Noise, Vibration and Harshness (NVH)

Howl:

A mid-range frequency noise between drumming and whine. Also described as a hum.

Hum:

Mid-frequency steady sound, like a small fan motor. Also described as a howl.

Intensity:

The physical quality of sound that relates to the strength of the vibration (measured in decibels). The higher the sound's amplitude, the higher the intensity and vice versa. See Amplitude.

Knock:

A heavy, loud, repetitious sound, similar to a knock on the door.

Moan:

A constant, low-frequency tone. Also described as a hum.

Ping:

A short-duration, high-frequency sound, which has a slight echo.

Pitch:

The physical quality of sound that relates to its frequency. Pitch increases as frequency increases and vice versa.

Pumping Feel:

A slow, pulsing movement.

Rattle:

A random and momentary or short-duration noise.

Reactor:

The component, or part, that receives a vibration from an originator and conductor and reacts to the vibration by moving.

Roughness:

A medium-frequency vibration. A slightly higher frequency than a shake. This type of vibration is usually related to drivetrain components.

Rustling:

Intermittent sound of varying frequency, sounds similar to shuffling through leaves.

Shake:

A low-frequency vibration, usually with visible component movement. Usually relates to tires, wheels, brake drums or brake discs if it is vehicle speed sensitive, or engine if it is engine speed sensitive. Also referred to as a shimmy or wobble.

Shimmy:

An abnormal vibration or wobbling, felt as a side-to-side motion of the steering wheel in the driveshaft rotation. Also described as waddle.

Shudder:

A low-frequency vibration that is felt through the steering wheel or seat during light brake application.

Slap: