Right hemisphere specialization for intensity discrimination of musical and speech sounds

Sound intensity is the primary and most elementary feature of auditory signals. Its discrimination plays a fundamental role in different behaviours related to auditory perception such as sound source localization, motion detection, and recognition of speech sounds. This study was aimed at investigating hemispheric asymmetries for processing intensity of complex tones and consonant-vowel syllables. Forty-four right-handed non-musicians were presented with two dichotic matching-to-sample tests with focused attention: one with complex tones of different intensities (musical test) and the other with consonant-vowel syllables of different intensities (speech test). Intensity differences (60, 70, and 80 dBA) were obtained by altering the gain of a synthesized harmonic tone (260 Hz fundamental frequency) and of a consonant-vowel syllable (/ba/) recorded from a natural voice. Dependent variables were accuracy and reaction time. Results showed a significant clear-cut left ear advantage in both tests for both dependent variables. A monaural control experiment ruled out possible attentional biases. This study provides behavioural evidence of a right hemisphere specialization for the perception of the intensity of musical and speech sounds in healthy subjects.     

Effect of interaural level and phase cues on intervening interference in auditory working memory for loudness

The focus of this study was to gauge the influence of intervening interference on an intensity standard held within auditory working memory through measurement of the just noticeable difference (JND) for intensity. Additionally, the use of interaural phase differences and interaural level differences as spatial cues were employed to identify whether these indicators provided a means for release from interference. A series of tones, both with and without spatial cues, were presented to subjects and responses were obtained using the method of constant stimuli. The JND for intensity was measured in a control condition with a silent inter-comparison interval and three conditions containing intervening tones within the temporal gap between the standard and comparison stimuli. The presence of intervening interference produced a significant increase in the intensity difference needed for discrimination. Further, the provision of spatial cues did not result in a significant release from this interference. These results indicate that a release from interference is not obtained when listeners are required to rely entirely on information used for spatial location (i.e., overall intensity differences and interaural phase/intensity differences) without unique information identifying the sound source to aid in retention of relevant information within auditory working memory.     

A Comparison of Variability among Measurements of Subjective Tinnitus and Objective Stimuli

8 patients with subjective tinnitus were trained in pitch-matching, loudness-matching, and simultaneous-masking tasks using narrow-band noise and/or pure-tone stimuli. Extensive pitch-matching, loudness-matching and masking measurements were then obtained for their tinnitus, after which the same measurements were obtained for objective stimuli which approximated the frequency and intensity of the tinnitus. Variability for pitch and loudness matching to tinnitus was extremely large relative to the same measurements for objective stimuli. This was particularly true for pitch-matching where even the most consistent patients showed variability for matches to their tinnitus which was an order of magnitude greater than for matches to objective stimuli in the same frequency region. No evidence of frequency-specific masking of tinnitus was seen in any of the patients although such evidence was obtained for the masking of objective stimuli. The results suggest that the large variability in matches to tinnitus, and the lack of normal frequency-specific masking of tinnitus in these patients may reflect interactions at levels higher than the end-organ rather than a degradation in peripheral auditory function.     

Simple and Induced Loudness Adaptation

Simple loudness adaptation is the decrease in loudness that takes place when a continuous sound is presented alone for a period of time. Simple adaptation normally occurs only when a sound is soft to begin with, no more than 30 dB above threshold; except for some persons with a retrocochlear lesion, sounds above 30 dB SL do not diminish in loudness over time. However, adaptation can be induced in at least two ways: (1) A steady sound to one ear, presented together with an intermittent sound to the contralateral ear, decreases in loudness by 50-60% within 3 min. (2) An otherwise steady sound that is intermittently increased in level by at least 5 dB becomes softer during its weaker periods. When, for example, a 40-dB tone is increased every 20 s to 60 dB for 15 s, its loudness decreases by about 50% within 3 min. We report measurements of both simple and induced adaptation on 10 persons listening to a 1 000-Hz tone via earphones or from a loudspeaker. The results provide an overview of both types of adaptation. They also permitted a correlational analysis that reveals some of the similarities and differences between the two kinds of adaptation.

L'adaptation de sonie simple est la décroissance de sonie que l'on perçoit au cours du temps à 1'écoute d'un son continu isolé de niveau constant. L'adaptation simple ne se produit qu'avec des sons de faible niveau, á moins de 30 dB du seuil environ. Au-dessus de cette limite on n'observe pas de diminution de sonie en fonction du temps, excepté chez des personnes atteintes de lésions rétrocochléaires. II est cependant possible d'in-duire l'adaptation, et ceci de deux manières au moins. Tout d'abord, si l'on présente simultanément un son continu sur une oreille et un son intermittent sur l'autre, on peut provoquer en 3 min une réduction de 50 à 60% de la sonie du son continu. D'autre part, un son dont on augmente momentanément le niveau d'au moins 5 dB, par intermittence, diminue également de sonie. Par exemple un son de 40 dB, porté toutes les 20 s à 60 dB pendant 15 s, subit une réduction de sonie de l'ordre de 50% en 3 min. Nous présentons ici une série d'expériences résumant les différents cas d'adaptation simple et induite. Les expériences ont été faites avec l'aide de 10 sujets sur un son pur à 1 000 Hz présenté par écouteurs ou par haut-parleur. A partir d'une analyse des variabilés interindividuelles on tente d'évaluer les similitudes et les différences des deux types d'adaptation.     

The Sharpening of cochlear frequency selectivity in the normal and abnormal cochlea

In the normal (anaesthetized) animal cochlea, the frequency threshold curves for single primary fibres are up to an order of magnitude sharper than the analogous functions derived from various reported measurements of the basilar membrane amplitude of vibration. This enhanced neural frequency selectivity is found in the same species and under conditions similar to those in which the mechanical measurements are taken. The sharpening process (at least near threshold) appears to be linear and is not dependent upon lateral inhibitory mechanisms. The variability of the neural frequency selectivity and its vulnerability to metabolic, chemical and pathological influences suggests the hypothesis that the sharpening is due to some form of ‘second filter’ subsequent to the relatively broadly tuned basilar membrane.

All fibres recorded from in the cochlear nerve in the normal cochlea show this enhanced frequency selectivity; in contrast, in pathological cochleas, all fibres, or a substantial proportion, have high-threshold, broadly tuned characteristics, approximating to those of the basilar membrane.

The frequency selectivity of normal cochlear fibres is adequate to account for the analogous psychophysical measures of hearing. It is proposed that loss of this normal frequency selectivity occurs in deafness of cochlear origin, accounting for widening of the critical band. A new hypothesis for recruitment is proposed on this basis.

Finally, invetigations of the cochlear nerve fibre frequency responses under conditions of hypoxia give grounds for the speculation that more than one mechanism is involved in the excitation of a single fibre, related to the separate functioning of the inner and outer hair cells.     

Test-Retest Stability and Effects of Psychophysical Methods on the Speech Loudness Discomfort Level

It is generally agreed that the saturation sound pressure level of a hearing aid should not exceed the patient's loudness discomfort level (LDL) for speech. This study investigated (1) the stability of the test and retest LDLs when obtained on different days using McCandless's and Berger's instructional sets and (2) the effects of a psychophysical method (adjustment versus limits) on the speech LDL using McCandless's instructions. Good reliability was observed since one-half of the listeners had test-retest differences of 2 dB or less and nearly all subjects obtained LDLs within 8 dB. The mean LDLs for the respective methods of adjustment and limits were 86.8 and 92.9 dB SPL, and statistically significant. Additionally, a significant interaction between the two methods was observed. The LDL measurement is also discussed in relation to other tests used to evaluate hearing aid performance.

II est généralement admis que le niveau de saturation en SPL d'un appareil de correction auditive ne doit pas dépasser le niveau du seuil d'inconfort du malade pour la parole (SIP). L'importance de ce SIP nous a done amené a en étudier les conditions d'établissement. Considérant d'abord sur 25 sujets normaux la stabilité des valeurs SIP au cours de plusieurs jours en utilisant les instructions données au sujet soit d'après McCandless, soit d'après Berger, nous n'avons trouvé que de faibles variations (différence test-retest de 2 dB ou moins) pour la moitié des sujets, écart de 8 dB si Ton considere l'ensemble des sujets. Considérant ensuite sur 20 sujets normaux les effets de la méthode psycho-physique employée (méthode des limites ou methode d'adjustement), nous avons pu montrer que les effets sont significatifs: la moyenne des niveaux de SIP se situe à 86,8 dB SPL par la méthode d'adjustement et à 92,3 dB SPL par la méthode des limites. De plus nous avons pu observer une certaine interaction entre les deux méthodes lorsqu'elles sont utilisées successivement. Nous discutons en terminant la valeur comparée du SIP et de celle d'autres tests.     

响度优势联合纯音听阈在患者听功能检测中的应用

【目的】评价响度优势测试与纯音听阈检测相结合用于患者听功能检测的效果。【方法】对2011年1月至2014年12月于本院耳科就诊的386例听力下降患者,在标准环境条件下进行纯音听阈检测与响度优势测试,观察伪聋检测效果。对于伪聋测试阳性患者进一步行听性脑干诱发电位（ABR）阈值检查,验证伪聋测试结果。【结果】386例患者接受了纯音听阈检测提示听功能异常,同时进行响度优势测试,结果提示46例（11．92％）患者因较强的主观意愿、配合不佳、心理或精神疾患、各种因素涉及保险或赔偿等原因影响纯音检测结果,46例患者ABR验证伪聋测试结果准确率达到100％。【结论】响度优势测试能够在一定程度上区分影响听功能检测的因素,将其用于评价主观意愿较强或纯音听阈测试配合不佳人群听功能的可靠性具有一定价值。     

Dopamine receptor stimulation does not modulate the loudness dependence of the auditory evoked potential in humans

Rationale The Loudness Dependence of the Auditory Evoked Potential (LDAEP) has been suggested as a reliable measure of central serotonin function in humans; however, its specificity for the serotonin system remains a topic of debate, with possible modulation of this purported serotonin marker by other neurotransmitters, including dopamine.Objectives We examined the effect of dopaminergic modulation on the LDAEP using the D₁/D₂/D₃ dopamine receptor agonist pergolide and the D₂/D₃ agonist bromocriptine.Methods The study was a double-blind, placebo-controlled repeated-measures design in which healthy participants were tested under three acute treatment conditions: placebo, bromocriptine (2.5 mg), and pergolide (0.1 mg). Changes in the amplitude of the N1/P2 at intensities (60, 70, 80, 90, and 100 dB) were examined at C _Z.Results Acute stimulation of D₁/D₂/D₃ receptors with pergolide and D₂/D₃ receptors with bromocriptine in comparison with placebo had no effect on the LDAEP.Conclusion These findings indicate that acute stimulation of dopamine D₁, D₂, and D₃ receptors does not modulate the LDAEP in humans. Although the findings suggest that the LDAEP may not be modulated by acute changes in dopamine neurotransmission, further studies are needed to fully characterize its dopaminergic sensitivity.     

Advantage of Quasi-Simultaneous Stimulation in ERA

Variations of amplitude, shape, and latency of evoked responses with time may falsify the recorded ear-characteristics. Reduction of such errors is possible by special stimulation and proper averaging. The evoked responses are recorded qusai-simultaneously and not in separate sets for each sound pressure. For this purpose, the memory (2 048 addresses) of the averager is subdivided into 4 or 8 groups. Each of these groups corresponds to a certain sound pressure. The evoked responses are obtained by cyclic repetition of averaging in all groups (scrambling technique); as each group is reached in turn, its corresponding sound pressure is triggered     

Spectral loudness summation as a function of duration for hearing-impaired listeners

Spectral loudness summation was measured for 10- and 1000-ms long bandpass-noise signals with bandwidths in the range of 0.2 to 6.4 kHz centered at 2 kHz for nine listeners with hearing impairment of primarily cochlear origin. Loudness matches between signals with the same duration and different bandwidth were obtained using an adaptive two-interval, two-alternative forced-choice procedure with interleaved tracks. The 3200-Hz wide reference signal had a level of 45 dB or 65 dB SPL. Every signal was individually frequency equalized prior to presentation in order to ensure audibility of all spectral components for the two reference input levels. Generally the same amount of spectral loudness summation for 10- and 1000-ms long signals was obtained for both reference levels. However, some hearing-impaired listeners show, similarly to normal-hearing listeners, a larger spectral loudness summation for short than for long duration signals, indicating that duration effects in spectral loudness summation are caused by retrocochlear processes.