Does Slap Back Echo give
CombFilter coloration?
Perforated gypsym
(mid-freq.-absorber)
Sam Philips
ELVIS
Tor Halmrast
2017
Jerry Lee Lewis,
Carl Perkins
Elvis Presly
Johnny Cash
SUN STUDIOS
Dec.4th, 1956
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
0
-0.4562
0.99
0
-0.4562
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Time (s)
1
-0.5
0
0.5
-0.5
0
Pitch (semitones re 440 Hz)
0.99
4
3
2
1
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-10
-11
-12
-13
-14
-15
-16
-17
-18
-19
-20
-21
-22
-23
-24
A
A
D
0
1.956
Time (s)
0.5
0
1
Time (s)
137 ms
70
Power Cepstrum (Praat)
Amplitude (dB)
Amplitude (dB)
110.4
32.95
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Quefrency (s)
1
50
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 1.41.486
Quefrency (s)
Zoom in:
65
Amplitude (dB)
Power Sepctrum
55
0
0.05
0.1
Quefrency (s)
CBTB=1/DeltaT=1000/135= 7 Hz
Too small to be observed in FFT:
0.15
ca 134?-137? ms
0.2
Tryin´to get to you
Cepstrum
16000
Cepstrum (MIR toolbox)
14000
-6
Pitch (semitones re 440 Hz)
12000
magnitude
10000
8000
6000
4000
2000
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
Waveform
autocorrelation
quefrency
(s)
1
-7
-8
-9
IIII´ve BEEN
-10
TRAAAV----LING
OOO-VER
-11
-12
-13
-14
0
Autocorrelation (MIR toolbox)
0.8
65
Power Cepstrum (Praat)
137 ms
Amplitude (dB)
coefficients
0.6
0.4
1.797
Time (s)
0.2
0
-0.2
0
0.02
0.04
0.06
0.08
0.1
lag (s)
0.12
0.14
0.16
0.18
0.2
55
0
0.05
0.1
Quefrency (s)
0.15
0.2
Tomorrow Night
Cepstrum
Pitch (semitones re 440 Hz)
-8
Autocorrelation
TOO---------MORROW
-9
-10
H (B)
-11
-12
A
-13
Waveform autocorrelation
1
-14
0
0.8
1
150 ms
coefficients
0.6
0.4
0.2
Overdubbing??
0
-0.2
-0.4
0
0.02
0.04
0.06
0.08
0.1
lag (s)
0.12
0.14
0.16
0.18
0.2
2
Time (s)
3
44.191
Heartbreak Hotel
82 msec
Heartbreak Hotel
Pitch (semitones re 440 Hz)
6
0
-5
E
PowerCepstrum (orig Heartbreak)
-12
119.2
-24
0
Amplitude (dB)
-36
2.972
Time (s)
Heartbreak Hotel
500
-71.08
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 1.41.486
Quefrency (s)
E=330
300
200
Heartbreak Hotel
119.2
100
PowerCepstrum
0
0
2.972
Time (s)
Amplitude (dB)
Pitch (Hz)
400
-22.58
0
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1
Quefrency (s)
Amplitude (dB)
70
55
0
0.05
0.1
Quefrency (s)
0.15
deltaT=0,08 s (80 ms)
CBTB=1/deltaT=1000/80=12.5 Hz
0.2
Heartbreak Hotel (forts.)
1500 Hz
75 Hz
22.000 Hz
80 Hz
Heartbreak Hotel
(cont.)
FORMANTS
(wEEEl,
sIIIIInce )
Vowel, Formant1/Formant2 (from litt.)
E: 402 / 2020,
i: 291/2210
TEST
LPC
LINEAR PREDICTIVE CODING
Orig.
Music with Noise
REMOVE «Voice» in order to
eliminate the Pitch+Overtones
for the Autocorrelation analysis
LPC w/WhiteNoise
Did not work for detecting echoes,
beacuse the LPC smoothes also the attacks,
so the delayed echo is not detectable
LPC Residue
-30
-32
0
Long
Tall Sally
Time (s)
1.788
0.6492
0
-0.8913
0.6492
0
-0.8913
1.788
0
Time (s)
Pitch (semitones re 440 Hz)
0
-6
-12
-18
-24
-30
-32
0
1.788
Time (s)
Long Tall Sally
Cepstrum
12000
10000
magnitude
8000
6000
4000
2000
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
quefrency (s)
ZOOM IN:
FLUTTER-EKKO
MELLOM SIDEVEGGER
I EN KORRIDOR??
Cepstrum
12000
10000
Ca. 9ms??
magnitude
8000
6000
4000
2000
0
0.005
0.01
0.015
0.02
quefrency (s)
0.025
0.03
Long Tall Sally Power Sepctrum(Praat)
70
Amplitude (dB)
12
ms??
12
ms??
55
0
0.05
0.1
Quefrency (s)
0.15
0.2
Long Tall Sally
AutoCorr for TESTING STERO/MONO
AutoCorr LOngTallSally ch1
0.99
0
-0.3893
0
1
Time (s)
0.99
CrossCorrelation Long Tall Sally ch1 X ch2
0
-0.3893
0
1
Time (s)
…This is 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:
Normalised. PS! All curves have 1 at time 0
Known/measured time delay of echo on recording
Out
Added (negative) new echo at 2x measured time delay
Imp.Resp of Test-Echo-Canselation