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Speech compression or speech coding is inevitable for effective communication of speech signals in resource limited scenarios and researcher's have been working on achieving lower and lower transmission bit rates (BR) without much compromise on the quality of speech. Medium BR hybrid speech coding schemes have gained much interest in the recent years with most of them based on CELP, the basic medium bit-rate coding scheme. In this work, we provide an insight to the capabilities of compressive sensing (CS) in speech processing and propose a novel idea in the quantized framework. Three major aspects demonstrated in this paper are (1) Inherent denoising of noisy speech by the CS based coder along with compression (2) Quantization of CS measurements to achieve medium transmission bit-rates and (3) Enhancement of quality and compression performance of the coder with better sparse representations of speech using dictionaries. The results indicate that the proposed scheme offers better compression in comparison with basic Gaussian codebook CELP. The CS scheme has the added advantage of inherent noise suppression and provides more robustness to background noise in comparison with parameter extraction based medium bit-rate speech coding systems.

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Magnetism is an omnipresent phenomenon with potential applications in various fields. Immense research has gone into the ways in which magnetism can be used for practical applications. Apart from day-to-day applications such as mobile phones, laptops, railways etc., it finds applications in the aerospace sector as well, for interplanetary studies, navigation, and space robotics. Accurate sensing of the magnetic field is essential for these applications, for which efficient magnetic sensors are used. The precise calibration of these sensors is necessary to quantify various parameters and associated uncertainties to ensure accuracy. For this, a field simulator which can generate a highly accurate and controlled magnetic field is essential. The design and development of a Tri-axis Helmholtz coil field simulator based on Model Reference Adaptive Controller (MRAC) is presented here. It provides a simple, compact, and cost-effective solution for aerospace magnetic sensor calibration. The proposed system offers a uniform magnetic field with 0.1% uniformity within a cubic volume space of 3375cm 3 . The intensity of the magnetic field can be varied within the full-scale range of 200µT with a resolution of 0.01µT by appropriate current control. The MRAC was finalized after a detailed analysis with various types of controllers such as basic PI, PID and LQI, as it provides precise closed loop control and field stability, which is of paramount importance for aerospace magnetic sensor calibration. It exhibits lesser computational complexity, lower settling time, better adaptability to external field disturbances, lesser overshoot and higher phase margin indicating better closed loop stability compared to other controllers.