Hearing Aid Directional Gain Estimation via Time-Frequency Masking
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Solution Overview
Problem
Hearing aid users, particularly those using behind-the-ear models, face challenges in sound localization and speech intelligibility due to the unnatural placement of microphones, which affects the directionality of sound signals and increases interference from noise sources.
Innovation Solution
A method is introduced to estimate a direction-dependent time-frequency gain by comparing directional signals from front and rear microphones, allowing for improved sound localization and speech intelligibility by synthesizing an output signal using a time-frequency mask that separates target and noise signals based on their power ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the microphone is placed behind the external portion of the ear in BTE hearing aids, then the hearing aid can be worn comfortably and the ear canal is accessible, but sound signals from behind and sides are not attenuated by the pinna, degrading sound localization and creating unnatural sensation
Solution Approach 1:
The patent introduces a directional microphone as an intermediary device that mediates between the physical constraint of BTE placement and the acoustic requirement for natural pinna attenuation. The directional microphone creates a virtual pinna effect through signal processing, allowing the system to achieve natural sound localization cues without requiring the microphone to be physically positioned where the pinna can naturally attenuate rear and side sounds.
Solution Approach 2:
The patent changes the directional sensitivity parameters of the microphone system by implementing adaptive beamforming that dynamically adjusts the pickup pattern. This allows the system to simulate the frequency-dependent attenuation characteristics of the natural pinna, transforming the acoustic parameters to match natural hearing conditions despite the unnatural microphone placement.
2Reliability
If a directional microphone is incorporated to improve directionality and focus on frontal sounds, then speech intelligibility improves in crowded places, but the system complexity increases and requires multiple microphones or complex signal processing
Solution Approach 1:
The patent implements dynamic beamforming that continuously adapts the directional pattern based on the acoustic environment. The system dynamically adjusts the weighting functions and beamforming parameters in real-time to track speech sources and adapt to changing noise conditions, allowing a single microphone to achieve directional selectivity that would otherwise require fixed multi-microphone arrays.
Solution Approach 2:
The directional microphone system performs self-adjustment through adaptive signal processing that automatically identifies and tracks speech sources without requiring manual configuration or complex hardware. The system uses its own output to continuously refine its directional pattern, eliminating the need for external calibration or complex pre-configured microphone geometries.
3Measurement precision
If multiple microphones are used to create directionality patterns, then sound localization improves, but the device complexity and processing requirements increase
Solution Approach 1:
The patent segments the frequency spectrum into multiple bands and applies different weighting functions to each band. This frequency-dependent segmentation allows the system to process different frequency components independently, reducing the computational complexity compared to processing the full spectrum uniformly, while still achieving accurate sound localization through the combined effect of segmented processing.
Data Source
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AI summary
Disclosed is method of generating an audible signal in a hearing aid by estimating a weighting function of received audio signals, the hearing aid is adapted to be worn by a user; the method comprises the steps of: estimating a directional signal by estimating a weighted sum of two or more microphone signals from two or more microphones, where a first microphone of the two or more microphones is a front microphone, and where a second microphone of the two or more microphones is a rear microphone; estimating a direction-dependent time-frequency gain, and synthesizing an output signal; wherein estimating the direction-dependent time-frequency gain comprises: • obtaining at least two directional signals each containing a time-frequency representation of a target signal and a noise signal; and where a first of the directional signals is defined as a front aiming signal, and where a second of the directional signals is defined as a rear aiming signal; • using the time-frequency representation of the target signal and the noise signal to estimate a time-frequency mask; and • using the estimated time-frequency mask to estimate the direction-dependent time-frequency gain.