Does Slap Back Echo give

CombFilter coloration?

Tor Halmrast

2017

Jerry Lee Lewis,

Carl Perkins

Elvis Presly

Johnny Cash

SUN STUDIOS

Dec.4th, 1956

Perforated gypsym (mid-freq.-absorber)

Sam Philips

ELVIS

Les Paul: Early 50´s At SUN studios ca. 1954 Sam Philips: Echo using two Ampex 350 recorders Discussions about the delay time 60-120 ms? 163 ms? 150-200 ms? 530 ms (!!!???) General: Slap Back Echo 75-250 ms?

Assume a distance between the recording and playback head of 4 inches and echo tape speeds of 7.5 ips: Delay = 4/7.5 = 0.53 seconds (most likely the most common echo tape speed). 15 ips: Delay = 4/15 = 0.27 seconds (When It Rains It Really Pours). (7.5 ips as the common speed of the echo tape machine has been confirmed by Roland Janes of Sam Phillips studio)

RCA January 1956, Heartbreak Hotel had to use the stairwell

Baby Let´s Play House

Time (s)

0 1

-0.4562

0.99

0

-0.4562

0.99

0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Time (s)

0 1

0.5

-0.5

0

0.5

-0.5

0

Quefrency (s)

0 1

Am

pli

tud

e (d

B)

32.95

110.4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Time (s)

0 1.956

Pit

ch (

sem

iton

es r

e 4

40

Hz)

-24

4

-24-23-22-21-20-19-18-17-16-15-14-13-12-11-10-9-8-7-6-5-4-3-2-101234

A

A

D

137 ms

Quefrency (s)

0 1.486

Am

pli

tude

(dB

)

50

70

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4

Power Cepstrum (Praat)

Quefrency (s)

0 0.2

Am

plitu

de (d

B)

55

65

0 0.1 0.20 0.05 0.1 0.15 0.2

Power Sepctrum

Zoom in:

ca 134?-137? ms

CBTB=1/DeltaT=1000/135= 7 Hz

Too small to be observed in FFT:

Tryin´to get to you

Time (s)

0 1.797

Pit

ch (

sem

iton

es r

e 4

40

Hz)

-14

-6

-14

-13

-12

-11

-10

-9

-8

-7

-6

IIII´ve BEEN TRAAAV----LING OOO-VER

0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18

quefrency (s)

2000

4000

6000

8000

10000

12000

14000

16000

mag

nitu

de

Cepstrum

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

lag (s)

-0.2

0

0.2

0.4

0.6

0.8

1

coeff

icie

nts

Waveform autocorrelation

137 ms

Quefrency (s)

0 0.2

Am

pli

tude

(dB

)

55

65

0 0.1 0.20 0.05 0.1 0.15 0.2

Quefrency (s)

0 0.2

Am

pli

tude

(dB

)

55

65

Power Cepstrum (Praat)

Cepstrum (MIR toolbox)

Autocorrelation (MIR toolbox)

Tomorrow Night

0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2

lag (s)

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

co

eff

icie

nts

Waveform autocorrelation

Cepstrum

Autocorrelation

Time (s)

0 4.191P

itch

(se

mit

on

es r

e 4

40

Hz)

-14

-8

0 1 2 3 4-14

-13

-12

-11

-10

-9

-8

H (B)

A

TOO---------MORROW

150 ms

Overdubbing??

Heartbreak Hotel

Time (s)

0 2.972

Pitc

h (s

emito

nes

re 4

40 H

z)

-36

6

-36

-24

-12

0

-5 E

Heartbreak Hotel

Time (s)

0 2.972

Pitc

h (H

z)

0

500

0

100

200

300

400

500

E=330E=330

Heartbreak Hotel

Quefrency (s)

0 1.486

Am

pli

tude

(dB

)

-71.08

119.2

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4

PowerCepstrum (orig Heartbreak)

Quefrency (s)

0 0.1

Am

plitu

de (

dB)

-22.58

119.2Heartbreak Hotel

PowerCepstrum

0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

82 msec

Quefrency (s)

0 0.2

Am

plit

ude

(dB

)

55

70

0 0.05 0.1 0.15 0.2

deltaT=0,08 s (80 ms)

CBTB=1/deltaT=1000/80=12.5 Hz

Heartbreak Hotel (forts.)

1500 Hz

75 Hz

22.000 Hz

80 Hz

Heartbreak Hotel (cont.)

(wEEEl, sIIIIInce ) Vowel, Formant1/Formant2 (from litt.) E: 402 / 2020, i: 291/2210

FORMANTS

TEST

LPC LINEAR PREDICTIVE CODING

Music with Noise

REMOVE «Voice» in order to eliminate the Pitch+Overtones for the Autocorrelation analysis

Did not work for detecting echoes, beacuse the LPC smoothes also the attacks, so the delayed echo is not detectable

Orig. LPC w/WhiteNoise LPC Residue

Long Tall Sally Time (s)

0 1.788

Pit

ch (

sem

iton

es r

e 4

40

Hz)

-32

0

-30

-24

-18

-12

-6

0

Time (s)

0 1.788

-0.8913

0.6492

0

-0.8913

0.6492

0

Time (s)

0 1.788

Pitc

h (s

emito

nes

re 4

40 H

z)

-32

0

-30

-24

-18

-12

-6

0

Time (s)

0 1.788

-0.8913

0.6492

0

-0.8913

0.6492

0

Long Tall Sally

0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09

quefrency (s)

2000

4000

6000

8000

10000

12000

mag

nitu

deCepstrum

0.005 0.01 0.015 0.02 0.025 0.03

quefrency (s)

0

2000

4000

6000

8000

10000

12000

mag

nitu

de

CepstrumZOOM IN:

FLUTTER-EKKO MELLOM SIDEVEGGER I EN KORRIDOR?? Ca. 9ms??

Quefrency (s)

0 0.2

Am

pli

tude

(dB

)

55

70

0 0.05 0.1 0.15 0.2

Long Tall Sally Power Sepctrum(Praat)

12 ms??

12 ms??

Long Tall Sally

Time (s)

0 1-0.3893

0.99

0

Time (s)

0 1-0.3893

0.99

0

AutoCorr LOngTallSally ch1

CrossCorrelation Long Tall Sally ch1 X ch2

…This is MONO!!

AutoCorr for TESTING STERO/MONO

DOES SUCH LONG DELAYED REFLECTIONS GIVE COMB FILTER COLORATION?

Example: Delay 130 ms (45m exces distance)

DOES SUCH LONG DELAYED REFLECTIONS GIVE COMB FILTER COLORATION?

Example: Delay 82 ms (28m excess distance)

DOES SUCH LONG DELAYED REFLECTIONS GIVE COMB FILTER COLORATION?

Example: Delay 9ms (3.1 m ecxes s distance) LongTall Sally (Corridor??)

ANALYSIS of

POSSIBLE

PERCEIVED

COMB FILTER COLORATION

Comparing the CBTB (Comb Between Teeth Bandwidth)

with the Critical Bandwidth of our hearing organ (basilar membran)

SUN SlapBack No CombColoration

Heartbreak VeryLittleColoration

LongTallSally CorridorColoration?

ECHO CANSELLATION is HARD!!!!! We cannot just take a filter/impulse response of one pulse at time 0, and a negative puls at the detected time delay of the echo, as this will add a new reflection (negative) at twice the delay time:

Out

Known/measured time delay of echo on recording

Imp.Resp of Test-Echo-Canselation

Added (negative) new echo at 2x measured time delay

Normalised. PS! All curves have 1 at time 0