Hearing Signal Spectrum Shifting Beyond Nyquist Limits
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Solution Overview
Problem
Current digital hearing devices are limited by a sampling rate of 16 to 20 kHz, which restricts the audio bandwidth to 8 to 10 kHz, resulting in loss of useful information above the Nyquist frequency, affecting sound localization and intelligibility of sharp consonants.
Innovation Solution
A method that involves converting the analog input signal to a first output signal with a final sampling rate and an intermediate signal with a higher sampling rate, applying a band-pass filter to shift the spectrum below the final sampling rate, and decimating the intermediate sampling rate to the final sampling rate, allowing additional information above the Nyquist frequency to be processed while reducing energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the sampling rate is increased to extend the audio bandwidth above the Nyquist frequency, then the usable frequency range is improved, but the energy consumption increases proportionally because algorithms run on a faster pace
Solution Approach 1:
The signal processing is segmented into two paths: one processing base-band information at the final sampling rate and another processing extended frequency information at the intermediate sampling rate. This segmentation allows the system to utilize higher frequency information without requiring the entire processing system to run at the higher rate, thus extending the usable frequency range while controlling energy consumption.
Solution Approach 2:
The system dynamically adjusts processing rates for different frequency components. Base-band information is processed at the lower final sampling rate while extended frequency information is processed at the higher intermediate sampling rate. This dynamic approach allows the hearing device to adapt processing resources to the specific frequency content being analyzed, improving frequency range without proportionally increasing energy consumption.
2Loss of information
If the sampling rate is increased to capture information above the Nyquist frequency, then the intelligibility and localization are improved, but the processing complexity increases
Solution Approach 1:
The processing architecture is segmented into multiple stages with different sampling rates. The intermediate sampling rate processing handles extended frequency information while the final sampling rate handles base-band information. This segmentation reduces processing complexity by avoiding the need to process all information at the highest sampling rate, while still capturing and utilizing information above the traditional Nyquist frequency.
Solution Approach 2:
The system applies partial high-rate processing only to the extent necessary for capturing extended frequency information, rather than processing the entire signal at the high intermediate sampling rate. The band-pass filter unit selectively processes only the extended frequency range at the higher rate, while base-band processing occurs at the lower final sampling rate, reducing overall processing complexity.
Data Source
AI summary
The present invention is directed to a method and a hearing device for extending a usable frequency range of an analog input signal (i) being processed by a hearing device, the method comprising the steps of converting the analog input signal (i) to a first output signal (o1) and to an intermediate signal (om), the first output signal (o1) having a final sampling rate and the intermediate signal (om) having an intermediate sampling rate that is greater than the final sampling rate, applying a band-pass filter unit (31) to the intermediate signal (om) in order to obtain a filtered intermediate signal (omf), a lower cut-off frequency of the band-pass filter unit (31) being above half the final sampling rate, an upper cut-off frequency of the band-pass filter unit (31) being below half the intermediate sampling rate, and shifting a spectrum of the filtered intermediate signal (omf) to a frequency range being below the final sampling rate to obtain an intermediate output signal (om2).