um sort of the delay a we come to my presentation on a spatial temporal signal

was

multichannel acoustic a cook

relation

uh that's

or like like to give an outline of my presentation

i would introduce my presentation by you

brightly

maybe on the problem of multichannel acoustic echo it in constellation

a a a a a a that a a approach

i i i would present

yeah

in my lecture

can say

uh

massive multichannel reproduction systems and for that i would like to

we interviews

some basic properties of a method of the channel

reproduction systems

a that i one

introduced a the novel approach for spatial can problem

preprocessing

and

give

a to or

uh um

a

a roles of this i

or practical

implementations and after that i

to

with no

so i

think

you have a

seen

similar a

block yet from

in this section so forth that

i

i is suppose you know what is says you know so we have here just a a a a a

and and and you and strong

and i i yeah

all what acoustic E

constellation it to create

a replica of sandy the or in room

um

model model as um my

F I R

filter

and the that

got

of

that my my by a filter

okay

are usually a minute

by by at least squares optimized addition

the optimal

solution

right

a or is given by the you know how to equation

also known

and a normal

equation here

we have that in terms of

are are X

it's which uh

if uh inverse of the

correlation metrics of the loudspeaker the signals in then used and

role

and are it's Y D notes

that

a cross correlation

metrics tricks between the loudspeaker signals

and the microphone signals

he's any and room

um

in

in practise

there

at the filters

are

the term and

at optimally

because

that acoustic of the own

could be

i of over at a time

is that it can be

shown

that

that's speed

of con veterans

oh adaptive filters depends of on that i gains

spread

of the autocorrelation metrics

and for some fleeting

in a typical

uh a for the the like

communication

scenarios we have only

you

if source source as in the are end room

and Z sources

are

right by

many loudspeakers speakers in there

near and room

hence we have a

and

ill conditioned

are

X six

and

how to cool

where

just problem

that i do yeah

is to preprocessed process that allows loudspeaker signal

in that near in troll in order to

decorrelate the channels with rest

but to each other

that

the preprocessing techniques

have to fulfil fill

at least

in three but

and first one is

for for of that convergence enhancement

that's

second requirement

if

is that a preprocessing technique

that doesn't introduce

all people

um uh the distortion on the signal

and

also

that

there

preprocessing technique doesn't

in use

in the yeah

uh

compute uh

uh

audition them

complexity complexity factors

for

to oh

for us

T your isn't to their production systems

you can find

many approaches

for preprocessor loudspeaker signals a

and T i mention only two

the first one was introduced by

the the is T

and to the idea

oh it is to rate up to introduce nonlinearities as the signal

this approach

feature a very low complexity

but that distortion that it

in uses

bit come quite to a problem for high quality

signals

for for them for music

conference or something like that

and uh and a second to a perceptually when motive that up holds well

introduced used by you can hear to

and the i

B is this

one have

for use on a frequency selective

phase modulation

of the a loudspeaker

signal

so the uh he of of that a loudspeaker signals

are decomposed

in in bands

in the

by means of uh analysis filter

and the sub-band signals

uh a or the face of the subband signals

and modified

in a frequency dependent

am modulating signal

and the now i

a to come to the second point

and what is like to introduce

that massive multichannel reproduction systems

the sound field

sinc to is this

systems

in at is that to use this

of the sound field to put used might have the actual source

S

with an an extended yeah yeah

V

using and i'm bill

of a speakers on the boundary of that area

here

the

the delta be in

that go

this many techniques

um you for

solving this

problem

and the

we

some of them are are this specialised

on specific

a a is you for example is that near field compensated tie i what i'm based on it

which is the

a specialised

on a circle and say and

and is

we have also for a planet and lean yeah and i is

is that

so called

it's spectral division method

it's the M

and the

more or less

is more one

uh

and i rate in an independent

technique technique it is is a a a a a W F S is the wave field synthesis techniques

which words for linear plan a and other convicts

and i image

for sure as a a low or

to kill implementations of for sound field sent to just

are

discrete

and therefore

the except

the the except if something like an aliasing frequency

and we can say that the control ability of the sound field is available only up to a given

frequency

and

here we see use this simulation one and linear very

with

twenty loudspeakers speaker

and here at the frequency have it

it's hundred

have which is below the

and you in frequency of of this yeah

right

that wave front can

be response

set correctly

and here for the two thousand

a time the test which i

all the figure that L in frequency we see that

that

where front

and a be reconstructed

firstly

so

and the

two our

problem

that we like to implement

and uh

uh acoustic echo canceller

for such a set up who with with massive multichannel

systems

this problem is

a challenging

not only be a is that is the autocorrelation matrix as

are are very last and in condition

when

addition

uh it can be shown that the someone

you to synthesized

by a massive multichannel

the production techniques

are

very sensitive to any day deviation

on the tiring

signals

uh

do you to build a preprocessing

and to hear it should be

not

that is that best section

or from from and uh so i got the point of view

that's a perception of

that is synthesized

wave fields

by

sound and to the synthesis

techniques

are

completely

i is completed different the then of stereophonic funny

the based techniques

and haynes

any

temporal preprocessing should be avoided

the so we can

do and a preprocessing

techniques

and how to cope with this problem

and

therefore we

have

it a novel approach for spatial or temporal i E C preprocessing

and this is is never a novel approach

basis

actually on how a very

all

with them

namely prevention is better than Q

and

what we would like to do

what we do

would like to do if actually

two

that

but

here and in addition and that the channel

and uh processing you

it

is that a i is that a loudspeaker signals in such a way

that is that a wave feel is set to zero euro the positions

of the i

ones

so we light

two

D lee

is are listening yeah yeah in two

two the ones

one own is quite where some microphone and i is supposed to be

and then another listening

yeah yeah

where is the desired

feel is a construct a

lee

is the

but

problem of creating

own on i i'd this not new and the in the literature

you can find many

start days

on it

and here i have listed

only some also

but to

here i i'd like to introduce

and you and a local

approach

for a

at uh the uh

creating zones of quiet with linear

and i this approach is best

it just straight

by

uh uh but is illustrated but be thing on the method of spectral division method and therefore i would like

two

just

give that say or tickle be six

of

that

mm method

and in is it is this method

assume assume what

or or to be is is actually

one the idea that some wave

feel

reproduced produced by a linear distribution

of the second outing

source of

can

B

it it's press

by a convolution of the thinks signals of

is that a second so that's was the green

function

of that services

and that that are green

functions can be and just to

as a

spatial temporal transform domain

to but also a

secondary source

in the following derivation we will restrict our configuration on a reference line

and the

uh what if we do that we can

see

is that

we have a

one time in the novel

the um

the one dimensional convolution

and for it

exact convolution theorem holds

so if we do a fourier yeah transform

we get a multiplication

and to by to be an announcement we get an expression for that mean

function

for

uh

so and uh

here is idea for creating the role of quite is actually just by multiplying

that desired wave field white i by L we don't by a specific we

and the if

we we be formally that in the wave number can mean we get them a

and expression for the desired wave field

in the wave number mean

and we get after that an expression for the subscribing

signals

that

to to prove that our approach

can i is applicable

to a a acoustic it constellation we have computed that attenuation innovations that can be done

by

this approach by creating as a of quite and we uh and

put

here

and microphone

and

right that's in an we shouldn't with that

a point which

is supposed to be

in the sweet spot

and we got an at wishing up to

seventy

D V

which is comparable was to become

yeah it cool return last

enhancement quite

S

i have a

shown

hmmm is that uh the control ability of there

wave if it's can be done only up "'cause" the anything frequent and frequency and they for for higher frequencies

acoustic it go

constellation or a typical acoustic echo equal constellation

must be still

a applied

and therefore for

we propose

here

at

divide in

the or or a yeah i don't like or decomposing "'cause" the signal into to sub bands and for a

lower

frequencies

just to so

right to use our approach and for i higher frequencies

to apply and the acoustic you constellation

yeah and say that approach

can be also

uh

use

well with the equal colour

and is

which are

more interest

interesting

for spatial audio reproduction systems

for example by applying

that output

but it represented presented by a problem

and i come to the conclusion

and the intuition of my work well

to show that is that

at to the acoustic you constellation can be done in a a distributed

manner

on the loudspeaker a

side

and on some microphone side and not

only

at it has been

the done

does on the microphones side

and i have shown one yeah

um a method to can for creating zones of quiet as linear allows loudspeaker i

and is i have sons that

that imitation that we have a

yeah is

and and on that

uh anything frequency

of the loudspeaker a rate

therefore for frequency selective implementation should be done

thank

uh we have time for questions two

T

uh i would you like

i got got a scalar

oh

i was wondering if

you have

oh

people

in side

you're or right

would they change

uh

as they move around

with you

the quiet

the G

yeah actually

we

yeah

we have

um

um

consider

only

that analytical cave yeah and we have a set for the right functions a free feel

yeah

and

hmmm

as the for the free field the green function

but for

a practical of imitation should be implemented in now

at that

man

and

so so we will have a just a mismatch between that's that's supposed

green function and a real one green function

and therefore we will not get

is that

performance of

going to quite on as we have

my my

uh what would the geometry of a relationship of the microphone

and a loudspeaker

would like thing to the lead the microphones

you're the low

result

just

in

you know maybe you

consider a circle

uh

you know where have you thought about that would be a very sad

or

a microphone geometry we we are independent actually from the microphone german trace

a a always a loudspeaker to and we have

simulated with omnidirectional

lower speed

oh

okay

and you did you in

room reflections so

so i just want

is the low frequency stuff you you do by

well making the by

yeah

it becomes an active noise can

a problem if you

microphones phones in the five

you can use that

able

to full the null

at a point to the mic

and an active noise

relation

yeah maybe

it's is a good idea i now we have a we haven't considered that

it

seems to be

with a

i

yeah think is that when you are no you the microphone

was it microphone

and the the markers

yeah

that will not

that will not that it is are yeah exactly

they were not

so

i

yeah yeah actually

therefore why have someone is that it is more interesting

to

yeah to thing to do that consideration

with in closing a right

because uh can one can include

yeah because we can define here at someone of quite

which is restricted on the position of the microphone

so only at a microphone position you

do you wouldn't

here anything

but in the listening position so for example if you can imagine

that

if

that is there a conference room and here's a table able with a microphone is on it

so it two would be with B

actually very practical

for the people to put their head on the table

the city

if they hear something on a

yeah that is actually i

a well thank you very much to little a is off

thus