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Transcript of Distortion
I am Lucya Koroleva from St.-Petersburg, Russia.
This lesson is for week 4 of Introduction to Music Production at Coursera.org (which is a super awesome course I must say).
The topic of today's lesson is Distortion and some ways in which it can be both musical and problematic.
Let's start! Distortion In general term distortion is the alteration of the original shape (or other characteristic) of something. Audio distortion refers to any kind of deformation of an output waveform compared to its input. It is a modification or addition to the wave form of a signal by any kind of equipment. Non-linearity Distortion is a result of non-linearity in signal amplification. For example, a linear (high fidelity) amplifier with a gain of 10 is driven with a 0.1 volt signal, the amp will deliver exactly 1.0 volt at its output, should the input go to 0.2 volt, the output becomes 2.0 volts, etc. This straight-line relationship continues to the maximum output level the amp can deliver (its threshold), which is determined by its power supply voltage and circuitry limitations. At this point the amplifier becomes non-linear and clips (chops off the top and bottom of the signal waveform), as it is not physically capable of delivering more output voltage. Harmonic distortion A pure tone, as produced by a sine-wave oscillator, has little more sonic character than silence. It is one frequency alone, a fundamental pitch without overtones, or as engineers call them, harmonics. The presence of harmonics in varying proportions gives an instrument the unique timbre. Distortion, however, generates harmonics not present in the original signal, which is intolerable in high-fidelity reproduction. It adds overtones that are whole number multiples of a sound wave's frequencies. Clipping As it was said before there is some point at which an amplifier becomes non-linear and clips. Clipping is a form of waveform distortion that occurs when an amplifier is overdriven and attempts to deliver an output voltage or current beyond its maximum capability. When an amplifier is pushed to create a signal with more power than its power supply can produce, it will amplify the signal only up to its maximum capacity, at which point the signal can be amplified no further. As the signal simply "cuts" or "clips" at the maximum capacity of the amplifier, the signal is said to be "clipping". The extra signal which is beyond the capability of the amplifier is simply cut off, resulting in a sine wave becoming a distorted square-wave-type waveform. Change in a waveform Musical usage Avoiding distortion Distortion in music can be intentionally used as an effect. Distortion effects create "warm", "dirty", and "fuzzy" sounds by compressing the peaks of a musical instrument's sound wave and adding overtones. It makes the sound of an instrument brighter and sometimes helps a musician to emphasize musical dynamics and lets sound come through in a mix. This kind of "good distortion" is any signal alteration that adds to musical quality or produces a desired effect. To an engineer in high fidelity, however, less distortion means better sound. The goal is to reproduce the incoming signal with perfect accuracy; what goes in electrically is what comes out acoustically, no more and no less. While recording, any piece of gear can create an unwanted distortion. There are some guidelines to avoid it:
Careful microphone placement
Use of a pop filter
Careful gain staging: stay in the green at every point of signal flow
Thanks Thank you for your time!
This lesson provides some basic on distortion and the positive and negative aspects of its presence in sound recording. I hope it may trigger your interest towards exploring in more details the effects that can be created in music using the distortion of an audio signal.