Ricardo’s NVH test centre Remseck, Germany.
When you read car reviews or car brochures, you might occasionally come across the acronym NVH.
It usually appears when the reviewer or manufacturer explains how refined the car is.
What are they referring to? What exactly is NVH?
What is NVH?
The acronym is short for noise, vibration and harshness.
It’s a catch-all phrase used to describe the shakes, rattles, squeaks or annoyances of that sort that can be heard while driving.
NVH applies both outside and inside the car.
Toyota’s new-generation taxi is far more comfortable than old Crown Comfort
For example, if you hear some squeaks in the cabin while driving or your rear-view mirror vibrates excessively, that’s poor NVH control.
It could be caused by something like bad fitment of interior panels.
If you feel serenely cocooned in a car, with nary a sound, then that car’s NVH is excellent.
Similarly, if a car drives by without a lot of engine roar, that car’s got great NVH suppression.
This is why most German cars are considered very “solid” with good interior build quality – they’re designed to go up to high speeds on the autobahns!
Anything as mechanically complex as a car is bound to produce lots of noise, and it’s up to engineers to dampen or remove undesirable sound.
There are many sources of NVH, such as:
- Air-conditioning (car’s HVAC system)
- Drivetrain
- Transmissions
- Tyres
- Brakes
- Electric motors on an electric vehicle (EV)
These sources of noise can propagate through the chassis and into the cabin.
How can NVH be lessened?
Short of flying on a magic carpet, complete eradication of NVH is not possible in any vehicle.
That’s because you’re still travelling on the road, which has bumps and ruts that can send shocks throughout the chassis in many different ways.
This is not styrofoam! It’s a slab of ARPRO Porous, used extensively in car interiors to reduce noise levels without increasing weight.
However, engineers can mitigate NVH.
If NVH travels throughout the chassis, engineers can isolate the source to prevent it from rattling the whole car.
If NVH is transmitted through the air (ie engine noise), then sound-deadening materials can be placed strategically around the engine bay to reduce noise.
Engineers will use instrumentation like microphones, accelerometers and anechoic chambers to test a car’s NVH.
What should I listen for when buying my new car?
When you’re buying a car, it’s essential to listen out for all these annoyances which will become harder to bear over the course of ownership.
What sounds trivial during a test drive will come back to irk you while you’re actually driving the car.
For example, if you hear a squeak from the rear and dismiss it, you will doubtless be annoyed by it when you want a quiet drive home.
A close-up of ARPRO Porous sound-absorption material. OK, fine, it does look like styrofoam.
As far as NVH goes, keep your ears open for these things on your next test drive:
- Rattles or squeaks around the cabin
- Vibration through the steering wheel or pedals
- Excessive engine noise in the cabin
- Noisy air-con at full blast
- Noisy brakes
- Overly harsh ride as a result of rigid suspension
Take your time to drive the car and observe its behaviour at different speeds.
If possible, try to drive over rough road surfaces (like unevenly-paved surfaces) to see how it performs.
Reducing all these NVH factors will ensure a smooth and comfortable ride for you and your passengers!
