Fine Structure Processing Research Articles

The effects of fine structure stimulation on pitch perception with cochlear implants

Introduction One of the major expectations concerning stimulation strategies that incorporate temporal fine structure is an improved perception of pitch (Smith et al., 2002). The first such coding strategy that is commercially available is the fine structure processing strategy implemented in the OPUS sound processor family (MED-EL, Austria). This strategy is based on the concept of channel-specific sampling sequences (CSSS) (Arnoldner et al., 2007). In CSSS, the zero crossings within several apical band-pass channels trigger a sequence of stimulation pulses. Thus, each fine structure channel explicitly encodes the instantaneous withinchannel frequency. A different approach is used in the concept of coherent fine structure (CFS). With CFS, the temporal fine structure information is derived from a dedicated broad-band channel and presented simultaneously on multiple apical electrodes (Zierhofer 2009; Zierhofer et al., 2009). Subjectively, cochlear implant users usually report an overall downshift of pitch when they switch from envelope-based strategies like continuous interleaved sampling (CIS) to fine-structure-based strategies. Since the very first perception with a CIS processor at hook-up is mostly that of a high-pitched machinelike voice, this shift can be regarded as a step in the right direction. In the current study, this pitch shift was explored in two distinct fine structure strategies, one based on CSSS and the other on CFS.

Effects of fine structure and extended low frequencies in pediatric cochlear implant recipients

ObjectiveIn recent years, new speech coding strategies have been developed with the aim of improving the transmission of temporal fine structure to cochlear implant recipients. This study reports on the implementation of one such strategy (fine structure processing, FSP) in children. MethodsThis was a prospective study investigating the upgrade to a new speech processor. The upgrade used a repeated measures design with an alternating order of conditions (A-B-A-B design). Twelve pre- and perilingually deaf children with MED-EL C40+ cochlear implants were enrolled in the study. Patients were upgraded from their Tempo+ speech processor, which used continuous interleaved sampling (CIS) in combination with a frequency spectrum of 200–8500Hz, to an Opus speech processor, which used FSP with an extended frequency spectrum of 70–8500Hz. The primary means of testing was an HSM (Hochmair, Schulz and Moser) sentence test at 65 and 80dB in quiet. In addition, the “Mainzer Kindersprachtest” (Mainz audiometric speech test for children) was applied at 65 and 70dB. ResultsWhen the new FSP speech processor was used together with the extended low frequency range, HSM sentence tests at 65 and 80dB resulted in scores indicating statisticially significant improvements of 7.1 and 9.9 percentage points, respectively. Scores in the “Mainzer Kindersprachtest” at 65 and 70dB indicated statistically significant improvements of 9.3 and 6.1 percentage points, respectively. ConclusionsThe present study clearly shows that children benefit from the fine structure speech coding strategy in combination with an extended frequency spectrum in the low frequencies, as is offered by the Opus speech processors. This should be taken into consideration when fitting pre- and perilingually deaf children implanted almost a decade previously.

The Effect of Acute Introduction of Fine Structure Processing on Music and Speech Perception in Adult Cochlear Implant Users

The Effect of Acute Introduction of Fine Structure Processing on Music and Speech Perception in Adult Cochlear Implant Users

Comparison of the fine structure processing (FSP) strategy and the CIS strategy used in the MED-EL cochlear implant system: Speech intelligibility and music sound quality

Objective: The aim of the present study was to evaluate MED-EL's Fine Structure Processing (FSP) strategy in comparison with their variations of the standard Continuous Interleaved Sampling (CIS) strategy denoted CIS+ and High Definition CIS (HDCIS). Study Sample: Twenty experienced adult CI users participated in the study in connection with upgrading to a new speech processor and at a two-year follow-up. Design: Blinded paired-comparisons between FSP and HDCIS were performed for speech intelligibility and music sound quality. Standard speech recognition tests in quiet and in noise were also accomplished to monitor the participants’ actual performance and to evaluate long-term outcomes. Results: Overall, the paired-comparison results showed no significant differences between the strategies, however, the total numbers of significant individual preferences were: 11 FSP vs. 12 HDCIS for speech, and 4 FSP vs. 15 HDCIS for music. The average speech recognition score decreased significantly after one month with FSP, but after two years there were no significant difference compared to the initial results with CIS+. Conclusions: Owing to the large individual differences in subjective preference, and the fact that the FSP strategy was not superior to the CIS variations, the recipients should be given the opportunity of choosing between the strategiesSumarioObjetivo: El objetivo de este estudio fue evaluar la estrategia de procesamiento de la estructura fina (FSP) de MED-EL en comparación con las variaciones de la estrategia estándar de muestreo intercalado continuo (CIS) denominado CIS+ y el CIS de alta definición (HDCIS). Muestra: Veinte adultos usuarios experimentados de CI participaron en este estudio en conexión con el ascenso a un nuevo procesador y el seguimiento durante dos años. Diseño: Se efectuó una comparación ciega pareada entre FSP y HDCIS para la inteligibilidad del lenguaje y la calidad del sonido musical. Se efectuaron también pruebas estándar de reconocimiento del lenguaje en silencio y en ruido para monitorear el desempeño de los participantes y para evaluar los resultados a largo plazo. Resultados: En general el resultado de la comparación pareada no mostró diferencias significativas entre las estrategias, sin embargo, los números totales de preferencias por sujeto fueron: 11 FSP vs 12 HDCIS para lenguaje y 4 FSP vs 15 HDCIS para la música. La puntuación promedio del reconocimiento del lenguaje disminuyó significativamente después de un mes con FSP, pero después de dos años no hubo diferencias significativas al comparar con los resultados iniciales del CIS+. Conclusiones: Debido a las amplias diferencias individuales en las preferencias de los sujetos y al hecho de que la estrategia FSP no fue superior a las variaciones de CIS, los receptores del CI deben tener la oportunidad de escoger entre las estrategias.

Processing of Temporal Fine Structure as a Function of Age

The purpose of this study was to determine whether the processing of temporal fine structure diminishes with age, even in the presence of relatively normal audiometric hearing. Temporal fine structure processing was assessed by measuring the discrimination of interaural phase differences (IPDs). The hypothesis was that IPD discrimination is more acute in middle-aged observers than in older observers but that acuity in middle-aged observers is nevertheless poorer than in young adults. Two experiments were undertaken. The first measured discrimination of 0- and π-radian interaural phases as a function of carrier frequency. The stimulus was a 5-Hz sinusoidally amplitude-modulated tone in which, in the signal waveform, the interaural phase of the carrier was inverted during alternate modulation periods. The second experiment measured IPD discrimination at fixed frequencies. The stimulus was a pair of tone pulses in which, in the signal, the trailing pulse contained an IPD. A total of 39 adults with normal audiograms ≤2000 Hz participated in this study, of which 15 were younger, 12 middle aged, and 12 older. Experiment 1 showed that the highest carrier frequency at which a π-radian IPD could be discriminated from the diotic, 0-radian standard was significantly lower in middle-aged listeners than young adults, and still lower in older listeners. Experiment 2 indicated that middle-aged listeners were less sensitive to IPDs than young adults at all but the lowest frequencies tested. Older listeners, as a group, had the poorest thresholds. These results suggest that deficits in temporal fine structure processing are evident in the presenescent auditory system. This adds to the accumulating evidence that deficiencies in some aspects of auditory temporal processing emerge relatively early in the aging process. It is possible that early-emerging temporal processing deficits manifest themselves in challenging speech in noise environments.

Fine Structure Processing improves speech perception as well as objective and subjective benefits in pediatric MED-EL COMBI 40+ users

Objectives Presently, there are only few studies examining the benefits of fine structure information in coding strategies. Against this background, this study aims to assess the objective and subjective performance of children experienced with the C40+ cochlear implant using the CIS+ coding strategy who were upgraded to the OPUS 2 processor using FSP and HDCIS. Methods In this prospective study, 60 children with more than 3.5 years of experience with the C40+ cochlear implant were upgraded to the OPUS 2 processor and fit and tested with HDCIS (Interval I). After 3 months of experience with HDCIS, they were fit with the FSP coding strategy (Interval II) and tested with all strategies (FSP, HDCIS, CIS+). After an additional 3–4 months, they were assessed on all three strategies and asked to choose their take-home strategy (Interval III). The children were tested using the Adaptive Auditory Speech Test which measures speech reception threshold (SRT) in quiet and noise at each test interval. The children were also asked to rate on a Visual Analogue Scale their satisfaction and coding strategy preference when listening to speech and a pop song. However, since not all tests could be performed at one single visit, some children were not able complete all tests at all intervals. Results At the study endpoint, speech in quiet showed a significant difference in SRT of 1.0 dB between FSP and HDCIS, with FSP performing better. FSP proved a better strategy compared with CIS+, showing lower SRT results of 5.2 dB. Speech in noise tests showed FSP to be significantly better than CIS+ by 0.7 dB, and HDCIS to be significantly better than CIS+ by 0.8 dB. Both satisfaction and coding strategy preference ratings also revealed that FSP and HDCIS strategies were better than CIS+ strategy when listening to speech and music. FSP was better than HDCIS when listening to speech. Conclusions This study demonstrates that long-term pediatric users of the COMBI 40+ are able to upgrade to a newer processor and coding strategy without compromising their listening performance and even improving their performance with FSP after a short time of experience.

Better Speech Recognition in Noise with the Fine Structure Processing Coding Strategy

Background: Recently, a new speech coding strategy named ‘fine structure processing’ (FSP) has been launched. Methods: 32 subjects, all users of the MED-EL PULSARCI¹⁰⁰ system, have been switched over from a TEMPO+ to an OPUS 2 speech processor. In 22 subjects, the FSP strategy could be implemented (FSP group), in 10 patients not (high-definition continuous interleaved sampling, HDCIS, group). Subjects were tested with the Tempo+ (CIS+) just before switch-over and after 12 months of OPUS 2 (FSP/HDCIS) use. Performance with FSP/HDCIS was tested at switch-over, and after 1, 3, 6 and 12 months. A sentence-in-noise test and a Speech Spatial and Qualities of Hearing Scale (SSQ) questionnaire were assessed at each test interval. Results: In the FSP group, the speech reception threshold shows a deterioration of 3.3 dB (n.s.) at the acute switch-over interval, but a significant improvement over time (p < 0.001) with a final benefit of 6.5 dB after 12 months of FSP use. A significant improvement over time can also be seen on the spatial subscore of the SSQ questionnaire (p = 0.009). No significant differences could be seen in the HDCIS group. Conclusion: The results show that by enhancing fine structure coding in the lower frequencies, as implemented in the FSP coding strategy, speech perception in noise can be enhanced.

Speech Perception and Subjective Benefit in Paediatric C40+ Users after the Upgrade to Fine Structure Processing (FSP)

Speech Perception and Subjective Benefit in Paediatric C40+ Users after the Upgrade to Fine Structure Processing (FSP)

Processing of Temporal Fine Structure as a Function of Age

Processing of Temporal Fine Structure as a Function of Age

Relations between frequency selectivity, temporal fine-structure processing, and speech reception in impaired hearing

Frequency selectivity, temporal fine-structure (TFS) processing, and speech reception were assessed for six normal-hearing (NH) listeners, ten sensorineurally hearing-impaired (HI) listeners with similar high-frequency losses, and two listeners with an obscure dysfunction (OD). TFS processing was investigated at low frequencies in regions of normal hearing, through measurements of binaural masked detection, tone lateralization, and monaural frequency modulation (FM) detection. Lateralization and FM detection thresholds were measured in quiet and in background noise. Speech reception thresholds were obtained for full-spectrum and lowpass-filtered sentences with different interferers. Both the HI listeners and the OD listeners showed poorer performance than the NH listeners in terms of frequency selectivity, TFS processing, and speech reception. While a correlation was observed between the monaural and binaural TFS-processing deficits in the HI listeners, no relation was found between TFS processing and frequency selectivity. The effect of noise on TFS processing was not larger for the HI listeners than for the NH listeners. Finally, TFS-processing performance was correlated with speech reception in a two-talker background and lateralized noise, but not in amplitude-modulated noise. The results provide constraints for future models of impaired auditory signal processing.

Abnormal processing of temporal fine structure in speech for frequencies where absolute thresholds are normal

The identification of nonsense syllables that were lowpass filtered at 1.5 kHz was compared for subjects with normal hearing and subjects with mild-to-severe hearing loss at high frequencies but with normal or near-normal hearing at low frequencies. Absolute thresholds were mostly within the normal range (<20 dB hearing level) for both groups for frequencies below 1.5 kHz. Performance was assessed with intact speech, speech that had been processed to preserve only temporal envelope cues in a few frequency bands (E speech), and speech that had been processed to remove envelope cues as far as possible while preserving temporal fine structure cues, again in a few frequency bands (TFS speech). For the intact speech and E speech, the hearing-impaired subjects performed slightly more poorly than the normal-hearing subjects, but this effect was significant only for the intact speech. For the TFS speech, the hearing-impaired subjects performed significantly more poorly than the normal-hearing subjects, with 12 out of 16 of the former performing at chance. The results indicate that, for people with hearing loss at medium to high frequencies, the processing of the TFS of speech can be degraded for frequencies where absolute thresholds are within the normal range.

The Role of Temporal Fine Structure Processing in Pitch Perception, Masking, and Speech Perception for Normal-Hearing and Hearing-Impaired People

Complex broadband sounds are decomposed by the auditory filters into a series of relatively narrowband signals, each of which can be considered as a slowly varying envelope (E) superimposed on a more rapid temporal fine structure (TFS). Both E and TFS information are represented in the timing of neural discharges, although TFS information as defined here depends on phase locking to individual cycles of the stimulus waveform. This paper reviews the role played by TFS in masking, pitch perception, and speech perception and concludes that cues derived from TFS play an important role for all three. TFS may be especially important for the ability to "listen in the dips" of fluctuating background sounds when detecting nonspeech and speech signals. Evidence is reviewed suggesting that cochlear hearing loss reduces the ability to use TFS cues. The perceptual consequences of this, and reasons why it may happen, are discussed.

A New Fine Structure Speech Coding Strategy

One of the most commonly used speech coding strategies for cochlear implants is continuous interleaved sampling (CIS), which codes the envelope information of an acoustic signal. Based on this strategy, MED-EL has recently developed the new fine structure processing (FSP) speech coding strategy, which also transmits subtle pitch and temporal cues. The aim of this study was to investigate the number of active channels necessary for good speech perception with FSP and whether there is an advantage for FSP compared with CIS at a reduced number of channels. Ten postlingually deafened patients using MED-EL Pulsar cochlear implants participated in this study. Patients were tested with all 12, 8, 5, 3, and 2 channels with CIS and FSP strategy, resulting in a total of 10 conditions. Performance was tested with numbers, monosyllables, and sentence tests. Our results showed an improvement in speech perception, with up to 5 channels for numbers and for monosyllables and sentence tests. Statistically significant increases in performance were noted from 3 to 8 channels for numbers, from 3 to 5 channels for monosyllables, and from 5 to 8 channels for sentence tests. No statistical significance was observed whether FSP or CIS was used. Based on these findings, the number of channels necessary for speech perception with FSP is similar to published results using CIS. There seems to be no advantage for FSP compared with CIS in the conditions of the present experiment.

Speech and music perception with the new fine structure speech coding strategy: preliminary results

Conclusions. Taking into account the excellent results with significant improvements in the speech tests and the very high satisfaction of the patients using the new strategy, this first implementation of a fine structure strategy could offer a new quality of hearing with cochlear implants (CIs). Objective. This study consisted of an intra-individual comparison of speech recognition, music perception and patient preference when subjects used two different speech coding strategies with a MedEl Pulsar CI: continuous interleaved sampling (CIS) and the new fine structure processing (FSP) strategy. In contrast to envelope-based strategies, the FSP strategy also delivers subtle pitch and timing differences of sound to the user and is thereby supposed to enhance speech perception in noise and increase the quality of music perception. Patients and methods. This was a prospective study assessing performance with two different speech coding strategies. The setting was a CI programme at an academic tertiary referral centre. Fourteen post-lingually deaf patients using a MedEl Pulsar CI with a mean CI experience of 0.98 years were supplied with the new FSP speech coding strategy. Subjects consecutively used the two different speech coding strategies. Speech and music tests were performed with the previously fitted CIS strategy, immediately after fitting with the new FSP strategy and 4, 8 and 12 weeks later. The main outcome measures were individual performance and subjective assessment of two different speech processors. Results. Speech and music test scores improved statistically significantly after conversion from CIS to FSP strategy. Twelve of 14 patients preferred the new FSP speech processing strategy over the CIS strategy.

New techniques in electron energy-loss spectroscopy and energy-filtered imaging

This article is a survey of hardware and software advances that promise to increase the power and sensitivity of electron energy-loss spectroscopy (EELS) and energy-filtered imaging (EFTEM) in a transmission electron microscope. Recent developments include electron-gun monochromators, lens-aberration correctors, and software for spectral sharpening, spectral processing and interpretation of fine structure. Future improvements could include the deployment of new electron sources. The expected enhancements in energy and spatial resolution are compared with fundamental limitations that arise from the natural widths of spectral peaks, the delocalization of inelastic scattering and the problem of electron-irradiation damage.

Characteristics of the mixing effect of small-scale internal waves in the upper layer of the Black Sea according to the data of fine-structure sounding

A method of statistical separation of fine-structure fluctuations according to their origin is applied to the analysis of the characteristics of mixing in a layer located below the summer temperature minimum in the Black Sea. The simplification of the procedure of numerical evaluation of the coefficient of vertical wave exchange enabled us to perform the comprehensive fine-structure processing of the data of regular surveys of the Black Sea with an aim to determine the spatial distribution of the field intensity of small-scale internal waves and the intensity of mixing caused by these waves in the analyzed layer.

Fabrication and characterisation of transparent-gate field effect transistors using indium tin oxide

Ion-implanted GaAs MESFETs with transparent indium oxide (ITO) gate electrodes have been fabricated using both sputtered and evaporated ITO gates. High-quality ITO films with transparency greater than 90% and low sheet resistance of 8/spl Omega///spl square/ have been used in the fabrication of RF sputtered transparent gates. Transparent-gate FETs have also been fabricated using thermally evaporated ITO which have shown excellent electrical device performance comparable to the conventional GaAs MESFET. The optical responsivity of these devices is about 4.5 A/W for a radiation wavelength of 6328 /spl Aring/. Fabrication details are also discussed for optoelectronic devices with transparent electrodes where the fine-structure processing are not compatible with standard lithography techniques.

Fine structure, microstructure, and vertical mixing processes in the upper ocean in the western Weddell Sea

The upward flux of heat from the subsurface core of Warm Deep Water (WDW) to the perennially ice‐covered sea surface over the continental slope in the western Weddell Sea is estimated using data obtained during February–June 1992 from a drifting ice station. Through the permanent pycnocline the diapycnal heat flux is estimated to be about 3 W m−2, predominantly because of double‐diffusive convection. There is no evidence that shear‐driven mixing is important in the pycnocline. The estimated mean rate of heat transfer from the mixed layer to the ice is 1.7 W m−2, although peak heat fluxes of up to 15 W m−2 are found during storms. It is hypothesized that isopycnal mixing along sloping intrusions also contributes to the loss of heat from the WDW in this region; however, we are unable to quantify the fluxes associated with this process. Intrusions occur intermittently throughout this experiment but are most commonly found near the boundary of the warm‐core current and the shelf‐modified water to the east. These heat fluxes are significantly lower than the basin‐averaged value of 19 W m−2 (Fahrbach et al., 1994) that is required to balance the heat budget of the Weddell Gyre. Other studies suggest that shelf processes to the west of the ice station drift track and more energetic double‐diffusive convection in the midgyre to the east could account for the difference between our flux estimates for this region and those based on the basin‐scale heat budget.

Fine structure of the high-latitude ionosphere in the cleft and cusp

The results of studies of the fine structure and dynamic processes in the high-latitude ionosphere in the cleft and cusp region by the data of complex radiophysical observations on high-latitudinal paths are presented. They are based on experimental material obtained on board the research vessel ‘Professor Vize’ during July-September 1990 when the vessel was at the Greenwich meridian and the latitudes 75–78°N. The distinctive feature of the radiophysical observations on the vessel was the simultaneous observations by the Doppler method at two fixed frequencies in the decameter range and by the method of oblique sounding of the ionosphere at a frequency sweeping the range from 3.5 to 27.5 MHz. From the observations, the typical feature of the cleft and the cusp has been found to be the presence of wave processes of various periods from 30–40 s to 3–8 min. It is suggested that the emergence of typical negative tracks on the dynamic spectra of HF signals is related to the ionospheric manifestations of flux transfer events.

Left-right asymmetry in superelastic collisions of polarized electrons with unpolarized laser-excited sodium atoms

Polarized electrons have been scattered superelastically from laser-excited unpolarized sodium atoms (deexcitation of the 32P1/2 or 32P3/2 states). The left-right scattering asymmetry, which results from an interplay of the atomic charge cloud orientation, atomic fine-structure interaction and exchange processes, has been measured for energies between 6 and 20 eV and scattering angles ranging from 40 to 120°. Within the experimental uncertainty the Percival-Seaton hypothesis, which is the basis of current theoretical calculations for electron-sodium collisions, has been confirmed. However, the quantitative agreement between experimental and numerical results is satisfactory only for a 2-state close-coupling calculation of Moores.