Navarun Gupta

HRTF database at FIU DSP Lab

Head Related Transfer Functions (HRTFs) are signal processing models that represent the modifications undergone by the acoustic signal as it interacts with the listeners body. HRTFs can be used to generate binaural sound as they contain all the information about the sound sources location. This paper describes a database of head-related transfer functions based on ear/head measurements measured at the FIU DSP Lab. HRTF data from 15 subjects at 12 different azimuths and 6 different elevations are included. This database also includes 3-D images of the subjects pinnae (outer ears). Anthropometric measurements of the various parts of the pinna are included.

Performance Comparison of Two Identification Methods for Analysis of Head Related Impulse Responses

-Head-Related Impulse Responses (HRIRs) are used in signal processing to model the synthesis of spatialized audio which is used in a wide variety of applications, from computer games to aids for the vision impaired. They represent the modification to sound due to the listener’s torso, shoulders, head and pinnae, or outer ears. As such, HRIRs are somewhat different for each listener and require expensive specialized equipment for their measurement. Therefore, the development of a method to obtain customized HRIRs without specialized equipment is extremely desirable. In previous research on this topic, Prony’s modeling method was used to obtain an appropriate set of time delays and a resonant frequency to approximate measured HRIRs. During several recent experimental attempts to improve on this previous method, a noticeable increase in percent fit was obtained using the Steiglitz-McBride interative approximation method. In this paper we report on the comparison between these two methods and the statistically significant advantage found in using the Steiglitz-McBride method for the modeling of most HRIRs.

Decomposition of Head Related Impulse Responses by Selection of Conjugate Pole Pairs

Currently, to obtain maximum fidelity 3D audio, an intended listener is required to undergo time consuming measurements using highly specialized and expensive equipment. Customizable Head-Related Impulse Responses (HRIRs) would remove this limitation. This paper reports our progress in the first stage of the development of customizable HRIRs. Our approach is to develop compact functional models that could be equivalent to empirically measured HRIRs but require a much smaller number of parameters, which could eventually be derived from the anatomical characteristics of a prospective listener. For this first step, HRIRs must be decomposed into multiple delayed and scaled damped sinusoids which, in turn, reveal the parameters (delay and magnitude) necessary to create an instance of the structural model equivalent to the HRIR under analysis. Previously this type of HRIR decomposition has been accomplished through an exhaustive search of the model parameters. A new method that approaches the decomposition simultaneously in the frequency (Z) and time domains is reported here.

A new selected points to enhance radio wave propagation strength outside the coverage area of the mobile towers in the dead spots of cellular mobile WiFi downloads

Mobile phone base station (tower) provides coverage for one or more geographical areas, known as cells. A mobile phone network is made up of a base station operating in conjunction with adjacent base stations. Base stations must be carefully located in relation to each other, so each cell in the network functions efficiently to ensure minimum interference between cells and good signal quality. One of the major problems for cellular wireless devices is calls being dropped and failure in downloading data. Our research uses a new recommendation in determining tower positions. Thus, providing an easy interface to replace traditional control methods and maintain signal levels. The weak WiFi wave propagation outside towers coverage areas is investigated at the University of Bridgeport (UB) campus. The campus serves as good experimental settings because it exemplifies typical signal dead spots, locations where little to no WiFi signal is available. In this paper, we investigate path loss propagation between the base stations and we identify and categorize these problems. We then apply our path loss propagation algorithmic models to show that signal strength is significantly improved when applying the proposed model. Finally, we show the efficiency of the proposed positions.

A new mathematical model for wireless signal path loss under varying conditions

The Measurement of radio wave propagation into and within buildings at 900 and 1800 MHz frequencies have been undertaken using the library building at the University of Bridgeport campus in CT, USA. Furthermore, the signal propagation for the cases into and within elevator has also been investigated. Signal loss is a major problem for cellular wireless devices, resulting in dropped calls and failure in downloading data. In this research explores the radio transmission model of buildings that depend on the measured penetration loss values. Furthermore, this study will focus on and bring to light a better understanding of the modeling of radio transmission within and outside buildings. The lossy WiFi wave propagation around and within buildings is studied utilizing college buildings at the University of Bridgeport (UB) campus in Bridgeport CT. These buildings serve as good experimental settings because they exemplify typical signal dead spots, locations where little to no WiFi signal is available. In this paper, we investigate path loss propagation inside and outside buildings and we identify and categorize these problems. We then apply our path loss propagation algorithmic models to show that signal strength is significantly improved when compared to existing algorithms. Finally, we show the efficiency of our model and explain the specifics of our algorithm.

Two case reports: electrothermal (aka contact) burns and the effects of current density, application time and skin resistance.

Electrical properties can be changed by the passage of current, where increased current/voltage reduces resistivity [3–8]. Electrical resistive heating is generated within the skin. Decreased skin resistance often correlates with increased skin permeability [3,9,10]. Results indicate that skin resistance depends strongly on V = voltage (V), J = current density (A/ cm), I = current (A) and A = electrical contact area (cm). Early studies show that high current densities occur in lowresistance pathways. This occurs only with dry or dirty electrodes, which make poor skin contact [10–12]. Several skin burn cases were reported because of poor electrode design [13] and poor electrode–skin contact [14,15]. Skin can be damaged by resistive heating due to the passage of current. A persistent temperature of 45 8C is generally accepted as the safety limit for skin burns [16]. Using the results of previous studies [13,17] the burn factor (BF) is defined as

2-D auditory mapping of virtual environment using real-time head related transfer functions

The human brain is capable of localizing sounds from events occurring in its surroundings. It is able to identify and pinpoint from which directions the sounds come. This project takes advantage of that ability to create a simple auditory map of a virtual environment with the use of head related transfer functions (HRTF). HRTF are the basis of the most prominent techniques for digital sound spatialization. In this project a synthetic virtual environment is defined by a maze of vertical and horizontal walls drawn on the computer screen using Matlabs graphic user interface (GUI) components. In this virtual environment the subject is represented by the computer cursor. The distances from the cursor to the nearest virtual walls are calculated continuously and used to control the intensity of four virtual sounds that are simulated as if originating at the front, back, left and right of the subject. These four spatialized sounds are delivered through headphones to a blindfolded user as he/she navigates the virtual environment stepping the cursor with the four arrow keys on the keypad of the computer. Virtual navigation tests with 14 subjects confirm that the remote navigation cues provided by the spatialized sounds are more helpful in avoiding collisions with the virtual walls than a simple warning tone provided to the blindfolded user in the immediate vicinity of the walls.

The effect of pinna protrusion angle on localization of virtual sound in the horizontal plane

The transformation of a sound from its origin to each of the eardrums of a listener, due to the head, torso, and outer ear of the listener, are modeled by the so‐called head‐related transfer functions (HRTFs) for each individual and each location around the listener. These HRTFs can be used to transform a monoaural sound into left and right sounds that will give the subject the illusion of a virtual sound placement, at the location associated with the HRTF used. However, subjects tend to confuse sounds virtually placed in the front hemisphere with sounds placed symmetrically in the back hemisphere, i.e., points that lay in a cone of confusion. This paper reports on a study that involved the measurement of the HRTFs of 20 subjects, and the analysis of their performance in locating virtual sources in a horizontal plane. The subjects were tested using their own individual HTRFs and also using the HRTFs of a prototype subject who has particularly protruding pinnae. Results indicate that the additional shadowi...

On the Use of van der Pauw Technique to Monitor Skin Burning in Patients Undergoing Interferential Current Therapy (IFC) with Extension to Other E-Stim Monitoring

Interferential Current (IFC) therapy is routinely used on patients in order to reduce pain, to speed up the healing of wounds in muscles, and to strengthen muscles and bodily structure. The van der Pauw (vdP) technique is a process used to measure a material’s sheet resistance when the material has a geometric shape that has a uniform thickness, but whose other two dimensions are arbitrary. By combining these techniques, the skin’s sheet resistance can be measured before, after, and during IFC therapy, and this will show a disturbance in skin sheet resistance caused by accidental burning. This technique can also be extended to monitoring TENS (transcutaneous electrical nerve stimulation) and other types of e-stim monitoring.

New Mathematical Model for Wireless Signal Path Loss inside Buildings

Mobile communications have evolved in a very rapid manner along with other fast-growing communication technologies. The widespread use of this technology has turned mobile communications into a life style. Thus the necessity for high quality and high capacity networks with thorough coverage has become one of the major demands. Many models have been proposed to cover the signal strength measurements and estimations, which make it easy to provide an efficient and reliable coverage area. One such model is the Okumura model, an accepted standard. In this paper we propose a new mathematical model for calculating the path loss inside buildings especially in elevators which are considered a very critical metropolitan feature where signal drops occur. In our work, radio wave propagation and frequency measurements were taken inside various buildings at the University of Bridgeport campus in Bridgeport CT, USA. These measurements were incorporated into the Okumura model to derive a new path loss model utilizing power measurements inside buildings. The experimental work shows very accurate and improved results for our model with respect to path loss detection inside elevators as compared to the Okumura model.