What Is NVH | NVH Noise | NVH Vibration | NVH Harshness | Noise And Vibration Theory | NVH Basics


Noise is defined as any unpleasant or unexpected sound created by a vibrating object.


Vibration is defined as any objectionable repetitive motion of an object, back-and-forth or up-and-down.


Harshness is defined as an aggressive suspension feel or lack of “give” in response to a single input.

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Noise and Vibration Theory:

A vibrating object normally produces sound, and that sound may be an annoying noise. In the case where a vibrating body is the direct source of noise (such as combustion causing the engine to vibrate), the vibrating body or source is easy to find. In other cases, the vibrating body may generate a small vibration only.This small vibration may cause a larger vibration or noise due to the vibrating body’s contact with other parts. When this happens, attention focuses on where the large vibration or noise occurs while the real source often escapes notice. An understanding of noise and vibration generation assists with the troubleshooting process. The development of a small noise into a larger noise begins when a vibration source (compelling force) generates a vibration. Resonance amplifies the vibration with other vehicle parts. The vibrating body (sound generating body) then receives transmission of the amplified vibration.

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A sound wave’s cycle, period, frequency, and amplitude determine the physical qualities of the sound wave.

The physical qualities of sound are:

  • Audible range of sound
  • Pitch
  • Intensity

For sound to be heard, the resulting acoustic wave must have a range of 20 to 20,000 Hz, which is the audible range of sound for humans. While many vehicle noises are capable of being heard, some NVH noises are not in the audible range.

Biodiesel | Transesterification Reaction | Biodiesel Materials | Biodiesel Feedstock’s | Biodiesel Blends

What Is Biodiesel?

Biodiesel is a fuel made from vegetable oils and alcohols (Methanol / Ethanol / ISO-Propanol) utilizing a chemical process called Transesterification. The resulting Mono-Alkyl Esters have an acceptable viscosity and can be used interchangeably with petroleum diesel.

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What Is Transesterification?

The major components of vegetable oils and animal fats are Triglycerides. To obtain biodiesel, the vegetable oil or animal fat is subjected to a chemical reaction termed transesterification.01-Transesterification-process

In that reaction, the vegetable oil or animal fat is reacted in the presence of a catalyst with an Alcohol (usually methanol) to give the corresponding Alkyl Esters (or for methanol, the methyl esters) of the fatty acid mixture that is found in the parent vegetable oil or animal fat.

Biodiesel Materials / Biodiesel Feedstock:

  • Vegetable Oils
  • Soybean
  • Cotton seed
  • Palm
  • Peanut
  • Rape Seed / Canola
  • Sunflower
  • Safflower
  • Coconut
  • Animal Fats
  • Tallow
  • Waste Oils
  • Used Frying oils

Biodiesel Blends:

Biodiesel is often blended with petroleum diesel to produce a fuel that is compatible with diesel engines. Biodiesel blends reduce harmful emissions. Biodiesel blends will become more common as drivers are made aware of the many benefits.

B2 – 2% Biodiesel and 98% Diesel

B5 – 5% Biodiesel and 95% Diesel

B20 – 20% Biodiesel and 80% Diesel

Note: These blends with Petro diesel are not Biodiesel.

Advantages Of Biodiesel:

  • Derivation from a renewable domestic resource, thus reducing dependence on and preserving petroleum
  • Biodegradability
  • Reduction of most exhaust emissions (Exception NOx)
  • Higher flash point leading to safer handling and storage
  • Excellent lubricity

Disadvantages Of Biodiesel: