The Science of Vibrotactile Frequency Response in Modern Mobile Devices

When you touch a physical object—a piano key, a glass windshield, or a velvet curtain—your fingertips register thousands of mechanical micro-displacements per second. Recreating these textures through a solid smartphone chassis is a delicate balance of biology and physics.

Human Tactile Biology: The Four Mechanoreceptors

The glabrous skin of human hands contains four primary mechanoreceptor classes, each sensitive to distinct frequency bands:

Actuator Physics: LRA vs. Voice Coil

Linear Resonant Actuators operate with a mechanical resonant frequency ($f_0 \approx 170\text{Hz}$). Driving signals far outside this resonance band results in rapid energy attenuation. Apple's Taptic Engine overcomes this using a wideband voice-coil architecture capable of spanning 80Hz to 350Hz with flat frequency response.