Linear Resonant Actuator Audio Control for Resonance Distortion
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Solution Overview
Problem
Mobile devices face challenges in meeting the acoustical requirements for wideband speech, particularly in handset mode, due to the resonant frequency peaks of linear resonant actuators (LRAs) which can lead to inadequate low-frequency response and increased distortion, especially when acoustic leakage occurs.
Innovation Solution
A linear resonant actuator controller that includes a haptic driver, switch module, audio processor, and audio amplifier, which switches between haptic and audio modes to equalize and compress audio signals, attenuating resonant frequencies and boosting non-resonant frequencies, allowing the LRA to function as both a haptic motor and a loudspeaker, improving frequency response and reducing distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the LRA is used to transmit broadband speech signals, then the low-frequency response is improved, but the resonant frequency peak causes increased distortion
Solution Approach 1:
The patent converts the harmful resonant peak at the LRA's resonant frequency into a beneficial feature by using equalization to attenuate that specific frequency while boosting adjacent frequencies. The resonant frequency peak, which normally causes distortion, is deliberately suppressed to improve overall frequency response accuracy and reduce distortion across the broadband speech spectrum.
Solution Approach 2:
The patent applies dynamic equalization parameters to the LRA driver signal, adjusting the frequency response in real-time based on the LRA's known resonant characteristics. By changing the gain parameters across different frequency bands (attenuating the resonant peak, boosting non-resonant frequencies), the system achieves accurate broadband speech transmission without the harmful effects of the resonant peak.
2Measurement precision
If the receiver speaker is used for broadband speech transmission, then the frequency response is adequate, but the device complexity increases with multiple transducers
Solution Approach 1:
The patent makes the LRA multi-functional by enabling it to perform both its traditional haptic feedback function and broadband speech transmission function. Through equalization processing that attenuates the resonant peak and boosts other frequencies, the LRA becomes a universal transducer that can handle both vibration generation and audio output, eliminating the need for a separate receiver speaker in handset mode.
Solution Approach 2:
The patent merges the functions of the LRA (originally designed for haptic feedback only) with the receiver speaker function. By combining the LRA's vibration capability with equalized audio signal processing, the system consolidates multiple transducer functions into a single device, reducing overall device complexity while maintaining broadband speech transmission capability.
3Power
If the LRA is driven at high power for speech transmission, then the audio output level is sufficient, but the actuator may be overdriven causing mechanical damage
Solution Approach 1:
The patent carefully controls the power distribution across different frequency bands through equalization. By attenuating the resonant frequency peak and selectively boosting non-resonant frequencies, the system achieves sufficient overall audio output power while preventing excessive power concentration at the resonant frequency that could cause mechanical overdrive and damage to the LRA.
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
This solution enhances the low-frequency reproduction of speech in mobile devices, stabilizing audio quality across varying acoustic couplings and positions, without overdriving the receiver speaker, and allows the LRA to replace traditional speakers for broadband speech transmission.
Implementation Method 1
linear resonant actuator ('LRA') having a resonant frequency includes receiving a haptic effect signal for the haptic effect, where the haptic effect comprises a desired frequency that is off-resonant from the LRA
Implementation Method 2
equalize and compress audio signals, attenuating resonant frequencies and boosting non-resonant frequencies
Implementation Method 3
A linear resonant actuator controller that includes a haptic driver, switch module, audio processor, and audio amplifier
Data Source
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AI summary
A linear resonant actuator controller for a mobile device having a linear resonant actuator is described. The linear resonant actuator controller comprises a controller output configured to be coupled to a linear resonant actuator; an audio processor having an audio processor input and an audio processor output coupled to the controller output. The audio processor is configured to receive an audio signal comprising speech, to process the audio signal by attenuating the audio signal frequency components at the resonant frequency of the linear resonant actuator with respect to at least some other audio signal frequency components, and to output the processed audio signal on the audio processor output.