NVH at the Start of the New Car Development Program 1

[vibrostics]

Could any one explain me about "How the NVH is looked at the start of the any New Car Development cycle" ?

 

[GregLocock]

1) measure competitors NVH
2)set targets
3) break targets down into budgeted performance for each sub system
4) deliver sub system targets in production
5) confirm that this meets overall targets set in 2)
6) take a well earned break and get a pat on the back

Item 1 often goes to plan. After that it gets a bit messy.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[vibrostics]

Greg,

Thanks for the reply. Could you tell me more about the
1) Measure competitors NVH

What all will be measured in NVH? Is that the tactile responses and the noise intensity at the driver’s ear location? Just only that?

What all targets will be derived from the above measured NVH for the sub systems?

I think I am asking too much in one question. It will be helpful if you through some information on this.

Thanks.

 

[GregLocock]

Well really that depends on what you are doing. I'm not going to go into specifics, each company probably does it a different way.

But, say, for interior noise I'd be looking at front and rear passenger locations, for the following conditions:

1)
full throttle

light throttle

coast

at all engine speeds in appropriate gears

2) Noise at failry low speed on a coarse chipped surface, and the same on a very smooth surface

3) windnoise at various speeds and yaw angles

4) HVAC noise at avarious operating conditions

5) Noise from hitting a strip on the road (impact noise)

6) Noise at idle

These would then be analysed in various ways and targets set.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[vibrostics]

What about the tactile responses? Is that done in similar way you explained above for the full throttle, light throttle and Idle? What are the most critical and contributing subsystems for the tactile responses and structure borne noise and how they are dealt with?

 

[GregLocock]

Yes the tactiles would be similar.

"What are the most critical and contributing subsystems for the tactile responses and structure borne noise and how they are dealt with?"

Aye well, that's for me to know, and you to find out. Sorry, I would describe that sort of info as competitive advantage.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[vibrostics]

Do you suggest any good NVH books and readings which gives more perspectice on the practical aspects?

Thanks.

 

[GregLocock]

The lack of a good, general, NVH textbook is an obvious gap in the market. It may be that it is too difficult to write about in a coherent fashion.

Anyway, start with all the free stuff on the B&K website. Then look at SAE papers, particularly the bundled NVH proceedings. The IMechE also has some useful conference papers.

Then you've got acoustics textbooks, like Beranek, and vibration control by Harris.

This is a good one:
Noise and vibration 1982, edited by R. G. White and J. G. Walker.






Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Rob45]

Hey, Greg!
I'm embarking on a completely new vehicle program right now, and am even as I write this in the midst of defining our NVH targets just as you outlined - except I'm not bothering with that benchmark the competitors bit: I know some are better than us, and I know where we can get to, and where we can't.

Besides, the Chairman has already said we'd have "Lexus" interior noise levels... in a Class 8 (U.S.A.) heavy truck!
LOL!
That'll only require dropping interior noise 11 dBA (or more) from where we are today!

Ah,well, that's job security, eh?

Regards,
Rob

 

[GregLocock]

Ah, well. The Lexus LS400 was the ONLY car I've really respected as a mobile drawing-room. Nakamichi stereo, woo woo.

11 dBA is a fun task. Hydromounts. Dual mass flywheels. Harmonic absorbers. Intake isolators. Exhaust modes. Intake and exhaust acoustc tuning. Leak paths. Body sensitivity. Heavy glass. Ignition timing optimisation. Stiffen all the ancillary brackets.

That'll get you 3-5 dBA. Then it gets tricky. As my good friend Crowther-san once said, the first 5 dB is easy.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Rob45]

Actually, I can get 3 dB with fairly simply barrier and panel damping treatments.
Then such radical ideas as isolating the exhaust system from the frame will be employed...

The engine unfortunately have never been given any NVH treatments, and our engine suppliers don't at present even have a hemi-anechoic dyno, nor have they put to use any of their FEA analyses of block structures.

This should be entertaining.
I think I may post periodic updates.
Regards,
- R