y=Dy*x+Ey*u+Fy*z; ... Nonlinear block with 8 parameters (4 · gi , 4 · m(x)). Iterative adaption ... ABC/HR - style: Similarity of items and reference should be rated.
Professur Allgemeine Nachrichtentechnik Prof. Dr.-Ing. Udo Zölzer
Guitar Amplifier Modeling: Perceptual Evaluation of Audio Similarity Felix Eichas, Udo Zölzer
May 2018
Outline
Introduction Circuit Modeling Techniques Measurement Setup System Identification Perceptual Evaluation of Audio Similarity Conclusion
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
2 / 14
Vintage Guitar Amplifier: VOX AC30
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
3 / 14
White Box & Black Box Modeling
Eq
+
Dq
solver
Fy
C B
+ z −1 A
Dy
+
Ey
p=Dq*x+Eq*u; z=approx_solve(p); y=Dy*x+Ey*u+Fy*z; x=A*x+B*u+C*z;
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
4 / 14
White Box & Black Box Modeling
Eq
+
Dq
solver
Fy
C B
+ z −1 A
Dy
+
Ey
p=Dq*x+Eq*u; z=approx_solve(p); y=Dy*x+Ey*u+Fy*z; x=A*x+B*u+C*z;
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
4 / 14
Measurement Setup
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
5 / 14
Identification of Linear Subsystems 1. Low amplitude sine sweep: H1 · H2 = Htotal 2. High amplitude sweep: H2 → H1 =
Htotal H2
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
6 / 14
Identification of Linear Subsystems 1. Low amplitude sine sweep: H1 · H2 = Htotal 2. High amplitude sweep: H2 → H1 =
Htotal H2
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
6 / 14
Nonlinear Block Nonlinear block with 8 parameters (4 · gi , 4 · m(x )) Iterative adaption of NL parameters with Levenberg–Marquardt method
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
7 / 14
Optimization of Nonlinear Parameters H1 and H2 : measured and approximated by recursive filters Optimization of NL parameters with Levenberg–Marquardt
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
8 / 14
Optimization of Nonlinear Parameters H1 and H2 : measured and approximated by recursive filters Optimization of NL parameters with Levenberg–Marquardt
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
8 / 14
Optimization of Nonlinear Parameters H1 and H2 : measured and approximated by recursive filters Optimization of NL parameters with Levenberg–Marquardt
Input Signal for Optimization Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
8 / 14
Perceptual Evaluation of Audio Similarity
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
9 / 14
Perceptual Evaluation of Audio Similarity
eRMS =
PEAS 0.0637
v uP u N (y (n)−ˆy (n,p))2 ref mod t n=1
N
Bassman 100 (Clean) eRMS rxy eESR 0.0001 0.9952 0.0100
N P
eESR =
(yref (n)−ˆ ymod (n,p))2
n=1 N P
2 (n) yref
n=1
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
10 / 14
Perceptual Evaluation of Audio Similarity
eRMS =
v uP u N (y (n)−ˆy (n,p))2 ref mod t n=1
N
JCM 900 (Strong Distortion) PEAS eRMS rxy eESR 0.3717 0.0414 0.0792 1.7936
N P
eESR =
(yref (n)−ˆ ymod (n,p))2
n=1 N P
2 (n) yref
n=1
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
10 / 14
Listening Test ABC/HR - style: Similarity of items and reference should be rated 35 participants – 19 selected for final evaluation → Criterion for exclusion: HR rated with 80 or less
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
11 / 14
Listening Test ABC/HR - style: Similarity of items and reference should be rated 35 participants – 19 selected for final evaluation → Criterion for exclusion: HR rated with 80 or less
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
11 / 14
Listening Test: Madamp A15Mk2
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
12 / 14
Listening Test: Marshall JCM 900
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
12 / 14
Results – Sound Examples Fender – Bassman 100 (Clean) (Input Recording:
)
Simulation:
Marshall – JCM900 Lead Channel Low Gain Medium Volume – Input Recording:
Simulation:
Marshall – JCM900 Lead Channel Medium Gain Medium Volume – Input Recording:
Simulation:
Madamp – A15Mk2 Lead Channel (gain boost) High Gain High Volume – Input Recording:
Simulation:
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
13 / 14
DEMO / VIDEO
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
13 / 14
Conclusion
Wiener–Hammerstein model is suited for modeling guitar amplifiers
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
14 / 14
Conclusion
Wiener–Hammerstein model is suited for modeling guitar amplifiers More distortion → more nonlinear behavior → results get worse
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
14 / 14
Conclusion
Wiener–Hammerstein model is suited for modeling guitar amplifiers More distortion → more nonlinear behavior → results get worse Listening Test: No amplifier rated worse than ‘Minor Differences’ (on average)
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
14 / 14
Conclusion
Wiener–Hammerstein model is suited for modeling guitar amplifiers More distortion → more nonlinear behavior → results get worse Listening Test: No amplifier rated worse than ‘Minor Differences’ (on average) Similarity score (PEAS) better for evaluation than conventional error metrics
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
14 / 14
Thank you!
Eichas,Zölzer – Perceptual Evaluation of Audio Similarity
14 / 14
