Acoustics and Psychoacoustics Flashcards
Regeneration
signal fed back through an effects processor to intensify or extend an effect; for example, in a delay effect, signal passes through the processor, is delayed and sent out as an echo of the original sound
Reverberant decay
amount of time for the tail of a reverb to fall by 60 dB compared to the first reflection
Reverberant field
part of the sound field radiated by a source which has experienced at least one reflection from a boundary of the room or enclosure containing the source
Reverberation
multitudinous reflections off of the surfaces of an enclosed space; consists of early and late reflections
Room tone
the natural ambience of sound that exists in any space—enclosed, outdoors, or otherwise
RTAS
Real Time Audio Suite; plugin format which is designed to run like hardware inserts, in real time, instead of using renders like normal audiosuite; replacement for RTAS is the AAX style of plugin
Slapback
short low feedback delay effect often heard in ’50s pop and rockabilly styles; range of 40-120ms
Sound field
the space in which we hear sound, including location, reflections, and reverberations
Stomp box
percussion instrument consisting of a small box placed under the foot, which is tapped or stamped on rhythmically to produce a sound similar to that of a bass drum; used by guitarists and singers to create self-accompaniment
Time division multiplexing
method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line so that each signal appears on the line only a fraction of time in an alternating pattern
Tempo
rate of speed of a musical piece or passage indicated by one of a series of directions (such as largo, presto, or allegro) and often by an exact metronome marking measured in bpm
Time-based effect
all processes where some form of manipulation of time occurs to the signal; includes delay, echo, chorus, flanging, reverbs, pitch transposers, harmonizers
Wet
part of signal that is coming straight from the effects processor
Wet/dry mix
the ratio of the original signal to the processed signal
Fletcher-Munson
graph of observed data where loudness varies across frequencies to the human ear, and the level of a signal also shapes whether the frequency response is flatter or more varied; the louder a signal is, the more even the frequency balance and the more highs and lows we perceive as compared to mids
Equal loudness curves
another way to describe Fletcher Munson curves
Critical distance
distance at which the direct and reflected reverberations are equal in level
Direct signal
first instance of the sound arriving at the listener and hence provides an important psychoacoustic cue
Drum booth
an acoustically isolated room that allows for accurate and dry recording and representation of a drum kit
Early reflections
reflections happening shortly after direct sound that provide our brain with most of the information regarding space properties and will contribute greatly to the realism of depth
Inverse square law
the intensity (I) of a sound is proportional to (α) the inverse of the square of the distance (r) from the sound source; for every doubling of distance away from a source, we get a drop in level of 6 dB
Isolation booth
small windowed room or booth within a recording studio where a performer, such as an announcer, soloist, or drummer can be situated with her microphone(s) while recording and be isolated from the sound made by the other musicians
Isolation
sounds are separate from other sounds, decreasing or eliminating bleed
Initial time delay
time interval between a listener’s hearing of the direct sound from a source and the earliest reflected sound from
the walls or ceiling
Late diffuse reflections
reflections bounced from many surfaces many times; later reflections are absorbed more as they encounter a growing number of surfaces, resulting in reverb with decaying amplitude
Live room
the part of a studio where the musicians record, usually in a group setting; the largest part of a studio
Masking
the ability of one sound to cover up another, whether spectrally, through amplitude, or otherwise
Pascal
SI unit of pressure, abbreviated Pa, equal to 1 newton per square meter; reference pressure equivalent to 0 dB sound pressure level is 20 micropascals
Phase
a number of degrees relative to some reference; for example, two waveforms of identical frequency are in-phase when their compression (positive) and rarefaction (negative) half-cycles coincide exactly in time and space
Out-of-phase
in two waveforms of the same frequency, positive half-cycle of one coincides with the negative half-cycle of the other
Phase cancellation
out-of-phase waveforms are added together, causing silence
Vocal booth
a small isolated room where a vocalist can sing without having bleed from other musicians
Ohm’s law
when resistances/impedances are in series, the greater
resistance receives the proportionally greater voltage; resistance=voltage/intensity
Hertz
internationally agreed-upon symbol to indicate frequency in cycles per second
FFT
Fast Fourier Transform; algorithm for the extraction
of a frequency spectrum from a time waveform
Fourier
18th-century physicist who proved all waveforms can be broken down into individual component simple waves; the relative amplitude and phase of the individual harmonics
determine the overall wave shape and resulting timbre
Absorption coefficient
describes, on a scale from 0 to 1, how much energy is absorbed; 1 indicates total absorption, 0 indicates total reflection
Absorption
measure of the amount of energy removed from the sound wave as the wave passes through a given thickness of material
Absorber
acoustic insulation that traps sounds
Air absorption
high-frequency attenuation that accrues over transmission distance in air; humidity, ambient temperature, and atmospheric pressure all play a part in the parameters of this filter function
Acoustic treatment
solutions that help to absorb or diffuse sound to improve the acoustic quality of a space
Ambience
the acoustical qualities of a listening space
Anechoic
without echo
Baffle
construction or device which reduces the strength (level) of airborne sound
Beats per minute
the pace of music measured by the number of beats occurring in 60 seconds
Broadband absorber
absorber constructed to control all frequency bands with the same efficiency
Cent
frequency increments of 1/100th of a semitone
Correlated
sound comes from several sources that are related, either by a simple reflection or a common electrical source
Damping
addition of friction to a resonance to remove energy from it and thus reduce its magnitude
Dead
the effect of very little reverberation
Decorrelated/uncorrelated
sound comes from several sources that are unrelated
Decay time
synonym for reverberation time, or the time it takes a sound to decay to one millionth of its former strength (60dB)
Diffraction
the bending of a sound wave around an obstacle and the reflection of a sound wave from a discontinuity in its path
Delay
electronic device designed to store a signal for a specified period of time and then release it, thereby delaying the signal relative to other parts of an audio program
Density
mass per unit volume
Diffusion
process of spreading or dispersing radiated energy so it is less direct or coherent
Diffuser
device that spreads/disperses radiated energy so it is less direct or coherent
Discrete reflections
reflections that are perceived by the listener as individual sounds
True stereo
stereo signal consists of two related channels, with correlated material in the left and right outputs
Doppler effect
apparent change in the pitch of a sound when the source of the sound is moving with respect to the listener
Dry
lacking in reverberation; dead
Echo
a discrete sound reflection arriving at least 50 milliseconds after the direct sound
Effect
hardware or software device that manipulates how an audio signal sounds
Effects processor
device that takes in a signal, processes it in some way, and outputs the affected signal
AAX
Avid Audio eXtension; plug-in format developed by Avid as both a native and a DSP-powered replacement for RTAS and TDM
Audio unit
set of application programming interface (API) services provided by the operating system to generate, process, receive, or otherwise manipulate streams of audio in near-real-time with minimal latency
VST
Virtual Studio Technology; digital interface standard that is used to connect and integrate software audio effects, synthesizers and effect plugins with recording systems and audio editors
Flutter echo
acoustic effect in some rooms where sound is reflected back and forth between two parallel surfaces, such as opposite walls, fewer than about 15 echoes per second
Haas effect
an audible delay will only be perceived if the time gap between two similar waveforms is bigger than 30–40 ms
Late reflections
those that are distinguishable as separate acoustic events from the direct signal; not reverb
Multi-effects processor
audio signal processing unit that combines several
different audio effects
Multiplexing
signals are combined in such a way that they can later be separated
Parameter
a factor that determines a range of variables, like frequency band, level, etc.
Predelay
delay between the initial impulse and the onset of reverberation
