Comb filter In 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 spikes, giving the appearance of a comb. Applications[edit] Comb filters are used in a variety of signal processing applications. These include: In acoustics, comb filtering can arise in some unwanted ways. Technical discussion[edit] Comb filters exist in two different forms, feedforward and feedback; the names refer to the direction in which signals are delayed before they are added to the input. Comb filters may be implemented in discrete time or continuous time; this article will focus on discrete-time implementations; the properties of the continuous-time comb filter are very similar. Feedforward form[edit] Feedforward comb filter structure The general structure of a feedforward comb filter is shown on the right. where is the delay length (measured in samples), and . . , giving . .
Flanging Origin[edit] As an audio effect, a listener hears a "drainpipe" or "swoosh" or "jet plane" sweeping effect as shifting sum-and-difference harmonics are created analogous to use of a variable notch filter. The term "flanging" comes from one of the early methods of producing the effect. The finished music track is recorded simultaneously to two matching tape machines, then replayed with both decks in sync. The playback-head output from the two recorders is mixed to a third recorder. Despite subsequent claims over who originated flanging, Les Paul discovered the effect in the late 1940s and 1950s, however, he did most of his early phasing experiments with acetate disks on variable-speed record players. Others have attributed it to George Chkiantz, an engineer at Olympic Studios in Barnes, London. Kendrick's setup to control flanging A similar "jet plane-like" effect occurs naturally in long distance shortwave radio music broadcasts. Artificial flanging[edit] "Barber pole" flanging[edit]
The technology of Phase Shifters and Flangers Copyright 1999 R.G.Keen. All rights reserved. No portion of these materials may be reproduced without written permission of the author. The technology of phase shifters and flangers Practically every guitarist has heard the swirling, spacey sounds characteristic of a phaser or its cousin, the flanger. These boxes have a unique sound that is immediately recognizable to us in rock and processed acoustic music. What is phase shift? There is only a little electronics knowledge needed here. If we have another sine wave that is the same size and frequency but has different zero crossing times, it is said to be shifted in phase relative to the first wave. If we have a situation where two waves of the same frequency, perhaps the same wave, but one image delayed a tiny bit of time, are added together somehow, they may reinforce one another or partially cancel one another. Take a little time... This same result happens for higher frequencies. Phase up to it... More than one way to make a shift
Phaser (effect) A phaser is an electronic sound processor used to filter a signal by creating a series of peaks and troughs in the frequency spectrum. The position of the peaks and troughs is typically modulated so that they vary over time, creating a sweeping effect. For this purpose, phasers usually include a low-frequency oscillator. Spectrogram of an 8-stage phaser modulated by a sine LFO applied to white noise. The electronic phasing effect is created by splitting an audio signal into two paths. The definition of phaser typically excludes such devices where the all-pass section is a delay line; such a device is called a flanger.[1] Using a delay line creates an unlimited series of equally spaced notches and peaks. The number of all-pass filters (usually called stages) varies with different models, some analog phasers offer 4, 6, 8 or 12 stages. Additionally, the output can be fed back to the input for a more intense effect, creating a resonant effect by emphasizing frequencies between notches.
What is a Chorus Effect? | TestTone.com A chorus (or ensemble) is a modulation effect used to create a richer, thicker sound and add subtle movement. The effect roughly simulates the slight variations in pitch and timing that occur when multiple performers sing or play the same part. Chorus is a common guitar pedal effect that gives a clean electric guitar a "dreamy" quality. It's also widely used on acoustic guitar, electric piano, and clavinet. On strings and synth pads, chorus creates a richer, more complex sound. How does it work? The chorus effect is based upon a short delay. To add movement, chorus effects slowly modulate the delay time with a low-frequency oscillator (LFO). Principal controls Most chorus effects include knobs to adjust the LFO speed (a.k.a. rate or period) and depth (a.k.a. amplitude or intensity). Some plugins include control of the wet/dry mix. Common variations Mono, stereo, and surround chorus A surround chorus applies the effect to each surround channel using independent delays. Complex LFOs
Understanding Compressors and Compression Jan 1, 1999 12:00 PM, Barry Rudolph Compression is one of the most common processes in all audio work, yet the compressor is one of the least understood and most misused processors. Compressed audio is an everyday fact of modern life, with the sound of records, telephones, TV, radios and public address systems all undergoing some type of mandatory dynamic range modification. The use of compressors can make pop recordings or live sound mixes sound musically better by controlling maximum levels and maintaining higher average loudness. Compressors and limiters are specialized amplifiers used to reduce dynamic range-the span between the softest and loudest sounds. When sound is recorded, broadcast or played through a P.A. system, the dynamic range must be restricted at some point due to the peak signal limitations of the electronic system, artistic goals, surrounding environmental requirements or all the above. "Hard knee" compression describes this moment as sudden and certain. MixLine
EMusicTips Elements of Home Studio Mastering Though the picture shows Logic setup for mastering, you can achieve this with Cubase, Sonar, Performer or others just as easily. Everyonewants thebest sound quality. That is perhaps one of the only statements we can make about "everyone" involved in music production that always holds true. Think about all the issues we have covered: 16 vs. 24 bit, digital audio converters, analog vs. digital, which monitors? Let me say up front that I am not a mastering engineer. Mastering, or finalizing, is the last stage of the process of making audio. But for many of us who have yet to discover our magnum opus, we may want to try our own hand at it, to make the cd for friends sound better, or to make the demos we hand out sound great. Getting Started You may already be doing your own form of home mastering. Develop 2 listening environments. Software file formats Your mix should have ended with an uncompressed stereo file, ideally at high resolution, without any dither. Loudness Not so easy. Buzzwords.
ADVANCED COMPRESSION TECHNIQUES Technique : Effects / Processing Part 2: Paul White further explores the secrets of successful compression, and explains how to use advanced techniques for mastering your mixes. This is the last article in a two-part series. Read Part 1. In this second installment, I'll be covering compression in mastering and multi-band compression. But first I'd like to take a closer look at the main ways in which a full-band compressor can be used — after all, if you are going to set the appropriate controls correctly, you have to know what you are trying to achieve. Double Vision The first use of compression is for controlling signal peaks, so if you want to reduce peak levels without affecting the dynamic range of the rest of the recording, the usual approach is to set a threshold that's just above the average music level. The second basic way in which you can use a compressor is for compressing the dynamic range of an entire signal, not just the peaks. Mastering The Art Many Bands Make Light Work
Audio Limiters A limiter is a type of compressor designed for a specific purpose — to limit the level of a signal to a certain threshold. Whereas a compressor will begin smoothly reducing the gain above the threshold, a limiter will almost completely prevent any additional gain above the threshold. A limiter is like a compressor set to a very high compression ratio (at least 10:1, more commonly 20:1 or more). The graph below shows a limiting ratio of infinity to one, i.e. there is no gain at all above a the threshold. Input Level vs Output Level With Limiting Threshold Limiters are used as a safeguard against signal peaking (clipping). See also: