What SEAT expresses
SEAT stands for Seat Effective Amplitude Transmissibility. It is a ratio between frequency-weighted vibration measured on a seat and at its base, commonly expressed as a percentage. A result below 100% indicates attenuation under the conditions assessed; a result above 100% indicates amplification. It is neither a general comfort certificate nor a direct measure of an individual worker’s likelihood of injury.
Why frequency matters
A suspension seat does not reduce all vibration equally. It may amplify vibration close to its resonance and attenuate other frequencies. Consequently, good performance under a particular test input does not guarantee the same performance in every vehicle or on every surface. Selection needs to consider the vehicle spectrum, dominant movement, occupant weight and the operating conditions for which the seat was designed.
Planning a performance check
Comparison requires compatible recordings at the seat base and supporting surface, with the occupant and seat correctly prepared. A competent assessor should define axes, weighting, duration and representative tasks. Record speed, transported load, surface condition and adjustment settings. Comparing measurements taken on different routes without controlling these variables can incorrectly credit the seat for an improvement actually caused by a smoother road surface.
What to request from a supplier
Ask for the intended application, test method and conditions behind the declared result, together with adjustment and maintenance instructions. A percentage alone in a catalogue cannot support comparison between differently tested products. Check that controls are accessible and adjustment can accommodate the user. Installation must not compromise access to vehicle controls or the driving position. Retain the relevant instructions with the equipment documentation.
From seat performance to daily exposure
Even with effective attenuation, exposure may remain high when input vibration or driving time is substantial. Assessment of whole-body vibration covers the complete activity. Repairing surfaces, adjusting routes and speed, maintaining the vehicle and reducing shocks can achieve more than changing a cushion alone. Posture and manual handling also matter when assessing the overall demands placed on a driver.
When to review the result
Review performance following changes to the machine, route, seat or operating conditions, and when suspension bottoming, deterioration or complaints arise. The maintenance plan should check the system’s actual condition rather than simply retain its purchase report. SEAT evaluates a particular performance characteristic; it does not replace exposure assessment or, on its own, demonstrate compliance with the applicable occupational vibration exposure limits.
