Musical fitting of cochlear implants
A method of developing a weighting matrix for a cochlear implant patient is described. An electrode stimulus signal is derived from a first musical signal. A set of further stimulus signals is derived that have a defined musical relation to the first musical signal. A set of weighting values are selected for the stimulation electrodes for the electrode stimulus signal. Then the weighting values are set for the stimulation electrodes for each of the further stimulus signals. Each of the stimulus signals is consecutively presented to the patient and the weighting values individually adjusted for each of the further stimulus signals until the series of stimulus signals elicits an increasing pitch percept according to the defined musical relation. The adjusted weighting values are stored and assigned to a corresponding analysis channel. The process is iteratively repeated using one of the further stimulus signals as the first electrode stimulus signal until weighting values for a complete frequency range have been derived.
1. A method of developing a weighting matrix for a cochlear implant patient comprising:
deriving an electrode stimulus signal from a first musical signal including frequency harmonics;
deriving a set of further stimulus signals having a defined musical relation to the first musical signal;
selecting a set of weighting values for the stimulation electrodes for the electrode stimulus signal;
setting the weighting values for the stimulation electrodes for each of the further stimulus signals;
consecutively presenting each of the stimulus signals to the patient and individually adjusting the weighting values for each of the further stimulus signals as a function of the frequency harmonics until the series of stimulus signals elicits an increasing pitch percept according to the defined musical relation;
storing the adjusted weighting values and assigning them to a corresponding analysis channel;
iteratively repeating the process using one of the further stimulus signals as the first electrode stimulus signal until weighting values for a complete frequency range have been derived so as to map musical intervals to individual stimulation electrodes.
2. A method according to claim 1 , further comprising:
interpolating unobserved weighting values.
3. A method according to claim 1 , wherein the first musical signal is a musical note.
4. A method according to claim 1 , wherein the defined musical relation is based on a musical melody known to the patient.
5. A method according to claim 1 , wherein the electrode stimulus signal is based on a lowest pitch percept for the patient.
6. A method according to claim 1 , wherein the electrode stimulus signals are delivered simultaneously to the stimulation electrodes.
7. A method according to claim 1 , wherein deriving the electrode stimulus signal is based on deriving temporal fine structure from a plurality of band pass signals.
8. A method according to claim 7 , wherein the band pass signals are derived from a semitone filter bank.
9. A method according to claim 7 , wherein the number of band pass signals is much greater than the number of stimulation electrodes.