Interaural Intensity Research Articles

The Influence of Asymmetric Hearing Loss on Peripheral and Central Auditory Processing Abilities in Patients With Vestibular Schwannoma.

Asymmetric or unilateral hearing loss (AHL) may cause irreversible changes in the processing of acoustic signals in the auditory system. We aim to provide a comprehensive view of the auditory processing abilities for subjects with acquired AHL, and to examine the influence of AHL on speech perception under difficult conditions, and on auditory temporal and intensity processing. We examined peripheral and central auditory functions for 25 subjects with AHL resulting from vestibular schwannoma, and compared them to those from 24 normal-hearing controls that were matched with the AHL subjects in mean age and hearing thresholds in the healthy ear. Besides the basic hearing threshold assessment, the tests comprised the detection of tones and gaps in a continuous noise, comprehension of speech in babble noise, binaural interactions, difference limen of intensity, and detection of frequency modulation. For the AHL subjects, the selected tests were performed separately for the healthy and diseased ear. We observed that binaural speech comprehension, gap detection, and frequency modulation detection abilities were dominated by the healthy ear and were comparable for both groups. The AHL subjects were less sensitive to interaural delays, however, they exhibited a higher sensitivity to sound level, as indicated by lower difference limen of intensity and a higher sensitivity to interaural intensity difference. Correlations between the individual test scores indicated that speech comprehension by the AHL subjects was associated with different auditory processing mechanisms than for the control subjects. The data suggest that AHL influences both peripheral and central auditory processing abilities and that speech comprehension under difficult conditions relies on different mechanisms for the AHL subjects than for normal-hearing controls.

Examining How Interaural Differences Owing to Head Rotation during Walking Improve the Distance of Auditory Obstacle Perceptions among Individuals with Visual Impairment: A Case Study in Small-Scale Blind Group.

The ability of individuals with visual impairment to recognize an obstacle by hearing is called "obstacle sense". This ability is facilitated while they are moving, though the exact reason remains unknown. This study aims to clarify which acoustical factors may contribute to obstacle sense, especially obstacle distance perception. First, we conducted a comparative experiment regarding obstacle distance localization by individuals who are blind (N = 5, five men with blindness aged 22-42 (average: 29.8)) while they were standing and walking. The results indicate that the localized distance was more accurate while walking than while standing. Subsequently, the head rotation angle while walking and acoustic characteristics with respect to obstacle distance and head rotation angle were investigated. The peaks of the absolute head rotation angle during walking ranged from 2.78° to 11.11° (average: 6.55°, S.D.: 2.05°). Regarding acoustic characteristics, acoustic coloration occurred, and spectral interaural differences and interaural intensity differences were observed in the blind participants (N = 4, four men including two blind and two control sighted persons aged 25-38 (average: 30.8)). To determine which acoustic factors contribute, we examined the threshold of changes for interaural differences in time (ITD) and intensity (IID) (N = 11, seven men and four women with blindness aged 21-35 (average: 27.4)), as well as coloration (ICD) (N = 6, seven men and a woman with blindness aged 21-38 (average: 29.9))-depending on the head rotation. Notably, ITD and IID thresholds were 86.2 μs and 1.28 dB; the corresponding head rotation angles were 23.5° and 9.17°, respectively. The angle of the ICD threshold was 6.30° on average. Consequently, IID might be a contributing factor and ICD can be utilized as the cue facilitating the obstacle distance perception while walking.

The impact of phase on auditory situational awareness

A person’s situational awareness is the ability to understand and correctly interpret the world as it exists around them. One component of auditory situational awareness is sound localization, or the ability to identify where a sound is in space relative to the listener. Different aural cues contribute to a listener’s sound localization: the difference in the time it takes for a sound to reach one ear compared to the other (interaural time difference, or ITD) and the difference in the level of the sound at each ear (interaural intensity difference, or IID). The relative contribution of these interaural differences changes with frequency regime, with ITD/IPD being more dominant at low frequencies and IID being more dominant at high frequencies. These cues, as well as a spectral coloration dependent upon the shape of the listener’s pinna and concha bowl, contribute to what is called the head-related transfer function (HRTF). This study examines the impact of a phase inversion in one ear on a person’s auditory situational awareness. Testing was conducted in accordance with ASA/ANSI S3.71-2019, Method 3 to measure the impact on response time, using full spectrum stimuli as well as band-limited stimuli to focus testing on each aural cue.

Sensitivity to Envelope Interaural Time Differences: Modeling Auditory Modulation Filtering.

For amplitude-modulated sound, the envelope interaural time difference (ITDENV) is a potential cue for sound-source location. ITDENV is encoded in the lateral superior olive (LSO) of the auditory brainstem, by excitatory-inhibitory (EI) neurons receiving ipsilateral excitation and contralateral inhibition. Between human listeners, sensitivity to ITDENV varies considerably, but ultimately decreases with increasing stimulus carrier frequency, and decreases more strongly with increasing modulation rate. Mechanisms underlying the variation in behavioral sensitivity remain unclear. Here, with increasing carrier frequency (4-10kHz), as we phenomenologically model the associated decrease in ITDENV sensitivity using arbitrarily fewer neurons consistent across populations, we computationally model the variable sensitivity across human listeners and modulation rates (32-800Hz) as the decreasing range of membrane frequency responses in LSO neurons. Transposed tones stimulate a bilateral auditory-periphery model, driving model EI neurons where electrical membrane impedance filters the frequency content of inputs driven by amplitude-modulated sound, evoking modulation filtering. Calculated from Fisher information in spike-rate functions of ITDENV, for model EI neuronal populations distinctly reflecting the LSO range in membrane frequency responses, just-noticeable differences in ITDENV collectively reproduce the largest variation in ITDENV sensitivity across human listeners. These slow to fast model populations each generally match the best human ITDENV sensitivity at a progressively higher modulation rate, by membrane-filtering and spike-generation properties producing realistically less than Poisson variance. Non-resonant model EI neurons are also sensitive to interaural intensity differences. With peripheral filters centered between carrier frequency and modulation sideband, fast resonant model EI neurons extend ITDENV sensitivity above 500-Hz modulation.

An optical beam deflection based MEMS biomimetic microphone for wide-range sound source localization

Miniature microphones inspired by the ears of the parasitic fly Ormia Ochracea are an important means to overcome the fundamental size constraint of microphone arrays for sound source localization (SSL). However, the signal demodulation performance and the SSL range of the biomimetic microphones need to be improved. This study aims to develop a miniature biomimetic microphone with good signal demodulation capability and wide SSL range. Specifically, in this paper, an optical beam deflection (OBD) demodulation system was designed and combined with a micro-electro-mechanical system omimetic diaphragm to form a miniature microphone for SSL. The OBD-based biomimetic microphone shows many merits in signal demodulation, including low noise floor (⩽−110 dB), high repeatability of sound pressure measurement, and linear temperature response. The theoretical and experimental results demonstrated that the two wings of the biomimetic microphone have the bi-directional polar patterns with different sizes of lobes at the rocking-mode eigenfrequency, and have omnidirectional response at the bending-mode eigenfrequency. Furthermore, a new SSL method was proposed, which effectively extends the SSL range of the biomimetic microphone at the rocking-mode eigenfrequency to ±90° by combining the interaural intensity difference between the two wings. The proposed OBD-based biomimetic microphone not only has the advantages of small volume and low power consumption, but also has the stable and wide-range SSL capability, which shows that it has a great prospect in the practical applications of SSL, such as wearable devices and rescue robots, etc.

STUDYING THE ACCURACY OF SOUND LOCALIZATION IN NORMAL HEARING SUBJECTS WITH TINNITUS

Tinnitus is a phantom auditory sensation that affects approximately 10- 20 % of the general population. Subjective tinnitus is characterized by an ongoing conscious perception of a sound in the absence of an actual external sound source. Previous studies reported that tinnitus hinder concentration, attention ability and hearing performance, even in normal hearing patients. The sound localization ability is one of the higher functions of the hearing system.Binaural hearing is important for sound Localization as it needed for the perception of interaural intensity differences (IID) and interaural time differences (ITD). As the effect of tinnitus on localization is still controversial. We examine whether tinnitus can affect sound localization ability or not in normal hearing individuals with and without tinnitus using different stimulus at different situation.Aim of the studyThe aim of this study was to test localization accuracy in tinnitus patients with normal hearing.PATIENTS AND METHODS Patients: This study involved two groups of subjects a 20 patient in tinnitus group and 20 patient ingroup who never experienced tinnitus before both groups with normal conventional PTA. The study was conducted in the audiology unit, Otorhinolaryngology department of Alexandria main university hospital.

Evaluating the effectiveness of dichotic training in the elderly adults: a single subject study

Background and Aim: Elderly people usually show poor performance in dichotic listening tasks. In this condition, the left ear being often the weaker one shows a performance below the normal limits. Studies have shown the effectiveness of dichotic listening training in auditory and language processing for adults and children with neurological disorders. This study aimed to develop a home-version of dichotic training and investigate its effectiveness in elderly adults. Methods: Participants in this single-subject interventional study (AB design) were four elderly subjects (two males and two females) aged 65−75 years. The main inclusion criteria were dichotic listening deficit demonstrated by the dichotic digit test (DDT), no neurological or cognitive disorders, and normal hearing threshold. Dichotic listening training was performed with an informal home-version of dichotic interaural intensity difference (DIID) training program for seven weeks. DDT was performed seven consecutive weeks before (phase A) and after the intervention (phase B) at the end of each week. Results: Data were analyzed by single-subject study statistics. Findings demonstrated an improvement in DDT scores for the left ear and decrease in right ear advantage scores in all the elderly adults after DIID training program. It seems that this training program could remediate poor performance in dichotic listening tasks in elderly people. Conclusion: The advantage of this method is that it can be easily done at home and is costeffective. However, further studies are needed to approve the neuroplasticity and structural changes in the brain after the DIID training program in this population. Keywords: Auditory rehabilitation; dichotic training; dichotic listening; elderly; singlesubject study

Binaural sound source localization based on weighted template matching

In robot binaural sound source localization (SSL), locating the direction of the sound source accurately in the shortest time is important. It refers to the algorithm complexity, but even more to the shortest duration of the required signal. A novel binaural SSL method based on feature and frequency weighting is proposed. More specifically, in the training stage, the direction-related interaural cross-correlation function(CCF) and interaural intensity difference(IID) in each frequency band are calculated under noiseless conditions, which are considered the templates. In the testing stage, first the cosine similarities between the CCF and IID of the test signal and templates are calculated in all features and frequency bands. Then, the direction likelihood can be obtained by weighting the similarities. Finally, the direction with maximum likelihood is specified as the direction of the sound source. Experiments were carried out on CIPIC dataset subject 003 with different noises in the noisex-92 dataset and demonstrated that the method can accurately locate the sound source with a short signal duration.

Estimation of sound source directions using a biological coupled sensor array with a multistage iteration method

Sound source localization (SSL) uses interaural time difference (ITD) or interaural intensity difference (IID) cues, and most of the methods based on ITD are limited by the aperture of array. However, a kind of parasitoid fly called Ormia ochracea with coupled ears has a remarkable ability to localize the calling of the host regardless of fly’s small body size. It is believed that the ITD is amplified by the auditory organ of Ormia. This paper proposes a biological coupled sensor array, which is generalized by the structure of Ormia’s ear. The array contains two pairs of microphones with a multistage iteration passive localization algorithm. Four microphones are symmetrically placed on the x- and y- axis of the array respectively. The proposed localization algorithm transforms the received signals to coupled signals by means of coupled calculator. The phase difference between two coupled signals is amplified. The ITD information is achieved based on the generalized cross-correlation function and amended by iteration of the coupled calculator and phase shift operation. To validate the effect of the proposed sensor array, experiments are conducted using sine waves from different angles of incidence. The ITDs between two microphones are amplified as expect. The localization results are achieved with localization error less than 0.5 degree with single-source cases in the experiment. The localization error is reduced by using this biological coupled sensor array with the multistage iteration method.

Behavioral and Hemodynamic Changes Following Dichotic Training in Patients with Neurological Deficits of the Auditory Nervous System: A Case Series.

Dichotic listening occurs when one attends to different acoustical messages presented simultaneously to both ears. This is important for understanding speech in compromised listening situations, such as background noise. Deficits in dichotic listening can be remediated by participating in auditory training. We present two patients with binaural integration deficits who underwent dichotic interaural intensity difference (DIID) training. The purpose of this investigation is to demonstrate improvement of dichotic listening deficits following DIID training in neurological patients seen clinically for hearing issues. This was a case series utilizing a pre- and posttreatment design. This case series utilized two female participants who demonstrated binaural integration deficits during an auditory processing evaluation. The participants underwent a pretraining auditory processing evaluation and functional magnetic resonance imaging (fMRI). Participants then underwent 12, 30-minute DIID training sessions followed by posttreatment auditory processing evaluations and fMRI. Data was collected at the pretreatment appointment and then immediately following the completion of the training. Each patient demonstrated varying degrees of improvement on the posttreatment assessment. Case 1 showed significant improvement on the Speech-in-Noise-Revised (SPIN-R) test. fMRI showed changes in activation patterns following training. Case 2 demonstrated improved scores on the Dichotic Digits Test and SPIN-R and increased activation of the calcarine sulcus following training. Dichotic training can be an efficacious treatment for binaural integration deficits and may show evidence of improving speech understanding in noise. This case series demonstrates a promising therapy to help patients improve auditory function by improving dichotic listening skills.

Current Perspectives in Management of Unilateral Sensorineural Hearing Loss and Single Sided Deafness

Unilateral Sensorineural Hearing Loss (USNHL) or even Single Sided Deafness (SSD) were mistakenly believed in the past that they could not induce a notable negative effect on the average individual adult. Respectively, a child with USNHL could eventually develop typically and adequately with no particular challenges. Today, it is well established that both children and adults with USNHL and SSD experience difficulties locating sound sources than their normal peers attributable to the concomitant deprivation of data utilized for localization; interaural time differences along with interaural intensity differences, especially for high frequency sounds. Moreover, USNHL and SSD patients suffer from the absence of the binaural benefits that permit people with bilateral Normal Hearing (NH) to perform relatively well in challenging listening environments. These benefits encompass binaural summation that causes improved speech perception, and binaural release from masking that facilitates word recognition in noise. Rising treatment strategies, involving various type of amplification, Assistive Listening Devices (ALSs) and Cochlear Implantation, can greatly widen our overall approach regarding USNHL and / or SSD. Nevertheless, most recent evidence points out that both prompt and adequate intervention is crucial to promote optimal outcomes.

Discrimination of interaural intensity differences and monaural intensity increments

This study assessed the equivalence of a binaural task (two-interval discrimination of interaural intensity differences, IIDs) and a monaural two-interval increment-discrimination task, in which each interval consisted of two noise bursts of different intensities, with listeners identifying the interval with the larger intensity change. Stimuli were broadband noise, with trial-by-trial feedback provided. An overall level rove between intervals forced listeners to compare the two signals within each interval (across ears in the binaural task and across bursts in the monaural task). Both tasks involved presentation of four signals of different intensities, yielding the same optimal decision statistic. Assuming (1) discrimination of IIDs across intervals amounts to discrimination of lateral position and (2) variability in lateral position increases with IID leads to a prediction of Weber's law. Functions relating threshold IID delta (or monaural increment delta) in dB to the standard IID (or increment) in dB had nearly equal slopes in binaural (0.054) and monaural (0.058) conditions. While the derived binaural decision statistic is based on discrimination of an emergent percept of the stimulus (intracranial position), the similarity of results suggests that monaural increment-discrimination may be based on discrimination of a similarly emergent percept (a loudness step). [Work supported by NIH R01DC00683.]

Comparison of Persian staggered spondaic word test’s scores before and after rehabilitation in children with amblyaudia

Background and Aim: Amblyaudia is a diag­nostic issue in central auditory processing disor­der (CAPD), which is characterized by asymme­try in dichotic listening performance. This disor­der negatively affects the academic performance of children by influencing their information pro­cessing, reading, attention, etc. The present study aimed to investigate the effect of the dichotic interaural intensity difference (DIID) training on all auditory processing categories of the Buffalo Model using the Persian staggered spondaic word (P-SSW) test. Methods: The study was conducted on 17 chil­dren (11 girls and 6 boys) aged 8−12 years old diagnosed with amblyaudia. All children were first evaluated by the P-SSW test, and then parti­cipated in 10−12 sessions of the DIID training. The P-SSW test was taken again after completing the training program in order to evaluate the training effect. Results: The paired t-test results showed a sig­nificant reduction in the mean scores of decoding (p < 0.001) and tolerance fading memory (p < 0.004) categories as well as the total mean score of P-SSW test after training. The Wilcoxon test also showed the effect of this training on the integration category (p < 0.025). The McNemar test, however, showed no statistically significant effect of the DIID training on the organization category. Conclusion: The DIID training causes signifi­cant improvement in some central auditory pro­cessing categories of the Buffalo Model, inclu­ding decoding, tolerance fading memory and integration. Keywords: Dichotic interaural intensity difference; central auditory processing disorder; amblyaudia

Visual Gender Cues Guide Crossmodal Selective Attending to a Gender-Congruent Voice During Dichotic Listening.

Visual input of a face appears to influence the ability to selectively attend to one voice over another simultaneous voice. We examined this crossmodal effect, specifically the role face gender may have on selective attention to male and female gendered simultaneous voices. Using a within-subjects design, participants were presented with a dynamic male face, female face, or fixation cross, with each condition being paired with a dichotomous audio stream of male and female voices reciting different lists of concrete nouns. In Experiment 1a, the female voice was played in the right ear and the male voice in the left ear. In Experiment 1b, both voices were played in both ears with differences in volume mimicking the interaural intensity difference between disparately localized voices in naturalistic situations. Free recall of words spoken by the two voices immediately following stimulus presentation served as a proxy measure of attention. In both sections of the experiment, crossmodal congruity of face gender enhanced same-gender word recall. This effect indicates that crossmodal interaction between voices and faces guides auditory attention. The results contribute to our understanding of how humans navigate the crossmodal relationship between voices and faces to direct attention in social interactions such as those in the cocktail party scenario.

Auditory localisation in hearing impaired schoolchildren with and without hearing aids

Auditory localisation is part of central auditory processing. The study examined the impact of hearing aids on the auditory localisation ability of non-linguistic stimuli in hearing impaired schoolchildren. Above threshold acoustic signals were presented to 20 children (7-17 years) in a free field condition with 45 loudspeakers placed on a semicircular array. All participants had a bilaterally symmetric moderate sensorineural hearing loss (WHO grade 2) and used behind the ear style (BTE) hearing aids with conventional earmolds. The children had to indicate the position of the signal by a laser pointer. Both high- and low-frequency noise bursts were employed in the tests to separately address spatial auditory processing based on interaural time differences and interaural intensity differences. The examination was performed with and without BTE hearing aids. There was no significant difference between results in the aided and the unaided condition: neither for the different frequency bands nor for the signal positions. The auditory localisation of the hearing impaired children was reduced by 3°-4° for frontal and 5°-11° for lateral positions compared to normal-hearing children. There was no age-relation. In our experimental setting, BTE hearing aids could not compensate the impaired auditory localisation ability of children with sensorineural hearing loss.

Spatial release from masking in a bottlenose dolphin Tursiops truncatus.

The impact of maskers on the receiving beam of a bottlenose dolphin, Tursiops truncatus, was investigated using the auditory evoked potential (AEP) method. The test signal was a train of tone pips with a 64 kHz carrier frequency. The stimulus produced AEPs as a sequence of waves replicating the pip rate: the rate following response (RFR). The masker was band-limited noise, with a passband of 45 to 90 kHz and a level of 105 dB re 1 μPa. Masker azimuths were at 0°, ±30°, ±60°, and ±90° relative to the head midline. The receiving beam was evaluated in terms of the RFR threshold dependence on the signal azimuth. The masked thresholds were higher than the baseline thresholds, which appeared mostly as a shift rather than a deformation in the receiving beam. The largest threshold shift appeared when the masker source was located in the most sensitive direction (zero azimuth); at lateral masker source positions, the threshold shift decreased. When the masker source was not at the head midline, the masked thresholds were higher at signal positions ipsilateral to the masker source than at positions contralateral to the masker source. The largest asymmetry was observed at the 30° masker azimuth in conjunction with the ±30° and ±120° signal azimuths; the asymmetries were 5.6 and 8.1 dB, respectively. This masking asymmetry was lower than expected from the previously found interaural intensity difference, which may be explained by the conflict between the test signal and the masker when it appeared at a binaural level of the auditory system.

Cytoarchitecture of the superior olivary complex of three neotropical species of bats (Noctilio leporinus, Phyllostomus hastatus and Carollia perspicillata) with different foraging behavior.

The understanding of the echolocation by studying different auditory nuclei of echolocating bats can be an important link in elucidating questions arising in relation to their foraging behavior. The superior olivary complex (SOC) is the primary center for processing the binaural cues used in sound localization since echo locating bats rely on acoustic cues to navigate and capture prey while in flight. The present study was taken to test the hypothesis that the SOC of echolocating neotropical bats with different foraging behavior will exhibit morphological variations in relative size, degree of complexity and spatial distribution. The brains were collected from six male adult bats of each species: Noctilio leporinus (fish eating), Phyllostomus hastatus (carnivorous/omnivorous) and Carollia perspicillata (fruit eating). They were double-embedded and transverse serial sections were cut and stained with cresyl fast violet. The SOC measured as 640 ± 70 µm in the N. leporinus bat, 480 ± 50 µm in the P. hastatus and 240 ± 30 µm in the C. perspicillata bat. The principal nuclei of the SOC of in all three bats were the LSO, MSO and MNTB. The MSO and LSO were very well developed in N. leporinus bats. The MSO of N. leporinus bat subdivided into DMSO and VMSO. The main cell type of cells present in MSO and LSO are dark staining multipolar cells in all the bats studied. The well-developed MSO and LSO of N. leporinus bats indicate that these bats are highly sensitive to low frequency sounds and interaural intensity differences, which help these bats to forage over water by using various types of echolocation signals. The average size of SOC in P. hastatus and C. perspicillata bats can be attributed to the fact that these bats use vision and smell along with echolocation to forage the food.

Intrinsic and Miniature Postsynaptic Current Changes in Rat Principal Neurons of the Lateral Superior Olive after Unilateral Auditory Deprivation at an Early Age

Unilateral auditory deprivation results in lateralization changes in the central auditory system, interfering with the integration of binaural information and thereby leading to a decrease in binaural auditory functions such as sound localization. Principal neurons of the lateral superior olive (LSO) are responsible for computing the interaural intensity differences that are critical for sound localization in the horizontal plane. To investigate changes caused by unilateral auditory deprivation, electrophysiological activity was recorded from LSO principal neurons in control rats and rats with unilateral cochlear ablation. At one week after unilateral cochlear ablation, the excitability of LSO principal neurons on the side ipsilateral to the ablation (the ablated side) was greater than that on the side contralateral to the ablation (the intact side); however, the input resistance increased on both sides. Furthermore, by analysing the miniature inhibitory postsynaptic currents and miniature excitatory postsynaptic currents, we found that unilateral auditory deprivation weakened the inhibitory driving force on the intact side, whereas it strengthened the excitatory driving force on the ablated side. In summary, asymmetric changes in the electrophysiological activity of LSO principal neurons were found on both sides at postnatal day 19, one week after unilateral cochlear ablation.

Speech Comprehension and Its Relation to Other Auditory Parameters in Elderly Patients With Tinnitus.

Deteriorated speech comprehension is a common manifestation of the age-related decline of auditory functions (presbycusis). It could be assumed that when presbycusis is accompanied by tinnitus, general hearing functions, and particularly comprehension of speech in quiet and speech in noise (SIN), will be significantly affected. In this study, speech comprehension ability and other parameters of auditory function were assessed in elderly subjects with (T, n = 25) and without (NT, n = 26) tinnitus, aiming for examination of both peripheral and central auditory processing. Apart from high-frequency audiograms in quiet and in background noise, speech recognition thresholds in silence or in competitive babble noise, and the ability to understand temporally gated speech (GS), we measured also sensitivity to frequency modulation (FM) and interaural delay, gap detection thresholds (GDT), or the difference limens of intensity. The results show that in elderly participants matched by age (mean ages around 68 years), cognitive status (median MoCA scores around 27), and hearing thresholds [median pure-tone averages (PTA) around 16 dB hearing loss (HL)], tinnitus per se has little influence on speech comprehension. The tinnitus patients also show similar GDT, sensitivity to interaural intensity difference, and sensitivity to FM as the NT subjects. Despite these similarities, nevertheless, significant differences in auditory processing have been found in the tinnitus participants: a worse ability to detect tones in noise, a higher sensitivity to intensity changes, and a higher sensitivity to interaural time differences. Additional correlation analyses further revealed that speech comprehension in the T subjects is dependent on the sensitivity to temporal modulation and interaural time delay (ITD), while these correlations are weak and non-significant in the NT subjects. Therefore, despite similarities in average speech comprehension and several other parameters of auditory function, elderly people with tinnitus exhibit different auditory processing, particularly at a suprathreshold level. The results also suggest that speech comprehension ability of elderly tinnitus patients relies more on temporal features of the sound stimuli, especially under difficult conditions, compared to elderly people without tinnitus.

A child with (central) auditory processing disorder: a case report

Background: Subjects with (central) auditory processing disorder (C)APD may manifest a range of complaints including difficulty in spee­ch perception in noise, following directions, and discrimination of similar speech sounds. Other disorders may also have the same behavioral manifestations. The Case: Here we present an 8-year-old boy who was misdiagnosed and mismanaged as a child with learning disability. His speech, language and cognition problems at initial eva­luation included semantic problem, a short len­gth of speech, phonological sound disorder, and attention disorder. He showed abnormality in the dichotic digits test with free recall approach and monaural selective auditory attention test. Based on his performance and test results, he was suffering from (C)APD especially in dicho­tic listening and speech perception in com­petition. It was suggested that binaural hearing training with differential interaural intensity, informal localization training including loca­lization clock, and auditory training in noise be added to his classic auditory training program. Conclusion: Studying this subject was impor­tant because (C)APD diagnosis needs a team approach. Evidently, the parents, teacher and speech-language pathologist (SLP) did not seek a central auditory processing evaluations early enough but some of his behaviors could poten­tially be a red flag for (C)APD and could guide SLPs to refer him for central auditory testing. As we may not be able to evaluate central auditory processing in the early childhood, iden­tifying the possible (C)APD signs by a SLP may help them to plan a more suitable program even before reaching a definite diagnosis.