Noise, Vibration and Harshness
Remove the outer skin and here is what's inside a typical car door
Noise, Vibration and Harshness or NVH constitutes a major focal area for new cars today. There was a time in the 1970’s and 1980’s that NVH seemed to have very little significance. Today, NVH has major significance.
Today’s NVH Reality
Cars today cost a lot of money and owners keep them for a long time. Design can get you to fall in love with the car by saying that car is really great or I have to have that which is precisely what the manufacturer wants to get you to head to your local dealership showroom and buy that car.
One facet of vehicle ownership that has become much more important over the past decades is NVH because if the vehicle sounds like a tin can that certainly is not the sound of quality. If the door does not close with authority and a solid sounding thunk, again the vehicle does have the sound of quality.
Car Door Construction Technique
Car door cutaway with operational power window and power mirrors
Let’s assess a basic car door. It has an inside and outside pieces of sheet metal and can let the window retract into the door cavity and an interior trim piece is attached. Now, imagine that you shut this door. This door will rattle and vibrate. Spray the inside of the door with an elastomeric and the sheet metal resonant frequency will go way down and the NVH Engineer can work to get that door to close with a resounding high-value solid sounding thunk.
Doors for the Verano have special welded inner panels and have three layers of fiberglass acoustic sound-absorber materials to minimize wet road sizzle-like sound intrusion into the passenger compartment.
Lexus and Buick
Lexus has gone to great lengths to create quiet vehicles. Buick is on a quest to battle the market directly against Lexus.
Buick officially indicates that they will begin sales for the Verano in the fourth quarter of 2011. It appears that all of the automotive press magazines have recently tested the Verano and compared it to the similar sibling Chevrolet Cruze. It seems very clear that the two vehicles are significantly different. Here are some items identified in a recent press release:
Buick Verano Press Release
Here is some information from a Buick press release. It is clear that Buick has gone after NVH issues in a major way. This is only a partial list associated with the 12 areas that the engineers considered in making this a very quiet vehicle:
- A 5.4-mm-thick acoustic-laminated windshield and 4.85-mm-thick acoustic laminated side glass that minimizes wind noise
- Acoustic insulation material on both sides of the front steel dash panel and under the hood that reduce engine noise
- Five layers of acoustic insulation material in the headliner, including a premium fabric on the visible outer layer that muffles wind noise
- Triple-sealed doors that keep out exterior noise
- Three layers of acoustic insulation material in the doors that reduces the sound of wet-road sizzle
- Dual-density carpet on the floor that block coarse road and tire noise
- Underbody paneling that lowers wind and low road-surface noise while improving fuel economy
- Liquid-applied sound deadener that supports a solid body structure
- Specially tuned air intake and exhaust systems that enable pleasing engine sound quality without sacrificing engine performance
- Isolated chassis components that reduce vibrations over irregular road surfaces for a solid road feel
- A patented rear suspension that enables crisp road feel and superior ride and handling performance without sacrificing quietness
- Hydraulic suspension bushings and an isolated engine cradle that reduces or eliminates vibrations.
Another Buick information sheet says that more than twice the amount of liquid-applied sound deadner (LASD) that is used on the Cruze is robotically applied in the body shop to reduce potential noise paths and improve body structural rigidity.
Verano’s headliner is composed of a five layer matrix of acoustic insulation. The A pillars are wrapped with the same fabric as the outer layer of the headliner.
A Real World Noise Test
Here is what happens you you put the entire sound deadening package to the test. You can hear the result for yourself.