echo and reverberation

8/9/2019 Echo and Reverberation

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SlideSlide 33©© 2007 Texas Instruments Inc,2007 Texas Instruments Inc,

$c!o

• %cho is audible becausethe speed o& sound isrelativel' slo#( about )**meters per second.

• Click on icon to listen toecho.

Sound Source

Listener

Direct

Sound

Echo


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Block "ia)ram o* $c!o

• +or the time being( #e #ill consider onl' one echopath.

• ,utput - Input !ela'ed Input.

• /ecause o& losses in the dela'ed path( 0ain 1.

Delay

Input +

+

Simplified Echo

GainDelayed Input

Output


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$+uation *or Simli*ied $c!o

)1()(

).()()( N

N

z Gn x

z n xGn xn y−

−

⋅+⋅=

=⋅+=

z -N

x(n) y(n)+

+

Simplified Echo

G.x(n).z -N G


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Fre+uenc- Resonse

• The &re2uenc' response o& echo can be calculated using the

&ollo#ing .m &ile.


7/31SlideSlide 77©© 2007 Texas Instruments Inc,2007 Texas Instruments Inc,

Fre+uenc- Resonse o* $c!o



Multile $c!o #at!s

• 3 real room #ill have several echo paths.

Delay1

Input

+

+

Multiple Echo Paths

Gain1

Delayed Input 1 Output

Delay2 Gain2

Delayed Input 2

+



Summar- o* $c!o

• The %cho output is derived solel' &rom theinput.

• Certain &re2uencies are attenuated.

• /ecause the poles lie inside the unit circle(echo is stable.



Re%er&eration

• 4everberation is similar to echo( but uses a slightl' di&&erent con&iguration.

• Click on the icon to hear reverberation.



Re%er&eration on Sta)e

Microphone

Performer

LoudspeakerLoudspeaker

Sound reaches the microphone &rom boththe per&ormer and the the loudspeakers.


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©© 2007 Texas Instruments Inc,2007 Texas Instruments Inc,

Block "ia)ram o* Re%er&eration

• ,utput - Input !ela'ed ,utput

Delay

Input Output+

+

Delayed Output

Simplified Revereration

Gain




Simli*ied Re%er&eration $+uation

)1/()()()()( N

N

z Gn x z n yGn xn y

−

−

⋅−=

=⋅⋅+=

! "#

$%n& y%n&+

+

G'y%n&'!"#

Simplified Revereration

G




Matla& Model o* Re%er&eration




Re%er&eration Fre+uenc- Resonse




Summar- o* Re%er&eration

• The output is derived &rom both the input and the previous output.

• 3t certain &re2uencies( the output #ill be ampli&ied.

• /ecause the poles lie on the unit circle( reverberation can become unstable.




Real .orld $c!o and Re%er&eration

• 3 real room #ill have several echo paths.

• 5hen sound is re&lected o&& a sur&ace there #ill be coloration. Certain &re2uencies #ill be absorbed and there #ill be phase changes.

• There&ore( a commercial echo $ reverberation unit #ill contain man' di&&erent dela' paths.


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Simulink Models


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Simulink Model o* $c!o


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Simulink Model o* Re%er&eration


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Modi*ications *or TI /71


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/71 "S3 Model o* $c!o


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Samlin) and Inte)er "ela-

• The samplingrate is 8*** 9:.

• 3n Integer!ela' o& )***produces a

dela' time o&)***$8*** -*.; seconds.


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/71 "S3 Model o* Re%er&eration


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Simulink Model o* Re%er&eration

•


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Introduction to La&orator-


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T!e /omlete Simulink Model

• In the Aaborator' 'ou #ill build a SimulinkBodel &or echo and reverberation.

• ou #ill be able to run di&&erent echo andreverberation e&&ects on the C671 !S".


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/71 "S3 Setu


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T!e /omlete /71 Model


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"S3 Sitc! Settin)s

!ecimal S51

*

S51

1

S51

F

S51

!escription

*


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©© 2007 Texas Instruments Inc2007 Texas Instruments Inc

Re*erences

• 3 !igital Signal Drocessing Drimer b' "enSteiglit:. IS/G *H8*;H168)H1.

echo and reverberation

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