07-08-2012, 12:18 PM
MUSICAL SOUND PROCESSING
[attachment=30341]
INTRODUTION
All musical programs are produced in basically two stages.
Sound from each individual instrument is recorded in an acoustically inert studio on a single track of a multi track tape recorder.
The signals from each track are manipulated by the sound engineer to add special audio effects and are combined in a mix-down system to finally generate the stereo recording on a two-track tape recorder.
TIME-DOMAIN OPERATIONS
Commonly used time-domain operations
Carried on musical sound signals are echo generation ,reverberation , flanging , chorus generation ,and phasing.
SINGLE ECHO FILTER
Echo are simply generated by delay units.
Because of the comb like shape of the magnitude response, such a filter is known as comb filter
MULTIPLE ECHO FILTER
To generate a fixed number of multiple echoes spaced R sampling periods apart with exponentially decaying amplitudes ,
REVERBERATION
The reverberation is composed of densely packed echoes.
The IIR comb filter by itself does not provide natural-sounding reverberation for two reasons.
First , its magnitude response is not constant for all frequencies, resulting in a “coloration” of many musical sound that are often unpleasant for listening.
The output of echo density given by number of echoes per second generated by a unit impulse at the input is much lower than that observed in a real room thus causing a “fluttering” of the composite sound.
FLANGING
There are a number of special sound effects that are often used in the mix-down process.one such effect is called flanging.
It was created by feeding the same musical piece to tape recorders and then combining their delayed outputs while varying the difference between their delay.
One way of varying t is to slow down one of the tape recorders by placing the operators thumb on the flange of the feed reel, which led to the name flanging.
CHORUS GENERATOR
The chorus effect is achieved when several musicians are playing the same musical piece at the same time but with small changes in the amplitude and small timing differences between their sounds.
The phasing effect is produced by processing the signal through a narrowband notch filter with variable notch characteristics and adding a scaled portion of the notch filter out put the original signal,
FREQUENCY-DOMAIN OPERATIONS
These effects are achieved by passing the original signals through an equalizer, the purpose of equalizer is to provide “presence” by peaking the mid frequency components in the range 1.5Hz to 3Hz and to modify the bass-treble relationships by providing boost or cut to components outside this range.
HIGHER-ORDER EQUALIZERS
A graphic equalizer with tunable gain response can be built using a cascade of first-order and second-order equalizers with external control of the maximum gain values of each section in the cascade.
CONCLUSION
The audio effects are artificially generated using various signal processing circuits and devises , and they are increasingly being performed using digital signal processing techniques.
[attachment=30341]
INTRODUTION
All musical programs are produced in basically two stages.
Sound from each individual instrument is recorded in an acoustically inert studio on a single track of a multi track tape recorder.
The signals from each track are manipulated by the sound engineer to add special audio effects and are combined in a mix-down system to finally generate the stereo recording on a two-track tape recorder.
TIME-DOMAIN OPERATIONS
Commonly used time-domain operations
Carried on musical sound signals are echo generation ,reverberation , flanging , chorus generation ,and phasing.
SINGLE ECHO FILTER
Echo are simply generated by delay units.
Because of the comb like shape of the magnitude response, such a filter is known as comb filter
MULTIPLE ECHO FILTER
To generate a fixed number of multiple echoes spaced R sampling periods apart with exponentially decaying amplitudes ,
REVERBERATION
The reverberation is composed of densely packed echoes.
The IIR comb filter by itself does not provide natural-sounding reverberation for two reasons.
First , its magnitude response is not constant for all frequencies, resulting in a “coloration” of many musical sound that are often unpleasant for listening.
The output of echo density given by number of echoes per second generated by a unit impulse at the input is much lower than that observed in a real room thus causing a “fluttering” of the composite sound.
FLANGING
There are a number of special sound effects that are often used in the mix-down process.one such effect is called flanging.
It was created by feeding the same musical piece to tape recorders and then combining their delayed outputs while varying the difference between their delay.
One way of varying t is to slow down one of the tape recorders by placing the operators thumb on the flange of the feed reel, which led to the name flanging.
CHORUS GENERATOR
The chorus effect is achieved when several musicians are playing the same musical piece at the same time but with small changes in the amplitude and small timing differences between their sounds.
The phasing effect is produced by processing the signal through a narrowband notch filter with variable notch characteristics and adding a scaled portion of the notch filter out put the original signal,
FREQUENCY-DOMAIN OPERATIONS
These effects are achieved by passing the original signals through an equalizer, the purpose of equalizer is to provide “presence” by peaking the mid frequency components in the range 1.5Hz to 3Hz and to modify the bass-treble relationships by providing boost or cut to components outside this range.
HIGHER-ORDER EQUALIZERS
A graphic equalizer with tunable gain response can be built using a cascade of first-order and second-order equalizers with external control of the maximum gain values of each section in the cascade.
CONCLUSION
The audio effects are artificially generated using various signal processing circuits and devises , and they are increasingly being performed using digital signal processing techniques.