Default intensity must account for body-worn versus hand-held use

What it is

Default intensity must account for whether the device is worn against the body or held in hand. At the same amplitude, body-worn use (wrist, pocket) transfers energy straight into the body and feels obvious or even too strong, while hand-held or table-top use can be too weak to notice. A single default leaves half of users unhappy in each mode.

Why it happens

The difference is coupling efficiency: worn against the body, contact is stable and lightly damped, so most mechanical energy enters the body; held in hand, muscles and grip posture absorb part of it and the moving user adds interference; on a table, energy mostly becomes surface vibration and sound. Vendors adopting one default usually calibrate it for the easiest demo condition—hand-held—making worn use too strong and table-top use too weak. The better approach binds the default to a detectable usage state.

Studying it

Fix the default and measure detection and discomfort across usage states: in hand, pocket, worn, and on a table, measure detection of critical haptics and "too strong" ratings to find the intensity band where both remain acceptable. Variables include usage state, device type, and user activity. Include error rates in both directions, too strong and too weak.

Where it stops holding

For a single-use product—say a band always worn—one calibration suffices and adaptation is unnecessary. If the system can detect usage state reliably, adaptive intensity is workable, though detection costs permissions and sensors. After a user adjusts manually, that choice should persist rather than being overwritten by defaults or adaptation.

Applying it

• Calibrate defaults per common usage state instead of adopting a single number.
• Provide adaptive intensity where usage state is detectable, and let users override it.
• Preserve user intensity preferences rather than resetting them through automation.
• Verification: measure detection and over-strength ratings across usage states and confirm the default lands in a band where both error directions are acceptable.

Related

• Within the group: D3.12.1 Haptics need a global off switch rather than forced always-on · D3.12.2 Graded control keeps critical haptics while silencing decorative ones
• Adjacent: D3.02.2 Perceived intensity depends on how the device is held · D2.04.1 Output volume should account for ambient noise
• Search terms: default intensity · wearable calibration · haptic coupling