Abstract: A system for locating a sound source includes at least four emitter/receiver pairs, each emitter/receiver pair of the at least four emitter/receiver pairs including a laser emitter and a receiver external to an enclosed structure. The laser directs a laser beam onto a respective reflector surface location on an outer surface of the structure, the respective reflector surface location being caused to vibrate due to sound waves generated from a sound source at a sound source location within the enclosed structure. The receiver receives vibrational signals from the laser beam on the surface at the respective reflector surface location and converting the vibrational signals to acoustic signals. A processor coupled to the emitter/receiver pairs for utilizing the acoustic signals to determine a time difference of arrival of the sound waves to the respective reflector surface locations to determine the sound source location based on the time difference of arrivals.

Abstract: A system and method of determining blood pressure includes measuring heart sounds, separating the measured heart sounds into a first heart sound (S1) and a second heart sound (S2), mathematically characterizing S1 and S2, and determining a blood pressure based on the characterization.

Abstract: A system and method of determining blood pressure includes measuring heart sounds, separating the measured heart sounds into a first heart sound (S1) and a second heart sound (S2), mathematically characterizing S1 and S2, and determining a blood pressure based on the characterization.

Abstract: A system and method for tracking and tracing motions of multiple incoherent sound sources and for visualizing the resultant overall sound pressure distribution in 3D space in real time are developed. This new system needs only four microphones (although more could be used) that can be mounted at any position so long as they are not placed on the same plane. A sample configuration is to mount three microphones on the y, z plane, while the 4th microphone on a plane perpendicular to the y, z plane. A processor receives signals from the microphones based on the signals received from noise sources in unknown locations, and the processor determines the locations of these sources and visualizes the resultant sound field in 3D space in real time. This system works for broadband, narrowband, tonal sound signals under transient and stationary conditions.

Abstract: A system and method allow for extracting target signals from the overall measurement data without knowing how and where these data are collected, the locations and characteristics of target sources as well as those of random background noise sources. In essence, it uses an innovative and advanced signal processing technique to reveal certain critical information from a mixture of data that is hard to obtain otherwise. In particular, it allows for denoising the measured data that have been contaminated by various interfering and background noise, making it possible to extract certain target information that may be otherwise difficult to observe. The only assumption made in this method is that the target signal is incoherent with respect to all interfering signals and background noise. The more information about a target signal is available, the more complete the extracted signal becomes.

Abstract: A sound monitoring system provides autonomous and silent)) surveillance to monitor sound sources stationary or moving in 3D space and a blind separation of target acoustic signals. The underlying principle of this technology is a hybrid approach that uses: 1) passive sonic detection and ranging method that consists of iterative triangulation and redundant checking to locate the Cartesian coordinates of arbitrary sound sources in 3D space, 2) advanced signal processing to sanitize the measured data and enhance signal to noise ratio, and 3) short-time source localization and separation to extract the target acoustic signals from the directly measured mixed ones.

Abstract: A system provides an in situ or non-invasive vibro-acoustic (VA) analysis of an arbitrary complex vibrating structure. The noise diagnostic system includes a plurality of first transducers for measuring acoustic pressure in a sound field near a noise source. At least one second transducer measures normal surface velocity on the noise source. A computer acquires acoustic pressure data from the plurality of first transducers and normal surface velocity data from the at least one second transducer. The computer generates a transfer matrix representing a correlation between normal surface velocity on the noise source and the acoustic pressure in the sound field.

Abstract: A system and method allow for extracting target signals from the overall measurement data without knowing how and where these data are collected, the locations and characteristics of target sources as well as those of random background noise sources. In essence, it uses an innovative and advanced signal processing technique to reveal certain critical information from a mixture of data that is hard to obtain otherwise. In particular, it allows for denoising the measured data that have been contaminated by various interfering and background noise, making it possible to extract certain target information that may be otherwise difficult to observe. The only assumption made in this method is that the target signal is incoherent with respect to all interfering signals and background noise. The more information about a target signal is available, the more complete the extracted signal becomes.

Abstract: A centrifugal blowing apparatus for reducing flow-induced noise is disclosed. The apparatus includes a blower housing having a scroll section formed about a rotational axis and an exhaust section extending from the scroll section. The scroll section includes an opening defining an inlet configured to draw in air and the exhaust section defines an outlet in fluid communication with the inlet. The scroll section commences with a reduced cross-sectional area defining a cutoff and expands to an increased cross-sectional area. An impeller is disposed in the opening of the scroll section about the rotational axis and includes an outer surface having impeller blades radially disposed thereon. The impeller blades rotate to direct a flow of air from the inlet through the scroll section to the outlet. A plurality of indentations is formed along an inner surface of the scroll section at the cutoff.

Abstract: A system and method for tracking and tracing motions of multiple incoherent sound sources and for visualizing the resultant overall sound pressure distribution in 3D space in real time are developed. This new system needs only four microphones (although more could be used) that can be mounted at any position so long as they are not placed on the same plane. A sample configuration is to mount three microphones on the y, z plane, while the 4th microphone on a plane perpendicular to the y, z plane. A processor receives signals from the microphones based on the signals received from noise sources in unknown locations, and the processor determines the locations of these sources and visualizes the resultant sound field in 3D space in real time. This system works for broadband, narrowband, tonal sound signals under transient and stationary conditions.

Abstract: A centrifugal blowing apparatus for reducing flow-induced noise is disclosed. The apparatus includes a blower housing having a scroll section formed about a rotational axis and an exhaust section extending from the scroll section. The scroll section includes an opening defining an inlet configured to draw in air and the exhaust section defines an outlet in fluid communication with the inlet. The scroll section commences with a reduced cross-sectional area defining a cutoff and expands to an increased cross-sectional area. An impeller is disposed in the opening of the scroll section about the rotational axis and comprises an outer surface having impeller blades radially disposed thereon. The impeller blades rotate to direct a flow of air from the inlet through the scroll section to the outlet. A plurality of indentations is formed along an inner surface of the scroll section at the cutoff.

Abstract: An algorithm diagnoses the noise source strength distribution on an arbitrarily shaped object based on acoustic pressures measured in the far field, known as FANS. FANS enable one to acquire a quick estimate of the acoustic pressure at locations that are off limit to traditional measurement microphones. Generally, in the method of the present invention, the noise source is modeled in terms a plurality of virtual spherical wave sources distributed on an auxiliary surface conformal to a source boundary from the inside, but not on the source boundary itself. Sound is then measured at a plurality of measurement points external to the source boundary. The sound field is reconstructed on the source boundary surface itself.

Abstract: A technique for determining particulate density in a fluid monitors the changes in the speed of sound. Since the speed of sound is intimately related to the composites of the air mixture and since the speed of sound of clean air at any temperature and humidity can be calculated exactly, it is possible to estimate the density of any foreign particulates in the air by observing changes in the speed of sound. Formulations are derived that correlate the change in the speed of sound of the air mixture to their density fluctuations, thus allowing people to estimate the mass density of foreign particulates under any temperature and humidity. Alternatively, the change in density of the air mixture can be detected, thereby indicating the presence of contaminants and a possible alarm, even if the contaminants are not yet identified.

Abstract: General algorithms are developed for reconstructing the acoustic field generated by an arbitrary object subject to an arbitrarily time-dependent excitation. These algorithms enable one to visualize a time-domain acoustic pressure wave as it travels through three-dimensional space. Such a tool can be used to diagnose general noise sources and transmission since in engineering applications most structures are subject to arbitrarily time-dependent excitations. To facilitate the derivations of the temporal solutions, we make use of Laplace transform and expand the acoustic pressure in terms of the spherical Hankel functions and the spherical harmonics. The expansion coefficients are settled by solving an over-determined system of equations obtained by matching the assumed-form solutions to the measured acoustic pressures.

Abstract: Acoustic field reconstruction is performed by expanding basis function which represent outgoing and incoming waves, without prior knowledge of the source geometry and dimensions. The reconstruction is based on acoustic pressures measured in the field only, and can be accomplished on a piece-wise basis. There are no restrictions on the locations of measurements. Moreover, the present invention can be used to reconstruct acoustic radiation from a plurality of sources or from a single source surrounded by multiple reflecting surfaces.

Abstract: A technique for determining particulate density in a fluid monitors the changes in the speed of sound. Since the speed of sound is intimately related to the composites of the air mixture and since the speed of sound of clean air at any temperature and humidity can be calculated exactly, it is possible to estimate the density of any foreign particulates in the air by observing changes in the speed of sound.

Abstract: Acoustic field reconstruction is performed by expanding basis function which represent outgoing and incoming waves, without prior knowledge of the source geometry and dimensions. The reconstruction is based on acoustic pressures measured in the field only, and can be accomplished on a piece-wise basis. There are no restrictions on the locations of measurements. Moreover, the present invention can be used to reconstruct acoustic radiation from a plurality of sources or from a single source surrounded by multiple reflecting surfaces.

Abstract: An alternate formulation is derived for predicting acoustic radiation from a vibrating object in an unbounded fluid medium. The radiated acoustic pressure is shown to be expressible as a surface integral of the particle velocity, which is determinable by using a non-intrusive laser Doppler velocimeter. Solutions thus obtained are unique. Moreover, the efficiency of numerical computations is high because the surface integration can be readily implemented numerically by using the standard Gaussian quadratures. This alternate formulation can be desirable for analyzing the acoustic and vibration responses of a lightweight, a flexible or a structure with a hostile environment for which a non-intrusive laser measurement technique must be used.

Abstract: A method for reconstructing the acoustic field on the surface of a vibrating object based on measurements of the radiated acoustic pressure includes solving the Helmholtz equation directly using the expansion of a set of independent functions that are generated by the Gram-Schmidt orthonormalization with respect to the particular solutions to the Helmholtz equation. The coefficients associated with these independent functions are determined by requiring the assumed form of solution to satisfy the pressure boundary condition at the measurement points. The errors involved in these coefficients are minimized by the least squares method. Once these coefficients are specified, the acoustic pressure at any point, including the source surface, is completely determined.