David A. Berkley

Bio: David A. Berkley is an academic researcher from Bell Labs. The author has contributed to research in topics: Teleconference & Microphone. The author has an hindex of 13, co-authored 29 publications receiving 4217 citations. Previous affiliations of David A. Berkley include AT&T & Alcatel-Lucent.

Image method for efficiently simulating small‐room acoustics

Abstract: Image methods are commonly used for the analysis of the acoustic properties of enclosures. In this paper we discuss the theoretical and practical use of image techniques for simulating, on a digital computer, the impulse response between two points in a small rectangular room. The resulting impulse response, when convolved with any desired input signal, such as speech, simulates room reverberation of the input signal. This technique is useful in signal processing or psychoacoustic studies. The entire process is carried out on a digital computer so that a wide range of room parameters can be studied with accurate control over the experimental conditions. A fortran implementation of this model has been included.

Multimicrophone signal‐processing technique to remove room reverberation from speech signals

Abstract: It is well known that room reverberation can significantly impair one’s perception of sounds recorded by a microphone in that room. Acoustic recordings produced in untreated rooms are characterized by a hollow echolike quality resulting from not locating the microphone close to the source. In this paper we discuss a multimicrophone digital processing scheme for removing much of the degrading distortion. To accomplish this the individual microphone signals are divided into frequency bands whose corresponding outputs are cophased (delay differences are compensated) and added. Then the gain of each resulting band is set based on the cross correlation between corresponding microphone signals in that band. The reconstructed broadband speech is perceived with considerably reduced reverberation.

Active user registry

Abstract: An Active User Registry system includes a database which is integrated with the POTS network and a packet network to exploit the outstanding strengths of both of its constituents. The Active User Registry database is a dynamic data structure of all the ways in which one or more users can be reached via some type of communication network. A key feature of the Active User Registry is the ability to broker between a subscriber's request for communications contact information corresponding to a user and the user's preferences of being reached by various communications alternatives.

Determination of Spatial Distribution of Charges in Thin Dielectrics

Abstract: We describe a high-resolution method to determine the spatial distribution of trapped charged or of a permanent dipole polarization in dielectrics. The method is capable of a resolution of 1 \ensuremath{\mu}m in a 25-\ensuremath{\mu}m-thick film.

Computer simulation of charge dynamics in electron‐irradiated polymer foils

Abstract: A computer simulation is described which allows the study of charge motion in thin polymer films of the type used for electret transducers. The simulation operates with a variety of possible boundary conditions and can include nonlinear transport terms as well as time‐varying radiation‐induced conductivity. Electron‐irradiation parameters, including radiation‐induced conductivity and electron deposition profiles, are computed using a single‐scattering Monte Carlo model of the polymer. The time‐dependent charge‐transport equations are solved by direct discretization of the partial differential equations. Using a fast minicomputer, the charge‐transport solutions run approximately in real time for realistic polymer parameters. Results are discussed for open‐ and short‐circuit irradiation and for charge recall experiments.

Image method for efficiently simulating small‐room acoustics

Abstract: Image methods are commonly used for the analysis of the acoustic properties of enclosures. In this paper we discuss the theoretical and practical use of image techniques for simulating, on a digital computer, the impulse response between two points in a small rectangular room. The resulting impulse response, when convolved with any desired input signal, such as speech, simulates room reverberation of the input signal. This technique is useful in signal processing or psychoacoustic studies. The entire process is carried out on a digital computer so that a wide range of room parameters can be studied with accurate control over the experimental conditions. A fortran implementation of this model has been included.

Signal estimation from modified short-time Fourier transform

Abstract: In this paper, we present an algorithm to estimate a signal from its modified short-time Fourier transform (STFT). This algorithm is computationally simple and is obtained by minimizing the mean squared error between the STFT of the estimated signal and the modified STFT. Using this algorithm, we also develop an iterative algorithm to estimate a signal from its modified STFT magnitude. The iterative algorithm is shown to decrease, in each iteration, the mean squared error between the STFT magnitude of the estimated signal and the modified STFT magnitude. The major computation involved in the iterative algorithm is the discrete Fourier transform (DFT) computation, and the algorithm appears to be real-time implementable with current hardware technology. The algorithm developed in this paper has been applied to the time-scale modification of speech. The resulting system generates very high-quality speech, and appears to be better in performance than any existing method.

Voice over data telecommunications network architecture

Abstract: The present invention describes a system and method for communicating voice and data over a packet-switched network that is adapted to coexist and communicate with a legacy PSTN. The system permits packet switching of voice calls and data calls through a data network from and to any of a LEC, a customer facility or a direct IP connection on the data network. The system includes soft switch sites, gateway sites, a data network, a provisioning component, a network event component and a network management component. The system interfaces with customer facilities (e.g., a PBX), carrier facilities (e.g., a LEC) and legacy signaling networks (e.g., SS7) to handle calls between any combination of on-network and off-network callers. The soft switch sites provide the core call processing for the voice network architecture. The soft switch sites manage the gateway sites in a preferred embodiment, using a protocol such as the Internet Protocol Device Control (IPDC) protocol to request the set-up and tear-down of calls. The gateway sites originate and terminate calls between calling parties and called parties through the data network. The gateway sites include network access devices to provide access to network resources. The data network connects one or more of the soft switch sites to one or more of the gateway sites. The provisioning and network event component collects call events recorded at the soft switch sites. The network management component includes a network operations center (NOC) for centralized network management.

3-D sound for virtual reality and multimedia

Abstract: Technology and applications for the rendering of virtual acoustic spaces are reviewed. Chapter 1 deals with acoustics and psychoacoustics. Chapters 2 and 3 cover cues to spatial hearing and review psychoacoustic literature. Chapter 4 covers signal processing and systems overviews of 3-D sound systems. Chapter 5 covers applications to computer workstations, communication systems, aeronautics and space, and sonic arts. Chapter 6 lists resources. This TM is a reprint of the 1994 book from Academic Press.