First Paper: Human Response to Intense Low-Frequency Noise and Vibration

10 male and 10 female undergraduates were asked to estimate 5-, 10-, 15-, and 30-sec. intervals under five intensities of ambient noise (50, 60, 70, 80, and 90 dB). Interval estimates became shorter as the intensity of noise increased from 50 to 80 dB but became longer at 90 dB. The effects of intensity of noise were most prominant in the two longest intervals. These results are interpreted in terms of CNS arousal theory.

Experiments on individual and combined effects of noise and vibration of low or moderate intensity were conducted concerning paired associates learning task. The experiments concerned randomly intermittent noise at 64, 74 and 79 dB (A)(re 20 μPa, peaks az) and continuous or intermittent vibration at 66 and 76 dB (re 10-5 m/s2, vertical wholebody sinusoidal in 5 Hz). The learning task was evaluated by error rates in mean and standard deviation for each condition of noise and vibration. Subjective ratings of disturbance by noise and vibration were also made after the task. Sixty-four and 79 dB (A) noise produced detrimental effects on the learning. Seventy-nine dB (A) noise added with the continuous vibration indicated elimination of the effects of noise and vibration alone. Further, high disturbance did not always accompany high error rates in mean or standard deviation.

The laser is an important component of the resonator fiber-optic gyroscope (RFOG) and the optical noise of the laser severely limits the performance of the RFOG system. The mathematical model which presents the effect of the intensity noise on the RFOG is established. In order to verify the correctness of the model, an acousto-optic modulator is innovatively used to generate the intensity noise of the laser, through which the intensity noise could be quantitatively changed without introducing unexpected noises of the laser. The experimental results indicate the intensity noise results in the deterioration of the scale factor nonlinearity and the increase of detected rotation rate error. In addition, a scheme based on the second harmonic demodulation of the intensity-modulated signal is proposed to compensate the light intensity fluctuation of the laser in the RFOG. The test results show the drift of the gyro introduced by the light intensity fluctuation could be reduced >8 dB through this method.

The synchronization transition in coupled piecewise map lattices is studied. The average order parameter is calculated to diagnose synchronization of coupled piecewise maps. As a result, it shows that coexistence of a period cluster and synchronization states in the synchronization transition process. A detailed research shows that the period clusters consist of two coexisting period attractors, and their period orbit is an unstable periodic orbit of the isolate map. The unstable periodic orbit is stabilized again by the mutual interactions of the local nonlinearity and the spatial coupling. The influence of noise on the complete synchronization (CS) in coupled piecewise map systems is also studied in this work. Synchronization probability densities and average order parameters as a function of the coupling strength with various noise intensities are calculated. When the noise intensity is small, the noise can postpone synchronization transition processes. However, if the noise intensity is larger, the noise can destroy the period clusters states, shorten the synchronization transition and enhance the CS in coupled piecewise maps.

Given the increasing number of citizen complaints about port noise and the lack of relevant studies assessing resident exposure, the effects of port noise are gaining increasing public attention. It is especially significant in ports near residential areas, where excessive noise emissions can seriously impact the urban environment. This paper aimed to investigate the perceptions and attitudes of the population living near the cargo terminals in the Port of Split regarding the impact of port noise in the urban area, focusing on their health and standards of living. The research methodology included a questionnaire distributed in the areas where the residents are most affected by noise. In addition to conventional descriptive survey analysis, the authors used regression analysis and two-way ANOVA with the Tukey post hoc test as a parametric data analysis tool. The survey results showed the harmful effects of port noise on most set parameters, and perceived noise intensity for three different times of the day caused a high level of concern for the urban environment. In addition, the regression analysis results showed a weak and reverse dependency between the distance of the selected residences from the noise sources and the perceived noise intensity. These findings support the validity of the respondents’ perceptions and the credibility of the obtained results. The application of parametric data analysis revealed a lack of formal knowledge of residents about the effects of noise and a strong differentiation between groups based on the variables that determine the level of education of residents and their assessments of the noise intensity of the cargo terminal. However, the subjective impressions and the psycho-physical and emotional states of the residents need also to be included in the validation of the results. The obtained results will facilitate the adoption of noise management policies and implementation of noise abatement programs in the Port of Split.

Effects of wind turbines on spatial distribution of the European hamster

In this study, the effects of mechanical vibration on the mechanical properties of ceramic diesel particulate filters (DPFs) were investigated. The goal is to determine how the mechanical vibration used in the regenerative ash cleaning process for these filters affects their mechanical integrity during subsequent reuse. Both virgin and vibrated DPF samples were subjected to com-pressive and 3-point flexural loading at three different loading rates along axial and tangential directions. Statistical analysis was conducted to determine the significance of variation in the compressive and flexural strengths of the DPFs as a result of exposure to mechanical vibration. The results show that there is no statistically significant difference in both compressive and flexural strengths of the virgin DPFs and the DPFs subjected to the same level of mechanical vibration typically used in ash cleaning of DPFs. When the intensity of vibration was doubled, the drop in compressive strength became statistically significant, but less than 10% under axial loading. However, no drop in flexural strength was observed for DPFs subjected to this high intensity of mechanical vibration. The safe threshold for mechanical vibration of ceramic filters is considered to be much higher than that currently used in vibration-based ash cleaning process.

The effects of industrial noise on resting heart rate and blood pressure were studied in 3,105 blue-collar workers. Heart rate and blood pressure were measured in different workers at various times during the workday. After controlling for several possible confounders, we found that resting heart rate in females was associated positively with noise intensity (p = .036) and with time of day (p = .054). In males, resting heart rate was associated with noise intensity; however, such association was related to time of day (p = .046). No such associations were found for blood pressure in either sex. We plotted the mean resting heart rate by time of day for workers exposed to high [ > or = 80 db(A)] and low noise, and no difference was evident with respect to morning heart rate in either sex. After 4 h of noise exposure for males (and less time for females), individuals who were exposed to high noise had higher heart rates; however, in females this was not observed at the end of the workday. Thus, recurrent daily exposure to high noise at work has an acute, though not residual, effect on resting heart rate.

A low-noise single-frequency laser is a key component of the space-based gravitational wave detector, and the intensity noise of the laser directly affects the sensitivity of the space-based GW detector. In this work, we report a low-noise single-frequency laser designed for space-based gravitational wave detector. The laser is based on a master oscillator power amplifier (MOPA), which is designed to possess a low-power, narrow-linewidth seed laser acting as master oscillator (MO) and an all polarization-maintaining fiber amplifier acting as power amplifier (PA). The amplifier that uses a robust mechanical design consists of an Yb-doped double-clad fiber forward pumped by wavelength-locked 976 nm pump laser diode (LD) to achieve 2.13 W of output power and 70 dB of signal-noise ratio (SNR). To suppress the relative intensity noise (RIN) in a millhertz regime (1 mHz–1 Hz), we characterize the power stabilization of a pump diode laser based on a proportional-integral-derivative (PID) feedback control loop where an in-loop photodetector is used. The power fluctuation can be converted into the fluctuation of the current signal by the photodiode, the current signal is converted into the voltage signal and amplified by a transimpedance circuit. Then, the voltage signal is compared with the voltage reference signal, and the error signal is achieved to adjust real-timely the drive current of the pump laser diode. This is a good way to significantly suppress the RIN of a laser at low frequencies, but the measured RIN below 4 mHz is still higher than –60 dBc/Hz. In order to further suppress the RIN to lower than 4 mHz, an active precise temperature control technology is used to suppress the thermal noise from pump LD and fiber coupler. To assess the RIN milliertz regime, we design an RIN measurement system consisting of a high-precision signal acquisition card (24 bit) and a computer program based on LabVIEW. The measurement range of the system is 2 μHz–102.4 kHz and the frequency resolution up to 2 µHz, much better than the counterparts of commercial instruments. By stabilizing the fiber amplifier pump LD current and the temperature of pump LD and the temperature of fiber coupler, the out-of-loop RINs are measured to be –63.4 dBc/Hz@1 mHz and –105.8 dBc/Hz@1 Hz , and in a milliertz regime of 1 mHz–1 Hz, the RIN is below –60 dBc/Hz. The results show that the feedback control of the fiber amplifier pump LD current and the temperature control of the key devices can effectively suppress the RIN in the millihertz frequency band, which lays a foundation for further improving the intensity noise performance in the low frequency band.

Excess intensity noise in a low-noise single-frequency class-A VECSEL is experimentally investigated over the frequency range 10 kHz-18 GHz. An analytical model is derived, based on multimode Langevin equations, to describe the observed laser excess noise over the whole bandwidth. From 50 MHz to 18 GHz, class-A operation leads to a shot noise limited relative intensity noise (RIN), namely -155 dB/Hz for 1-mA detected photocurrent, except at harmonics of the cavity free spectral range (FSR). At these frequencies, the excess noise is shown to be due to the amplified spontaneous emission contained in the nonlasing side modes. The measured levels of excess noise correspond to side mode suppression ratios (SMSRs) ranging from 70 to 90 dB, in agreement with the model. At low frequencies, 10 kHz-50 MHz, the observed excess noise spectrum has the expected Lorentzian shape. Its bandwidth increases with the pumping rate to an upper limit given by the cavity photon lifetime. Below this cutoff frequency, we show that the pump RIN is the dominant source of noise, while it is filtered by the laser dynamics above. Finally, our model permits to design a semiconductor class-A laser with an intensity noise limited to the shot noise level over the whole 10 kHz-18 GHz bandwidth.

Low-frequency current and intensity noise in AlGaAs laser diodes

The generated noise of the Mi-8 helicopter will differ significantly in the mechanism of formation, resulting in a complex spectrum. Working conditions inside the helicopter correspond to harmful working conditions in terms of noise (class 3.2 – 3.3), and in terms of infrasound – acceptable (class 2). The simultaneous effect of intense noise, infrasound and General vibration creates high risks to the health of helicopter personnel.

The fidelity of gate operations on neutral atom qubits is often limited by fluctuations of the laser drive. Here, we quantify the sensitivity of quantum gate fidelities to laser phase and intensity noise. We first develop models to identify features observed in laser self-heterodyne noise spectra, focusing on the effects of white noise and servo bumps. In the weak-noise regime, characteristic of well-stabilized lasers, we show that an analytical theory based on a perturbative solution of a master equation agrees very well with numerical simulations that incorporate phase noise. We compute quantum gate fidelities for one- and two-photon Rabi oscillations and show that they can be enhanced by an appropriate choice of Rabi frequency relative to spectral noise peaks. We also analyze the influence of intensity noise with spectral support smaller than the Rabi frequency. Our results establish requirements on laser noise levels needed to achieve desired gate fidelities.

Lévy noise-induced transition and stochastic resonance in a tumor growth model

Workplace noise exposure gains growing attention in high tech industry. This study investigated the noise effect on physiological and subjective responses in semiconductor manufacturing clean room environment. Twenty subjects including 10 males and 10 females completed all phases of the experiment. Each subject was asked to participate in four treatment combinations of two noise intensities [65 dB(A) and 80 dB(A)] × two frequency levels [high and low]. For each treatment condition, the subject was exposed to the specified noise condition in a sound proof cabin for one hour. The physiological measures included blood pressure and heart rate. The subjective measures included noise sensitivity, fatigue and annoyance. The ANOVA results indicate that long-time noise exposure caused significant increase in blood pressure (p< 0.001). Furthermore, the noise intensity by time interaction effect was found to be significant on annoyance and fatigue. The findings suggest that prolonged exposure to noise intensity at 80 dB(A) would result in a significant increase in physiological cost and subjective discomfort feeling. Thus, some countermeasures should be taken to reduce noise exposure and to promote health, and quality of working life.