Design a New Speech Encoder for Cochlear Implants Using DRNL model. Prepared By: Koka Gopi 3 rd sem, M.tech Communication Systems.

Agenda: Introduction. Introduction. Cochlear implant devices. Cochlear implant devices. Methodologies. Methodologies. Comparisons. Comparisons. Proposed methodology. Proposed methodology. Conclusion. Conclusion.

Introduction Today, a prosthetic device, called cochlear implant, can be implanted in the inner ear and can restore partial hearing to profoundly deaf people. Today, a prosthetic device, called cochlear implant, can be implanted in the inner ear and can restore partial hearing to profoundly deaf people. Prosthetic device processors utilize the channel vocoder. Prosthetic device processors utilize the channel vocoder. Channel vocoder Channel vocoder Speech analyzer Speech Synthesizer

BPF1 BPFn Voice detector Pitch extraction rectifier Encode down sample LPF Encode down sample LPF Encode down sample LPFrectifier Voiced/unvoiced f0 SPEECH i/p FIG : Channel Vocoder Analyzer

C.I Devices Device Ineraid Nucleus Clarion Med_E1 Electrodes numberspacing configuration Type of Stimulation Transmission Link mm 0.75mm 2 mm 2.8mm Monopolar Bipolar monopolar /bipolar monopolar percutaneous transcutaneous Analog Pulsatile Analog/pu lsatile Pulsatile

Methodologies Single Channel implants : Single Channel implants : It provide electrical stimulation at a single site in the cochlea using a single electrode. Different methods in single channel implants are: It provide electrical stimulation at a single site in the cochlea using a single electrode. Different methods in single channel implants are: House/3M single-channel implant & House/3M single-channel implant & Developed: William House Developed: William House Electrodes: 22 Electrodes: 22 Vienna/3M single-channel implant. Vienna/3M single-channel implant. Developed: Technical University of Vienna Developed: Technical University of Vienna

Multiple Channel implants : Multiple Channel implants : Multi-channel implants provide electrical stimulation at multiple sites in the cochlea using an array of electrodes. Different methods in multi channel implants are: Multi-channel implants provide electrical stimulation at multiple sites in the cochlea using an array of electrodes. Different methods in multi channel implants are: 1) Compressed analog (CA) approach. 2) Continuous interleaved sampling (CIS) approach.

Compressed analog approach Device: Ineraid manufactured by Symbion. Device: Ineraid manufactured by Symbion. 1) Signal compressed using automatic gain control. 2) Filtered into four continuous frequency bands. 3) Sent through adjustable gain control. 4) Directly sent to electrodes. 5) Waveforms delivered to each electrode simultaneously in analog form.

Continuous interleaved sampling Device : Clarion device, the Med-El device, and the new Nucleus CI24M device. Device : Clarion device, the Med-El device, and the new Nucleus CI24M device. Research Triangle Institute (RTI) developed the Continuous Interleaved Sampling (CIS) approach. Research Triangle Institute (RTI) developed the Continuous Interleaved Sampling (CIS) approach. 1) Signal is pre emphasized & passed through BPF. 2) Filtered waveforms are extracted by rectification & LPF. 3) At last the signals are compared and used to biphasic pulses.

Comparisons Disadvantage: Interaction between channels. Interaction between channels. Advantage over C.A: Non-simultaneous stimulation. Non-simultaneous stimulation. Use of six channels rather than four. Use of six channels rather than four.Disadvantage: Performance is less in noisy conditions. Performance is less in noisy conditions. CA approach CIS approach

Proposed methodologies The dual-resonance nonlinear filter was presented as a digital time-domain algorithm to model nonlinear auditory frequency selectivity. The dual-resonance nonlinear filter was presented as a digital time-domain algorithm to model nonlinear auditory frequency selectivity. A DRNL model was adopted because it is simpler than other adaptive nonlinear models of the basilar membrane and can be readily integrated into the CI speech processor. A DRNL model was adopted because it is simpler than other adaptive nonlinear models of the basilar membrane and can be readily integrated into the CI speech processor. Fig: General Structure for Cochlear Implant

Decomposition Decomposition Center frequencies. Center frequencies. Gain & Bandwidth also changes. Gain & Bandwidth also changes. Fig : Frequency Decomposition Stage for DRNL Strategy

Input to both paths is the same & equal to x(t). Input to both paths is the same & equal to x(t). The transfer function of the DRNL filter can be expressed as the sum of the individual transfer functions of its two paths, HL( f ) and HN( f ). The transfer function of the DRNL filter can be expressed as the sum of the individual transfer functions of its two paths, HL( f ) and HN( f ).

Conclusion Cochlear implants have been very successful in restoring partial hearing to profoundly deaf people. Cochlear implants have been very successful in restoring partial hearing to profoundly deaf people. By using DRNL model for CI may produces better speech perception under noise conditions. By using DRNL model for CI may produces better speech perception under noise conditions.

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