Sharif Digital Repository

In this thesis we have investigated and improved the signal processing techniques which are used for monitoring the heart abnormalities in terms of ECG (ElectroCardioGram) signals in order to detect heart attacks before they occur. De-noising ECG signals are one of the most important research topics in computer and electrical engineering fields. There are many different algorithms for de-noising signals in various domains. It usually is needed to propose a suitable algorithm for each specific system. In some cases instead of developing a new algorithm, we could modify the available ones for de-noising in our system. ECG signals are output from an electrocardiograph which measures electrical... 

This thesis proposes a novel method for enhancing the speech signal based on compressed sensing. Compressed sensing, as a new rapidly growing research field, promises to effectively recover a sparse signal at the rate of below Nyquist rate. This revolutionary technology strongly relies on the sparsity of the signal and incoherency between sensing basis and representation basis. Exact recovery of a sparse signal will be occurred in a situation that the signal of interest sensed randomly and the measurements are also taken based on sparsity level and log factor of the signal dimension.
In this research, compressed sensing method is proposed to reconstruct speech signal and for noise... 

Recently, many studies show that Augmented Reality (AR) and Automatic Speech Recognition (ASR) can help people with disabilities. In this thesis we examine the ability of combining AR and ASR technologies to implement a new system for helping deaf people. This system can instantly take a narrator's speech and convert it into a readable text and show it directly on AR display. Also, with this system, people do not need to learn sign-language to communicate with deaf people. To improve the accuracy of the system, we use Audio-Visual Speech Recognition (AVSR) as a backup for the ASR engine in noisy environments. AVSR is one of the advances in ASR technology that combines audio, video and facial... 

Statistical learning plays a key role in many areas of science [38]. An example of learning problems is image matching, image matching plays an important role in many aspects of computer vision.Computers can be used in intelligent tasks, which are followed by logical inference, for example, visual scenes (images or videos) or speech (audios). For humans visual system of such task are performed hundreds of times every day so easily sometimes without any awareness. In this thesis we focus on the image matching phase which is the first phase of the classification process. One of the popular image matching methods is Scale Invariant Feature Transform (SIFT) which our proposed method is based on... 

Speech enhancement in noisy environments improves the quality and intelligibility of speech and reduces communication fatigue. High performance speech enhancement models are based on Bayesian estimation models, requiring estimations of the parameters of the functions that describe the likelihood and the prior distributions of the signal and noise processes. Two Bayesian speech enhancement models which are used in this thesis are Bayesian-Kalman filter and Bayesian MAP estimation.In real time applications including VoIP, in addition to additive noise, packet loss or packet delays might also occur. In real time communications the receiver terminal replaces silence for the duration of lost... 

Radar is a type of active remote sensing instrument that is used to create images of an object, such as a landscape. Synthetic Aperture Radar or SAR is another type of radar which is typically mounted on a moving platform such as an aircraft or a spacecraft and uses the motion of the antenna over the target region to provide finer spatial resolution than is possible with conventional beam-scanning radars. In fact SAR is an advanced form of Side-Looking Airborne Radar (SLAR). The movement of SAR antenna acts as another form of aperture; this aperture combined with the physical aperture of the antenna creates a large "synthetic" antenna aperture (the "size" of the antenna) which enables higher... 

This thesis proposes a novel method for enhancing the image signal based on compressed sensing. Compressed sensing, as a new rapidly growing research field, promises to effectively recover a sparse signal at the rate of below Nyquist rate. This revolutionary technology strongly relies on the sparsity of the signal and incoherency between sensing basis and representation basis. Exact recovery of a sparse signal will be occurred in a situation that the signal of interest sensed randomly and the measurements are also taken based on sparsity level and log factor of the signal dimension. In this research, compressed sensing method is proposed to reduce the noise and reconstruct the image signal.... 

In process of making prosthetic limb, each of the prosthetic limbs must be costume fitted and built since each amputation of the patient is unique. The design and fabrication process of artificial limb consists of several different steps and begins with a precise measurement process that will be used to design the prosthetic limb. If possible, a prosthetist begins taking measurements before the patient's limb is even amputated, so that the fabrication process can get started. Today, much research which has been done in Augmented Reality and 3D scanning technologies shows that these technologies can help people with disabilities to have better experience in their life by using them in... 

In speech processing, reflections of sound wave in a bounded space are considered as speech reverberation. Although for musical instruments and their related recording devices these reflections are useful, however, some other applications face serious problems receiving them along with speech signal. Reverberation causes speech degradation and intelligibility as well as highly quality reduction. Dereverberation algorithms are essential for Automatic Speech Recognition (ASR), telecommunication and hearing aid devices, which are some of the mostly used applications. While dereverberation itself is a challenging problem, dereverberate a speech signal recorded only by one microphone (channel)... 

Nowadays financial and business jobs without new technologies and new methods to manage are not that much useful. Managers are searching for all new methods in different areas for improving their profit, quality of services or increasing number of their customers. Because of this, they would check some ways to prove their issues. But the point is that they should have a great view about their products, customers and generally their own shop. One of the perfect methods to present the form and relation between their favorite factors is complex network. With complex network they can have perfect sight about their system. Also, with some remarkable and noticeable ways they can categorize their... 

The objective of this thesis is to develop a speech enhancement technique that can be applied for enhancement of speech degraded by additive background noise. The important aim of speech enhancement is to get better result after transmission at the receiver side. Additive noise such as White Gaussian Noise, Street Noise, Babble Noise, etc, is one of the speech enhancement problems degrading the intelligibility and quality of the signal. The important applications for speech enhancement are VOIP, Telephone services, mobile telephony, hands free voice control, communication between pilot cockpit, etc. Wiener filters are the mostly used techniques to reduce the uncorrelated additive noise with... 

This thesis aims to develop speech enhancement methods in the presence of additive noise, packet loss and band-limitation of speech signal. Noise reduction of speech improves the perceived quality and intelligibility. High performance noise reduction methods are based on Bayesian methods requiring estimates of the parameters of the functions that describe the likelihood and the prior distributions of the signal and noise processes. The Bayesian noise reduction method which is used in this thesis is Kalman filter.In packet-based speech processing applications such as Internet and Voice over Internet Protocol (VoIP), it is possibly expected that some packets during signal transmission are...