Abstract: A panel for ventilation and noise reduction and its manufacturing method are disclosed A left side and a right side of the panel each include one or a plurality of ventilation holes, and a sound insulation board for sound insulation is set near each ventilation hole along an inner side of the panel, so that at least certain sound from the inner of the electronic device needs to bypass the board to pass through the ventilation holes; and the ventilation hole on the left side and the right side of the panel are opened in a staggered position, so that when the panel is placed side by side with another panel, air exhausted from a ventilation hole at an adjacent side of the panel does not form strong face-to-face blowing interference with air exhausted from a ventilation hole at an adjacent side of another panel.

Abstract: The present application relates to a method and apparatus for module repair in software. In the method, when a module in the software has an error, correct content corresponding to the erroneous content is obtained by way of accessing a web page address; then the correct content obtained is directly loaded into a system memory and the corresponding correct content is invoked directly from the memory when the module is used. The method of the present application results in the software possessing a self-repairing function and self-detection function, and can be applied in any software device.

Abstract: A ventilation denoising device that includes at least one ventilation module disposed with at least two air ducts inside, the air ducts are communicated end-to-end to form a circuitous air duct. The ventilation module is provided with a first ventilation opening communicated with one end of the air duct, and a second ventilation opening communicated with the other end of the air duct. Also disclosed is a ventilation denoising system equipped with the above mentioned ventilation denoising device. The ventilation denoising device can be installed outside equipments, such as a machine cabinet, as ventilation means thereof, and also reduce the noise generated during the equipment operation.

Abstract: Embodiments of the present invention provide a noise reduction method, device, and system. In the embodiments of the present invention, operating condition information of a noise source is obtained, where the operating condition information represents an operating condition of the noise source, then sound wave information corresponding to the obtained operating condition information is determined according to a pre-set mapping between the operating condition information and the sound wave information, and active noise reduction is performed by using the corresponding sound wave information. Steps such as collection, conversion, and calculation for noise generated by the noise source are not required, thereby shortening time for the active noise reduction.

Abstract: A method for controlling noise of a rotating device includes: obtaining a sound wave signal of noise generated by the rotating device, where the sound wave signal is fed back by a reference sensor; obtaining rotational speed information of the rotating device; and searching a predefined function mapping table according to the rotational speed information to obtain transfer functions; generating a sound emitting command according to the transfer functions and the sound wave signal; and sending the sound emitting command to a secondary source emitting device, so that the secondary source emitting device emits a secondary sound wave, where the secondary sound wave is used to suppress the noise generated by the rotating device.

Abstract: Advantageous OFDM-based underwater acoustic (UWA) apparatus, systems and methods are provided according to the present disclosure. In general, OFDM transmissions over UWA channels encounter frequency-dependent Doppler drifts that destroy the orthogonality among OFDM subcarriers. The disclosed apparatus, systems, and methods use a two-step approach to mitigate frequency-dependent Doppler drifts for zero-padded OFDM transmissions over fast-varying channels: (1) non-uniform Doppler compensation via resampling to convert a “wideband” problem into a “narrowband” problem; and (2) high-resolution uniform compensation on the residual Doppler. The disclosed apparatus, systems and methods are based on block-by-block processing and do not rely on channel dependence across OFDM blocks. Thus, the disclosed apparatus, systems and methods are advantageously applicable for fast-varying UWA channels.

Abstract: Trellis-based methods for reducing feedback while maintaining performance in a Multiple Input, Multiple Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system. The methods involve: receiving a plurality of symbols from a plurality of sub-carriers at a receiver; selecting a plurality of indices of codewords corresponding to a codebook of pre-coding weighting matrices for the sub-carriers based on vector quantization compression of the codewords, including selecting a plurality of indices based on trellis-based feedback encoding; and transmitting the selected indices over a wireless channel to a transmitter. Optimal precoding matrices are selected at the same time for all subcarriers by searching for the optimum choice of matrices along a trellis. Selecting a plurality of indices based on trellis-based feedback encoding includes constructing a trellis by specifying a state transition table.

Abstract: Advantageous OFDM-based underwater acoustic (UWA) apparatus, systems and methods are provided according to the present disclosure. In general, OFDM transmissions over UWA channels encounter frequency-dependent Doppler drifts that destroy the orthogonality among OFDM subcarriers. The disclosed apparatus, systems, and methods use a two-step approach to mitigate frequency-dependent Doppler drifts for zero-padded OFDM transmissions over fast-varying channels: (1) non-uniform Doppler compensation via resampling to convert a “wideband” problem into a “narrowband” problem; and (2) high-resolution uniform compensation on the residual Doppler. The disclosed apparatus, systems and methods are based on block-by-block processing and do not rely on channel dependence across OFDM blocks. Thus, the disclosed apparatus, systems and methods are advantageously applicable for fast-varying UWA channels.

Abstract: Techniques are provided for reducing feedback while maintaining performance in a MIMO-OFDM system. The disclosed techniques employ finite-rate feedback methods that uses vector quantization compression. The disclosed methods/techniques generally involve: receiving a plurality of symbols from a plurality of sub-carriers at a receiver; selecting a plurality of indices of codewords corresponding to a codebook of pre-coding weighting matrices for the sub-carriers based on vector quantization compression of the codewords; and transmitting the selected indices over a wireless channel to a transmitter. Finite state vector quantization feedback makes use of a finite state vector quantizer (FSVQ), which is a recursive vector quantizer (VQ) with a finite number of states. In finite state vector quantization feedback, optimal precoding matrices (beamforming vectors) are selected sequentially across subcarriers.