Dependence of binaural loudness summation on interaural level difference and frequency for pure tones

Most of the existing loudness models are based on the diotic listening hypothesis,though human beings always hear in dichotic listening conditions.In this situation,the arithmetic mean of loudness at both ears is usually taken as the approximate value of overall perceived loudness,unaffected by the interaural level difference(ILD).The present work investigated the overall perceived loudness for pure tones in dichotic listening conditions through a subjective experiment.Two experimental procedures and systematic errors were investigated to prove the accuracy of the subjective test.The results showed that fluctuation was insignificant in the low frequency range,while apparent fluctuation of overall loudness could be observed at a high frequency.The overall loudness deviated from the arithmetic mean value as the ILD became larger.A revised model for overall loudness in dichotic listening conditions was proposed.The proposed model and experiment are consistent.

A study on vestibular-evoked myogenic potentials via galvanic vestibular stimulation in normal people

Objectives: The aim of our study is to examine vestibular-evoked myogenic potentials(VEMPs) elicited by the galvanic vestibular stimulation in the sternocleidomastoid muscle(SCM) in healthy subjects for clinical applications of auditory neuropathy or vestibular neuropathy in the future.Methods: We enrolled sixteen healthy subjects to record the average responses of SCM to galvanic vestibular stimulation(GVS) [current 3 mA;duration 1 ms] by electromyography(EMG). SPSS 18.0 software was used to analyze the obtained data for mean and standard deviation.Results: In all healthy subjects mastoid-forehead galvanic vestibular stimulation produced a positive-negative biphasic EMG responses on SCM ipsilateral to the cathodal electrode. The latency of p13 was 11.7 ± 3.0 ms. The latency of n23 was 17.8 ± 3.4 ms. The amplitude of p13-n23 was147.0 ± 69.0 μV. The interaural asymmetry ratio(AR) of p13, n23 latency and the amplitude was respectively 0.12 ± 0.09, 0.08 ± 0.08 and0.16 ± 0.10.Discussions: Galvanic vestibular stimulation could elicit biphasic EMG responses from SCM via the vestibular nerve but not from the otolith organs. Galvanic stimulation together with air conducted sound(ACS) or bone conducted vibration(BCV) can elicit VEMPs and may enable the differentiation of retrolabyrinthine lesions from labyrinthine lesions in vestibular system.

Head-related transfer function database and its analyses

Based on the measurements from 52 Chinese subjects (26 males and 26 females), a high-spatial-resolution head-related transfer function (HRTF) database with corre- sponding anthropometric parameters is established. By using the database, cues relating to sound source localization, including interaural time difference (ITD), interaural level difference (ILD), and spectral features introduced by pinna, are analyzed. Moreover, the statistical relationship between ITD and anthropometric parameters is estimated. It is proved that the mean values of maximum ITD for male and female are significantly different, so are those for Chinese and western sub- jects. The difference in ITD is due to the difference in individual anthropometric parameters. It is further proved that the spectral features introduced by pinna strongly depend on individual; while at high frequencies (f≥ 5.5 kHz), HRTFs are left-right asymmetric. This work is instructive and helpful for the research on bin- aural hearing and applications on virtual auditory in future.