RESUMO
Efficacy of the SPEAK and ACE coding strategies was compared with that of a new strategy, MP3000™, by 37 European implant centers including 221 subjects. The SPEAK and ACE strategies are based on selection of 8-10 spectral components with the highest levels, while MP3000 is based on the selection of only 4-6 components, with the highest levels relative to an estimate of the spread of masking. The pulse rate per component was fixed. No significant difference was found for the speech scores and for coding preference between the SPEAK/ACE and MP3000 strategies. Battery life was 24% longer for the MP3000 strategy. With MP3000 the best results were found for a selection of six components. In addition, the best results were found for a masking function with a low-frequency slope of 50 dB/Bark and a high-frequency slope of 37 dB/Bark (50/37) as compared to the other combinations examined of 40/30 and 20/15 dB/Bark. The best results found for the steepest slopes do not seem to agree with current estimates of the spread of masking in electrical stimulation. Future research might reveal if performance with respect to SPEAK/ACE can be enhanced by increasing the number of channels in MP3000 beyond 4-6 and it should shed more light on the optimum steepness of the slopes of the masking functions applied in MP3000.
Assuntos
Implantes Cocleares , Processamento de Sinais Assistido por Computador , Estimulação Acústica/instrumentação , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Implante Coclear/instrumentação , Eletrônica , Desenho de Equipamento , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Mascaramento Perceptivo , Psicofísica , Processamento de Sinais Assistido por Computador/instrumentação , Análise Espectral , Acústica da Fala , Telemetria/métodos , Adulto JovemRESUMO
Speech intelligibility is degraded in the presence of a competing talker for cochlear implantees, presumably because of impaired tracking and integration of speech segments glimpsed in the masker valleys. This hypothesis was tested by assessing the intelligibility of periodically-interrupted bisyllables produced by a male and female talker, for normal-hearing listeners and implantees. A 4-Hz square-wave modulator with random phase was used to interrupt bisyllables from each talker. Stimuli were either presented alone (Experiment I) or interleaved (Experiment II: the two talkers were alternated). In Experiment I, the mean identification score for each voice was 88% for normal-hearing listeners and 35% for implantees. In Experiment II, the mean score corresponding to correct identification of both voices was 50% for normal-hearing listeners and 5% for implantees. Implantees identified at least one bisyllable among the two well above chance level but showed difficulties assigning it to the correct talker. This suggests that implantees can make use of partial information, but cannot track and integrate the non-adjacent components of interleaved speech as well as normal-hearing listeners. Additional results obtained with normal-hearing listeners tested with tone-vocoded syllables suggest that impaired tracking/integration for implantees stems from limited reception of spectral and temporal fine structure cues.
Assuntos
Implante Coclear , Correção de Deficiência Auditiva , Pessoas com Deficiência Auditiva/reabilitação , Inteligibilidade da Fala , Estimulação Acústica , Adulto , Idoso , Audiometria da Fala , Estudos de Casos e Controles , Sinais (Psicologia) , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Ruído/efeitos adversos , Mascaramento Perceptivo , Percepção da Altura Sonora , Espectrografia do Som , Percepção do Tempo , Adulto JovemAssuntos
Estimulação Acústica/métodos , Auxiliares de Audição , Perda Auditiva/terapia , Adulto , Audiometria/métodos , Implantes Cocleares , Estudos de Coortes , Europa (Continente) , Feminino , Seguimentos , Perda Auditiva/diagnóstico , Humanos , Percepção Sonora , Masculino , Pessoa de Meia-Idade , Música , Satisfação do Paciente , Percepção da Altura Sonora , Desenho de Prótese , Estudos Retrospectivos , Índice de Gravidade de Doença , Resultado do TratamentoRESUMO
Recent studies have demonstrated that the detection of complex temporal envelopes relies - at least partially - on the perception of a distortion component generated by a peripheral (cochlear) and/or central (post-cochlear) non-linearity. In the present study, first- and second-order amplitude modulation (AM) detection thresholds were obtained in normally hearing (NH) and hearing-impaired (HI) listeners using a 2-kHz pure-tone carrier. In both groups of listeners, first-order AM detection thresholds were measured for AM rates fm ranging between 4 and 87 Hz, and second-order AM detection thresholds were measured for second-order AM rates fm' ranging between 4 and 23 Hz, using a fixed first-order 'carrier' AM rate fm of 64 Hz. When the sound pressure level was adjusted in order to yield equal detectability in both groups for the 64-Hz first-order carrier modulation, (i) first-order AM detection thresholds for the HI listeners were normal at fm=87 Hz, and better-than-normal at fm=4 and 16 Hz, and (ii) second-order AM detection thresholds were identical at all modulation rates in NH and HI listeners. Similar results were obtained when the audibility of the 2-kHz pure-tone carrier was equated for both groups, i.e. when listeners were tested at the same sensation level. These results demonstrate clearly that cochlear damage has no effect on the detection of complex temporal envelopes, and indicate that the distortion component must be generated by a more central non-linearity than cochlear compression, transduction, or short-term adaptation.