Hum Noise Research Articles

Lead-free Bi2CuO4 interspersed into PDMS matrix-based bifunctional piezoelectric nanogenerator for vibrational energy harvesting and visible light photodetection applications

Lead-free materials with superior piezoelectric properties are gaining much interest due to their high performance and increased long-term sustainability. In this context, bismuth-based ternary oxides exhibit perovskite crystal structures with high piezoelectric coefficients and mechanical damping. Thus, in this work, we report a Bi2CuO4: Polydimethylsiloxane (BCO: PDMS) composite -based photoinduced-piezoelectric nanogenerator for harvesting weak mechanical vibrations which are abundant in the atmosphere. Notably, the BCO nanoparticles exhibit a highly crystalline tetragonal structure with 2D-nanoflake-like morphology providing a high surface area for the PENG applications. Further, the optical studies of BCO illustrate an enhanced absorption in the visible region with a bandgap of 2.5 eV. BCO: PDMS-based PENG displays a maximum open circuit voltage of 50 V and short circuit current of 300 nA upon application of 0.15 kgf vertical compressive force without any electrical poling. The PENG device exhibits an 18 % increment in output voltage upon illumination of visible light of 5 mW/cm2 intensity with superior photodetection properties. The obtained response can be attributed to the synergistic effect, i.e., the generation of exciton pairs upon illumination and separation of charge carriers due to the inbuilt piezoelectric field. Moreover, the PENG exhibits a distinct and accurate response for feeble and subtle frequencies in the range of 3–22 Hz such as atmospheric noise, and gravity hum noise. thus, proving the superior sensitivity. The fabricated PENG device displayed a stable response for 30 min of continuous vibration displaying superior cyclic stability. This work demonstrates a combination of perovskite crystalline material and PDMS leading to the development of high-performance piezoelectric nanogenerators with future scope in frequency detection systems for security and safety applications.

Design of N-path notch filter circuit with switched-capacitor resistor

Hum noise such as power line interference is one of the critical problems in biomedical signal acquisition. Various techniques have been proposed to suppress power line interference, such as an N-path notch filter. The notch depth in the conventional N-path notch filter is limited by the number of paths. The previous 10-phase N-path notch filter circuit achieved deeper notch depth but has a problem with capacitor size. The previous circuit requires more input–output pin because the large capacitance and therefore can not be implemented on an integrated circuit. This work proposed a new N-path notch filter with a switched-capacitor resistor to enable on-chip implementation. The proposed N-path notch filter achieved deeper notch depth than previous circuits with smaller capacitors. The proposed circuit still reached notch depth deeper than 40 dB with a total capacitance of 1 nF.

Hum Noise Reduction using Novel Complementary Pair VSSLMS Algorithm

This paper presents a novel Complementary Pair Variable Step-size (CPVSS) Least Mean Square Algorithm which is implemented for active noise cancellation application. The result presents the effect of filtration to remove the 50 Hz ac hum noise from the 500 Hz audio tone. Discrete Fourier Transform, Short Time Fourier Transform, and Welch Periodogram of the noisy signal and filtered signal have been presented which shows effective improvement in SNR. The simulation study has shown the superiority of this algorithm over other algorithms under consideration.

Sound quality degradation of audio equipment by hum noise induced by non-audible high frequency electrical noise

In recent audio equipment, induction and inflow of non-audible high frequency (HF) electrical noise to audio equipment is increasing more and more due to implementation of personal computer / network connectivity and high-resolution capability in digital audio equipment. In this study, in order to investigate another causes of influence of non-audible HF electric noise on playback sound, we measured a loudspeaker output of an audio amplifier by the audio analyser with inputting single HF sine wave from a function generator to analog input of the audio amplifier. From measured results, it was found that the power of harmonics of 60 Hz (hum noise) on the loudspeaker output of some audio amplifiers increased when single HF sine wave was inputted. Tendency of the increasing of the hum noise component depended on the frequency of the inputted sine wave and model of audio amplifier. These results show the importance of consideration of HF characteristic and countermeasure to the HF noise also in circuit design and tuning of audio equipment.

Japanese Janken Recognition by Support Vector Machine Based on Electromyogram of Wrist

We propose a method which can discriminate hand motions in this paper. We measure an electromyogram (EMG) of wrist by using 8 dry type sensors. We focus on four motions, such as “Rock-Scissors-Paper” and “Neutral”. “Neutral” is a state that does not do anything. In the proposed method, we apply fast Fourier transformation (FFT) to measured EMG data, and then remove a hum noise. Next, we combine values of sensors based on a Gaussian function. In this Gaussian function, variance and mean are 0.2 and 0, respectively. We then apply normalization by linear transformation to the values. Subsequently, we resize the values into the range from -1 to 1. Finally, a support vector machine (SVM) conducts learning and discrimination to classify them. We conducted experiments with seven subjects. Average of discrimination accuracy was 89.8%. In the previous method, the discrimination accuracy was 77.1%. Therefore, the proposed method is better in accuracy than the previous method. In future work, we will conduct an experiment which discriminates Japanese Janken of a subject who is not learned.

A Touch Sensing Technique Using the Effects of Extremely Low Frequency Fields on the Human Body.

Touch sensing is a fundamental approach in human-to-machine interfaces, and is currently under widespread use. Many current applications use active touch sensing technologies. Passive touch sensing technologies are, however, more adequate to implement low power or energy harvesting touch sensing interfaces. This paper presents a passive touch sensing technique based on the fact that the human body is affected by the surrounding extremely low frequency (ELF) electromagnetic fields, such as those of AC power lines. These external ELF fields induce electric potentials on the human body—because human tissues exhibit some conductivity at these frequencies—resulting in what is called AC hum. We therefore propose a passive touch sensing system that detects this hum noise when a human touch occurs, thus distinguishing between touch and non-touch events. The effectiveness of the proposed technique is validated by designing and implementing a flexible touch sensing keyboard.

Verification of the muscle fatigue detection capability of a unipolar-leads system using a surface electromyogram model.

In this study, the muscle fatigue detection capability of bipolar and unipolar lead systems used for surface electromyogram measurement was verified by simulation. The constructed model simplified the isometric contraction of the biceps brachii. There were two simulation experiments: 1) the addition and deletion of white noise and 2) the addition and deletion of hum noise. The pattern result of simulation 1) suggested the possibility that the muscle fatigue detection capability of a unipolar-leads system was high. The pattern 2) result showed the unipolar-leads system had a small influence of filtering, and suggested that the mixing of hum noise could be disregarded.

The Realization and Analysis of Capacitance Self Tracing (CST) Method for Wide Band Response Measurement of Carrier Type Dynamic Strain Amplifier

Carrier type dynamic strain amplifiers are frequently used for stress measurement with strain gages. That is because the carrier type dynamic strain amplifier can conduct high precision measurement since it is highly resistant against hum noise from the power supply frequency in principle and is free from the thermoelectomotive force even if a metal contact is used in wiring to a Wheatstone bridge for measuring.A problem of the carrier type dynamic strain amplifier is generation of Capacitive component (hereinafter referred to as the C component) in an input cable connecting from the amplifier to the input sensor (Wheatstone bridge for measuring). The C component varies with cable length, cable materials, or ambient temperature change. The aforementioned changing adversely affects the stability of the amplifier. In this paper, we realize and analyze the method that increases the stability of amplifier by detecting, eliminating and self tracking the above C component constantly. Used carrier frequency at 12kHz and 28kHz.We made amplifiers with noise resistant and wide band frequency of measurement range and verified the theory of the Capacitance Self Tracing with the above amplifiers.

Decomposition of Neurological Multivariate Time Series by State Space Modelling

Decomposition of multivariate time series data into independent source components forms an important part of preprocessing and analysis of time-resolved data in neuroscience. We briefly review the available tools for this purpose, such as Factor Analysis (FA) and Independent Component Analysis (ICA), then we show how linear state space modelling, a methodology from statistical time series analysis, can be employed for the same purpose. State space modelling, a generalization of classical ARMA modelling, is well suited for exploiting the dynamical information encoded in the temporal ordering of time series data, while this information remains inaccessible to FA and most ICA algorithms. As a result, much more detailed decompositions become possible, and both components with sharp power spectrum, such as alpha components, sinusoidal artifacts, or sleep spindles, and with broad power spectrum, such as FMRI scanner artifacts or epileptic spiking components, can be separated, even in the absence of prior information. In addition, three generalizations are discussed, the first relaxing the independence assumption, the second introducing non-stationarity of the covariance of the noise driving the dynamics, and the third allowing for non-Gaussianity of the data through a non-linear observation function. Three application examples are presented, one electrocardigram time series and two electroencephalogram (EEG) time series. The two EEG examples, both from epilepsy patients, demonstrate the separation and removal of various artifacts, including hum noise and FMRI scanner artifacts, and the identification of sleep spindles, epileptic foci, and spiking components. Decompositions obtained by two ICA algorithms are shown for comparison.

Experimental study on the prediction of hum noise from conductor bundles for UHV transmission lines

The audible noise produced by corona discharge from transmission line conductors comprises two major components, namely hum noise and random noise. Hum noise has a frequency that is twice the power line frequency and is generated primarily in rain, fog, and highly humid environments. It is one of the major factors affecting the design of conductor transmission lines for voltages above 500 kV, and it is very important to predict the level of hum noise near transmission lines. In this paper, using a comparison between measured values in the UHV Akagi test line and that using corona cage, an experimental prediction method of hum noise in rain condition is proposed. © 1998 Scripta Technica, Electr Eng Jpn, 125(1): 27–36, 1998

UHV交流架空送電線のコロナハム音予測法に関する実験的検討

The audible noise which is produced by corona discharge from transmission line conductors is composed of two major components, namely “hum noise” and “random noise”. Hum noise has a frequency of twice the power line frequency and is generated primarily in rain, fog, and highly humid environments. It is one of the major factors affecting conductor design of transmission lines for voltages above 500kV and it is very important to predict level of hum noise near transmission lines. In this paper, through comparison between measured values in the UHV Akagi test line and that using corona cage, an experimental prediction method of hum noise in rain condition is proposed.

交流送電線下の谷間地形におけるコロナハム音

交流送電線下の谷間地形におけるコロナハム音

Second harmonics of audible noise from AC transmission lines-Random walk model on space distribution

The statistical distribution function of 'hum noise', which is a 100 or 120 Hz pure tone which generates a complex standing wave near AC transmission lines, is derived from random walk theory. The results are verified by comparing them with data measured on the Akagi test line. In order to evaluate the hum noise level near transmission lines, a concept of a temporal and spatial average level is derived, and a method yielding it is shown. >

Hum noise performance of 6, 8, 10 conductor bundles for 1000 kV transmission lines at the Akagi test site: a comparative study with cage data

The hum noise performance of 6, 8, 10 conductor bundles (subconductor diameter: 3.84 cm) for 1000 kV transmission lines was measured at the Akagi test site and the results were compared with cage data. In general, hum noise levels calculated with cage data were higher than the long-term test results. It was found that the differences between calculated and measured levels were formulated with the maximum surface gradient. Based on this relationship a new prediction method for hum noise near AC transmission lines is proposed. >

A new efficient procedure for the estimation of onset times of seismic waves.

A computationally efficient procedure was developed for the fitting of a locally stationary autoregressive model. The amount of computations is bounded by a function of the data length and the model order only and does not depend on the number of possible arrival times. This facilitates automatic determination of arrival time by an on-line system. The on-line system FUNIMAR (fast univariate case of minimum AIC method of AR model fitting) was developed to implement the procedure. The method was checked by applying it to weak seismic signals from earthquakes which were superimposed with background noises such as traffic noise, electronic hum noise, and heavy microtremor. Experimental results confirm the effectiveness of the method for determining the onset time of P-wave and suggest that an AR model of the fifth order is sufficient to determine the onset time of the wave even if it is buried in considerably heavy noises. It is also shown that the onset time of S-wave can also be successfully determined by the method.

Solid-State Lighting Control

Solid-state lighting control will offer a great variety of both conventional and unique control capabilities to the lighting designer. Among these are feedback dimming, soft start, snap on, magnetic tape and optical programming, and frequency inversion. Special design considerations are voltage and current surges, audible hum, and radio noise.

Problems Involved in the Design and Use of Apparatus for Testing Radio Receivers

This paper deals briefly with (1) the desirable characteristics of measuring equipment employed in making the usual tests of radio receiver performance and (2) a description of apparatus and technique used in carrying out several special tests. Measuring equipment and methods are discussed with reference to the elements of the receiver, after which are remarks on the usual tests of sensitivity, selectivity, and fidelity. Under special tests is a discussion of measurements on hum, tube and circuit noise, modulation distortion, intermodulation, audio harmonic analysis, and volume control. Some specimen curves showing results obtained on model receivers are presented.