Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Faculty of Music, University of Oxford FHS 2012 – Logic Pro for Composers Tutors: Mr Chris Ferebee ,Dr Duncan Williams Seminar: n/a Duration: n/a Glossary of terms used in this course This glossary covers terminology used throughout the course. You may wish to follow the references below for further detail. Seminar 1 Glossary ADC Additive synthesis ADSR Amplitude Amplitude Envelope Audio DAC DAW DSP Fourier theorem Frequency Analogue-to-digital converter. Processor which converts voltage to binary data for signal processing within DAW (analogous to sound – converted from ‘real sound’ when sound pressure changes move coil or charged backplate to induce corresponding variation in voltage output in a dynamic or capacitor microphone) Method for generating complex waveforms by combining several oscillators Attack – Decay – Sustain – Release. A way of illustrating traditional amplitude envelopes Absolute loudness, usually measured logarithmically in dB (x) where x is a reference value (eg in volts, or a fraction of volts, sound pressure, watts, or some other reference value) The temporal dynamic variation in the onset of a sound Human perception of sound pressure changes (usually loudness, frequency, and timbre). Digital-to-analogue converter. Processor which converts binary data to voltage (analogous to sound – converted to ‘real sound’ when passed through loudspeaker to generate movement of air and corresponding change in sound pressure) Digital audio workstation. Computer equipped with DAC/ADC hardware, signal processing/sequencing software, and MIDI hardware Digital signal processing Jean-Baptiste Fourier stated that any complex waveform (ie, any sound) can be reproduced by combining the correct number of dynamically varying sine waves. The number of cycles of a signal, measured in Hz, inversely proportional to velocity/wavelength. Longer wavelengths result in lower frequencies. Lower frequencies are traditionally perceived as ‘bass’ frequencies. Typical human hearing range is usually 1 Faculty of Music, University of Oxford FHS 2012 – Logic Pro for Composers Tutors: Mr Chris Ferebee ,Dr Duncan Williams Gain Harmonic LFO Loudness Max MIDI Modifier keys MSP Object Partial Patcher (and incorrectly) quoted as 20 – 20,000 Hz (see Nyquist theorem) Traditionally a voltage gain applied to signals to amplify or attenuate their volume Integer multiple of fundamental frequency component of a signal (usually lowest prominent frequency, but can vary dependent on signal type) Low frequency oscillator. A particular and common type of signal manipulation used in many synthesiser designs. An oscillator with a low number of cycles per second (typically <30 Hz) is connected to the frequency or amplitude inlet of another signal generator, to create vibrato and tremolo effects, respectively. Perceptual measure of volume. Product of sound pressure and frequency (see References – Fletcher/Munson equal loudness contour). Bass frequencies appear more prominent when reproduced at higher sound pressure level. Data processing objects and pathways in Max/MSP. Also debugging window in Max/MSP Musical Instrument Digital Interface. Data format which allows musical information (note on, note off, pitch, loudness, pan, modulation etc) to be transmitted between controller keyboards, synthesisers, drum machines, and DAW for sequencing (amongst many other types of hardware). Typically uses 5-Pin DIN connector, cables are male-male. MIDI thru transmits an exact copy of MIDI in on MIDI capable equipment. Keys used to active shortcuts on Apple Mac computers. Ctrl-Alt-Cmd (Control, Option, Command/Apple). Also shift, tab. Ctrl-click usually corresponds to a ‘right click’ on a Windows machine. Cmd-x usually corresponds to equivalent shortcuts on Windows machines (eg, Cmd-O opens a file, Cmd-P prints, Cmd-C copies, Cmd-X cuts, Cmd-V pastes etc). Signal processing objects, modules, and pathways in Max/MSP. Can be connected to Max objects. Graphical programming elements used by both Max and MSP for a variety of tasks. Basis of all work in Max/MSP. Connected via patch cords to ‘inlets’. Altclicking an object opens a ‘help’ patcher with examples. Inharmonic overtone (see harmonic and timbre) A window allowing Max and MSP objects to be connected to facilitate signal generation and processing in Max/MSP. Cmd-clicking patcher ‘locks’ 2 Faculty of Music, University of Oxford FHS 2012 – Logic Pro for Composers Tutors: Mr Chris Ferebee ,Dr Duncan Williams Pitch Sawtooth Sine wave Square Wave Timbre Triangle Wave Delay Echo Equalisation Filtering Noise Q Reverberation or ‘unlocks’ the patcher for editing. Perceptual measure related to frequency. Mel scale is the just-noticeable-difference between one pitch and another. Frequency (in Hz, Hertz), usually used as shorthand. More complicated signal type – a harsh signal with even and odd harmonics with a ratio of 1/f Basic signal type comprised of one oscillator at one frequency. Also known as a sinusoidal wave. Signal type with only odd harmonics at 1/f Distinguishing element(s) of sound, apart from loudness and pitch. Eg, A4 played on piano, with equal loudness to A4 played on trombone, has a notably different sound. This is usually characterised by spectral shape (harmonic or inharmonic overtones aka partials), but can also be due to temporal acoustic correlations. Signal type with only odd harmonics at 1/fn^2 Used in two contexts in Max/MSP programming. In Max, a handy mathematical device to retrigger ‘bang’ objects. In MSP (and other audio contexts), an audio effect which causes a repeat (echo, echo, echo). Usually incorporates a ‘feedback’ control, which dictates the number and type of repeats. Laymans term which might mean delay or reverberation, or a combination of both. Developed by telephony engineers, practical application of a series of filters to ‘equalise’ signals which were not even across the frequency range. Can now include linear-phase equalisation whereby phase changes and unwanted frequency smearing is compensated by subsequent phase adjustment in the complete signal. A process of deliberately adjusting the phase of selected frequency components in a signal to amplify or attenuate them by positive or negative phase interference. Powerful sound shaping device. Typically white noise, a signal which has equal amplitude across the full frequency range. Also pink noise (equal amplitude per octave, a commonly used musical test signal) See width More traditional echo effect than delay – usually the sound of a real acoustic space. Large spaces have long decaying reverberation. Small spaces (tiled bathrooms etc) have shorter reverberation, which might include 3 Faculty of Music, University of Oxford FHS 2012 – Logic Pro for Composers Tutors: Mr Chris Ferebee ,Dr Duncan Williams Subtractive synthesis Width Balanced line Capacitor microphone Dynamic microphone ‘flutter’ echoes. Commonly now associated with mathematical convolution – a multiplicative signal processing device. Alternative to additive synthesis, whereby complex waveforms are created from noise using filtering. Good for noisy signals, or useful if combined with some additive synthesis to create hybrid signal types (eg voice) In conjunction with frequency and gain, the third control used by a fully parametric equaliser. Width specifies the spectral range around the target frequency that will be amplified or attenuated by the gain of the equaliser Minimum 2 core connection which carries a copy of the ‘hot’ signal out of phase. At receiver, ‘cold’ signal is inverted, causing positive phase interference with the original ‘hot’ signal, but negative phase interference with any unwanted induced noise incurred across the length of the cable run – effectively allows cable runs to be longer, and carry cleaner signals. Used in all professional audio contexts, including most microphones (not used by most HI-Fi, eg Phono connectors!). Device for converting sound pressure changes into voltage. Uses a charged backplate and moving front plate to induce voltage changes when moved by sound pressure. Typically associated with studio recording and higher frequency response. Device for converting sound pressure changes into voltage. Uses a moving coil wrapped around a semipermanent magnet to induce voltage changes when moved by sound pressure. Typically associated with live recording or higher SPL recording tasks in studio recording (kick drums and other percussion shells, distorted electric guitar, rap vocals) 4 Faculty of Music, University of Oxford FHS 2012 – Logic Pro for Composers Tutors: Mr Chris Ferebee ,Dr Duncan Williams Compression De-esser Expansion Nyquist theorem Plosives Sampling Sibilance Method for reducing the dynamic range of an audio signal by automatically reducing the level of signals beyond a threshold A combined dynamic and frequency sensitive signal processing routine which reduces the level of signals above a threshold only in specified frequency range (usually used to target the sibilant frequency of female vocal recordings, but also used to reduce overly bright recordings in mastering process) Method for increasing the dynamic range of an audio signal by automatically increasing the level of signals beyond a threshold (often used as a ‘noise gate’ for silencing amplifier hiss, unwanted background noise and so on) Theory which states that frequency of sampling (aka sample rate or the number of samples taken per second) should be at least twice the frequency of the highest frequency being sampled. Eg, a bass note at 1000 Hz should be sampled at least 2000 times per second. Failure to follow this rule can cause aliasing distortion, an unpleasant ‘folding over’ of the uncaptured frequencies. Bassy-thud caused by ‘b’ and ‘p’ consonants, usually in male vocal recording Part of the ADC process, wherein a series of measures of amplitude, frequency, and phase are taken of an input signal, to represent the signal in a given number of binary data. More samples equates to a better representation of the orginal signal (analogous to dotmatrix printers and painting – more dots looks smoother). Snake-like hiss sound, often in female vocals, on ‘s’ and ‘t’ consonants. 5 Faculty of Music, University of Oxford FHS 2012 – Logic Pro for Composers Tutors: Mr Chris Ferebee ,Dr Duncan Williams Analysis FFT FT Morphing Phase Resynthesis STFT Vocoding Wavelets Usually a Fourier analysis – assesses in input signal to establish its frequency, amplitude, and phase components Fast Fourier Transform – a quick STFT Fourier Transform (aka fourier analysis) – establishes all of the frequency components in a signal, and their relative magnitudes A technique for creating a hybrid sound, with characteristics derived partly from a source and target sound Measure of position in a cycle. Can cause positive interference – increase in volume, or negative interference – decrease in volume, if two signals with the same frequency and differing phase are combined. Sometimes used for this purpose to create ‘swirling’ sound effects. Strictly this is usually combined with analysis, and should just be synthesis, but is called resynthesis to clarify that an input signal has been generated as closely as possible by synthesis rather than sampling. Short time Fourier Transform –a FT over a short period of time Sound hybridisation system for bandwidth reduction in telephony, in which a hybrid sound is generated by combining properties derived partly from the target sound (the spectral envelope of speech, or tonal properties), and partly from the source sound (the noise being filtered). Series of independent signals with independently varying amplitude, frequency, and phase envelopes. Used for variety of signal processing tasks and novel sound manipulation (eg morphing). 6 Faculty of Music, University of Oxford FHS 2012 – Logic Pro for Composers Tutors: Mr Chris Ferebee ,Dr Duncan Williams References Analysis, Synthesis, and Perception of Musical Sounds: The Sound of Music (9781441921864): James W. Beauchamp Computer Music: Synthesis, Composition, and Performance (9780028646824): Charles Dodge, Thomas A. Jerse Psychoacoustics: Facts and Models: Eberhard Zwicker, Hugo Fastl, Springer 2002 Lee, K.H., Davies, P. & Surprenant, A., 2003. Methodology for quantifying the tonal prominence of frequency modulated tones. Journal of the Acoustical Society of Americal, 114(4), 2352-2352. Serra, X. & Bonada, J., 1998. Sound Transformations Based on the SMS High Level Attributes. In International Conference on Digital Audio Effects. Barcelona. 7