40 terms

# Audio Signal Processing

###### PLAY
audio signal processing
converted into audio signal
processed by various audio devices
signal transducers
signal controllers
signal monitors
signal processors
signal transducers
audio signal processing
convert one form of energy into another
signal controllers
audio signal processing
adjust signal intensity, mix signals, & direct signals towards specific output
mixers
splitters
attenuators
amplifiers
signal monitors
acquire & display info about signal properties
analog: volume unit meter (VU)
digital: digital sound level meter
signal: oscilloscope
spectrum: frequency spectrum analyzer
signal processors
modify audio signals & eliminate noise
limiters
compressors
filters
equalizers
amplifier
increases signal voltage, current, or both
increased by addition of power from DC current source
3 things:
input
output
gain
gain
difference betw output & input
If linear units are used to report input and output (i.e., volts), gain is equal to the slope of the line.
linear scale
how much you have inc signal
If input signal = 100 mV and output signal = 1 V (i.e., 1000 mV), gain = 10:1
dB scale
subtract difference to obtain gain
If input signal = 40 dB (re: 1 mV) and output signal = 60 dB, gain = 20 dB
preamplifiers
amplify very low-level signals
low-voltage amplifiers
(from mics, electrodes)
line amplifiers
amplify larger signals
when transfer function is in a straight line
nonlinear amplifier
not a straight line
ratio
transfer function
If the axes of I/O function are in linear units
gain determined by this
subtraction
axes of I/O function in decibels, gain determined by this
nonlinear systems
when magnitude of input exceeds certain value
output signal becomes distorted
distorted
nonlinear systems
when magnitude of input exceeds certain value
bad because output signal becomes this
input
nonlinera systems
gain of output function varies based on this
soft sound
want A LOT of gain
loud sounds
do not want a lot of gain
power amplifiers
classified by amount of time current flows through amplifier during each wave period
main types: A,B,AB, & D
linear amplifier
if transfer function is a straight line on linear scale
gain is equal to slope of line if
linear units are used to report input & output
nonamplifier
not a straight line
signal transformations
intentional modification of input signal
signal distortions
unintentional modifications of input signal
linear distortions
frequency-dependent changes in gain causing change in output specgtrum
nonlinear distortions
created by nonlinear transfer functions during signal transmission
limiters & compressors
nonlinear devices control level of audio signal & keep under certain limits
saturation level
max level that can be reached by output signal of amplifier
signal limiter
passes low level signals below certain threshold value & clips off peak of stronger signal
signal compressors
change dynamic range of signal
filter
restricts passage of energy to specific frequency range
equalizer
attenuates specific components to reshape the spectrum
filter parameters
center frequency, upper cutoff frequency, lower cutoff frequency, bandwidth, filter slope
slope
this is the steepness of the filter slope
equzalizers
devices that attenuate specific components to reshape spectrum
shelf
graphic
parametric
shelf equalizers
equalizer type
changes proportion between low & high frequency
graphic equalizers
equalizers
side by side band-pass filter
gain controlled by position of vertical sliders
parametric
equalizers
set of tunable filters in which bandwidth, center frequency, & slop can be adjusted
audio system
group of audio devices connected together
monophonic & stereophonic