Linear Resonant Actuator Audio Control for Resonant Peak Compensation
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Solution Overview
Problem
Existing mobile devices face challenges in meeting the acoustical requirements for wideband speech, particularly in handset mode, due to the resonant peak of linear resonant actuators (LRAs) which can lead to inadequate low-frequency response and increased distortion, and existing solutions either overdrive speakers or fail to meet the 3GPP frequency response mask.
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, allowing the LRA to operate as both a haptic motor and a loudspeaker, thereby compensating for its resonant peak and enhancing the frequency response to meet the 3GPP requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the linear resonant actuator is driven at its resonant frequency to achieve efficient haptic feedback, then the haptic performance is improved, but the low-frequency audio response deteriorates due to the resonant peak
Solution Approach 1:
The audio signal is segmented into different frequency components, with low-frequency components routed to the LRA and high-frequency components routed to the receiver speaker. This frequency-domain segmentation allows each transducer to operate in its optimal range, resolving the contradiction between haptic performance and audio fidelity.
Solution Approach 2:
An audio processor acts as an intermediary between the audio source and the transducers. It performs equalization to flatten the LRA's resonant peak response and dynamically routes frequency components to appropriate transducers, enabling both haptic and audio functions to coexist without interference.
2Power
If the receiver speaker is overdriven to meet the 3GPP frequency response mask requirements, then the audio output level is improved, but distortion increases
Solution Approach 1:
The audio processor serves as an intermediary that pre-processes the audio signal through equalization and dynamic range compression before amplification. This reduces the need to overdrive the receiver speaker, maintaining low distortion while meeting output requirements.
Solution Approach 2:
The system merges the output of the LRA and receiver speaker to achieve the required audio output level. The LRA contributes low-frequency energy while the receiver speaker handles mid and high frequencies, combining their strengths to meet 3GPP masks without overdriving either transducer.
3Manufacturing precision
If the linear resonant actuator is used as a loudspeaker to improve low-frequency response, then the audio quality is improved, but the device complexity increases
Solution Approach 1:
The linear resonant actuator is designed with multi-functionality, serving both as a haptic motor and as a low-frequency loudspeaker. This eliminates the need for a separate bass radiator or additional transducer, reducing overall device complexity while improving audio quality.
Solution Approach 2:
The LRA serves itself by simultaneously providing haptic feedback and audio output. The same actuator that generates vibration for haptic feedback also generates acoustic pressure for low-frequency sound reproduction, eliminating the need for dedicated separate systems.
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 improves the low-frequency reproduction and overall audio quality in mobile devices by using the LRA in conjunction with a receiver speaker, providing stable intelligibility even with varying acoustic coupling and positioning, without overdriving the speaker and reducing distortion.
Implementation Method 1
Linear resonant actuators are designed to resonate a specific frequency for example 200 Hz, which is particularly suitable for haptic feedback, and typically have a high Q factor of 15 or more
Implementation Method 2
The equalisation includes attenuating signal frequency components occurring at or close to the resonant frequency with respect to at least some other frequency components
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.