NVH评价方法

Threshold 50 40 Phon 50 Phon 60 phon 30 70 Phon
10
-10 10 100 1000 10000 100000
频率
F
• Loudness is defined relative to the loudness of a reference sound • Loudness in Phons (P) = SPL of an equivalently loud sound at 1000 hz . • Sones (S) is a linear measure of loudness – Double Sones, Double Loudness 11
• The speech is frequency related • A weighting factor W(f) is introduced for each frequency
250
315 400 500
69
71 73 75
2
3.25 4.25 4.5
630
800 1000 1250 1600 2000 2500 3150 4000
75
75 74 72 70 67 65 63 60
5.25
6.5 7.25 8.5 11.5 11 9.5 9 7.75
5000
6300
56
51
6.25
2.5 16
Articulation Index (AI)
AI Definition
AI W ( f ) D( f ) / 30
Noise is N(f).
频率 上限噪声 计权系数 噪声 1 噪声 2 D(f) 1 D(f) 2 带宽说话清晰因子 1 带宽说话清晰因子 2
200
64
1
60
70
4
0
0.13
0
250
315 400 500 630 800 1000 1250 1600 2000 2500
315
500
800
1250
2000
3150
5000
8000
20
50
80
Evaluation Cases
Idle: • Idle Park
•
•
Idle drive
Idle reverse
80 75 70
Wide Open Throttle (WOT)
dB(A)
Partial Open Throttle (WOT) Coastdown Reverse
• The vehicle NVH target is cascaded into system, then subsystems, then components
Example: Exhaust Tailpipe Noise Target Exhaust Vibration Muffler TL Hanger Force
Vehicle NVH Evaluation
1
The Factors Determining Vehicle NVH Evaluation:
• Customer Requirements • Company’s Technology • Government Regulation
Two Evaluations of Vehicle NVH
5
Subjective Evaluation
• Subjective Rating:
级度 接受对象 2 3 4 不能接受 所以顾客 绝大多数顾客 1 5 6 7 接受的过渡 比较挑剔的顾客 8 9 可以接受 受过培训的人员 10
Historical trend indicates NVH performance improves 1 VER for every 10 years
9
Noise Evaluation
Ear:
• People ear hearing frequency range: 20 Hz to 20,000 Hz
•
•
Most sensitive frequency is 1000 Hz
Not sensitive between 20 to 100 Hz and between 15,000 to 20,000 Hz
Loudness and Weighting
Loudness Ear's measures compensate the ear’s Sensitivity - Equal Loudness Curves for ( Av. Age 18-25 Year ) sensitivity
110
90
70
SPL (dB)
Weighting Factors
10 0
Weighting dB
-10 -20 -30 -40 -50 -60 "A-Weighting"
31.5
12500
Frequency
However, dB(L) is used for sound path calcu200
Loudness and Weighting
A - Weighting: An approximate estimate of loudness which adjusts the SPL in accordance with ear's sensitivity (at about 40 phon).
50%看得清楚
5%看得清楚
说话清晰因子是Beranek提出来的。这个参数描述了在噪声环境下说话的 清晰程度。说话清晰因子是用百分数来表示，100%表示说话完全听得清 楚，0%表示说话完全听不清楚。说话是否听得清楚有点象看字是否清楚 一样。
14
Articulation Index (AI) • Speech sound has a spectrum, H(f) • If background noise is 12 dB louder than speech spectrum H(f), the speech sound will be totally masked
• Loudness (P): as 1000 Hz sound as reference. The sound is listened the same loud. • Unit: Sone
Relation: Loudness and Sound Intensity
for
LN 30
P3 I
10
LL(f) = U(f) - 30 dB
15
Articulation Index (AI)
Frequency (Hz) 200 Weighting Factor 1
UL (f) 64
• The difference between UL(f) and LL(f) is 30 dB for all the frequency
65 60 55 50 1000
WOT POT
2000
3000 rpm
4000
5000
6000
13
Articulation Index (AI)
AI is a psycho-acoustic metric to determine the speech intelligibility
100%看得清楚 说话清晰因子是Beranek提出来的。这个参数描述了在噪声环境下说话的 清晰程度。说话清晰因子是用百分数来表示，100%表示说话完全听得清 楚，0%表示说话完全听不清楚。说话是否听得清楚有点象看字是否清楚 一样。 说话清晰因子是Beranek提出来的。这个参数描述了在噪声环境下说话的 清晰程度。说话清晰因子是用百分数来表示，100%表示说话完全听得清 楚，0%表示说话完全听不清楚。说话是否听得清楚有点象看字是否清楚 一样。
Benchmarking is the most useful way to determine
vehicle NVH levels
3
System and Component NVH Evaluations
• Vehicle NVH target is the base of vehicle NVH development
• Vibration: large or small, comfortable or uncomfortable
Different vehicle drivers have different opinions on NVH
• Sporty cars’ customers need strong engine sound and exciting feeling • Luxury cars’ customers need quite sound and comfortable riding Objective Evaluation: Use analytical method and test to evaluate NVH
• Upper Limit (UL(f)):
UL(f) = H(f) + 12 dB • If the background is 30 dB lower than Upper Limit (UL(f)), the speech sound can be totally heard
• Lower Limit (LL(f)):
• Seat vibration and human body vibration
Microphone
Accelerometer
7
Relation: Subjective Evaluation
and Objective Evaluation
10 9
主 观7 评 6 级
5 4 45 50 55 60 65 70
• NVH is one of the most factors influencing customers’ decision to buy vehicles
• Vehicle NVH is core of vehicle development
• Different vehicles have different NVH level • Luxury cars are more quite and less vibration than ordinary cars
• Sound Quality
6
Objective Evaluation
Items of Objective Evaluations:
• Driver and passenger ears sound: sound level and sound quality • Floor or seat track vibration • Steering wheel vibration
D(f) is defined as follows:
N ( f ) UL( f )
LL( f ) N ( f ) UL( f )
D( f ) 0
D( f ) UL( f ) N ( f )
N ( f ) LL( f )
D( f ) 30
17
Articulation Index (AI) Example: Two Sounds
• Interior NVH Evaluation
• Pass-by Noise Evaluation
2
Interior NVH Evaluation (Vehicle Level NVH Evaluation)
Why?
• Customers concern interior noise and vibration
Vehicle NVH target
4
Subjective Evaluation and Objective Evaluation
Subjective Evaluation: Customer intuitive feelings
• Sound: quite or loud, pleasant or anxious
8
噪声级 dB(A)
Some of subjective evaluation can be quantity identified
Sound Quality
8
Head Sound at Passenger Ears
Passenger
Driver
HEAD Acoustics
• More accurate measurement • Can be re-listened in lab • Database can be established