Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf ·...

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Introduction to Sound Quality A presentation by Dr. Colin Novak – NVH-SQ Group University 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

Transcript of Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf ·...

Page 1: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

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

Page 2: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

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

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Sound Quality

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Noise, Vibration, Harshness – Sound Quality Research Group

I like the colour

200 HP!

It soundscool!

Page 4: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

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

Page 5: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

Why Improve Sound Quality

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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

Page 6: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

Sound Quality Example

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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

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Sound Quality Example

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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

Page 8: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

Sound Quality Example

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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

Page 9: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

Sound Quality Example

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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

Page 10: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

What is Sound Quality?

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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.

Page 11: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

Sound Quality Metrics

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“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.

Page 12: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

Sound Quality Metrics

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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

Page 13: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

Sound Quality Metrics

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Typical stationary Zwicker loudness spectrum (ISO 532B):Curved line representsfrequency masking

Zwicker loudness is thearea under the curve.(about 45 sones)

SpecificLoudnessaxis

Page 14: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

Sound Quality Metrics

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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

Page 15: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

Sound Quality Metrics

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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.

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Jury Testing

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Recording Analysis and Editing Playback

section section section

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Jury Testing

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1. Original sound

2. Edited sound

3. Competitor’s

sounds

1 Play 2SubjectiveTests

Page 18: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

Sound Quality Process

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Objective

Test,

Metrics

SoundRecording

SubjectiveTest

ProductEngineering

Trouble-shooting

SoundQualityProgram Objective

Test,

Metrics

Sound

Recording SubjectiveTest

ProductEngineering

Trouble-shooting

SoundQuality

Program

Page 19: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

Sound Quality Process

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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

Page 20: Noise, Vibration, Harshness – Sound Quality Research … S2015/Lecture 15 2015 92-455.pdf · Noise vs Sound 4 Noise, Vibration, Harshness – Sound Quality Research Group Noise

Questions???

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Noise, Vibration, Harshness – Sound Quality Research GroupNoise, Vibration, Harshness – Sound Quality Research Group