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Our results suggest that reduced outer hair cell activity, as detected by reduced DPOAE levels, may manifest as tinnitus even before there is a shift on hearing threshold. We also postulate that further reduction of cochlear outer hair cell activity, as shown by further reduced DPOAE levels, may actually terminate the source of tinnitus.

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This paper discusses the comparison of micro machining process using conventional and micro wire electrical discharge machining (WEDM) for fabrication of miniaturized components. Seventeen toothed miniaturized spur gear of 3.5 and 1.2 mm outside diameter were fabricated by conventional and micro WEDM respectively. The process parameters for both conventional and micro WEDM were optimized by preliminary experiments and analysis. The gears were investigated for the quality of surface finish and dimensional accuracy which were used as the criteria for the process evaluation. An average surface roughness (R a ) of 50 nm and dimensional accuracy of 0.1-1 µm were achieved in micro WEDM. Whenever applied conventional WEDM for meso/micro fabrication, a R a surface roughness of 1.8 µm and dimensional accuracy of 2-3 µm were achieved. However, this level of surface roughness and dimensional accuracy are acceptable in many applications of micro engineering. A window of conventional WEDM consisting of low energy discharge parameters is identified for micromachining.

To our best knowledge, this is the first report of vestibulocochlear nerve aplasia and severe facial nerve hypoplasia in a case of ipsilateral duplication of the internal auditory canal. High resolution gradient echo magnetic resonance imaging sequences are advocated for assessment of neural integrity in patients with an abnormal internal auditory canal and facial and/or vestibulocochlear nerve dysfunction.

In spite of extensive research conducted in studying pitch memory processing, knowledge about the functional anatomy of the brain while performing pitch discrimination task is still lacking. The purpose of this study was to investigate the effects of background noise and tonal frequencies on brain activation during a pitch discrimination task. Thirteen participants were presented with categories of low-and high-frequency tones during an fMRI scan. They listen, recognize and discriminate the target tone with the last tone in a series of four distracting tones. Cortical responses during which the participants engaged with the pitch discrimination task were explored globally and differentially with tonal frequency and background condition as factors. Similar integrative network consisting of bilateral superior temporal gyrus, pre-central gyrus, cerebellum, insula, putamen, inferior parietal lobe and supplementary motor area is established during the four pitch discrimination task conditions. The bilateral A1 and right M1 are effectively activated by noise and action respectively. Background noise increases the participants' performance hence equalizing that in quiet, while participants performed significantly better in discriminating low-frequency tones as compared to high-frequency tones. This study revealed an integrative network that consists of areas responsible for pitch discrimination strategy. The bilateral primary auditory cortex played important roles in increasing participants' pitch discrimination performance in noisy surrounding and in discriminating low frequency category of tones.