Abstract: Provided is a method and apparatus for reproducing a three-dimensional (3D) sound field. A method of reproducing a 3D sound field may determine a control region based on a wavelength of an excitation frequency, set, based on a loudspeaker array, at least one candidate control point in the control region, and determine a non-uniform control point corresponding to a non-uniform loudspeaker.

Abstract: Provided is a method and apparatus for reproducing a three-dimensional (3D) sound field. A method of reproducing a 3D sound field may determine a control region based on a wavelength of an excitation frequency, set, based on a loudspeaker array, at least one candidate control point in the control region, and determine a non-uniform control point corresponding to a non-uniform loudspeaker.

Abstract: An electrochemical cell comprising a cathode, an anode and an electrolyte is provided, wherein: the cathode comprises mesoporous nickel having a periodic arrangement of substantially uniformly sized pores of cross-section of the order of 10?8 to 10?9 m; and the anode comprises a mesoporous material having a periodic arrangement of substantially uniformly sized pores of cross-section of the order of 10?8 to 10?9 m and selected from: carbon, cadmium, iron, a palladium/nickel alloy, an iron/titanium alloy, palladium or a mixed metal hydride.

Abstract: Turbulence in the boundary layer of a flow of air across a surface is controlled by sucking air from the surface. A plurality of turbulence detectors are located in the surface downstream of apertures provided in the surface. The apertures are connected to a suction pump. Air is sucked through the apertures until the air flow of the most downstream of the detectors is non-turbulent.

Abstract: To reduce noise inside a motor car passenger compartment, two loudspeakers 37.sub.1, 37.sub.2 are driven by signals derived from a reference signal x(n) by adaptive filtering carried out by a programmed microprocessor and memory unit 36 which adapts the filtering in dependence on error signals e.sub.l (n) from four microphones 42.sub.1, 42.sub.2, 42.sub.3 and 42.sub.4 distributed in the passenger compartment. Reference filtering coefficients are initially determined by analysis of finite impulse responses when white noise is acoustically coupled from the loudspeakers 37 to the microphones 42, a white noise generator 48 being coupled to the unit 36. The reference signal x(n) is restricted to one or more selected harmonics or subharmonics of the fundamental noise frequency by a filter 34 which tracks the selected frequency. The selected frequency may be obtained from a coil 31 in the ignition circuit of the vehicle.

Abstract: In propeller of fan driven aircraft, cabin noise levels may be reduced by adjustment of the phase relationship between a reference propeller or fan and some or all of the other propellers or fans. An aircraft cabin (1) contains four microphones and two loudspeakers which form the active elements of a noise control system. The microphone outputs are fed via amplifiers to a digital signal processor (11) having an adaptation algorithm in a memory store. The processor generates an error signal which is used to adjust the synchrophase angle between the reference propeller and a synchrophased propeller, controlled by a synchrophaser. Thus the synchrophase angle is varied dynamically during flight to minimize propeller noise in the cabin over a range of flying conditions.

Abstract: A high pressure drop cascade impactor wherein particles do not bounce from the collection plate; to a method for designing said impactor; a method for calculating and determing the particle size distribution of an aerosol wherein the particle size may have a Stokes (aerodynamic) diameter as small as 10 nanometers; and, to a method of manufacturing such an impactor. Particles drawn through the impactor exhibit substantially no reentrainment, or bounce, from the collection of surfaces. The impactor eliminates turbulence near the entrances to the jet holes by rounding the edges of the jet holes. This is accomplished on the small holes by means of electropolishing. The impactor is capable of capturing particles as small as 10 nanometers Stokes (aerodynamic) diameter.

Abstract: This invention is directed to a high pressure drop cascade impactor wherein the particles do not bounce from the collection plate; to a method for designing said impactor; a method for calculating and determining the particle size distribution of an aerosol wherein the particle size may have a Stokes (aerodynamic) diameter as small as 10 nanometers; and, to a method of manufacturing such an impactor.

Abstract: This invention is directed to a high pressure drop cascade impactor wherein the particles do not bounce from the collection plate; to a method for designing said impactor; a method for calculating and determining the particle size distribution of an aerosol wherein the particle size may have a Stokes (aerodynamic) diameter as small as 10 nanometers; and to a method of manufacturing such an impactor.The impactor that is the subject of this invention is different from and superior to previously described impactors in the following principal respects:1. The particles exhibit substantially no reentrainment, or bounce, from the collection surfaces. This property is achieved by (a) limiting the exit jet stream velocities such that the herein defined "bounce parameter", .beta., is never exceeded, and (b) increasing the thickness of the jet plates to elongate the jet passageways in order to reduce the jet velocities so that bounce will not occur.2.