Individual Differences in Stimulus Frequency Otoacoustic Emission Phase

Otoacoustic emissions (OAEs) are sounds that originate in the cochlea and are measured in the ear canal. OAEs provide a noninvasive tool for investigating cochlear mechanics. Stimulus-frequency OAEs (SFOAEs) are evoked by presenting a single frequency tone, called a probe tone, which have an advantage over other OAEs because they are the least influenced by cochlear nonlinearities. However, because the SFOAE are generated in the cochlea with the same frequency as the stimulus, additional techniques, such as the use of suppressor tones are needed to enable separation of the probe tone from the SFOAE. The primary goal of this investigation was to explore individual differences in SFOAE phase gradient delays. These delays were hypothesized to improve estimates of cochlear health, inferred from hearing thresholds. Efficient measures of phase gradient delays can be obtained using frequency swept tones analyzed with time-frequency filtering, such as the least squares (LS) fit. The least squares fit is a time-frequency filter because the LS fit estimates coefficients for a subset of the total signal which are then used to separate and estimate signals of interest. However, the limitations of the frequency swept tone procedure and LS fit for estimating SFOAEs are not well understood. This investigation first focused on identifying limitations of such SFOAE and refining the LS fitting procedure. It was determined that including a suppressor was necessary for obtaining optimal SFOAE estimates, and the investigation shifted from further refining the LS fitting procedure to exploration of alternative time-frequency analyses which permit clearer characterization of the various latency contributions to suppressor based SFOAEs estimates. The use of a fast, continuous filtered wavelet transform provided a unique perspective on the distribution of SFOAE energy in the time-frequency domain and confirmed that SFOAEs are a sum of both long and short latency contributions. The distributions of long and short SFOAE energy explain some the discrepancies between discrete tone and swept tone SFOAEs procedures. Predicting behavioral thresholds from SFOAE phase, magnitude, or phase and magnitude combined may be misleading when the analysis is not focused around the SFOAE latency contributions from the region where SFOAEs are most affected by cochlear damage. It was revealed that more focus should be given to understanding the best ways to separate the long and the short latencies for different stimulus parameters and individuals, in order to improve sensitivity to cochlear health

Role of The Cochlea and Efferent System in Children with Auditory Processing Disorder

Auditory processing disorder (APD) is characterized by difficulty listening in noisy environments despite normal hearing thresholds. APD was previously thought to be restricted to deficits in the central auditory system. The current work sought to investigate brainstem and peripheral mechanisms that may contribute to difficulties in speech understanding in noise in children with suspected APD (sAPD). Three mechanisms in particular were investigated: cochlear tuning, efferent function, and spatial hearing. Cochlear tuning was measured using stimulus frequency otoacoustic emission (SFOAE) group delay. Results indicate that children suspected with APD have atypically sharp cochlear tuning, and reduced medial olivocochlear (MOC) functioning. Sharper-than-typical cochlear tuning may lead to increased forward masking. On the contrary, binaural efferent function probed with a forward masked click evoked OAE (CEOAE) paradigm indicated that MOC function was not different in typically developing (TD) children and children suspected with APD. A third study with multiple OAE types sought to address this contradiction. Despite numerically smaller MOC inhibition in the sAPD group, MOC function was not significantly different between the two groups. Finally, spatial release from masking, localization-in-noise and interaural time difference thresholds were compared in TD and children with sAPD. Results indicate no significant difference in spatial hearing abilities between the two groups. Non-significant findings at group level in these studies may be related to the large heterogeneity in problems associated with APD. Fragmentation of APD into deficit specific disorders may facilitate research in identification of the specific anatomical underpinnings to listening problems in APD. Prior to conducting studies in children, three studies were conducted to optimize stimulus characteristics. Results of these studies indicate that the MOC may not be especially sensitive to 100 Hz amplitude modulation, as previously reported. Click stimulus presentation rates \u3e25 Hz activate the ipsilateral MOC reflex in typical MOC assays, contaminating contralateral MOC inhibition of CEOAEs. Finally, localization-in-noise abilities of TD children are on par with adults for a white noise masker, but not for speech-babble. This finding suggests that despite maturation of physiological mechanisms required to localize in noise, non-auditory factors may restrict the ability of children in processing complex signals

Arduino-based Digital Advanced Audiometer

The ear is an organ that is able to detect or recognize sound and also has a lot to play in the balance and position of the body. The ears are organs that are very vulnerable to noise. There are two common causes of hearing loss, namely decreased hearing conduction (hearing loss) and nerve hearing (sensorineural hearing loss). To prevent deafness, hearing control is necessary. Generally to test hearing function is done regularly by the ENT doctor at the hospital. This if done many times is deemed ineffective because it is time consuming and requires relatively expensive costs, therefore an early diagnosis of portable hearing loss is designed that is expected to be able to test independently independently over and over again. This tool is equipped with SD Card data storage, where the results of the data can be consulted by a doctor for further diagnosis. This tool uses an arduino uno R3 control, the frequency generator uses IC XR2206. The highest error is at the frequency of 8000 Hz which is 0.52%, but overall all systems on the device are functioning properly and the error is still within tolerance of 10%. From the results of these data, this tool can be recommended for early diagnosis of hearing function

Physiology, Psychoacoustics and Cognition in Normal and Impaired Hearing

otorhinolaryngology; neurosciences; hearin

Physiology, Psychoacoustics and Cognition in Normal and Impaired Hearing

​The International Symposium on Hearing is a prestigious, triennial gathering where world-class scientists present and discuss the most recent advances in the field of human and animal hearing research. The 2015 edition will particularly focus on integrative approaches linking physiological, psychophysical and cognitive aspects of normal and impaired hearing. Like previous editions, the proceedings will contain about 50 chapters ranging from basic to applied research, and of interest to neuroscientists, psychologists, audiologists, engineers, otolaryngologists, and artificial intelligence researchers.