Sound-processing strategy for cochlear implants

Abstract

A sound processing method for auditory prostheses, such as cochlear implants, which is adapted to improve the perception of loudness by users, and to improve speech perception. The overall contribution of stimuli to simulated loudness is compared with an estimate of acoustic loudness for a normally hearing listener based on the input sound signal. A weighting is applied to the filter channels to emphasize those frequencies which are most important to speech perception for normal hearing listeners when selecting channels as a basis for stimulation.

1 - 13 . (canceled)  
   
   
       14 . A method of processing sound signals for an auditory prosthesis comprising the steps of: 
 (a) determining an estimated excitation pattern of current levels for a plurality of electrodes;    (b) adjusting the current level of a first of the plurality of electrodes such that a specific loudness of the first electrode substantially matches a predetermined loudness from a normal hearing perception model;    (c) redetermining the estimated excitation pattern with the adjusted current level from the first electrode;    (d) repeating steps (b) and (c) for at least one of the remaining plurality of electrodes; and    (e) generating the electrical stimuli from the adjusted current levels.    
   
   
       15 . The method of  claim 14 , further comprising the steps of: 
 receiving the sound signals;    determining amplitudes within various frequency components of the sound signals within a predefined sample period; and    converting the amplitudes to the current levels using a look-up table.    
   
   
       16 . The method of  claim 14 , wherein the normal hearing perception model is derived from the Speech Intelligibility Index (SII).  
   
   
       17 . The method of  claim 14 , wherein the plurality of electrodes comprise a set of electrodes selected by a sound processor.  
   
   
       18 . The method of  claim 14 , wherein the specific loudness of the first electrode is larger than the remaining plurality of electrodes.  
   
   
       19 . The method of  claim 14 , wherein the current levels of the plurality of electrodes are adjusted in order from largest specific loudness to smallest specific loudness.  
   
   
       20 . The method of  claim 14 , wherein step (d) continues until an overall loudness determined from the adjusted excitation pattern substantially matches a predicted total loudness from the normal hearing perception model.  
   
   
       21 . The method of  claim 20 , wherein the overall loudness is determined by estimating the spatial spread of excitation, the temporal interactions effects, and summation of multiple pulses delivered on multiple electrodes.  
   
   
       22 . The method of  claim 21 , further comprising the step of reducing the adjustment to the current levels when the overall loudness exceeds a recipient's comfort level.  
   
   
       23 . The method of  claim 14 , wherein step (d) continues for each of the remaining plurality of electrodes.  
   
   
       24 . A method of processing sound signals for an auditory prosthesis comprising the steps of: 
 determining the specific loudness contributions of a first electrical stimuli delivered in a time interval;    determining a second excitation pattern of second current levels for a plurality of electrodes for a second spectral frame of the sound signal;    adjusting the second current level of each of the plurality of electrodes based on the specific loudness contributions from the first electrical stimuli such that specific loudness of each of the plurality of electrodes substantially matches a second predetermined loudness from a normal hearing perception model; and    generating a second electrical stimuli from the normalized current levels delivered in the time interval.    
   
   
       25 . The method of  claim 24 , further comprising storing the specific loudness contributions from the first electrical stimuli in a sound processor.  
   
   
       26 . The method of  claim 24 , wherein the first electrical stimuli is generated by the further steps of: 
 determining a first excitation pattern of first current levels for the plurality of electrodes for a first spectral frame of the sound signal;    adjusting the first current level of each of the plurality of electrodes such that specific loudness of each of the plurality of electrodes substantially matches a first predetermined loudness from the normal hearing perception model.    
   
   
       27 . A sound processor comprising: 
 first loudness estimator for determining normal overall loudness of a plurality amplitudes using a normal hearing perception model;    second loudness estimator for determining estimated overall loudness of a plurality of electrical levels; and    correction signal generator for adjusting each of the plurality of the electrical levels such that the estimated overall loudness substantially matches the normal overall loudness.    
   
   
       28 . The sound processor of  claim 27 , further comprising a memory for storing the normal hearing perception model.  
   
   
       29 . The sound processor of  claim 27 , further comprising spectral analysis circuitry for separating a received sound signal in one of the plurality of the amplitudes.  
   
   
       30 . The sound processor of  claim 29 , wherein the first loudness estimator is connected to the spectral analysis circuitry.  
   
   
       31 . The sound processor of  claim 29 , wherein the spectral analysis circuitry comprises a filter bank.  
   
   
       32 . The sound processor of  claim 29 , wherein the spectral analysis circuitry implementing a Fast Fourier Transform.  
   
   
       33 . The sound processor of  claim 27 , further comprising a look-up table for converting the plurality of amplitudes to the plurality of the electrical levels.  
   
   
       34 . The sound processor of  claim 33 , wherein the second loudness estimator is connected to the look-up table.  
   
   
       35 . The sound processor of  claim 27 , wherein each of the plurality of electrical levels is adjusted in a priority order.  
   
   
       36 . A method of processing sound signals for an auditory prosthesis comprising the steps of: 
 determining an estimated excitation pattern of current levels for a plurality of electrodes;    adjusting the current level for each of the plurality of electrodes such that specific loudness of the each of the plurality of electrodes substantially matches a predetermined loudness from a normal hearing perception model; and    generating the electrical stimuli from the adjusted current levels.    
   
   
       37 . The method of  claim 36 , further comprising the steps of: 
 receiving the sound signals;    determining amplitudes within various frequency components of the sound signals within a predefined sample period; and    converting the amplitudes to the current levels using a look-up table.    
   
   
       38 . The method of  claim 36 , wherein the plurality of electrodes comprise a set of electrodes selected by a speech processing strategy.  
   
   
       39 . The method of  claim 36 , wherein the current levels of each of the plurality of electrodes are adjusted in order from largest specific loudness to smallest specific loudness.  
   
   
       40 . The method of  claim 39 , wherein the order is determined by the normal hearing perception model.  
   
   
       41 . The method of  claim 36 , further comprising the step of reducing the adjustment to the current levels when an overall loudness determined from the adjusted excitation pattern exceeds a recipient's comfort level.  
   
   
       42 . A method of processing sound signals for an auditory prosthesis comprising the steps of: 
 determining a normal overall loudness using a normal hearing perception model and an estimated overall loudness from the same sound signal; and    adjusting a plurality of electrical levels for each of a plurality of channels such that the estimated overall loudness substantially matches the normal hearing perception model.    
   
   
       43 . The method of  claim 42 , wherein the normal overall loudness is determined using a plurality of amplitudes of the same sound signal.  
   
   
       44 . The method of  claim 42 , wherein the estimate overall loudness is determined using the plurality of electrical levels derived from a plurality of amplitudes of the same sound signal.  
   
   
       45 . The method of  claim 42 , wherein the channels are adjusted in a priority order.  
   
   
       46 . The method of  claim 45 , wherein the priority order is determined by the normal hearing perception model.  
   
   
       47 . The method of  claim 42 , further comprising the step of generating an electrical stimulus based on the adjusted plurality of electrical levels.  
   
   
       48 . The method of  claim 42 , wherein each of the plurality of channels comprises a set of selected by a sound processor.