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Abstract
Recent evidence suggests that sensitivity to the temporal fine structure (TFS) of sounds is adversely affected by cochlear hearing loss. This may partly explain the difficulties experienced by people with cochlear hearing loss in understanding speech when background sounds, especially fluctuating backgrounds, are present. We describe a test for assessing sensitivity to TFS. The test can be run using any PC with a sound card. The test involves discrimination of a harmonic complex tone (H), with a fundamental frequency F0, from a tone in which all harmonics are shifted upwards by the same amount in Hertz, resulting in an inharmonic tone (I). The phases of the components are selected randomly for every stimulus. Both tones have an envelope repetition rate equal to F0, but the tones differ in their TFS. To prevent discrimination based on spectral cues, all tones are passed through a fixed bandpass filter, usually centred at 11F0. A background noise is used to mask combination tones. The results show that, for normal-hearing subjects, learning effects are small, and the effect of the level of testing is also small. The test provides a simple, quick, and robust way to measure sensitivity to TFS.
| Abbreviations | ||
| D | = | Spectral ripple density (centre frequency divided by ripple spacing) |
| ΔF | = | Frequency shift of components in inharmonic tone |
| FFT | = | Fast Fourier transform |
| F0 | = | Fundamental frequency |
| H | = | Harmonic tone |
| I | = | Inharmonic tone |
| SD | = | Standard deviation |
| SL | = | Sensation level |
| TEN | = | Threshold equalizing noise |
| TFS | = | Temporal fine structure |
| TFS1 | = | Test of sensitivity to temporal fine structure |
| Abbreviations | ||
| D | = | Spectral ripple density (centre frequency divided by ripple spacing) |
| ΔF | = | Frequency shift of components in inharmonic tone |
| FFT | = | Fast Fourier transform |
| F0 | = | Fundamental frequency |
| H | = | Harmonic tone |
| I | = | Inharmonic tone |
| SD | = | Standard deviation |
| SL | = | Sensation level |
| TEN | = | Threshold equalizing noise |
| TFS | = | Temporal fine structure |
| TFS1 | = | Test of sensitivity to temporal fine structure |
Sumario
Evidencias recientes sugieren que la sensibilidad hacia las estructuras finas temporales (TFS) de los sonidos resulta afectada por la pérdida auditiva coclear. Esto puede explicar parcialmente las dificultades que experimentan las personas con esas pérdidas para entender el lenguaje cuando hay sonidos de fondo, especialmente si son fluctuantes. Describimos una prueba para evaluar la sensibilidad a las TFS. La prueba puede desarrollarse usando cualquier PC con una tarjeta de sonido. La prueba implica la discriminación de un tono armónico complejo (H) con una frecuencia fundamental F0 de un tono, en el cual todos los armónicos se desplazan hacia arriba en la misma proporción en Hertz, lo que resulta en un tono no armónico (I). Las fases de los componentes se seleccionan al azar para cada estímulo. Ambos tonos tienen una tasa de repetición de la envoltura igual a FO, pero los tonos difieren en su TFS. Para prevenir la discriminación basada en claves espectrales, todos los tonos pasan a través de un filtro pasabanda fijo, usualmente centrado en 11FO. Se usa un ruido de fondo para enmascarar los tonos combinados. El resultado muestra que en sujetos normo-oyentes, son pequeños los efectos de aprendizaje y que el efecto del nivel de la prueba también es pequeño. La prueba proporciona una forma simple, rápida y robusta para medir la sensibilidad a las TFS.