[The analysis of acoustic activity unsynchronized with the stimulus with the use of TEOAE]. / Analiz akusticheskoi aktivnosti, ne sinkhronizirovannoi so stimulom, pri registratsii zaderzhannoi vyzvannoi otoakusticheskoi emissii.

The presence of ambient noise or the troubled child's behavior during the registration of transiently induced optoacoustic emission (TEOAE) can lead to false positive results at the first stage of hearing screening. The aim of this study is to evaluate the effectiveness of the noise reduction method based on weighted averaging of the data in the frequency and time slot, to check TEOAE, and to improve the effectiveness of universal hearing screening. Particular attention is paid to the analysis of the origin of noise recorded during the UAE. PATIENTS AND METHODS: We have developed a method of noise reduction, based on weighted averaging of the data in the frequency and time cells. In this study, 20 people were examined (9 adults and 11 children). TEOAE was performed using the probe of the ILO 288 instrument manufactured by Otodinamics Ltd. that was connected to the E-MU 0204 sound card. The probe microphone was connected through the preamplifier to one input channel of the sound card, and the second channel was used to receive a signal from the ECG and the respiration recorder. Thereafter, the data thus obtained were processed by several methods, including the method of averaging in the frequency and time slot designed to average a set of implementations that contain a noisy signal. The comparison of the results of the use of noise suppression method based on weighted averaging of the data in the frequency and time cells showed that it increases the accuracy of TEOAE. MAIN RESULTS: Our work suggests that the use of the noise suppression method based on weighted averaging of the data in the frequency and time cells, increases the accuracy of TEOAE. Similar results were obtained by the weighted averaging method.

Hand-held device for OAE-based screening.

In this paper, the main concepts realized in a handheld OAE device are described. These concepts are: weighted averaging, non-linear MLS technique, acoustic probe with flat response, electronic passport of the probe, communication with clinical databases, special language for device control.

Effect of stimulation parameters on electrically evoked auditory brainstem responses.

It is evident that the conventional technique for cochlear implant adjustment is not suitable for children in their first years of life. In order to find a solution to this problem, the possibility of electrically evoked auditory brainstem response (EABR) recording was investigated. EABRs were recorded in 9 patients with the Nucleus multichannel cochlear implant. The main problems that have to be solved during EABR recording in cochlear implantees are: i) EABR distortion due to the stimulus artefact: and ii) difference in the stimulus presentation rate during EABR registration (low pulse rate) and conventional psychophysical threshold estimation (high pulse rate) in cochlear implant patients. The influence of stimulus artefact on the recording results was minimized by setting the implant to the widest amplifier frequency band and by zeroing the initial segment containing the stimulus artefact with subsequent zero-phase digital filtering. The dependence of the EABR amplitude and latency on the stimulus intensity, width, electrode location and interstimulus interval was investigated. It was concluded that despite the difference revealed between absolute values of EABR thresholds and psychophysical threshold levels, it is possible to calculate implant adjustment parameters based on the EABR data with the proper correction applied.

Ipsilateral suppression of transient evoked otoacoustic emission: role of the medial olivocochlear system.

Contralateral sound stimulation produces suppression of transient evoked otoacoustic emission (TEOAE), which is attributed to a reflex activation of the medial olivocochlear system. More pronounced suppression of TEOAE produced by ipsilateral masking could involve efferent-mediated effects along with effects of cochlear origin. However, this has not been investigated so far. Therefore, changes of click-evoked OAE under ipsi- and contralateral forward masking by clicks and noise-bursts were investigated in an extremely long-lasting experiment in one normal-hearing volunteer. The reduction of TEOAE under ipsilateral click-to-click forward masking was maximal during the first milliseconds after masker delivery implying that predominant role of the cochlear processes in TEOAE ipsilateral suppression. Ipsilateral forward masking by noise burst revealed additional TEOAE suppression with longer latency. Its time course was similar to that of the contralateral masking effect. The latter data suggest the involvement of the medial olivocochlear system in TEOAE ipsilateral suppression.