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Measurement and 5.0 rendering of spatial impulse responses of rooms - - PowerPoint PPT Presentation

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116 th AES Convention Berlin, 8-11 May 2004 Measurement and 5.0 rendering of spatial impulse responses of rooms Angelo Farina Dipartimento di Ingegneria Industriale, Universit di Parma, Via delle Scienze 181/A Parma, 43100 ITALY

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116th AES Convention Berlin, 8-11 May 2004

Angelo Farina Dipartimento di Ingegneria Industriale, Università di Parma, Via delle Scienze 181/A Parma, 43100 ITALY HTTP://pcfarina.eng.unipr.it - mail: angelo.farina@unipr.it

Measurement and 5.0 rendering

  • f spatial impulse responses of rooms
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116th AES Convention Berlin, 8-11 May 2004

Topics

  • This presentation is a tribute to M. Gerzon, who

had foreseen 3D impulse response measurements and 3D Auralization obtained by convolution.

  • Comparison between Auralizations based on

calculated and measured IRs (e.g. Theatre “La Fenice”, Venice)

  • The advantages (and disadavantages) of

employing measured IRs

  • Possible approaches to Auralization over ITU 5.0

“surround” systems

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Concept (Gerzon, 1975)

Portable PC with 4- channels sound board Original Room Sound Source SoundField Microphone B-format 4-channels signal (WXYZ) Measurement of B-format Impulse Responses MLS or sweep excitation signal Convolution of dry signals with the B-format Impulse Responses Sound Source Mono Mic. B-format Imp. Resp.

  • f the original room

B-format 4-channels signal (WXYZ) Convolver Ambisonics decoder Speaker array in the reproduction room

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116th AES Convention Berlin, 8-11 May 2004

Why do we measure these IRs?

1.

In case something happens to the original space (e.g.: La Fenice theater) they contain a detailed “acoustical photography” which is preserved for the posterity 2. They can be used for studio sound processing, as artificial reverb and surround filters for today’s (5.1) and tomorrow’s musical productions 3. Auralization in special listening rooms can be performed for subjective tests

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Theatre la Fenice, Venice

  • The first theatre was realised in 1792 by Gian Antonio Selva, after the burning
  • f Teatro San Benedetto
  • In December 1836 the theatre burned down again and was rebuilt by G. and T.

Meduna the year after

  • The theatre was closed in 1995 for maintainance; it had to open again in

February 1, 1996, but it burned two days before (January 29, 1996)

  • A few weeks before the fire, Tronchin measured binaural impulse responses
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Impulse Responses of La Fenice

In 27 positions a series of binaural impulse responses (with gun shots) was recorded Each recording is consequently a stereo file at 16 bits, 48 kHz During measurements the room was perfectly fitted, whilst the stage was empty (no scenery)

Point n. 12

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Numerical simulation vs. measurement

Prelude 1° act “La Traviata” by G.Verdi

  • Dry music
  • Convolution with

experimental I.R. (pt. 12)

  • Convolution with

simulated IR

Stop

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Advanced IR capture and rendering ( project)

  • Description of the measurement technique
  • Analysis of some acoustical parameters of

some theaters measured

  • Description of the processing methods to be

employed for transforming the measured data in audible reconstructions of the original spaces

  • Description of the usage of the measured data

for studio processing, musical production and for scientific Auralization tests

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Sound propagation in rooms

Direct Sound Reflected Sound Receiver Direct Sound Reflected Sound Point Source

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Measurement process

  • The desidered result is the linear impulse response
  • f

the acoustic propagation h(t). It can be recovered by knowing the test signal x(t) and the measured system output y(t). It is necessary to exclude the effect of the not-linear part K and of the background noise n(t).

Not-linear, time variant system K[x(t)] Noise n(t) input x(t)

+

  • utput y(t)

linear system w(t)⊗h(t) distorted signal w(t)

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Test signal: Log Sine Sweep

x(t) is a sine signal, which frequency is varied exponentially with time, starting at f1 and ending at f2.

⎥ ⎥ ⎥ ⎥ ⎦ ⎤ ⎢ ⎢ ⎢ ⎢ ⎣ ⎡ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ − ⋅ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⋅ ⋅ π ⋅ =

⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎝ ⎛ ⋅

1 e f f ln T f 2 sin ) t ( x

1 2

f f ln T t 1 2 1

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Test Signal – x(t)

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Measured signal - y(t)

The not-linear behaviour of the loudspeaker causes

many harmonics to appear

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Deconvolution of Log Sine Sweep

The “time reversal mirror” technique is emplyed: the system’s impulse response is obtained by convolving the measured signal y(t) with the time-reversal of the test signal x(-t). As the log sine sweep does not have a “white” spectrum, proper equalization is required

Test Signal x(t) Inverse Filter z(t)

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Inverse Filter – z(t)

The deconvolution

  • f

the IR is obtained convolving the measured signal y(t) with the inverse filter z(t)

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Result of the deconvolution

The last impulse response is the linear one, the preceding are the harmonics distortion products of various orders

1° 2° 3° 5°

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Maximum Lenght Sequence vs. Sweep

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Measurement Setup

The measurement method incorporates all the

known techniques:

Binaural B-format (1st order Ambisonics) WFS (Wave Field Synthesis, circular array) ITU 5.1 surround (Williams MMA, OCT, INA, etc.) Binaural Room Scanning

  • M. Poletti high-order virtual microphones

Any multichannel auralization systems

nowadays available is supported

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Transducers (sound source # 1)

  • Equalized, omnidirectional sound source:

Dodechaedron for mid-high frequencies One-way Subwoofer (< 120 Hz)

  • Dodech. LookLine D200

60.0 70.0 80.0 90.0 100.0 110.0 120.0

25 31.5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000

Frequency (Hz) Sound Power Level (dB)

Unequalized Equalized Lw,tot = 94.8 dB Lw,tot = 106.9 dB

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Transducers (sound source # 2)

  • Genelec S30D reference studio monitor:

Three-ways, active multi-amped, AES/EBU Frequency range 37 Hz – 44 kHz (+ /- 3 dB)

Genelec S30D 60.0 70.0 80.0 90.0 100.0 110.0 120.0

25 31.5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000

Frequency (Hz) Sound Power Level (dB)

Power Pressure

Lw,tot = 96.8 dB

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Directivity of transducers

  • 40
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  • 20
  • 1

5

  • 1
  • 5

30 60 90 120 150 180 210 240 270 300 330

1000 Hz

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5

  • 1
  • 5

30 60 90 120 150 180 210 240 270 300 330

2000 Hz

LookLine D200 dodechaedron

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5

  • 1
  • 5

30 60 90 120 150 180 210 240 270 300 330

250 Hz

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5

  • 1
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30 60 90 120 150 180 210 240 270 300 330

4000 Hz

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5

  • 1
  • 5

30 60 90 120 150 180 210 240 270 300 330

8000 Hz

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  • 25
  • 20
  • 1

5

  • 1
  • 5

30 60 90 120 150 180 210 240 270 300 330

16000 Hz

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Directivity of transducers

1000 Hz

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  • 30
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  • 20
  • 1
5
  • 1
  • 5

30 60 90 120 150 180 210 240 270 300 330

250 Hz

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  • 1
5
  • 1
  • 5

30 60 90 120 150 180 210 240 270 300 330

2000 Hz

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5
  • 1
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30 60 90 120 150 180 210 240 270 300 330

4000 Hz

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  • 1
5
  • 1
  • 5

30 60 90 120 150 180 210 240 270 300 330

8000 Hz

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  • 1
5
  • 1
  • 5

30 60 90 120 150 180 210 240 270 300 330

16000 Hz

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5
  • 1
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30 60 90 120 150 180 210 240 270 300 330

Genelec S30D reference studio monitor

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Transducers (microphones)

  • 3 types of microphones:

Binaural dummy head (Neumann KU-100) 2 Cardioids in ORTF placement (Neumann K- 140) B-Format 4 channels (Soundfield ST-250)

Turntable Binaural dummy head Cardioids (ORTF) Soundfield Microphone

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Directivity of transducers

Soundfield ST-250 microphone

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

30 60 90 120 150 180 210 240 270 300 330

125 Hz

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

30 60 90 120 150 180 210 240 270 300 330

250 Hz

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

30 60 90 120 150 180 210 240 270 300 330

500 Hz

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

30 60 90 120 150 180 210 240 270 300 330

1000 Hz

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

30 60 90 120 150 180 210 240 270 300 330

2000 Hz

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

30 60 90 120 150 180 210 240 270 300 330

4000 Hz

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

30 60 90 120 150 180 210 240 270 300 330

8000 Hz

0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

30 60 90 120 150 180 210 240 270 300 330

16000 Hz

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Directivity of transducers

Neumann K-140 (ORTF Cardioids)

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350

125 Hz

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350

250 Hz

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350

500 Hz

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350

1000 Hz

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350

2000 Hz

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350

4000 Hz

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350

8000 Hz

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350

16000 Hz

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Other hardware equipment

  • Rotating Table:
  • Outline ET-1

Computer and sound card:

– Signum Data Futureclient

P-IV 1.8 GHz

– Aardvark Pro Q-10 (8 ch., 96 kHz, 24 bits)

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Measurement procedure

  • A single measurement session play backs

36 times the test signal, and simultaneusly record the 8 microphonic channels

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Theatres measured

N. Theatre

  • N. sources/receivers

1 Uhara Hall, Kobe, Japan 2/2 2 Noh Drama Theater, Kobe, Japan 2/2 3 Kirishima Concert Hall, Kirishima, Japan 3/3 4 Greek Theater in Siracusa, Italy 2/1 5 Greek-Roman Theater in Taormina, Italy 3/2 6 Auditorium of Parma, Italy 3/3 7 Auditorium of Rome (Sala 700), Italy 3/2 8 Auditorium of Rome (Sala 1200), Italy 3/3 9 Auditorium of Rome (Sala 2700), Italy 3/5 10 Bergamo Cathedral, Italy 2/1 11 Teatro Valli, Reggio Emilia, Italy 5/1 12 Sydney Opera House, Opera Theatre 4/2 13 Sydney Opera House, Concert Hall 3/3 14 Sydney Opera House, The Studio 3/1 15 Tearo Regio, Parma, Italy 6/1

Reverberation Time T20

0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 31.5 63 125 250 500 1000 2000 4000 8000 16000 Frequency (Hz) T20 (s)

Uhara Noh Kirishima Siracusa Taormina

  • Audit. Parma

Roma-700 Roma-1200 Roma-2700 Bergamo Cathedral Valli-RE SOH Concert Hall SOH-Opera Theatre SOH-The Studio Regio Parma

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Uhara Hall, Kobe, Japan

T20 = 1.44 s

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Noh theater, Kobe, Japan T20 = 1.14 s

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Kirishima Concert Hall, Japan

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Kirishima Concert Hall, Japan T20 = 1.93 s

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Greek Theater in Siracusa T20 = 0.65 s

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Roman Theater in Taormina T20 = 1.15 s

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Parma Auditorium, Italy T20 = 2.08 s

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Rome Auditorium, 700 seats T20 = 2.04 s

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Rome Auditorium, 1200 seats T20 = 2.10 s

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Rome Auditorium, 2700 seats T20 = 2.56 s

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Bergamo’s Cathedral, Italy T20 = 2.95 s

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Teatro Valli, Reggio Emilia, Italy T20 = 1.55 s

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Sydney Opera House

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Sydney Opera House – opera theatre

T20 = 1.16 s

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Sydney Opera House – concert hall

T20 = 2.04 s

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Sydney Opera House – the studio

T20 = 0.76 s

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Teatro Regio in Parma (Italy)

T20 = 1.11 s

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Auralization by convolution

  • The

basic method consists in convolution of a dry signal with a set of impulse responses corresponding to the required output format for surround (2 to 24 channels).

  • The

convolution

  • peration

can nowadays be implemented very efficiently on a modern PC through an ancient algorithm (equally-partitioned FFT processing, Stockam 1966).

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116th AES Convention Berlin, 8-11 May 2004

Auralization types

  • Stereo (ORTF on 2 standard loudspeakers at + /- 30°)
  • Rotation-tracking

reproduction

  • n

headphones (Binaural Room Scanning)

  • Stereo Dipole (cross-talk cancellation)
  • Full 3D Ambisonics 1st order (decoding the B-format

signal)

  • ITU 5.1 “surround sound” systems
  • 2D Ambisonics 3rd order (from Mark Poletti’s circular

array microphone)

  • Wave Field Synthesis (from

the circular array of Soundfield microphones)

  • Hybrid methods (Ambiophonics)
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Approach # 1 – separate rendering for each recorded track (source)

Each of the dry recordings represents a source in a different position, so it must be separately convolved with its own set of impulse responses

M I X

5 ch.

1x5 1x5

1 ch. 1 ch. 5 ch. 5 ch.

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Approach # 2 – the recorded tracks are first panned to 5.0, then the “room” is added The “room effect” is a global filtering applied to a 5.0 “dry mix” of several tracks

M I X

5 ch. 5 ch. 5 ch.

5 (1x1)

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Full Auralization vs. Reverb

  • In “full auralization” also the direct sound comes from

the measured IRs

  • In “reverb” the dry signals are employed in place of

the direct sound, and the measured IRs are employed

  • nly for adding subsequent reverberant tail
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Software tools

  • Gerzonic’s Ambisonics decoders (Emigrator, DecoPro)
  • David McGriffy’s Visual Virtual Mike (VST & standalone)
  • Waves IR1 convolution reverb
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Approach # 1 – single source rendering – choice of 1x5 filter set

1.

Ambisonics (1° order) from a single B-format impulse response

2.

SIRR according to Ville Pulkki (sound intensity analysis of a single B-format IR)

3.

5 “virtual mikes” from 5 different B-format impulse responses

4.

5 selected Neumann cardioids

5.

(future) – 5°-order Ambisonics from the whole set of cardioid impulse responses

  • Tr. 01
  • Tr. 02
  • Tr. 03
  • Tr. 04

Turntable Soundfield Microphone Turntable Soundfield Microphone Turntable Soundfield Microphones Turntable Cardioids (ORTF)

Dry speech Dry music

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Approach # 2 – the recorded tracks are first panned to 5.0, then the “room” is added

5 ch.

Play track 5 to convolver...

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Approach # 2 – the recorded tracks are first panned to 5.0, then the “room” is added

Ambisonics IR 5 “virtual mikes”

Dry

Track 6 5 Neumann cardioids

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Conclusions

  • It is now possible to sample accurately the

spatial room impulse response, making it possible to store, analyze and preserve a “3D acoustical photography”

  • We are still learning what is the best way to

render these sets of impulse responses over a standard 5.0 (or 5.1) setup

  • The
  • nly

point which requires substantial enhancement: sound sources (loudspeakers) used for IR measurements

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Future enhancements

Sound source for realistic emulation of an human singer

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Future enhancements

Omnidirectional sound source with enhanced power & frequency response

  • Dodech. LookLine D300 + Sub Audio Pro B2.27

60 70 80 90 100 110 120

25 31.5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000

Frequency (Hz) Sound Power Level (dB)

Unequalized Equalized Lw,tot = 100.5 dB Lw,tot = 108.4 dB

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Acknowledgements

This research was started thanks to the support of Waves, Tel Aviv, Israel (www.waves.com) For years 2004 and 2005 the research is also supported by the Italian Ministry for the University and Research (MIUR) The following software tools were provided free: Adobe Audition, Gerzonic Decopro