Main Content

Spectral Features Based on Fault Bands

Rotating machinery produces a spectrum that reflects the harmonics of the system. These harmonics result from the relationships among the rotating components, such as gear ratios and bearing ball size. When you know the physical characteristics of your bearing or gear mesh component, you can identify the characteristic frequencies of the component where failures can occur. Fault bands are frequency bands that bound these characteristic frequencies. Rather than compute spectral metrics across the entire frequency range, you can concentrate app analysis on frequencies within the fault bands, and extract more focused and effective features that indicate specific mechanical faults.

The app provides three types of fault band-based metrics.

  • Bearing Faults

  • Gear Mesh Faults

  • Custom Faults

Use Bearing Faults Features and Gear Mesh Faults Features when you know the physical parameters of your bearing or gear mesh component and want the app to compute fault bands from those parameters. Use Custom Faults Features to specify the fault bands directly. Selecting any of these options opens a tab for you to specify the parameters. When you use specify rotation or fundamental frequency using Constant (rpm) or Constant (Hz) respectively, the app overlays a preview of the fault bands on the spectral plot. If you change a parameter on the corresponding tab, the app updates the preview. In the Features section of the tab, you can select the features that you want.

The Bearing Faults Features and Gear Mesh Fault Features tabs contain similar specifications, as the following table shows.

TypeRotationPhysical ParametersDefect TypesFault Band SettingsFeatures
Bearing Faults FeaturesRotation in rpm

Bearing parameters

  • Number of balls

  • Ball and pitch diameters

  • Contact angle

  • Outer race

  • Inner race

  • Rolling element

  • Cage

  • Harmonics

  • Sidebands (inner race, ball)

  • Fault band width

  • Fault band folding

  • Number of generated features

  • Peak frequency

  • Band power

  • Peak amplitude

  • Total band power

Gear Mesh Faults Features

Gear mesh parameters

  • Number of input and output teeth

  • Input shaft

  • Output shaft

  • Assembly phase pass

  • Gear mesh

  • Harmonics

  • Sidebands (input gear, output gear)

  • Fault band width

  • Fault band folding

  • Number of generated features

The Custom Faults Features tab contains the specifications shown in the following table.

TypeFundamental FrequencyFault Band SettingsAdvanced SettingsFeatures
Custom Faults FeaturesFundamental frequency in Hz
  • Harmonics

  • Sidebands

  • Fault band width

  • Sideband separation

  • Sideband separation type (additive or multiplicative

  • Fault band folding

  • Number of generated features

  • Peak frequency

  • Band power

  • Peak amplitude

  • Total band power

For more information about the parameters used for fault band metrics, see the Live Editor task description in Extract Spectral Features. For more information about the commands that the app uses, see