Intelligibility in noise using multimicrophone hearing aids

Electron probe X-ray microanalysis has been used for the last 25 years by biologists to obtain information about the distribution of elements at the cell and tissue level. During this period, progress has mainly been made through the development of more adequate techniques for specimen preparation (mainly low temperature techniques) and quantitative analysis, so that accurate analysis of the physiologically important cellular ions can be carried out. Use of in vitro systems and cell cultures may further increase the number of problems to which X-ray microanalysis can be applied. Among the numerous applications of X-ray microanalysis in cell biology and cell pathology, applications in the areas of epithelial ion transport, the role of calcium in secretory and contractile cells, and the role of ions in cell proliferation and cancer are discussed in more detail.     

An implantable microphone for electronic hearing aids

Fully implantable hearing aids and cochlea implants of the future require an implantable microphone. A hermetically sealed implantable microphone based on the idea of a microphone implanted in the posterior wall of the auditory canal, as suggested by Ohno et al. in 1988, is presented. Through consistent technological and clinical design optimization, it was possible to achieve a membrane diameter of only 4.5 mm (as opposed to 8 mm in the Japanese system) and a significant volume reduction of nearly 50%. The microphone weights only 0.4 g. In spite of this miniaturization, the performance characteristics of the microphone equal those of the Japanese model or are superior. The sound-pressure transfer function shows a very small ripple and the bandwidth amounts to approximately 10 kHz. Because of its high tuning and high no-load resonance frequency, the microphone is mostly insensitive to post-operational changes to the loading mass on the microphone membrane initiated by the covering skin of the auditory canal. The sound-pressure transfer factor at 1000 Hz is approximately 1.5 mV/Pa. Using different manufacturing technologies, this value can be increased in the range of 6-8 dB with a corresponding reduction in bandwidth. Due to the small mass, the microphone is highly insensitive to environmental mechanical disturbances. The module is made of pure titanium and is hermetically sealed according to Mil-Std 883 D. Full metal encapsulation and additional internal electronic components protect the microphone well against environmental electromagnetic influences (EMC).     

Comparison of two digital hearing aids

OBJECTIVE: The objective of this investigation was to compare real and perceived benefit for two currently marketed digital hearing aids, the Oticon DigiFocus and the Widex Senso. The hearing aids have different philosophies of design and fitting strategies; as a result, it was hypothesized that there would be performance differences. DESIGN: Twenty subjects with documented sensorineural hearing losses were fit with each of the two digital hearing aids. After 4 wk of use with each hearing aid, a battery of objective and subjective tests was completed to assess hearing aid benefit. RESULTS: No significant differences were found between the hearing aids as revealed by the objective testing of speech recognition and self-report inventories of hearing aid benefit. The DigiFocus was shown by real ear measurements to provide more high-frequency gain than the Senso. The Widex Senso was preferred by 13 of the 20 subjects (seven of 10 of the new hearing aid users). This may be explained, in part, by the increased high-frequency gain provided by the Oticon DigiFocus, which was perceived as having greater "harshness." CONCLUSIONS: Based on the results of this investigation, neither hearing aid processor was shown to be superior to the other. In addition, the least amount of objective benefit was shown in the presence of background noise.     

Speech intelligibility in noise with fast compression hearing aids

The effect of fast (syllabic) compression with overshoot reduction was studied in moderately hearing-impaired and in severely hearing-impaired listeners in quiet and in noisy situations. A test battery of daily masking noises was selected using multidimensional scaling techniques. Four relevant noises were selected: a multi-talker babble, the noise in an industrial plant, in a printing office and a city-noise background. The speech measurements show that only selected patients benefit from syllabic compression, i.e. listeners with a poor speech discrimination score. The effect in noisy surroundings was tested at the critical signal-to-noise ratio of each patient, showing whether they benefited from compression in the most critical condition or not. It turns out that the effect depends largely on the speech discrimination score and the modulation of the noise signal. When the speech discrimination score is good, compression tends to impair the results. When the speech discrimination score is poor, compression helps if the noise is modulated.     

Reliability of monosyllabic discrimination tests in white noise for differentiating among hearing aids

In spite of criticism, monosyllabic discrimination tests are widely employed for hearing aid selection. The current study was designed to investigate the following questions: (1) How reliable is aided speech discrimination of monosyllables in a background of white noise? (2) Can differences among hearing aids be reliably demonstrated by measuring intelligibility of monosyllables in a background of white noise? and (3) Do hearing aids interact with hearing loss? Twenty subjects with mild-moderate sensorineural hearing losses participated in two experimental sessions. Four hearing aids were evaluated using the NU-6 monosyllables in a background of white noise (s/n = +20 dB). Since the standard deviation of the test-retest differences was 6%, differences between aids were not considered significant unless they exceeded 12%. An interaction between subjects and hearing aids was found; that is, the best aid for one person was not the best for all. Measuring monosyllabic word intelligibility in a background of white noise does not reliably identify a single best aid. However, one or more inferior aids were consistently eliminated in 80% of the subjects.     

Procedure for clinical testing of hearing aids

Conservative treatment of thoracic outlet syndrome is frequently recommended but few studies reporting conservative management are present in literature. Thirteen out-patients with thoracic outlet syndrome (4 males, 9 females) were admitted to a conservative treatment (massage and kinesitherapy) involving the cervical spine and shoulder girdle. All the patients were satisfied with the outcome of the treatment. In particular rest symptoms completely disappeared after treatment in all patients. This study confirms the efficacy of physical therapy in the conservative treatment of patients with thoracic outlet syndrome. Further studies on long-term outcome are needed.     

Telephone communication with in-the-ear hearing aids using acoustic and electromagnetic coupling

The purpose of this study was to determine whether telephone communication was improved with electromagnetic coupling for in-the-ear hearing aid users with mild to moderate hearing losses. Each user adjusted his hearing aid gain to the level he determined to be best for telephone communication with each coupling method. Under these conditions, average word recognition scores in quiet and average high-frequency output levels measured at the tympanic membrane were not different for each coupling method. The ability to tolerate background noise was also studied. Background noise tolerance was not different for the two coupling methods. However, significantly greater levels of background noise were tolerated when telephone side-tone feedback was eliminated regardless of coupling method.     

Principle requirements of an electromechanical transducer for implantable hearing aids in inner hearing hearing loss. II: Clinical aspects]

In this retrospective study, 13 patients with subtle Lisfranc joint injuries were examined after a mean period of 23 months using clinical assessment, radiography and dynamic pedographic gait analysis. The aims were to identify the factors leading to a mobile flatfoot deformity, evaluate the functional and clinical outcome of these injuries, and draw practical conclusions for initial management and subsequent intervention. All patients showed a mobile flatfoot deformity, increased motion in the subtalar joint, increased load on the hindfoot, decreased load on the forefoot, and a prolonged contact phase during the stance phase. Radiographs revealed progressive osteoarthrosis in the joint and a residual displacement of the medial Lisfranc joint. An unstable medial Lisfranc joint results in the development of a mobile flatfoot. Initial treatment of a subtly displaced Lisfranc joint should consist of exact anatomical reduction and additional maintenance of the longitudinal arch of the foot. After failed initial treatment, early arthrodesis of the midfoot is recommended as a salvage procedure for the foot.     

Development and evaluation of a procedure for fitting multi-channel compression hearing aids

Hearing aids with multi-channel compression are often fitted on the basis of loudness scaling data obtained using narrow bands of noise or tones. Here, we report the development and evaluation of an alternative fitting procedure based on the use of speech signals. The parameters of the hearing aid (the gains in each channel for high and low input levels) are adjusted adaptively under computer control on the basis of the listener's responses. The goal is that speech at 85 dB SPL should be judged as 'loud', speech at 60 dB SPL should be judged as 'quiet', and speech at both levels should be judged as 'neither tinny nor boomy'. The procedure was evaluated using a two-channel compression hearing aid, the remote control of which allowed two programs to be stored. One program was based on our fitting procedure. The other was either based on the manufacturer's recommended full fitting procedure (which included loudness scaling with bands of noise), or was based on the audiogram alone, using the manufacturer's algorithm. After an acclimatization period of at least two weeks, subjects were then asked to fill in a questionnaire about their experiences with the two programs in different listening situations. The results generally indicated a preference for the program based on our adaptive fitting procedure. We also conducted laboratory measurements of speech intelligibility, in quiet and in a background of a single competing talker. These showed no clear difference between programs, although scores overall were very high. We conclude that our adaptive procedure gives very satisfactory results in everyday life. Parameter values giving good comfort also give good intelligibility. The procedure typically takes between five and 10 minutes per ear, which is quicker than most loudness scaling procedures.     

The relationship between listening conditions and alternative amplification schemes for multiple memory hearing aids

OBJECTIVE: The aim of this study was to determine a relationship among selected listening conditions and amplification schemes that could be provided in a multiple memory hearing aid. DESIGN: The study consisted of three laboratory tests: 1) A screening test to select hearing impaired subjects who appeared to benefit from multiple amplification schemes. 2) A category scaling test to rank 16 amplification schemes in 15 listening conditions. The 16 schemes were simulated with a digital master hearing aid and comprised 5 linear systems and 11 compression characteristics. The 15 listening conditions comprised 6 listening environments combined with 2 or 3 response criteria. 3) A paired comparison test in which the two highest ranked amplification schemes were evaluated together with a reference linear frequency response (NAL) in a round-robin test. RESULTS: The screening test demonstrated that 21 hearing impaired people out of 25 with mild or moderate, flat or gently sloping hearing losses appeared to benefit from multiple amplification schemes. Age or audiometric factors did not serve to discriminate between those who selected different schemes and those who did not. In general, the NAL-response was preferred or was as good as any other for listening to speech in quiet, speech in reverberation, speech in babble-noise, and for naturalness of all listening environments. The subjects consistently selected an amplification scheme other than the NAL-response for four specific listening conditions. The findings suggest that substantial high-frequency compression is preferred for the ease of understanding multiple talkers, whose voices differ in overall level, in quiet environments. The annoyance of low-frequency background noise can be reduced by low-frequency compression, whereas a frequency response steeper than the NAL-response makes it easier to understand speech in low frequency background noise. Finally, a frequency response flatter than the NAL-response can be used to make a high-frequency background noise sound less annoying. CONCLUSION: Hearing aid users with mild or moderate, flat or gently sloping hearing losses, fitted with equal and sufficient variation in amplification, prefer different amplification schemes depending on the number of talkers, the background noise and the response criterion.     

An epidemiologic method for assessing the effectiveness of hearing conservation programs using audiometric data

A hearing conservation program (HCP) must include audiometric monitoring. In keeping with this requirement, enormous bodies of audiometric data have been accumulated. However, only a limited number of methods are available for using audiometric data to assess HCP effectiveness. This study illustrates an epidemiologic method. The risk of developing hearing loss (measured by the standard threshold shift) was compared between study and reference populations using the risk ratio. The study population had an increased risk of nearly 3-fold. Epidemiologic risk comparison methods, using reference populations, offer an alternative to current methods for HCP evaluation using audiometric data.     

Simple formula aids for understanding the joint action of two predictors.

"It was demonstrated that the ratio of any two fixed validity coefficients will locate a value for the intercorrelation term in the two-predictor, multiple correlation formula such that the variable having the lower validity will contribute nothing to the variable having the higher validity. The resulting multiple correlation is thereby a minimum. A second formula is presented that determines two intercorrelation values for any fixed pair of validity coefficients which will result in a multiple correlation of 1.00. This second formula does not hold when both validity coefficients are exactly zero, and is restricted to determination of a single intercorrelation value when the two validity coefficients are exactly equal and not zero. From Psyc Abstracts 36:05:5AG85M. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Factors governing speech reception benefits of adaptive linear filtering for listeners with sensorineural hearing loss

Adaptive linear filtering can improve effective speech-to-noise ratios by attenuating spectral regions with intense noise components to reduce the noise's spread of masking onto speech in neighboring regions. This mechanism was examined in static listening conditions for seven individuals with sensorineural hearing loss. Subjects were presented with nonsense syllables in an intense octave-band noise centered on 0.5, 1, or 2 kHz. The nonsense syllables were amplified to maximize. the articulation index; the noises were the same for all subjects. The processing consisted of applying frequency-selective attenuation to the speech-plus-noise with the goal of attenuating the frequency region containing the noise by various amounts. Consonant recognition scores and noise masking patterns were collected in all listening conditions. When compared with masking patterns obtained from normal-hearing subjects, all hearing-impaired subjects had higher masked thresholds at frequencies below, within, and above the masker band except for one subject who demonstrated additional masking above the masker only. Frequency-selective attenuation resulted in both increases and decreases in consonant recognition scores. Increases were associated with a release from upward spread of masking. Decreases were associated with applying too much attenuation such that speech energy within the masker band that was audible before processing was partially below threshold after processing. Fletcher's [Speech and Hearing in Communication (Van Nostrand, New York, 1953)] version of articulation theory (without modification) accounted for individual subject differences within the range of variability associated with the consonant recognition test in almost every instance. Hence, primary factors influencing speech reception benefits are characterized by articulation theory. Fletcher's theory appears well-suited to guide the design of control algorithms that will maximize speech recognition for individual listeners.     

An implantable hearing aid for inner ear hearing loss. Short-term implantation of microphone and transducer

A microphone constructed for implantation in the posterior wall of the auditory canal and a piezoelectric transducer serving as the main components of an implantable hearing aid were temporally implanted in five patients during middle ear surgery under local anesthesia. The microphone was positioned beneath the skin of the auditory canal such that it completely covered the microphone membrane. The vibratory element of the transducer was coupled to the malleus in four patients with normal ossicular chains and directly to the stapes in one patient with missing incus. The microphone and transducer were electrically connected with an external battery-driven signal amplifier. Speech material and music were presented in the operation room at a sound level of 65 dB SPL under free-field conditions. The patients had to estimate the quality of speech, music, and their own voice as well as the effects of bone-conducting noises. All patients were able to hear with the system. An intraoperative talk without vision contact was possible without any problems, as was understanding of numerals ("Freiburger Zahlentest"). Perception of music was judged as "clear and undistorted with all broadband component." The estimation was also valid for one patient with a sensorineural hearing loss. One patient declared the music to be "a little of unnatural." Bone-conducted sound was estimated as normal in two patients, better than without an implant in one patient with sensorineural hearing loss, and "somewhat metallic" in another patient. Hearing the own voice was considered "normal" in two cases "monotonous" in one case, and "a little bit roaring" in another case. An amplification factor that can be technically realized in an implantable hearing aid was necessary for one of the patients with sensorineural hearing loss to perceive music at a pleasant volume. On the basis of this study, essential requirements for the construction of a fully implantable hearing aid are fulfilled.     

An adaptive mesh refinement scheme for solidification problems

Methods for adaptive mesh refinement, based on a quadtree data structure, have been developed with the specific objective of tracking solid/liquid front movement in two-dimensional solidification problems. These methods include mesh refinement and unrefinement algorithms for the finite element method applied to transient problems. Ana posteriori error estimator is described to locate regions in the finite element mesh needing refinement. One- and two-dimensional example applications are given, showing how the methods can be used to resolve a moving solidification front and its associated boundary layer in binary alloy solidification.     

动态噪声特性未知系统的多模型自适应卡尔曼滤波

针对常规自适应卡尔曼滤波器存在过渡过程差的问题,基于一个给定的指标切换函数,采用多个基于不同动态噪声协方差矩阵的卡尔曼滤波器和一个常规自适应卡尔曼滤波器共同组成多模型自适应卡尔曼滤波器.与常规自适应卡尔曼滤波器相比,多模型自适应卡尔曼滤波器可以在保持原有自适应滤波器性能的基础上极大地改善瞬态响应.     

Effects of signal processing on intelligibility of speech in noise for persons with sensorineural hearing loss

Rats bearing the Walker 256 intramuscular carcinosarcoma were treated intraperitoneally with tritium-labeled vernolepin or with its nontumor-inhibitory methanol adduct. Following treatment with 3H-vernolepin on several different dosage schedules, the tumors were found to contain significantly more radioactivity per gram wet weight than control tissue (muscle from the contralateral limb). After the administration of the nontumor-inhibitory methanol adduct, no such difference was observed. The distribution of radioactivity in various other organs (liver, kidney, spleen, intestine, lung, heat, fat, blood, and brain) was measured following treatment with the parent compound (3H-vernolepin). The implications of these data in terms of the suggested mechanism of action of sesquiterpene lactone tumor inhibitors is discussed.     

An active noise control algorithm for controlling multiple sinusoids

The filtered-x LMS algorithm and its modified versions have been successfully applied in suppressing acoustic noise such as single and multiple tones and broadband random noise. This paper presents an adaptive algorithm based on the filtered-x LMS algorithm which may be applied in attenuating tonal acoustic noise. In the proposed method, the weights of the adaptive filter and estimation of the phase shift due to the acoustic path from a loudspeaker to a microphone are computed simultaneously for optimal control. The algorithm possesses advantages over other filtered-x LMS approaches in three aspects: (1) each frequency component is processed separately using an adaptive filter with two coefficients, (2) the convergence parameter for each sinusoid can be selected independently, and (3) the computational load can be reduced by eliminating the convolution process required to obtain the filtered reference signal. Simulation results for a single-input/single-output (SISO) environment demonstrate that the proposed method is robust to the changes of the acoustic path between the actuator and the microphone and outperforms the filtered-x LMS algorithm in simplicity and convergence speed.