Abstract: A non-invasive brain assessment monitor is disclosed. An embodiment of the monitor includes a head-mounted brain sensor which passively senses acoustic signals generated from pulsing blood flow through a patient's brain. A reference sensor may be mounted at another location on the patient's body to sense an arterial pulse, and the signals from the brain sensor and reference sensor may be compared. Another embodiment includes transmitters which generate acoustic signals in the brain which are also detected by the brain sensor. The brain assessment monitor may be used to detect conditions such as head trauma, stroke and hemorrhage.

Abstract: A non-invasive brain assessment monitor is disclosed. An embodiment of the monitor includes a head-mounted brain sensor which passively senses acoustic signals generated from pulsing blood flow through a patient's brain. A reference sensor may be mounted at another location on the patient's body to sense an arterial pulse, and the signals from the brain sensor and reference sensor may be compared. Another embodiment includes transmitters which generate acoustic signals in the brain which are also detected by the brain sensor. The brain assessment monitor may be used to detect conditions such as head trauma, stroke and hemorrhage.

Abstract: The present invention relates to a non-invasive device for measuring physiological processes. More particularly, it concerns a device that can be applied externally to the body of an animal or human to detect and quantify displacement, force, motion, vibration and acoustic effects resulting from internal biological functions. Specifically, an inexpensive device is disclosed that is compact, light, portable and comfortable, and operates satisfactorily even with imprecise location on the body, ambient noise, motion and light.

Abstract: A non-invasive apparatus and method are disclosed for measuring intracranial pressure. The intracranial measurement system transmits acoustic signals through a cranium and provides an indication of intracranial pressure based on the received acoustic signals after interaction with the brain. Properties such as acoustic transmission impedance, resonant frequency, resonance characteristics, velocity of sound and the like may be measured and correlated with intracranial pressure. The acoustic signals have typical frequencies of less than 100 kHz, for example, in the audible and sub-audible frequency ranges. The intensity of the transmitted acoustic signals used to determine intracranial pressure is relatively low, resulting in little or no health risks during short term or long term monitoring.

Abstract: A transducer array according to the invention includes forty-two acoustic transducers for use in a fluid medium, with each of the transducers having maximum lateral dimensions of less than one acoustic wavelength in the medium, whereby the transducers themselves tend to radiate isotropically. The elements of the array are located at the vertices of an regular geodesic two-frequency icosahedron. The transducer array also includes a driver or a receiver, or both, and arrangements for coupling them to the array elements. A switching circuit can couple the array elements alternately to the driver or receiver, depending upon the operating mode. A conventional delay controller is coupled to the acoustic transducers, for controlling an acoustic beam formed by the array. In a particular embodiment of the invention, the array is operated at frequencies selected so that the inter-transducer spacing of any two mutually adjacent transducers does not exceed 2.lambda./3, and is not less than .lambda./3.

Abstract: An apparatus for sensing acoustic signals in a liquid wherein an omnidirectional hydrophone exhibits a hemispheric response pattern. A hydrophone, including a transducer element and a transmitting cable, is mounted such that the transducer element is adjacent the forward face of an acoustic baffle including a layer of sound-absorbing material. The rear face of the acoustic baffle is positioned adjacent an acoustic shield including a layer of sound-reflecting material. The transmitting cable is positioned in an aperture in the acoustic baffle and the acoustic shield, and passes beyond the rear face of the acoustic shield. A flow fairing is positioned adjacent the forward face of the acoustic baffle and encloses at least the forward portion of the transducer element.

Abstract: Each of the acoustic transducers (elements) of an array has a maximum dimension of less than .lambda.. They are located at the vertices of a regular polyhedron, which may be an icosahedron (12 elements), or a dodecahedron (20 elements). This placement effectively locates the elements on the surface of a sphere with diameter selected to provide an interelement spacing of .lambda./3 to 2.lambda./3. The signals are delayed for phasing to form directive "beams." A second array includes elements located at the vertices of a smaller polyhedron centered at the same point and included within the first array, and operated at a higher frequency than the outermost array. In order to reduce the effects of shadowing, the locations of the transducers of the smaller included array are selected to lie on radials passing through the centroids of the faces of the polygon defining the larger array.

Abstract: A flextensional transducer driven by magnetically biased rare earth rods 31. The rods 31 are arranged in stacks with rare earth magnets 34 mounted on each end of each stack for providing the bias field. The rods 31 are slotted to reduce eddy currents and surrounded by a slotted drive coil 32 with a slot 32a in the coil bobbin. The ends of the flextensional shell associated with the shell major axis have a full radius curvature which stiffens the shell ends so that the axial bias and drive forces will not break the rare earth magnets 34 in flexure.