FTA Vibration Criterion Screen

Compare residential maximum vibration velocity level with the FTA Category 2 criterion for frequent, occasional, or infrequent events.

Description

The FTA Category 2 residential vibration screen uses different criterion levels for event-frequency classes.

The FTA Category 2 residential vibration screen uses different criterion levels for event-frequency classes. Vibration decibels (VdB) must use the same reference as the criterion.^{[1, 2]}

The returned values include FTA Category 2 criterion, Margin to criterion, Within criterion. The How section below explains the calculation, input rules and interpretation.

When to use FTA Vibration Criterion Screen

Use FTA Vibration Criterion Screen when you need to evaluate the supplied records under the calculation and evidence rules below. This implements the embedded Category 2 screen only. It does not assign event frequency, establish applicability or evaluate ground-borne noise, other receptor categories or current project requirements.

Choose the measured quantities, units, weighting and measurement basis before entering values. For a reference, select the exact topic. For a catalog lookup, prepare complete source-backed records; for a screen, select an applicable caller limit.

How to use FTA Vibration Criterion Screen and understand its results

Choose the measured quantities, units, weighting and measurement basis before entering values. For a reference, select the exact topic. For a catalog lookup, prepare complete source-backed records; for a screen, select an applicable caller limit.
Enter eventFrequency, measuredVelocityLevelVdb using the field table and calculation rules, then run the tool.
Read criterionVdb, marginVdb, withinCriterion. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
eventFrequency	FTA event-frequency class	string; one of "frequent", "occasional", "infrequent"	Required
measuredVelocityLevelVdb	Measured vibration velocity level (VdB)	number	Required

Choose the exact event-frequency class frequent, occasional or infrequent and enter a finite measured VdB level. Look up 72, 75 or 80 respectively, subtract the measured level and return the criterion, finite margin and inclusive nonnegative-margin flag.

criterion=frequent?72:occasional?75:80 VdB; margin=criterion−measured

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
criterionVdb	FTA Category 2 criterion (VdB)	number
marginVdb	Margin to criterion (VdB)	number
withinCriterion	Within criterion	boolean

json

{
  "input": {
    "eventFrequency": "frequent",
    "measuredVelocityLevelVdb": 70
  },
  "output": {
    "criterionVdb": 72,
    "marginVdb": 2,
    "withinCriterion": true
  }
}

Limitations and assumptions

This implements the embedded Category 2 screen only. It does not assign event frequency, establish applicability or evaluate ground-borne noise, other receptor categories or current project requirements.

Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Extremely large text inputs are rejected. Missing fields without a declared default, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.

Alternative or Complementary methods

Use ISO 2631 Weighting Reference: ISO 2631-1 applies frequency weightings according to vibration direction, posture, and assessment purpose rather than one weighting for every axis. This reference explains the selected concept and the evidence needed to interpret it. For a complementary task, use Floor Footfall Frequency Screen: A forcing frequency near a floor mode can justify a closer footfall assessment. This tool checks proximity against a caller-chosen frequency tolerance.

Further background: Transit Noise and Vibration Impact Assessment Manual (2018).

References

FTA Vibration Criterion Screen — tool.io
Transit Noise and Vibration Impact Assessment Manual (2018) — Federal Transit Administration

Similar or alternative tools

ISO 2631 Weighting Reference
ISO 2631-1 applies frequency weightings according to vibration direction, posture, and assessment purpose rather than one weighting for every axis. This reference explains the selected concept and the evidence needed to interpret it.
Floor Footfall Frequency Screen
A forcing frequency near a floor mode can justify a closer footfall assessment. This tool checks proximity against a caller-chosen frequency tolerance.