EE 445S Real-Time Digital Signal Processing Lab Spring 2017OutlineComb filtersSlide 4Slide 5Allpass filtersNotch filtersSome special effectsSlide 9Slide 10Other effectsEE 445S Real-Time Digital Signal Processing Lab Spring 2017Lab 7Guitar Special EffectsChao Jia & Sam Kanawati2OutlineComb filtersAllpass filtersNotch filtersSpecial effects with filtersOther effectshttps://www.youtube.com/watch?v=leSaAaWrkK0&index=3&list=RDw2S0o4Sjwis https://www.youtube.com/watch?v=D5kLsQUHuIU&index=4&list=RDw2S0o4Sjwis3In signal processing, a comb filter adds a delayed version of a signal to itself, causing constructive and destructive interference. The frequency response of a comb filter consists of a series of regularly spaced notches, giving the appearance of a comb.Comb filtersWhen two loudspeakers are playing the same signal at different distances from the listener, there is a comb filtering effect on the signal. Listeners hear a mixture of direct sound and delayed reflected sound. A comb filter is created where the two combine at the listener4Comb filtersFIR comb filter (single echo)Number of stopbands is R/25Comb filtersIIR comb filter (multiple echoes)6Allpass filters7Notch filters8Some special effectsEchoFIR or IIR comb filters Delay > 100msFlangingFIR comb filter with (periodically) varying delayDelay between 1ms and 10mshttps://www.youtube.com/watch?v=9LWRgA597O4 https://www.youtube.com/watch?v=NAqQvs_WXs8&t=176s9Some special effectsChorusSeveral independent comb filtershttps://www.youtube.com/watch?v=zmN7fK3fKUE10Some special effectsReverbMimic a enclosed space (lots of echoes)https://www.youtube.com/watch?v=TZG2K0J_A3c11Other effectsSpecial effects can also be generated by altering the amplitude of the signal.TremoloRepetitive up/down variation in the volumeFuzzIntentionally introduced distortion like