Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf ·...
Transcript of Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf ·...
Introduction to Sound Quality
A presentation by Dr. Colin Novak – NVH-SQ GroupUniversity of Windsor
Noise, Vibration, Harshness –Sound Quality Research Group
Copyright 2015 by Colin Novak. All rights reserved no part of this publication may be reproduced or distributed in any form or by any means, or stored in a data base or retrieval, without the prior written permission of the author.
Copyright ©2015, Colin Novak
OUTLINE
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Noise, Vibration, Harshness – Sound Quality Research Group
• What is Sound Quality?
• Why improve the Quality of Sound?
• Noise vs. Sound
• Sound Quality Metrics
• Jury Testing or Subjective Tests
• Sound Quality Analysis Process
Sound Quality
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Noise, Vibration, Harshness – Sound Quality Research Group
I like the colour
200 HP!
It soundscool!
Noise vs Sound
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Noise, Vibration, Harshness – Sound Quality Research Group
Noise
Measured: to avoid hearing damage to fulfill regulations
Measured as: dBA Sound Power
Sound
Perceived as: pleasant sound unpleasant sound informative sound
Measured as: “Sound Quality”
it sounds bad
Power: 0.01 Watt
Lp = 88.5 dBALW = 100 dBA
Why Improve Sound Quality
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Noise, Vibration, Harshness – Sound Quality Research Group
L = 63 dBA L = 63 dBA
Good Sound Quality signals proper operation of the product
Sound Quality is a parameter that sells the product
A-weighted noise levels and sound power are fine to characterize noise, but useless for sound
Sound Quality is not static, but changes over time like fashion
L = 63 dBA
Sound Quality Example
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Noise, Vibration, Harshness – Sound Quality Research Group
You will hear 5 refrigerator signals, all presented at the same time-averaged A-weighted sound pressure level.
Question: Would you find all of these refrigerator sounds equally desirable in your kitchen?
Click to PlayClick to Play
Example
Sound Quality Example
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Noise, Vibration, Harshness – Sound Quality Research Group
Which refrigerator sound did you like the best?
Most people like refrigerator number 4 the best.
Did you? If not, why not listen again!
Click to Play
Example
Click to Play
Example
Sound Quality Example
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Noise, Vibration, Harshness – Sound Quality Research Group
Using traditional SPL measurements for these signals, you can’t really see much relationship to your preferences.
SPL in dB(A) for Each Refrigerator
20
25
30
35
40
1 2 3 4 5
Refrigerator Number
SPL
in d
B(A
)
Unweighted SPL for Each Refrigerator
202530354045505560
1 2 3 4 5
Refrigerator Number
SPL
in d
B
Sound Quality Example
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Noise, Vibration, Harshness – Sound Quality Research Group
Using Sound Quality metrics, it IS possible to measure differences in these signals which relate to your preferences! Here are just 4 such measures:
Max. Total Loudness
0
1
2
3
1 2 3 4 5Refrigerator Number
Loud
ness
in s
ones
Mean Total Loudness
0
1
2
3
1 2 3 4 5Refrigerator Number
Loud
ness
in s
ones
Percentile (N1) Instantaneous Loudness
0
1
2
3
1 2 3 4 5Refrigerator Number
Loud
ness
in s
ones
Refrigerator Number
Mean Zwicker Sharpness
0
1
2
3
1 2 3 4 5Shar
pnes
s in
acu
m
What is Sound Quality?
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Noise, Vibration, Harshness – Sound Quality Research Group
Having seen an example of a sound quality analysis what is the procedure to achieve these results?
Many manufacturers calculate simple models to predict how people will like their product sounds. These models are determined using either or both:
1) Sound quality metrics (i.e., objective measures) calculated with a sound quality software program, and/or
2) Jury Testing or Human preferences (i.e., subjective measures), determined by asking people to rate the product sounds.
Sound Quality Metrics
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Noise, Vibration, Harshness – Sound Quality Research Group
“Zwicker Loudness”
Loudness is a measure of how “strong” a sound is to humans. That is, it is a way of measuring a sound that corresponds to the subjective perception of humans. This is very different than sound pressure, sound intensity or sound power, which are physical quantities (remember the refrigerator demo).
There are several methods or algorithms for determining loudness. The Zwicker loudness method has been shown to have the highest correlation to human perceived loudness. Zwicker loudness is a very sophisticated algorithm and is used by most sound quality programs.
Sound Quality Metrics
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Noise, Vibration, Harshness – Sound Quality Research Group
Zwicker loudness can be used for 2 types of signals:
Stationary (“steady”) signals
- Starts with 1/3 octaves
- Linear averaging
- Uses frequency masking
- Computes 1 averaged loudness spectrum
- Standardized measurement: ISO 532B / DIN 45631
NonStationary (“non-steady”) signals
- Starts with 1/3 octaves
- Exponential averaging with time varying time constants
- Uses frequency masking
- Uses time masking
- Computes a loudness waterfall
- Not standardized just yet.
Click for
Signal
Click for
StationarySignal
Click for
Signal
Click for
NonstationarySignal
Sound Quality Metrics
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Noise, Vibration, Harshness – Sound Quality Research Group
Typical stationary Zwicker loudness spectrum (ISO 532B):Curved line representsfrequency masking
Zwicker loudness is thearea under the curve.(about 45 sones)
SpecificLoudnessaxis
Sound Quality Metrics
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Noise, Vibration, Harshness – Sound Quality Research Group
Typical Zwicker loudness waterfall plot of a nonstationary signal (a bell ringing after one hit): You get many loudness spectra, each spaced 2 msec apart!
Loudness non stationary spectrumOriginal Signal
2 4 6 8 10 12 14 16 18 20 22 24
0
4
500m
1
1.5
2
2.5
3
3.5
[Bark]
[sone/Bark]
[s]
Time
Sound Quality Metrics
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Noise, Vibration, Harshness – Sound Quality Research Group
Christie Digital – April 06 2009
Pleasantness
Annoyance
Tone-to-Noise Ratio
Prominence Ratio
Tonality, Pitch Strength
Speech Interference Levels (SIL)
Intelligibility, Articulation Index (AI)
Speech Transmission Index (STI)
Kurtosis
User Defined Metrics
etc.
Jury Testing
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Noise, Vibration, Harshness – Sound Quality Research Group
Recording Analysis and Editing Playback
section section section
Jury Testing
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Noise, Vibration, Harshness – Sound Quality Research Group
1. Original sound
2. Edited sound
3. Competitor’s
sounds
1 Play 2SubjectiveTests
Sound Quality Process
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Noise, Vibration, Harshness – Sound Quality Research Group
Objective
Test,
Metrics
SoundRecording
SubjectiveTest
ProductEngineering
Trouble-shooting
SoundQualityProgram Objective
Test,
Metrics
Sound
Recording SubjectiveTest
ProductEngineering
Trouble-shooting
SoundQuality
Program
Sound Quality Process
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Noise, Vibration, Harshness – Sound Quality Research Group
Frequency
What is Sound Quality?
Why improve the Quality of Sound?
Noise vs. Sound
Sound Quality Metrics
Jury Testing or Subjective Tests
Sound Quality Analysis Process
Questions???
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Noise, Vibration, Harshness – Sound Quality Research GroupNoise, Vibration, Harshness – Sound Quality Research Group