Perceived intensity depends on how the device is held

What it is

The same vibration feels different depending on grip and wear. Held in hand, in a trouser pocket, on a table, or under a thick coat, the fraction of mechanical energy reaching the body varies widely. The device emits a fixed amplitude; the user feels an intensity tied to the coupling condition.

Why it happens

Tactile perception depends on mechanical energy entering the body, not on motor output alone. A grip offers large contact area and good coupling, so most energy reaches the hand and the cue is clear; on a table, energy turns into surface vibration and radiated sound, so a hand-held feel weakens and is easily read as ambient noise. Clothing and cases change coupling and damping, and wearing the device against the body (pocket, wrist) is generally best while hanging or bagged it falls off. The same amplitude can therefore land on either side of the detection threshold.

Studying it

Hold device output constant and vary only coupling, measuring detection and rated intensity per condition. Variables include grip mode (hand, pocket, table, bag), case material, fabric thickness, and user activity. Outcomes include detection rate, intensity rating, and miss rate. Report the device model and amplitude setting, and note whether ambient noise was controlled.

Where it stops holding

Coupling differences are partly masked at high amplitude: far above threshold, the cue survives heavy attenuation. Near-threshold patterns, by contrast, are extremely sensitive and can pass on a lab bench and fail in a pocket or bag. Adaptive amplitude can partly compensate for coupling, but only with reliable detection of the current condition.

Applying it

• Validate intensity against the most adverse common condition—bag, table, thick clothing—rather than the hand-held case.
• Raise amplitude or add repetition for critical haptics to offset coupling loss.
• Never let a critical event rest on haptics alone; pair it with a visual or auditory cue.
• Verification: fix the pattern and measure detection in hand, pocket, table, and bag; if the spread exceeds what is acceptable, adjust intensity or move to multiple channels.

Related

• Within the group: D3.02.1 Too short a duration falls below the perceptibility threshold · D3.02.3 Rhythm carries meaning better than intensity
• Adjacent: D3.12.3 Default intensity must account for body-worn versus hand-held use · D3.14.4 External accessories are usually weaker than built-in motors
• Search terms: haptic coupling · wear position · perceived intensity