Abstract: A casing pipe is inserted into a drilled hole reaching the inside of a confined aquifer in which groundwater is stored and flows or a position near the confined aquifer. A measuring device measures an electromagnetic field at the distal end of the casing pipe. An analyzing device analyzes data concerning the electromagnetic field measured by the measuring device to sense motion of ground pore water, thereby predicting rapid motion in the earth's crust, such as a volcanic eruption, an earthquake, a landslide and ground collapse. The casing pipe is an electrically conductive pipe having a non-magnetic screen portion formed at the distal end thereof so that recycling groundwater passes through the screen portion. The measuring device includes an electromagnetic field sensor placed in the screen portion and the conductive casing pipe as an electrode for measuring an electric potential relative to an electric potential at the earth's surface detected with a reference electrode.

Abstract: In an automobile vehicle, fuel injection pulse outputted from an electronic control unit of an engine is transformed into a voltage value as a primary source. The voltage values is transformed by the convolution sum process and synthesized into a sound to cancel the engine noise. The synthesized sound is outputted through the speaker in the passenger compartment. On the other hand, the reduced noise sound is detected as an error signal by the microphone. The error signal is inputted to an LMS circuit where the filter coefficient is updated in accordance with both inputted error signal and the primary source. Since the fuel injection pulse before the combustion stroke is used, the noise sound can be precisely and immediately reduced even in the transient conditions of the vehicle operation.

Abstract: An ignition pulse shaped and demultiplied is used as a primary source and this primary source is converted into a canceling signal after being subjected to the sum of convolution products process with filter coefficients of an adaptive filter. Further the canceling signal is converted into a canceling sound by a speaker and outputted to the passenger compartment to cancel a vibration noise at a noise receiving point. The state of noise reduction is detected as an error signal by a microphone and the error signal is inputted to an exponential averaging circuit where the error signal is exponentially averaged with previous error signals by a trigger signal of the primary source from a trigger signal generating circuit. The error signal, as a result of this averaging, is compressed and then outputted to a LMS operational circuit. In the LMS operational circuit the filter coefficients are updated based on the primary source inputted via a C.sub.MNO circuit and the compressed error signal.