Hearing Aid

This article applies the gain and frequency response and maximum output selection procedures currently recommended by the National Acoustic Laboratories (NAL) of Australia to the audiograms of a representative group of adult and child clients of Australian Hearing Services (AHS) to specify the performance that is required of various types of hearing aids in order to ensure that they can provide adequate gain, frequency response, and maximum output levels for at least 90% of the AHS client population . Cumulative frequency distributions of required 2-cc coupler gain slopes were calculated for each type of aid and used to design required frequency response variations . Coupler slope requirements in different octaves were found to be independent of one another . The required range of gain-maximum output combinations was determined for each type of aid.

Cet article présente un nouveau procédé de correction auditive utilisant un modèle paramétrique du signal de parole. Ce procédé permet, en plus des opérations classiques de compression et d'amplification, d'effectuer des transformations élaborées (modification du rythme temporel, modification de l'enveloppe spectrale, etc.) tout en conservant la structure naturelle du signal de parole. Les premiers résultats d'une série de tests cliniques montrent que ce procédé est bien accueilli par les personnes atteintes de surdités intermédiaires (moyennes ou sévères) et pour lesquelles il n'existe pas véritablement de traitement prothétique adapté.

During the first half of the 20th century, communications engineers at Bell Telephone Laboratories developed the articulation model for predicting speech intelligibility transmitted through different telecommunication devices under varying electroacoustic conditions. The profession of audiology adopted this model and its quantitative aspects, known as the Articulation Index and Speech Intelligibility Index, and applied these indices to the prediction of unaided and aided speech intelligibility in hearing-impaired listeners. Over time, the calculation methods of these indices-referred to collectively in this paper as the Audibility Index-have been continually refined and simplified for clinical use. This article provides (1) an overview of the basic principles and the calculation methods of the Audibility Index, the Speech Transmission Index and related indices, as well as the Speech Recognition Sensitivity Model, (2) a review of the literature on using the Audibility Index to predict speech intelligibility of hearing-impaired listeners, (3) a review of the literature on the applicability of the Audibility Index to the selection and fitting of hearing aids, and (4) a discussion of future scientific needs and clinical applications of the Audibility Index.

The Smart Dust project is an attempt to create completely autonomous sensing and communication platforms in a cubic millimeter volume. With circuits currently in fabrication, we hope to create a system with a communication range of 100m, a power dissipation of 17µW, and a total volume of 80 cubic millimeters. The circuit described here consists of an optical receiver (onchip photodiode and amplifier), pseudo-random sequence generator, and charge pump. Other system components include a MEMS optical transmitter (modulated corner cube reflector) and a hearing-aid battery. With solar cells replacing the battery, total system volume should be less than 10 cubic millimeters.

Background: As in all western countries, Australia's older population experiences high levels of hearing impairment coupled with relatively low levels of hearing device usage. Poor hearing diminishes the quality of life of affected individuals and their families. This paper discusses how to improve Australian hearing health policies in order to better combat this impairment amongst older Australians. Method: We searched the databases Medline, Meditext and Web of Science to find articles that discussed strategies and innovations to assist the hearing health of older people, and related this material to observations made during the Blue Mountains Hearing Study in NSW between 1997 and 2003. Results and Discussion: The literature search identified five areas for inclusion in a comprehensive hearing health policy in Australia. These are: early intervention; addressing of hearing aid expense; the use of assisted listening devices; hearing rehabilitation, and; screening and education. Further research in Australia is critical if we are to develop a strong approach to the increasing prevalence of age-related hearing loss. Conclusion: Australia needs to act now to address hearing impairment as it is a major cause of disability in those aged 55 and over. Federal and State governments should collaborate to construct a comprehensive hearing health policy that tackles poor levels of hearing health through early intervention, addressing hearing aid expense, encouraging the use of assisted listening devices, rehabilitation, screening and education. A good start would be to declare age related hearing impairment as a National Health Priority Area.

The purpose of this study was to compare vowel productions by deaf cochlear implant (CI) children, hearing-impaired hearing aid (HA) children and normal-hearing (NH) children. 73 children [mean age: 9;14 years (years;months)] participated: 40 deaf CI children, 34 moderately to profoundly hearing-impaired HA children and 42 NH children. For the 3 corner vowels [a], [i] and [u], F(1), F(2) and the intrasubject SD were measured using the Praat software. Spectral separation between these vowel formants and vowel space were calculated. The significant effects in the CI group all pertain to a higher intrasubject variability in formant values, whereas the significant effects in the HA group all pertain to lower formant values. Both hearing-impaired subgroups showed a tendency toward greater intervowel distances and vowel space. Several subtle deviations in the vowel production of deaf CI children and hearing-impaired HA children could be established, using a well-defined acoustic analysis....

ObjectivesWith more children receiving cochlear implants during infancy, there is a need for validated assessments of pre-verbal and early verbal auditory skills. The LittlEARS® Auditory Questionnaire is presented here as the first module of the LittlEARS® test battery. The LittlEARS® Auditory Questionnaire was developed and piloted to assess the auditory behaviour of normal hearing children and hearing impaired children who

Newborn hearing screening has been recognized as an essential component of public health care in early childhood in developed countries. However, such screening is yet to be widely embraced in the developing world. The new national health policy in Nigeria seeks, for the first time, to reduce the impact of permanent hearing loss on early childhood development through early detection and timely intervention services. The aim of this paper is to ascertain if newborn hearing screening satisfies the conventional criteria for a screening programme as an early detection strategy in this developing country. A review of the available literature shows that permanent childhood hearing loss is a significant health condition and its detection through screening with oto-acoustic emissions and/or auditory brainstem response is feasible in the target population. Amplification with hearing aids is an effective and preferred option for early intervention by parents. The risk of maternal anxiety from potential falsepositives or the psychological cost of false assurance from false-negatives is unlikely to outweigh the benefit of screening. Newborn hearing screening is therefore a potential early detection strategy for permanent childhood hearing loss in Nigeria.

Very few assessment measures exist for evaluating progress in young deaf children with hearing aids and cochlear implants. To introduce and describe an early assessment package that covers auditory perception, communication/language development, and speech production in very young deaf children. Seven of the assessment measures (Listening Progress Profile, Categories of Auditory Performance, Tait Video Analysis, Stories-Narratives Assessment Procedure, Profile of Actual Linguistic Skills, Speech Intelligibility Rating, and the Profile of Actual Speech Skills) have been specifically developed at the Nottingham Cochlear Implant Programme, and a further one (Meaningful Auditory Integration Scale) was modified for use within the package. Moreover, two commercially available tests (Pragmatics Profile of Everyday Communication Skills and Preschool Language Scale) are included to complete the package. The present paper describes each measure, how to use it, and its time frame. In addition,...

Lunner T, Hellgren J, Arlinger S, Elberling C. Non-linear signal processing in digital hearing aids. Scand Audiol 1998;27 Suppl 49: 40-49. Three different non-linear digital signal processing algorithms were developed: LinEar, DynEar and RangeEar. All three provided individual frequency shaping via a seven-band low-power filterbank and compression in two channels. RangeEar and DynEar used wide dynamic range syllabic compression in the low-frequency (LF) channel, while LinEar used compression limiting. In the highfrequency (HF) channel, RangeEar used a slow-acting automatic volume control, while DynEar and LinEar used compression limiting. Wearable digital signal processing-based experimental instruments were used to evaluate the fitting algorithms under real world conditions with experienced hearing aid users. Evaluation included laboratory testing of speech recognition in noise and questionnaires on sound quality ratings. Results did not indicate one general good-for-all algorithm, but different algorithms resulting in preference and performance depending on the hearing loss configuration. Preference for any of the new algorithms could be predicted based on auditory dynamic range measurements. It was hypothesized that the different preferences were affected by different susceptibility to masking of HF sounds by amplified LF sounds.

With more children receiving cochlear implants during infancy, there is a need for validated assessments of pre-verbal and early verbal auditory skills. The LittlEARS Auditory Questionnaire is presented here as the first module of the LittlEARS test battery. The LittlEARS Auditory Questionnaire was developed and piloted to assess the auditory behaviour of normal hearing children and hearing impaired children who receive a cochlear implant or hearing aid prior to 24 months of age. This paper presents results from two studies: one validating the LittlEARS Auditory Questionnaire on children with normal hearing who are German speaking and a second validating the norm curves found after adaptation and administration of the questionnaire to children with normal hearing in 15 different languages. Scores from a group of 218 German and Austrian children with normal hearing between 5 days and 24 months of age were used to create a norm curve. The questionnaire was adapted from the German orig...

Infusing hierarchies with elements of market control has become a much-used way of simultaneously increasing entrepreneurialism and motivation in firms. However, this paper argues that such "internal hybrids," particularly in their radical forms, are inherently hard to successfully design and implement because of a fundamental incentive problem of establishing credible managerial commitments to not intervene in delegated decision making. This theme is developed and illustrated, using the case of the world-leading hearing aids producer, Oticon. In the beginning of the 1990s, Oticon became famous for its radical internal hybrid, the "spaghetti organization." Recent work has interpreted the spaghetti organization as a radical attempt to foster dynamic capabilities by organizational means, neglecting, however, that about a decade later the spaghetti organization has given way to a more traditional matrix organization. In contrast, an organizational economics interpretation of Oticon organizational changes is developed. This lens suggests that a strong liability of the spaghetti organization was the above incentive problem: Frequent managerial meddling with delegated rights led to a severe loss of motivation, and arguably caused the change to a more structured organization. Refutable implications are developed, and the discussion is broadened to more general issues of economic organization.

Geometrical-acoustics ͑GA͒ modeling techniques assume that surfaces are large relative to the wavelengths of interest. For a given scenario, practitioners typically create a single 3D model with large, flat surfaces that satisfy the assumption over a broad range of frequencies. Such geometric approximations lead to errors in the spatial distribution of the simulated sound field because geometric details that influence reflection and scattering behavior are omitted. To compensate for the approximations, modelers typically estimate scattering coefficients for the surfaces to account stochastically for the actual, wavelength-dependent variations in reflection directionality. A more deterministic approach could consider a series of models with increasing geometric detail, each to be analyzed at a corresponding frequency band for which the requirement of large surface dimensions is satisfied. Thus, to improve broadband spatial accuracy for GA simulations, we propose a multiresolution modeling approach. Using scale model measurements of a corrugated wall, comparisons of our method with non-GA techniques, and some simple listening tests, we will demonstrate that multiresolution geometry provides more spatially accurate results than single-resolution approximations when using GA techniques, and that this improved accuracy is aurally significant. 8:20 5aAAa2. On the analysis of the time spreading of sound diffusers. Acoustics'08 Paris ͑slit and "wide obstacle" with two edges͒. The results have again been compared with Svensson's exact wave-theoretical secondary edge source model. With some restrictions, they seem to indicate, that indeed even diffraction of sound -like light -may be handled as flow of particles. To avoid the feared explosion of computation time with higher order diffraction, a beam reunification may now be achieved by Quantized Pyramidal Beam Tracing.

Multi-channel self-steering microphone arrays for hearing aid ap- plications enable the hearing impaired user to follow conversa- tions coming from other directions than the front direction. Bin- aural connections between left and right hearing aids allow for (i) the estimation of the direction of arrival (DOA) and thus for auto- matic beam-steering, (ii) a higher noise reduction due to a greater number of sensors, and (iii) the preservation or reconstruc tion of binaural cues that can be used by the hearing impaired listener for object segregation. Since the microphones are placed near the human head, diffraction and shadowing effects have to be in- corporated into the beamformer design as well as into the DOA estimator. In this contribution a combined system of DOA estimation and a head-worn 6-channel binaural noise reduction scheme is pre- sented and evaluated using perceptual measures that are based on auditory models.

Hearing aid amplification can be used as a model for studying the effects of auditory stimulation on the central auditory system (CAS). We examined the effects of stimulus presentation level on the physiological detection of sound in unaided and aided conditions. P1, N1, P2, and N2 cortical evoked potentials were recorded in sound field from 13 normal-hearing young adults in response to a 1000-Hz tone presented at seven stimulus intensity levels. As expected, peak amplitudes increased and peak latencies decreased with increasing intensity for unaided and aided conditions. However, there was no significant effect of amplification on latencies or amplitudes. Taken together, these results demonstrate that 20 dB of hearing aid gain affects neural responses differently than 20 dB of stimulus intensity change. Hearing aid signal processing is discussed as a possible contributor to these results. This study demonstrates (1) the importance of controlling for stimulus intensity when evoking responses in aided conditions, and (2) the need to better understand the interaction between the hearing aid and the CAS.

Objective: For some patients, conventional hearing aids might have disadvantages that clearly limit the benefit of using them. The middle ear implant, Vibrant Soundbridge hearing prosthesis offers an approach to help such patients. Our study's objective was to identify the binaurality in a well-fitted digital hearing aid worn in the contralateral ear in recipients experienced with use of the Vibrant Soundbridge middle ear implant device. Study Design: In a prospective study, warble-tone thresholds and stereophony were evaluated for the following conditions:

This research explores the design and imp lementation of a microcontroller based electronic Hearing aid with output level indicator. The incoming sound oscillates the base of a transistor which in turn amplifies the signal at the collect or. The output is interfaced to an ADC wh ich converts the signal to digital output. After the conversion, the microcontroller processes the signal and further feeds it in to the DAC for an analog conversion. This output is now fed into the audio level indicator, LM 3915, to indicate the level of the audio signal at the ear phone.

Speech-evoked auditory event-related potentials (ERPs) provide insight into the neural mechanisms underlying speech processing. For this reason, ERPs are of great value to hearing scientists and audiologists. This article will provide an overview of ERPs frequently used to examine the processing of speech and other sound stimuli. These ERPs include the P1-N1-P2 complex, acoustic change complex, mismatch negativity, and P3 responses. In addition, we focus on the application of these speech-evoked potentials for the assessment of (1) the effects of hearing loss on the neural encoding of speech allowing for behavioral detection and discrimination; (2) improvements in the neural processing of speech with amplification (hearing aids, cochlear implants); and (3) the impact of auditory training on the neural processing of speech. Studies in these three areas are reviewed and implications for audiologists are discussed.

D istributed sensor networks have been proposed for a wide range of applications. The main purpose of a sensor network is to monitor an area, including detecting, identifying, localizing, and tracking one or more objects of interest. These networks may be used by the military in surveillance, reconnaissance, and combat scenarios or around the perimeter of a manufacturing plant for intrusion detection. In other applications such as hearing aids and multimedia, microphone networks are capable of enhancing audio signals under noisy conditions for improved intelligibility, recognition, and cuing for camera aiming. Recent developments in integrated circuit technology have allowed the construction of low-cost miniature sensor nodes with signal processing and wireless communication capabilities. These technological advances not only open up many possibilities but also introduce challenging issues for the collaborative processing of wideband acoustic and seismic signals for source localization and beamforming in an energy-constrained distributed sensor network. The purpose of this article is to provide an overview of these issues. Some prior systems include: WINS at RSC/UCLA [1], AWAIRS at UCLA/RSC [2]-[4], Smart Dust at UC Berkeley [5], USC-ISI network [6], MIT network [7], SensIT systems/networks [8], and ARL Federated Laboratory Advanced Sensor Program systems/networks [9].

ev. lev.: evidence level, AN/AD: auditory neuropathy/dys-synchrony, SNHL: sensorineural hearing loss, EABR: electric auditory brainstem responses, ESP: early speech perception, MAIS: meaningful auditory integration scale, GASP: Glendonald auditory screening procedure, and wnr: was not reported.

The purpose of the study was to determine an optimal hearing aid fitting procedure for a patient with well diagnosed high-frequency 'dead regions' in both cochleas. The patient reported non-symmetrical hearing problems of sensorineural origin. For binaural amplification two similar independent hearing aids were used as well as a pair of dependent devices with an ear-to-ear function. Two fitting methods were used: DSLi/o and NAL-NL1, and four different strategies of fitting were tested: the initial fitting based on the DSLi/o or NAL-NL1 method with necessary loudness corrections, the second fitting taking into account all the available functions of hearing instruments, the third fitting (based on the second one) but with significantly reduced amplification well above one octave of frequency inside dead region, and the final fitting with significantly reduced gain slightly below one octave inside dead regions. The results of hearing aids fitting were assessed using an APHAB procedure.

Alpha-mannosidosis is an inherited lysosomal storage disorder characterized by immune deficiency, facial and skeletal abnormalities, hearing impairment, and intellectual disability. It occurs in approximately 1 of 500,000 live births. The children are often born apparently normal, and their condition worsens progressively. Some children are born with ankle equinus or develop hydrocephalus in the first year of life. Main features are immune deficiency (manifested by recurrent infections, especially in the first decade of life), skeletal abnormalities (mild-to-moderate dysostosis multiplex, scoliosis and deformation of the sternum), hearing impairment (moderate-to-severe sensorineural hearing loss), gradual impairment of mental functions and speech, and often, periods of psychosis. Associated motor function disturbances include muscular weakness, joint abnormalities and ataxia. The facial trait include large head with prominent forehead, rounded eyebrows, flattened nasal bridge, macroglossia, widely spaced teeth, and prognathism. Slight strabismus is common. The clinical variability is significant, representing a continuum in severity. The disorder is caused by lysosomal alpha-mannosidase deficiency. Alpha-mannosidosis is inherited in an autosomal recessive fashion and is caused by mutations in the MAN2B1 gene located on chromosome 19 (19 p13.2-q12). Diagnosis is made by measuring acid alpha-mannosidase activity in leukocytes or other nucleated cells and can be confirmed by genetic testing. Elevated urinary secretion of mannose-rich oligosaccharides is suggestive, but not diagnostic. Differential diagnoses are mainly the other lysosomal storage diseases like the mucopolysaccharidoses. Genetic counseling should be given to explain the nature of the disease and to detect carriers. Antenatal diagnosis is possible, based on both biochemical and genetic methods. The management should be pro-active, preventing complications and treating manifestations. Infections must be treated frequently. Otolaryngological treatment of fluid in the middle ear is often required and use of hearing aids is invariably required. Early educational intervention for development of social skills is needed and physiotherapy is important to improve bodily function. Orthopedic surgery may be necessary. The long-term prognosis is poor. There is an insidiously slow progression of neuromuscular and skeletal deterioration over several decades, making most patients wheel-chair dependent. No patients manage to be completely socially independent. Many patients are over 50 years of age.

The aim of the study was to characterize the audiological consequences of congenital cytomegalovirus infection (CMV) and to evaluate the outcome of rehabilitation with hearing aids and/or cochlear implant (CI), associated with an adequate speech-language therapy. A retrospective review of data was made from a total of 16 infants, aVected by severe to profound hearing loss from congenital CMV infection, referred to a tertiary audiological center for rehabilitation. Audiological evaluation was performed using behavioral audiometry, auditory brainstem responses (ABR) and/or electrocochleography (ECochG). Of the 16 children (median age at diagnosis of hearing loss: 21.33 § 0.7 months) with CMV hearing loss, 14 were aVected by profound bilateral hearing loss and received a CI, while 2 were aVected by bilateral severe hearing loss and received hearing aids. Cochlear implants can provide useful speech comprehension to patients with CMV-related deafness, even if language development is lower when compared to a group of Connexin (Cx) 26+ cochlearimplanted children (eight subjects), matched for age. Congenital CMV infection still represents a serious clinical condition, as well as an important cause of hearing loss in children. More studies have claimed to identify the pathophysiological mechanisms of damage and thus to ensure a better therapeutic approach. Nonetheless, in cases of CMV-deafened babies, the overall outcome of cochlear implantation is good.

The main objective of this study was to assess the associations between self-reported listening habits and perception of music and speech perception outcomes in quiet and noise for both unilateral cochlear implant (CI) users and bimodal (CI in one ear, hearing aid in contra-lateral ear) users. Information concerning music appreciation was gathered by means of a newly developed questionnaire. Moreover, audiological data (pure-tone audiometry, speech tests in noise and quiet) were gathered and the relationship between speech perception and music appreciation is studied. Bimodal users enjoy listening to music more in comparison with unilateral CI users. Also, music training within rehabilitation is still uncommon, while CI recipients believe that music training might be helpful to maximize their potential with current CI technology. Music training should not be exclusively reserved for the good speech performers. Therefore, a music training program (MTP) that consists of different difficulty levels should be developed. Hopefully, early implementation of MTP in rehabilitation programs can enable adult CI users to enjoy and appreciate music and to maximize their potential with commercially available technology.

Introduction: Any hearing impaired person is an applicant of being a hearing aid wearer. International companies rule the market with a range of products those value added are inconsistent with the income of the population in developing countries. Objective: Design and development of digital low-cost hearing aid, BTE design, in a generic electronic configuration with electroacoustics features not lesser than those traded in the Brazilian marketplace. Method: Establish a strictly professional relationship with the predominant hearing aid suppliers in the hearing aid industry and develop BTE hearing aid. The electroacoustics outcomes of these hearing aids were performed at an independent acoustic investigation lab. Conclusion: It is possible the development of digital low-cost BTE hearing aid with performance features not lesser than those traded in the Brazilian marketplace but at low-cost operational costs.

30 healthy volunteers were recruited for this trial which took place in a controlled acoustic environment. Each of the individuals was required to consume a pre-set amount of alcohol and the hearing was tested (using full pure tone audiogram) pre-and post-alcohol ...

This study examined the speech intelligibility of profoundly, prelingually or congenitally deaf children who use hearing aids. Children were one to fifteen years old and they were classified into subgroups according to residual hearing (PTA between 90 and 100, 100 and 110 or greater than 110 dB HL) and communication mode (either oral or total communication). They read lists of standard sentences which were played back to panels of three "naive" listeners who were not familiar with the speech of the deaf and who did not know which subgroup the children belonged to. The data revealed a strong significant trend toward higher intelligibility for children with more residual hearing, and a significant trend toward higher intelligibility for users of oral communication than for total communication users. However, the latter trend was much more pronounced for some ranges of residual hearing than for others, and it may have been partly due to a sampling effect. A third trend showed significantly higher intelligibility levels at older ages, but this was particularly pronounced for children with PTA's between 90-100 dB HL, and for the majority of oral communication users (and only a few total communication users) with PTA's between 100-110 dB. These results suggest that the amount of residual hearing (possibly in interaction with the communication mode used by the child) may be an important factor in the development of intelligible speech.

Automatic program switching has been shown to be greatly beneficial for hearing aid users. This feature is mediated by a sound classification system, which is traditionally implemented using simple features and heuristic classification schemes, resulting in an unsatisfactory performance in complex auditory scenarios. In this study, a number of experiments are conducted to systematically assess the impact of more sophisticated classifiers and features on automatic acoustic environment classification performance. The results show that advanced classifiers, such as Hidden Markov Model (HMM) or Gaussian Mixture Model (GMM), greatly improve classification performance over simple classifiers. This change does not require a great increase of computational complexity, provided that a suitable number (5 to 7) of low-level features are carefully chosen. These findings indicate that advanced classifiers can be feasible in hearing aid applications.

In this article, we study how technological components affect the price of hearing aids. The main goals are to determine which functional and technological features have the greatest influence on manufacturer-based prices in the hearing aid industry, and to analyse the price-cost margins at the dispenser level using a unique data set that is compiled from a hearing clinic in West Texas. The result shows that style and signal processing scheme are the two most important determinants of hearing aid price. Other characteristics such as directional microphone, noise cancellation, and a certain shell type are also positively related to price. Further, on average, this particular local dispenser has a markup of about 35% per hearing instrument.

Bone anchored hearing aid is a favorable means of providing hearing in patients with congenital aural atresia and a severe conductive hearing loss. It is a combination of Branemark titanium implant and a bone conduction hearing aid. Objective: To present a case report of Bone Anchored Hearing Aid surgery this is done first time in Nepal. Case Report: We are

OBJECTIVES:
Two main digital signal processing technologies inside the modern hearing aid to provide the best conditions for hearing aid users are directionality (DIR) and digital noise reduction (DNR) algorithms. There are various possible settings for these algorithms. The present study evaluates the effects of various DIR and DNR conditions (both separately and in combination) on listening comfort among hearing aid users.

METHODS:
In 18 participants who received hearing aid fitting services from the Rehabilitation School of Shahid Beheshti University of Medical Sciences regularly, we applied acceptable noise level (ANL) as our subjective measure of listening comfort. We evaluated both of these under six different hearing aid conditions: omnidirectional-baseline, omnidirectional-broadband DNR, omnidirectional-multichannel DNR, directional, directional-broadband DNR, and directional-multichannel DNR.

RESULTS:
The ANL results ranged from -3 dB to 14 dB in all conditions. The results show, among all conditions, both the omnidirectional-baseline condition and the omnidirectional-broadband DNR condition are the worst conditions for listening in noise. The DIR always reduces the amount of noise that patients received during testing. The DNR algorithm does not improve listening in noise significantly when compared with the DIR algorithms. Although both DNR and DIR algorithms yielded a lower ANL, the DIR algorithm was more effective than the DNR.

CONCLUSION:
The DIR and DNR technologies provide listening comfort in the presence of noise. Thus, user benefit depends on how the digital signal processing settings inside the hearing aid are adjusted.

Currently, there are technology barriers inhibiting speech processing systems working under extreme noisy conditions. The emerging applications of speech technology, especially in the fields of wireless communications, digital hearing aids or speech recognition, are examples of such systems and often require a noise reduction technique operating in combination with a precise voice activity detector (VAD). This paper presents a new VAD algorithm for improving speech detection robustness in noisy environments and the performance of speech recognition systems. The algorithm measures the long-term spectral divergence (LTSD) between speech and noise and formulates the speech/ non-speech decision rule by comparing the long-term spectral envelope to the average noise spectrum, thus yielding a high discriminating decision rule and minimizing the average number of decision errors. The decision threshold is adapted to the measured noise energy while a controlled hang-over is activated only when the observed signal-to-noise ratio is low. It is shown by conducting an analysis of the speech/non-speech LTSD distributions that using long-term information about speech signals is beneficial for VAD. The proposed algorithm is compared to the most commonly used VADs in the field, in terms of speech/non-speech discrimination and in terms of recognition performance when the VAD is used for an automatic speech recognition system. Experimental results demonstrate a sustained advantage over standard VADs such as G.729 and adaptive multi-rate (AMR) which were used as a reference, and over the VADs of the advanced front-end for distributed speech recognition.