Planar Electromagnetic Tactile Module With Damped Low-Noise Bass Response
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Solution Overview
Problem
Existing audio-frequency tactile transducers produce unwanted acoustic noise and distort the audio response due to axial motion, un-damped eccentric rotating motors and linear resonant actuators have limited frequency range and linked acceleration and pitch, and in-plane vibrating modules lack critical damping, leading to underdamped tactile acceleration frequency response.
Innovation Solution
A thin, flat vibration module with electromagnetic actuation producing in-plane motion, damped using ferrofluid, oil, grease, gel, or foam, and mounted parallel to the sagittal plane to minimize acoustic noise, with flexures or bushings for suspension, and compliant materials for direct skin contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If axial shakers are used to produce tactile vibrations, then tactile stimulation is achieved, but unwanted acoustic noise is generated
Solution Approach 1:
The patent transitions from axial motion (z-axis) to planar motion (x-y plane) by reorienting the electromagnetic actuator. This dimensional change allows the transducer to stimulate the skin through lateral movement while minimizing the plunging motion that generates acoustic noise in the ear canal.
Solution Approach 2:
Instead of mounting the transducer with motion directed toward the ear canal (axial orientation), the patent inverts the approach by orienting the motion axis parallel to the sagittal plane. This reversal of the motion direction eliminates the coupling between tactile actuation and acoustic noise generation.
2Reliability
If axial shakers are mounted in headphone ear cups, then tactile feedback is provided, but audio fidelity is degraded
Solution Approach 1:
The patent changes the motion plane from axial (affecting air pressure in ear canal) to planar (shearing skin surface). This dimensional transition ensures that tactile stimulation occurs without the ear cup plunging against the head, thereby preserving audio fidelity while providing tactile feedback.
Solution Approach 2:
The patent separates the tactile stimulation function from the acoustic function by using independent planar motion. This segmentation allows the audio driver to operate without interference from the tactile transducer, maintaining audio fidelity while providing tactile feedback through a different mechanical pathway.
3Device complexity
If un-damped eccentric rotating motors are used for tactile actuation, then simple construction is achieved, but frequency response is limited
Solution Approach 1:
The patent replaces the mechanical resonance-based ERM system with an electromagnetic actuation system. This substitution eliminates the fixed resonance frequency constraint while maintaining construction simplicity, enabling broadband tactile actuation across the audio frequency range without complex mechanical tuning.
4Force
If linear resonant actuators are used for tactile stimulation, then high acceleration is achieved at resonance, but frequency range is restricted
Solution Approach 1:
The patent replaces the LRA's mechanical resonance mechanism with electromagnetic actuation. This substitution removes the single-frequency resonance constraint while maintaining the ability to generate high acceleration, enabling broadband tactile stimulation across the full audio frequency range from 20 Hz to 20 kHz.
5Object-generated harmful factors
If in-plane vibrating modules are used to minimize acoustic noise, then acoustic fidelity is improved, but damping is insufficient
Solution Approach 1:
The patent introduces a damping layer as an intermediary between the planar transducer and the skin contact surface. This damping layer critically damps the transducer's motion, preventing underdamped ringing and resonance while maintaining the planar motion geometry that minimizes acoustic noise generation.
Solution Approach 2:
The patent modifies the system's damping parameter by adding the damping layer, transitioning from an underdamped state (Q-factor 1.5-3) to a critically damped state. This parameter change eliminates the peaking and ringing issues while preserving the acoustic noise reduction benefits of planar motion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves uniform acceleration response over 40-200 Hz, minimizing acoustic noise and preserving audio fidelity by reducing unwanted sound, enabling high-fidelity tactile reproduction of bass frequencies.
Implementation Method 1
A thin, flat vibration module with electromagnetic actuation producing in-plane motion
Implementation Method 2
damped using ferrofluid, oil, grease, gel, or foam
Data Source
AI summary
A vibration module for applying vibrational tractions to a wearer's skin is presented. Use of the vibration module in headphones is illustrated for providing tactile sensations of low frequency for music, for massage, and for electrical recording and stimulation of the wearer. Damped, planar, electromagnetically-actuated vibration modules of the moving magnet type are presented in theory and reduced to practice, and shown to provide a substantially uniform frequency response over the range 40-200 Hz with a minimum of unwanted audio.