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Properties of Sound Wave
wavelength amplitude frequency period velocity
Wavelength
relationship btwn frequency and wavelength
the distance between successive crests of a wave in meters or ft
peak = max compression
trough = max rarefaction
frequency and wavelength = inverse relationship (i.e. lower frequency, longer wave)
Amplitude
standard measure of units
visualization of amplitude phenomenon
magnitude of the molecular displacement, sound pressure level
dB = standard measure of units
newton's cradle = visualization of the amplitude phenomenon -- magnitude of molecular displacement near a sound source will proportionately displace the molecules at a distance = changes in loudness
Frequency
standard measure of unit
relationship between waves in period and pitch
The frequency refers to the number of sound waves a sound produces per second.
fewer waves in period = lower pitch
f= 1/time period
Hz = standard unit of measure is the number of cycles per second
Period
time it takes to complete one cycle
where wave intersects x axis
Velocity
used to describe the speed at which sound waves travel
Mach 1.0 speed = 770 mph
Envelopes of Sound
what are the sections?
rise and fall in volume of one note
four sections of envelopes: attack, decays, sustain, release
Attack
note rises from silence to max lvl
Decays
max to midrange lvl
Sustain
middle level
Release
note falls from its sustain level back to silence
Damp
add resistance to vibrating object so that its vibrations die out more quickly after a note is sounded
sine wave
pure tone of a single frequency
complex wave
sine waves of three frequencies combined: fundamental, overtones, harmonics
fundamental frequency
determines the pitch of the sound
overtones
higher frequencies in the complex wave
result from frequencies whose interplay produces tones at the sum/difference of those component frequencies (44o Hz + 220 Hz = 660)
gives sound its timbre
harmonics
overtones that are integral multiples of the fundamental frequency
determines the tone quality/timbre
Psychoacoustics: how ear interprets sounds
locations of sounds are detected
how pitch is heard/perceived
how the ear separates complex auditory signals occurring simultaneously
attenuation
amplitude declines as the listener moves from the sound source
Audible Frequencies
20 Hz - 20,000 Hz
ear most responsive to 1,000 Hz - 6,000 Hz
shape and folds of the ear alter reception of frequency sounds
Principle of Equal Loudness (Fletcher Munson)
for all frequencies to be perceived as equally loud, the amplitude of frequencies outside the mid ranges (1,000 Hz - 6,000 Hz) must be increased
AKA. equalization
Frequency Masking
a sound at one frequency tends to mask softer sounds at nearby frequencies
i.e. 1000 Hz tendency to mask 500 Hz tone
ear's limited ability to simultaneously process sounds of multiple pitches
Inter-aural Time Difference
the short delay it takes for a sound to reach the ear furthest from the sound source
Interaural Level Difference
relative amplitudes of the sounds shadowing effect of the head lowers the amplitude of the more distant sound → comb filtering
Hearing
when a person speaks, air molecules around the ear are compressed.
The compression wave of air molecules moves away from the speaker by being pushed into the next layer of air molecules when molecules bounce back after being pushed, the air molecules produces a sharp reduction in their compression = rarefaction
Phase Cancellation
180 degree phase shift between two identical waves, the peak of one wave coincides with the trough of another. when two waves combine, they cancel each other out = no sound
Hearing Loss
120 dB = threshold of pain --> amplitude at which irreparable or permanent damage begins to occur
ear ringing = indication that sound pressure levels were at/near the threshold of pain
dependent on genetic predisposition and environmental hazards
typically occurs in 40s-60s
Hearing Loss
how many min and at what dB can person listen to music?
90 min/day = 90 dB
20 min/day = 100 dB
Temporal Masking
phenomenon in which the human ear has difficulty hearing a soft sound that follows a loud sound closely in time
Feedback
phenomenon that occurs when a microphone picks up sound from a speaker while that speaker is playing sound from the microphone, thus creating a loop.
Microphone Designs
Moving-Coil Dynamic Ribbon Condenser
Dynamic Moving Coil Microphone
How it Works
Application
Pickup Patterns
a coil wire attached to a diaphragm suspended in a magnetic field sound waves vibrate diaphragm → coil vibrates in magnetic field → generates electrical signal
application: guitar amps, drums
pickup patterns: uni and omni
Dynamic Ribbon Microphone
How it Works
Application
Pickup Patterns
thin metal foil suspended in magnetic field → sound waves vibrate ribbon in field → generates electrical signal
application: horns and guitar amps
pickup pattern: bi and hypercardioid
Condenser Microphone
How it Works
Application
Pickup Patterns
metal backplate and conductive diaphragm placed very close together → charged together → form two plates of a capacitor sound waves strike diaphragm → vibrates → varies spacing between plates → varies capacitance → generates signal using electrostatic field
application: acoustic instruments, cymbals, studio vocals
pickup patterns: uni, omni, and bidirectional
Pick-Up Patterns
omnidirectional
unidirectional
cardioid
supercardioid
hypercardioid
bidirectional
subcardioid
omnidirectional mic
equally sensitive to sounds from all directions
unidirectional mic
most sensitive to sound arriving from front but softens sounds entering the sides or rear
bidirectional mic
most sensitive to sounds arriving from two direction (front and back) but rejects sounds entering sides
subcardioid
partway btwn omni and cardioid
Cardioid (unidirectional)
sensitive to sounds arriving from a broad angle in front of mic 6 dB less sensitive at sides, 15-25 dB in the rear
rejects sound from the sides less than super and hyper cardioids
Supercardioid
8.7 dB less sensitive at the sides and two areas of least pickup at 125 degrees away from front
hypercardioid
12 dB less sensitive at the sides and two areas of least pickup at 110 degrees away from the front
Guitar Mic Technique
what if acoustic?
mic in front of guitar amp: cardioid dynamic w/ presence peak
direct box: higher input impedance --> avoids thin/dull sound
miked and direct: run Direct In track through guitar amp simulator plug in
signal processor or stomp box
IF ACOUSTIC: pencil type condenser w/ extended frequency frequency
Direct Boxes -- what do they fix
fixes loading problem when recording direct
ground-lift switch = prevents ground loops and hum
mixer mic inputs limit at 1500 ohms, guitar pickup = thousands ohms = overall = thin/dull sound
three-to-one rule
space mics at least 3x the mic-to-source distance
vocal mic technique
amp mic technique
Snare Drum Mic Placement
cardioid dynamic w/ presence peak, front of set on a boom, even w/ the rim, 2 in above head, aim down, place a mic on the bottom with opposite polarity
Hi Hat mic placement
cardioid condenser mic 6 in over the cymbal edge that's farthest from the drummer, mike above aiming down, filter lows below 500 kHz
Tom-Toms Mic placement
mic toms individually or put a mic between each pair of toms, cardioid dynamic mic 2 in over the drumhead and 1 in from the rim, angled down about 45 degrees toward the head
Kick Drum Mic Placement
large-diameter, cardioid dynamic type with an extended low frequency response, place inside on a boom few inches from where beater hits
Cymbals
cardioid condenser with an extended high frequency response or ribbon mic, place overhead 2-3 ft above cymbal edges
Drum Mic: One Mic Technique
large diaphragm cardioid condenser mic and mount over the kick drum top, even with beater head, aiming snare drum
Coincident Pair
two directional mics w/ grilles touching, diaphragms one above the other, angled apart
lvl differences btwn channels = stereo effect
Spaced Pair
two identical mics ft apart and aim straight ahead
time differences btwn channels = stereo effect
Near-Coincident Pair
angle apart two directional mics, spaec grilles few inches apart horizontally
lvl and time differences = stereo effect
Baffled Pair
two omni mics ear-spaced apart, separated by hard/soft baffle
lvl, time, spectral differences = stereo effect
Vocal Mic Techniques
coincident, spaced, near-coincident, baffled pair
lead vocal: flat response condenser mic w/ large diaphragm 8 in away
on-surface: place a mic near a hard reflecting surface
sibilance
emphasis of "s" or "sh" sounds --> strongest around 3-10 kHz
reduced by using mic w/ flat response
plosives
Sounds which release a sudden burst of air (pop sound) e.g. p,b,t
Recording Formats Timeline
Edison's Phonograph (1877)
Graphophone (mid 1880s)
Long Playing Records (1925)
Radio (early 1920s)
78 RPMs (early 1930s)
Vinyl LP (1948)
45 RPM (1949)
Magnetic Tape Recording (1935 intro, 1950 use)
Audio Compact Cassette (1963)
8-Track Stereo Cartridge (1966)
Sony Walkman Portable (1979)
Compact Disc (1982)
CD-ROM (1986)
R-DAT (1987)
Mini Disc/Philip's DCC (1990s)
MP3 (1989)
Edison's Phonograph
Date Mechanism Impact
1877
recorded and played back sound mechanically using metal stylus and cylinder wrapped with tin foil
diaphragm's mvmts = groove in the foil
established commercial presence
Gramophone
Date Mechanism
mid 1880s
Wax-coated cylinder (same mechanism as phonograph)
Long Playing Records
Date
1925
Radio
Original Intended Use Impact
originally developed for military use during WWI
1929 --> RCA --> modern era of music industry born
78 RPMs
Date When did it fade from scene? Playing Time
early 1930s faded from scene by 1955 playing time: 3-5 mins
Vinyl LP
Date Measurements, RPM? Playtime Faded from Scene?
1948
12-inch, 33 ⅓ RPM LP → much more durable than 78 RPMs
playtime: 20+ min per side
until late 1980s
45s
Date Measurements, RPM? Impact Faded from Scene?
1949 33 ⅓ competitor b/c they required diff record players w/ diff speeds early 1950s → industry came together → LPs for albums, 45s for singles until late 1980s
Magnetic Tape Recording
Date Mechanism Impact
1935 intro, 1950 main use
tapes are made of powdered ferrous oxide compound bonded to long strip of tough plastic = backing where oxide is painted + held in place w/ adhesive binder
manufactured in ¼, ½, 1, 2 in → most frequently used = ¼ in tape allowed for performances to be edited → allowed overdubbing, splicing → expanded creative freedom
reel-to-reel tape = professional; difficult and inconvenient for consumers
Audio Compact Cassette
Date Impact
1963 cassettes more reliable and less cumbersome than 8 track
8-Track Stereo Cartridge
Date Impact Mechanism
1966
broad success in automotive applications
single reel with two ends of the plastic recording tape joined with a piece of conductive foil tape to make one continuous loop -- motorized capstan in played rolled against a pinch wheel inside to pull the tape across the player's read head
Sony Walkman Portable
Date Impact
1979
established cassette's dominance of pre recorded tape market by 1983
record labels ceased production of 8-tracks
Compact Disc
Date Impact Sample Rate/Bit Depth Playback Time Advantages
1982
ushered in digital age
sample rate: 44.1 kHz
Bit Depth: 16-bit
playback: at least 74 min
no surface noise, can skip tracks
CD-ROM
Date Enabled?
1986
for personal computers mid 1990s → CD-ROM's multimedia capabilities utilized
add graphics, text, video to music CDs
R-DAT
Date Controversy? Intended Audience Benefits
1987
controversy: digital copying
SCMS introduced to break chain of perfect digital cloning adopted for professional and "pro-sumer"; not consumer format
low price, enhanced digital storage capabilities
MP3
1989
compression format that shrinks digital audio files w/ negligible sound quality degradation
MP3 Player made in 1997
Analog Tape Recorders
record the audio signal as magnetic patterns that rise and fall in strength
Analog Track Layouts
Mono: 1-channel/1-Track --> track occupies the full width of magnetic tape
Half-Track Stereo: 2-channel/2-track --> two magnetic tracks (occupied half of tape width each) separated by guard band
Multitrack: same number of tracks as channels
Tracks v. Channels
tracks = magnetic paths onto which the signals are recorded on a tape
channels = number of inputs-outputs a machine has
Tape Decks
quarter-track reel-to-reel tape machines
1960s
home stereo recording and playback systems
four interleaved track placed on 1/4 in
multitrack tape machines
1970s/1980s 4-track, 8-track, 16-track = 1/2 in tape
Tape Deck Transport Mechanism
three motors: feed reel, take-up reel, capstan
capstan/pinch roller = moves tape
feed reel moves opposite to the take-up reel → keeps tape taut
tape rewind: pinch roller/capstan disengaged, more power to feed reel
Tape Editing
Erase: pass tape under erase head --> magnetic properties of the tape oxide coating are scrambled
Splicing: mark off locations, take tape off head assembly, use razor blade to cut, splicing tape to join two ends, rethread tape onto deck
Connectors
XLR (male/female)
1/4-in phone jack (male/female)
Tip Ring Stereo 1/4-in
RCA Connector
1/8-in Connector
Adapters
Adapter Turnaround Coupler
Cords
Power Cable: AC extension/power cord
Speaker Cable: connects power amp to each loudspeaker
Patch cords: connect recorder-mixer to external devices
Splitter Y Cord: duplicate a single audio signal into 2 identical audio signals
Digital Recorder
store the audio signal as a numerical code of ones and zeros
Pulse Code Manipulation: signal from mixer goes through low-pass filter, filtered signal goes through analog-to-digital converter, measures the voltage of waveform, quantization
Non-Destructive Editing
only the pointers change; the data on disk is not changed/destroyed; not permanent
Destructive Edits
they write over the data on disk
Delete Noises
delete background noise (i.e. chair squeak) → don't close up the space you create after deleting
Clean-Up Tracks
cut out silence, noises → prevents leakage and tightens up sound
Duplicate Musical Parts
copy vocals from one chorus and paste them at the measures where the chorus is repeated
Replace Wrong Notes
delete a wrong note, copy an in-tune note where the wrong note was
Make Special FX
copy a syllable and paste it several times to create stuttering, copy guitar track and paste it 20-30 ms delayed in another to create stereo sound
Fade Out, Fade In
slow drop in volume to silence; fade in slow rise in volume from silence
Crossfade
fade out of one clip while fading into another; cross fade across an edit
Fix Timing Errors
visually align start times of notes in various tracks
Remove or Rearrange Song Sections
create zero crossing at edit point so that the waveform crosses the 0 dB line
Sampling Rate
rate at which the A/D converter measures the analog signal while recording
Bit Depth
determines the number of possible amplitude values we can record for each audio sample
Signal Levels Modes
RMS: readings correspond to the avg lvls -- how loud the sound is
Peak: readings show the lvl of peaks or short transients -- how close the signal is to clipping (always use peak)
Advantages of Good Levels
prevent inter-sample clipping
won't overdrive mic preamp
create headroom for plug-ins
Level Setting
max gain until red light flashes then bring it down a little below
(-3 to -6 dBFS)
on any stem, master output, output of each plug-in
Note
Flashcard