮ slow variation (0.1 Hz) of the delay (couple of phaser leslie pitch-shift - time scaling milliseconds) time reversal signal restoration clicks tape speed variations hum noise examples back
Audio signal flanger: comb filter processing effects ◮ → comb filter for delay τ : equalizer compressor, limiter ◮ maxima: f = 0 , 1 τ , 2 τ , 3 noise gates τ flanger chorus ◮ minima: f = 2 τ , 3 1 2 τ , 5 phaser 2 τ leslie pitch-shift - time scaling time reversal signal restoration clicks tape speed variations hum noise examples back
Audio signal flanger: comb filter processing effects equalizer compressor, limiter noise gates flanger chorus phaser leslie pitch-shift - time scaling ◮ time dependency of the delay variation function time reversal ◮ e.g. sinusoidal → uneven variation of the signal restoration clicks maxima/minima frequencies tape speed variations hum ◮ in general → non-sinusoidal time function noise examples back
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