Theory Exam Term 2 PDF

Microphones (17/50) Wikipedia: A microphone, colloquially called a mic or mike, is a transducer that converts sound into an electrical signal. FAMILIES Condensers ○ need phantom power ○ diaphragm acts as one plate of a capacitor ○ vibrations produce changes is the dist...

Microphones (17/50) Wikipedia: A microphone, colloquially called a mic or mike, is a transducer that converts sound into an electrical signal. FAMILIES Condensers ○ need phantom power ○ diaphragm acts as one plate of a capacitor ○ vibrations produce changes is the distance between the plates → changes in electrical energy ○ lightest diaphragms → fastest transient response → more fragile than dynamic mics ○ broadest and flattest frequency response → most accurate types Ribbons ○ do not require phantom power Dynamics ○ Do not require phantom power SPECIFIC MICROPHONES AKG D12 ○ Transducer: Moving Coil ○ Polar Pattern: Cardioid ○ Popular Kick Out Microphone AKG D112  ○ Transducer: Moving Coil ○ Polar Pattern: Cardioid ○ Max SPL: >160 dBSPL → good for kick drum AKG C414 ○ Transducer: Condenser ○ Polar Pattern: Cardioid AKG C451B ○ Transducer: Condenser ○ Polar Pattern: Cardioid AKG C12 ○ Transducer: Condenser ○ Polar Pattern: Variable Neumann U47 FET  ○ Transducer: Condenser ○ Polar Pattern: Cardioid ○ Popular Kick Out Microphone Neumann KM184 ○ Transducer: Condenser ○ Polar Pattern: Cardioid Neumann TLM 170 ○ Transducer: Condenser ○ Polar Pattern: Variable Neumann U87 ○ Transducer: Condenser ○ Polar Pattern: Variable ○ THE modern vocal mic Shure SM57  ○ Transducer: Moving Coil ○ Polar Pattern: Cardioid ○ Versatile and robust Shure SM58 ○ Transducer: Moving Coil ○ Polar Pattern: Cardioid Shure SM7B ○ Transducer: Moving Coil ○ Polar Pattern: Cardioid Shure KSM141 ○ Transducer: Condenser ○ Polar Pattern: Variable Shure BETA 57A ○ Transducer: Moving Coil ○ Pattern: Supercardioid Shure Beta 91A  ○ Transducer: Condenser ○ Polar Pattern: half cardioid ○ optimized for kick drums as kick in mic Coles 4038 ○ Transducer: Ribbon ○ Polar Pattern: Bi-Directional ○ Max. SPL: ∼125 dBSPL Sennheiser MD 421 ○ Transducer: Moving Coil ○ Polar Pattern: Cardioid ○ Pop filter guard in front of it Beyerdynamic M201 ○ Transducer: Moving Coil ○ Polar Pattern: Hypercardioid → very directional, good for snare and toms Earthworks QTC 50  ○ Transducer: Condenser ○ Polar Pattern: Omni Royer R121 ○ Transducer: Ribbon ○ Polar Pattern: Bi-Directional RCA 44BX ○ Transducer: Ribbon ○ Polar Pattern: Bi-Directional Telefunken U47 ○ Transducer: Condenser ○ Polar Pattern: Cardioid and omni Electrovoice RE20 ○ Transducer: Moving Coil ○ Polar Pattern: Cardioid MIC PLACEMENT on a speaker / guitar/bass amp  ○ Fredman Technique for guitar different mic angles with two SM57 ○ mics for bass amps dynamic with strong low end response (AKG D112) large diaphragm condenser (u87, 414) STEREO RECORDING TECHNIQUES 3 - 1 Rule ○ place mic 2 3 times as far away from mic 1, as mic 1 is from the sound source. Coincident Pairs → based on level difference ○ XY 90° narrower spread ○ Blumlein 2 bi-directional mics, facing each other angled 90°to each other facing left and right sides of sound source ○ Mid Side stereo image is created by differences in loudness 1 Cardioid and 1 bidirectional great mono compatibility (sides cancel each other out) lack of spaciousness solved by +4dB shelving boost at 400Hz on side channels / -4dB shelving cut at 400Hz on mid Near-Coincident → based on level AND time difference wider, more accurate stereo field 2 Directional (usually cardioid) microphones ○ ORTF Office de Radiodiffusion Television Francaise (Radio France) capsules spaced 17 cm apart angled at 110° ○ NOS  30 cm apart 90° ○ DIN 20 cm apart 90° similar to ORTF FURTHER STANDARD TECHNIQUES ○ OSS Optimal Stereo Signal 2 omni mics 16,5 cm separated by a hard 28cm disk, covered by absorbent material ○ Faulkner Array (similar to AB) 20 cm apart placed at ear height ○ Stereo Boundary Array mounted within a boundary construction Spaced Pairs → based on time difference ○ AB Parallel to each other facing the sound source generally utilizes Omni mics, but also cardioid more spacious sound unfocused center image, risk of hole in the middle poor mono compatibility ALSO FAMOUS: Decca Tree THE STEREOPHONIC ZOOM Recording Angle ○ Meaning: sector of the sound field in front of the microphone system which will produce a virtual sound image between the loudspeakers Angular Distortion ○ We have L, LC, C, RC, R. When a recording is represented on speakers, LC and RC are shifted slightly outwards towards L and R. ○ Measured in °(usually around 4 or 5) Reverberation distribution Early reflection localisation POLAR PATTERNS ⇩ actually sub/wide cardioid?? ⇩ Loudspeakers (1/50) TRANSDUCER device which converts one form of energy into another → TYPES Moving Coil ○ circular coil of wire within a magnetic field, supported so it could move axially Ribbon ○ reversing the process ○ requires high flux permanent magnets Electrostatic Piezoelectric ENCLOSURES Baffle ○ sealed enclosure of a speaker where the sound radiates. It separates front and back of a speaker to increase the time it takes for the air molecules to travel Flat Baffle Folded Baffle ○ Reduces the size but maintains the same characteristics. Infinite baffle ○ closed box which separates the low frequencies from the highs improving bass response vented enclosure ○ cabinet which has a hole in it that acts as a helmholtz resonator. This generates more bass than a sealed box. auxiliary bass radiators Ducted Port Enclosure ○ Port attached to hole on the speaker. The port has a resonant frequency which gives a double hump called the bass reflex. RADIATION direct radiators ○ A direct radiating loudspeaker is a speaker which is attached to the air molecules it's pushing. The speakers are facing the same direction. horns LOUDSPEAKER SPECIFICATIONS sensitivity ○ measured in dBs ○ indicates the speaker’s “Loudness” ○ a microphone is placed 1 meter away ○ 1 watt of power is applied to the speaker (usually 1kHz) ○ the higher the dB reading, the better the sensitivity of the speaker. impedance ○ meaning: total opposition / effective resistance to the flow of alternating current (AC) in an electric circuit resistance → “width of road” ○ for speakers → “nominal impedance” (8 Ohm) ○ speaker impedance varies with frequency ○ is related to the power a speaker can extract from an amp  frequency response ○ comparison of the speaker’s on axis power output vs. frequency output ○ typical full range speaker frequency response may be: 30Hz to 15kHz +/- 3dB (frequencies reproduced within 6dB range) efficiency and power (compliance, damping, etc) ○ efficiency → percentage of acoustic power output radiated in all directions if 2 speakers have the same sensitivity, the one with the wider dispersion is more efficient ○ power handling indicates the amount of power the speaker can take from the amp without damage ○ Compliance is the force exerted by the suspension of a speaker ○ Damping is the relationship between the speaker and the amp higher damping factor → amp has greater “control” of speaker movement polar response coverage angle STUFF THAT CILLIAN THINKS IS IMPORTANT Dipole ○ Cone driver mounted in a flat panel with figure 8. Noise reaches the audience by the reflections not directly. Wadding ○ This is to stop high frequencies from reflecting in a box using insulation material. A coaxial speaker ○ It has a high frequency driver and a low frequency driver mounted on the same shaft. Phasing plug ○ Disperses high frequency content away from the driver. A bass bin is a scoop or a subwoofer. Digital Audio (3/50) lat ‘Digitus’ => refers to the human fingers What it is: ○ the value of the signal is only known at discrete instances in time ○ A discrete-time signal is not represented by a continuous waveform but instead by a series of values. Binary → 0 means OFF, 1 means ON Bit (Binary Digit) → a 0 or a 1 ○ 1000 b = Kilobit (kb) ○ 1000 kb = Megabit (Mb) ○ 1000 Mb = Gigabit (Gb) Byte → 8 Bits ○ 1000 B = Kilobyte (kB) ○ 1000 kB = Megabyte (MB) ○ 1000 MB = Gigabyte (GB) ○ 1000 GB = Terabyte (TB) Nibble → 4 bits Equations 𝑁 ○ 𝑅 =𝑉 ○ 𝑁 = 𝑙𝑜𝑔𝑉(𝑅) ○ R = The range of numbers that can be represented. ○ V = 2 (The base counting system being used.) ○ N = The number of digits being used (word length). Sample Rate ○ Samples are taken a certain number of times per second. ○ Each sample will have a number of bits assigned to store the instantaneous amplitude level. ○ Measured as a Frequency in Hertz (Hz) ○ Common Sample Rates: 44,1 kHz - CD Quality  48 kHz - Originally from DAT (Digital Audio Tape) Machines 88,2 kHz - (2 x 44,1 kHz) 96 kHz - most common high common high quality format (2 x 48 kHz) 192 kHz - Uber high quality format (2 x 96 kHz) Bit Depth ○ one bit depth equals 6 dB of dynamic range ○ Common Bit Depths are 16 or 24 bits ○ higher the bit value → more accurately represented amplitude Quantisation ○ act of assigning a binary value to the voltage (amplitude) that is read for each sample in the Sample & Hold circuit ○ voltage values will often fall between discrete binary values ○ raising and lowering of the voltage is called Q Distortion (aka Quantisation Noise) Nyquist Theorem ○ it takes for example 40 kHz to reproduce 20 kHz ○ sample rate must be at least 2x the highest frequency you wish to represent in the digitized audio. Aliasing ○ false frequencies that were not present in the original sound ○ happens when the sample rate is less than 2x the highest frequency you wish to sample ○ Anti-Aliasing filter cuts off the Nyquist Frequency ○ Oversampling sample rate is temporarily higher to allow more room for the low pass filter 8 bit laws ○ u law slightly larger dynamic range used in north america worse distortion ○ A law used across Europe Integer Notation ○ whole number, no decimals ○ sign bit → either positive or negative ○ overflow → two positive values added together results in a negative value Fixed Point Binary  Floating Point Binary ○ use of mantissa and an exponent ○ exponent tells us where to put decimal place ○ standard: 23 Mantissa, 8 Exponent, 1 sign bit Jitter ○ occurs when the sample clock doesn’t work 100% ○ Random Jitter → similar to noise ○ Periodic Jitter → distortion → frequency modulation → introducing frequencies Dither → added noise which makes quiet audio measurable Bit Rate ○ 𝑆𝑎𝑚𝑝𝑙𝑒 𝑅𝑎𝑡𝑒 * 𝐵𝑖𝑡 𝐷𝑒𝑝𝑡ℎ * 𝐶ℎ𝑎𝑛𝑛𝑒𝑙𝑠 = 𝑥 𝑘𝑏𝑖𝑡/𝑠 Synthesis (5/50) additive → stacking sound subtractive → filters applied BREAKDOWN VCO → Voltage Controlled Oscillators ○ most synths will have at least two to combine them VCF → Voltage Controlled Filter ○ common settings: low-pass, high-pass, bandpass, notch VCA → Voltage Controlled Amplifier ○ envelopes control how the volume of an amp changes over time fours stages → ADSR LFO → Low Frequency Oscillator ○ provides movement to the sound ○ only effect is heard HISTORY First Synthesizer → Telharmonium (1896) Theremin (1920) → reacts to water in the body, has amp and pitch control Hammond Organ (1933) Electronic Sackbut (1945) RCA Mark 2 (1954) Moog Modular (1964) → East Coast ○ Switched-On Bach (1968) Buchla (1965) → West Coast ○ not focused on subtractive synthesis FM SYNTHESIS FM → Frequency Modulation Oscillators become ‘Operators’ ○ Modulator → modulates carrier ○ Carrier → modulated signal, amount of tonal change is based on the FM modulation depth. Sampling (3/50) TAPE BASED SAMPLING Mellotron (1963) ○ most famous tape based sampler ○ evolved from the similar Chamberlin, but could be mass-produced more efficiently COMPUTER BASED SAMPLING Fairlight CMI (1979) ○ Sample Rate: 24 kHz, Nyquist 12 kHz ○ Bit Depth: 8 bit SAMPLE AND SYNTHESIS Samplers are synthesizers which source their sound from samples instead of oscillators. SOFTWARE SAMPLING Acoustics (6/50) The study of the production, control, transmission, reception and effects of sound and the properties or qualities of a room or building that determine how sound is transmitted within it. Reference Monitors ○ should not add anything ○ reveal the truth about a track ○ Yamaha NS-10M → legendary ref monitors used by Bob Clearmountain Listening Area ○ front → listening setup ○ 60º angle between monitors ○ tweeter → ear height Frequency Propagation Nodes and Anti-Nodes 𝑆𝑜𝑢𝑛𝑑 𝑉𝑒𝑙𝑜𝑐𝑖𝑡𝑦 (𝑉) 𝑆𝑜𝑢𝑛𝑑 𝑊𝑎𝑣𝑒𝑙𝑒𝑛𝑔𝑡ℎ (λ) = 𝑆𝑜𝑢𝑛𝑑 𝐹𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 (𝐹) Room Modes ○ Axial → reflection between one pair of parallel surfaces ○ Tangential → reflection between two pairs of parallel surfaces ○ Oblique → reflections between three pairs of parallel surfaces  ○ Calculation: 𝐹= 𝐶 2 * (( ) + ( ) + ( ) ) → only P/L is important for exam 𝑃 2 𝐿 𝑄 2 𝑊 𝑅 2 𝐻 F = resonant frequency (Hz) C = speed of sound (m/s) L = length W = width H = height calculating the lowest possible wave → pick the longest dimension in the room → the lower the sound, the longer the wave → we will pick the primary reflection of the axial room mode Modal Frequencies ○ natural resonance frequencies of a room ○ follow the harmonic series ○ modal density is the number of resonant frequencies in a given range ○ higher modal density is better and more common in larger spaces ○ mode decay → bass reverb Schröder Frequency 𝑇 ○ 2000 * 𝑉 T = reverberation time (s) 3 V = volume (𝑚 ) ○ describes the point at which rooms change from resonators to reverberators Golden Room Ratios (Height : Width : Length) ○ 1 : 1,14 : 1,39 ○ 1 : 1,28 : 1,54 ○ 1 : 1,6 : 2,33 Schumann Resonance ○ subliminal resonance between the ozone and earth’s crust  ○ 7,83 Hz ○ excited by thunderstorms RT60 (Reverberation Time 60) ○ the timespan where the sound pressure in a room decreases by 60 dB ○ dry sound, gap (pre delay), early reflexions, reverb tail (RT60) ○ works for specific frequency 0161*𝑉 ○ 𝑅𝑇60 = 𝑆*𝛂 → formular by Wallace Clement Sabine RT60 = reverb time (s) 3 V = volume of room (𝑚 ) 2 S = surface area (𝑚 ) 𝛂 = absorption coefficient 𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑑 𝑠𝑜𝑢𝑛𝑑 𝑒𝑛𝑒𝑟𝑔𝑦 𝛂 = 𝑖𝑛𝑐𝑖𝑑𝑒𝑛𝑡 𝑠𝑜𝑢𝑛𝑑 𝑒𝑛𝑒𝑟𝑔𝑦 𝛂 = 1 → total absorption 𝛂 = 0 → total reflection frequency dependent Concave surface → focused sound convex surface → diffused sound flat surface → reflective sound Reflective Properties ○ Hard, Dense & Flat Absorptive Materials ○ convert sound into heat ○ thickness of material influences amount of low frequencies absorbed ¼ wavelength of lowest frequency of interest ○ space between wall and material enhances absorption aswell mechanisms ○ porous dissipative absorption thickness and distance between absorber and wall dictate frequency absorption overuse of thin porous absorbers may lead to excessive absorption of high frequencies ○ induced vibrational movement ○ helmholtz resonators  used in architectural acoustics to reduce undesirable low frequency sounds (standing waves, etc.) by building a resonator tuned to the problem frequency, and putting absorbing material inside, thereby reducing it. Frequency of maximum absorption 60 ○ 𝐹= 𝑀*𝐷 F = Frequency of maximum absorption (Hz) M = surface density of panel (kg/m2) D = depth of air space (m) Schöder Diffusers aka Quadratic Residue Diffusers (QRD) ○ well depth → low freq cutoff 2 ○ 𝑛 𝑚𝑜𝑑𝑢𝑙𝑜 𝑝 n = integer (gives well number) p = prime number (proportional well depth) Music Theory (10/50) ARRANGING Cluster → very close (less than 3rd) Closed Position ○ notes are arranged within a narrow range, usually with no more than an octave between the top and bottom notes. ○ avoid intervals of minor second between two top and bottom voices Open Position ○ more than an octave between the top and bottom notes. For Drop 2 / Drop 2 and 4, just keep in mind: ○ 1 → highest ○ 4 → lowest (if 4 voices used) ○ drop the wanted voice one octave For way voicings → max 1 tension Strings ○ keep it simple, no complex shit ○ not too low, not too high ○ violin one octave per string NO double stops, ONE voice pizzicato in comfortable range ○ Viola ○ Cello ○ Double Bass ○ Harp avoid chromaticism effective in glissando Woodwinds ○ Flute ○ Clarinet ○ Saxophone ○ Oboe ○ English Horn ○ Bassoon Brass ○ Trumpet ○ Trombone ○ Horn ○ Tuba  ○ typical combination in pop: 2 trumpets, sax, trombone Percussion ○ Definite Pitch Chimes Crotales Glockenspiel Marimba → wooden bars Timpani Vibraphone Xylophone → wooden bars, smaller than marimba Celesta ○ Indefinite Pitch Bass Drum Cymbals Percussion (Snare, Tenor, Drum and Conga) ○ time signatures bar → certain number of beats, one repetition each beat can be subdivided in different way → simple (one and two and …) / thirds (one and uh two and uh) simple subdivision example: 3/4, 4/4 compound subdivision example: 3/9, ○ play percussion with sth that is softer than the percussion instrument, otherwise it breaks HARMONY Intervals ○ Compound intervals ○ correct terms  Chord Groups ○ Tonic = I, III and VI ○ Subdominant = II and IV ○ Dominant = V Cadences ○ V - I = Perfect or authentic cadence or resolution ○ IV - I = Plagal cadence or resolution ○ V - (_≠I) = Interrupted cadence or resolution ○ _ - V = imperfect cadence ○ The II - V - I Cadence Extensions ○ 1, 3, 5 and 7 = chord tones ○ 9, 11 and 13 = tensions Substitute Dominant Chords ○ Dominant Chord is one semitone above resolving chord Summary of Chords ○ I Maj7 (C Maj7 in the key of C) ○ II -7 (D -7 in the key of C) ○ III -7 (E -7 in the key of C) ○ IV Maj7 (F Maj 7 in the key of C) ○ V7 (G7 in the key of C) ○ VI -7 (A -7 in the key of C) ○ VII -7(♭5) (B -7(♭5) in the key of C) ○ V7/II (A7 in the key of C) ○ V7/III (B7 in the key of C) ○ V7/IV (C7 in the key of C) ○ V7/V (D7 in the key of C) ○ V7/VI (E7 in the key of C) ○ Sub V7 (D♭7 in the key of C) ○ Sub V7/II (E♭7 in the key of C) ○ Sub V7/IV (G♭7 in the key of C) ○ Sub V7/V (A♭7 in the key of C) Harmonic Minor Scale → minor 2nd between VII and VIII Melodic Minor Scale → like harmonic + major 2nd between V and VI Modulation ○ when songs move from one key or tonal center to another Modal Interchange ○ when songs incorporate passages where chords are ‘borrowed’ from alternative keys DAW (4/50) Amplifiers (0/50 ?) An electronic device for increasing the amplitude of electrical signals, used chiefly in sound reproduction. Tube / Valve ○ facilitates a high rate of flow for a small amount of effort ○ places DC current across its plate and heated cathode element ○ between those two elements, a wire mesh grid acts as as a control valve allowing electrons to pass from the plate to the cathode Transistor (Trans-Resistor) ○ capable of varying its resistance ○ DC power source placed across the transistors collector and emitter ○ control voltage at transistors input allows a larger output current to flow ○ if you ask for an output signal higher than the DC supply voltage → saturation Op Amps (Operational Amplifiers) ○ Output controlled through phase flipped feedback loop which is controlled by a variable resistor the feedback loop passes through. EQ → frequency discriminating amplifier Summing amplifier Distribution amplifier VCA (Voltage Controlled Amplifier) & DCA (Digitally Controlled Amplifier) ○ control voltage increases → output voltage decreases AMPLIFIER CLASSES A → contributing to high sound quality B → distorted sound quality, used when high quality sound is not needed AB → majority of high quality amps, low class a amp G → several different voltage rails which progressively come into action as the signal voltage is increased H → variation of G D → uses pulse width modulation AMPLIFIER SPECIFICATIONS  Power Ratings ○ Bandwidth frequency response bandwidth within which an amplifier can sustain a specified output must be considered when matching amps to loads such as subs or HF horns ○ frequency response measure of the limits within which an amp reproduces frequencies at a low power output ○ slew rate measures amps ability to accurately react to high level transients defined as Vus (Volts per microsecond) ○ Distortion → should be 0,1% THD (Total Harmonic Distortion) ○ Signal to Noise Ratio ○ Damping factor numerical value given to an amplifiers ability to control a speaker speakers tend to continue to move after the driving signal has stopped low output impedance “shorts” the speaker and damps this movement ○ phase response ○ coupling Input Sensitivity ○ how much voltage input is required to produce the amps maximum rated output ○ the equipment must not be able to deliver more voltage than the sensitivity rating or clipping will occur OTHER AMPLIFICATION CONCEPTS Bridging Cabling Analogue Audio (0/50 ?) Meaning: Comparable in certain respects Describes a continuous waveform and has a continuous range of amplitude Telegraphone (1899) → first electromagnetic recording machine  Ampex 200A (1948) → first commercial tape machine Les Paul invented the multitrack with the octopus Biasing ○ an additional, inaudible high frequency (40 - 150 kHz) to increase the recording level Ferrous Metals ○ Iron ○ Steel Non Ferrous Metals ○ Copper ○ Aluminium ○ Silver ○ Brass Electro Magnetism ○ coil of wire creates magnetic Field, a ferrous metal is in the middle, diaphragm pushes metal back and forth TAPE MACHINE EQ curves are designed to reduce hiss ○ different types of removal ○ use right curves for playback pinch roller (rubber wheel) pushes tape against the capstan capstan → controls tape speed Record/sync head ○ tape gets magnetized in the gap of the record head ○ record head can be used for low quality playback due to delay for overdubbing repro head → reverse of recording erase head → removes audio ○ engaged when in record mode 20 - 30 dB less dynamic range than digital moving oxide particles passing the playhead cause noise floor nanowebers → unit of magnetic strength Multi Track tape heads are separated by guard bands EMI tape formulars ○ 888 (early 60s) “lo-fi” and "granier" more distortion between 1kHz and 8kHz ○ 811 (mid to late 60s) better high frequency response slightly less distortion than 888 ○ 815 (early 70s)  flatter high frequency response less distortion than 811 used when minimal coloration was desired