Hearing Instrument Linearization Stage for Speaker Distortion
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Solution Overview
Problem
Hearing instruments face significant distortion issues due to the non-linearity of speakers, which vary significantly from user to user, making it challenging to achieve optimal sound quality.
Innovation Solution
The hearing instrument incorporates a linearization stage that adjusts the driving signal for the speaker unit using a comparator and delay stage to reduce distortion, allowing for improved sound quality by compensating for the non-linearity of the speaker in real-time, utilizing a pulse modulating unit and analogue-to-digital conversion for efficient power utilization and digital processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a speaker is used in a hearing instrument, then electro-mechanical transduction is achieved, but distortion is introduced due to non-linearity
Solution Approach 1:
The patent implements a feedback loop where a second microphone captures the actual sound output from the speaker, converts it to an electrical signal, and feeds it back to a signal processor. The processor compares this feedback signal with the original processed sound signal, detects distortion, and generates a correction signal that is combined with the original signal to compensate for non-linearity. This closed-loop feedback system continuously monitors and corrects speaker distortion in real-time.
Solution Approach 2:
The patent employs a linearization stage that pre-distorts the input signal in the opposite direction of the expected speaker non-linearity. By applying preliminary correction to the electrical signal before it reaches the speaker, the system anticipates and counteracts the distortion that would otherwise occur during electro-mechanical transduction, thereby improving sound quality before the distortion can manifest.
2Object-generated harmful factors
If pre-compensation filter is used to correct speaker distortion, then distortion reduction is achieved, but adaptability to individual speaker variations is lost
Solution Approach 1:
Instead of using a fixed pre-compensation filter, the patent implements an adaptive feedback system that measures the actual output of each individual speaker through a second microphone. The system characterizes the specific non-linearity of each speaker in-situ and generates customized correction signals tailored to that particular speaker's characteristics. This feedback-based approach enables the system to adapt to speaker variations without requiring manual calibration or pre-programmed filter profiles.
Solution Approach 2:
The hearing instrument performs self-characterization and self-correction by using its own components (second microphone, signal processor) to measure and compensate for its speaker's non-linearity. The system automatically adapts to each speaker's unique characteristics without external intervention, making the distortion correction inherently adaptive to individual speaker variations while maintaining ease of manufacture.
3Object-generated harmful factors
If linearization stage with digital processing is implemented, then distortion is reduced, but device complexity increases
Solution Approach 1:
The patent integrates the linearization functionality into the existing hearing instrument architecture by utilizing the signal processor that is already present for hearing aid signal processing. The second microphone shares the instrument's existing analog-to-digital converter and processing resources. This multi-functional approach allows distortion correction without adding separate dedicated hardware for each function, thereby reducing the increase in device complexity while still achieving effective linearization.
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 effectively reduces distortion and enhances sound quality by adaptively compensating for speaker non-linearity, providing a compromise between efficiency and linearity in the electro-mechanical conversion process.
Implementation Method 1
A speaker is an electro-mechanical transducer that reproduces an electrical signal as an acoustical signal
Implementation Method 2
a second microphone 116 converting the processed sound into an electric monitor sound signal
Implementation Method 3
The output stage 106 may comprise a pulse modulating unit adapted to receive said processed sound signal and generate a pulse train signal based thereon
Data Source
Figure 1~2
AI summary
This invention relates to a hearing instrument (100), which comprises a first microphone (102) converting ambient sound to an ambient sound signal, a signal processor (104) generating a processed sound signal based on the ambient sound signal, a controllable output stage(106) generating a driving signal based on the processed sound signal and in accordance with a control signal, a speaker unit (110) generating a sound in the ear canal based on said driving signal, a second microphone (116) located in the ear canal of the user and converting the sound in the ear canal to the monitor sound signal, and a linearization stage (108) comparing the processed sound signal and the monitor sound signal and generating the control signal based thereon.