ОПЫТ ИСПОЛЬЗОВАНИЯ В УСЛОВИЯХ МКС ТЕХНИЧЕСКИХ СРЕДСТВ НАУЧНОЙ АППАРАТУРЫ «БАР». ЧАСТЬ 1. АКУСТИЧЕСКИЕ ПРИБОРЫ

The paper presents the results of operational testing of two acoustic components of research equipment «Bar» (a leak detector and ultrasound analyzer) onboard the ISS Russian segment. It was found that the ultrasonic (US) background noise interferes in leak search; besides, it exceeds dramatically the adopted noise level constraint thus impacting crew health and efficiency, and oral communication. The narrow-band noise spectra were measured and the expressed tone property of the US noise was demonstrated. The authors make the point that the present noise level constraints for space habitats do not take into account all realities of the life of cosmonauts and lack a solid medical and acoustic background.

Frequency Masking Effects for Vertical Whole-Body Vibration for Seated Subjects

Masking occurs when the perception of a stimulus is affected or covered by the presence of another signal in close proximity either in time or frequency. This study investigated frequency masking effects across a wide frequency range for whole-body vibration (WBV). The hypothesis that masking effects for WBV might be caused by sub-channels within the Pacinian channel was explored in two experiments. One experiment explored the masking effects of narrow band noise (NBN) on the perception threshold of sinusoidal vibrations; another explored the effect of different widths of NBN on the shift of the perception threshold for vertical vibration of seated subjects. The results show distinct masking effects for WBV based on frequency, albeit they do not support the existence of sub-channels within the Pacinian channel. Neither the typical masking effects associated with critical bands nor threshold shifts dependent on the bandwidth of the narrow band noise can be shown. Thus, the hypothesis does not appear to hold for WBV, but frequency masking must be considered for future studies and tactile applications.

Detection of weak multi-target with adjacent frequency based on chaotic system

As a promising technology in signal detection, the chaotic detection system can significantly improve the accuracy of weak signal detection in strong background noise. It benefits from its characteristics of the sensitivity to the initial condition and the immunity to the Additive White Gaussian Noise. However, the fundamental challenges of the existing chaotic detection system are the sensitivity to narrow-band noise and the influences of multi-target detection with adjacent frequency, which bring great difficulties in the real application. To address these problems, in this article, we focus on the weak multi-target detection with adjacent frequency under the narrow-band noise, and a novel chaotic detection system that integrates the detection algorithm based on period-chaos duration ratio is proposed. In order to enhance the robustness to narrow-band noise, the Melnikov method is used to analyze the Duffing difference system. To realize the detection of weak multi-target with adjacent frequency, we proposed the detection system using the rule named general critical state. Furthermore, simulation results corroborate that the proposed system based on period-chaos duration ratio can achieve satisfactory performance in terms of the weak multi-target detection under narrow-band noise, and it is well investigated by extensive simulation for testing its effectiveness.