On the Influence of Noise on the Critical and Oscillatory Behavior of a Predator-Prey Model: Coherent Stochastic Resonance at the Proper Frequency

Noise induced changes in the critical and oscillatory behavior of a Prey-Predator system are studied using power spectrum density and Spectral Amplification Factor (SAF) analysis. In the absence of external noise, the population densities exhibit three kinds of asymptotic behavior, namely: Absorbing State, Fixed Point (FP) and an Oscillatory Regime (OR) with a well defined proper (natural) frequency. The addition of noise destabilizes the FP phase inducing a transition to a new OR. Surprisingly, it is found that when a periodic signal is added to the control parameter, the system responds robustly, without relevant changes in its behavior. Nevertheless, the "Coherent Stochastic Resonance" phenomenon is found only at the proper frequency. Also, a method based on SAF allows us to locate very accurately the transition points between the different regimes.Comment: RevTex, 18 pgs, 6 figures. Submitted to Physics Letters A (2000

Holistic noise and vibration abatement within the EU 7FP. The SILENV Project: Ship Innovative soLutions to rEduce Noise and Vibrations.

Transports are well known to be major contributors to noise pollution. Noise and vibrations (N&V) abatement naturally appears as an important objective for the greening of surface transports. The SILENV project is a response to this requirement for the maritime domain. The consequences of N&V emissions from the ships are multiple. N&V emissions constitute a disturbance for both passengers and harbour area residents, and in some cases it may be a health issue for crew members. Moreover, the increasing ship traffic-generated underwater noise causes ecological nuisances on marine wildlife. The project assesses the problem of reducing the ship-generated Noise & Vibration pollution with a holistic approach. After a definition of realistic target levels, existing experimental data from main types of ships and on-site measurements have been analysed to identify the most critical sources of noise and vibration. Innovative solutions have been individually assessed on technical and economical criteria. Finally a pre-normative requirements formulation, called \u201cGreen Label\u201d, is presented, aiming at reducing the noise inside the ships as well as outside in air and water