The Experts below are selected from a list of 9588 Experts worldwide ranked by ideXlab platform

N.w. Millard - One of the best experts on this subject based on the ideXlab platform.

  • On the Radiated Noise of the autosub autonomous underwater vehicle
    ICES Journal of Marine Science, 2001
    Co-Authors: Gwyn Griffiths, Peter Enoch, N.w. Millard
    Abstract:

    Autonomous Underwater Vehicles (AUVs) can be very quiet platforms from which to make observations of marine living resources. With few moving parts and very low propulsion power they should have a very low underwater Radiated Noise signature. The purpose of this paper is to describe measurements on Autosub to test this assumption. The measured Noise level and spectrum are compared to the ICES proposal for the Radiated Noise of fisheries research vessels. Integrated over the band 100 Hz to 5000 Hz the AUV source level, at 124 dB relative to 1mPa at 1 m, was about 39 dB below of the ICES specification and about 30 dB quieter than the Noise-reduced vessel "Scotia". Autosub is in fact exceedingly quiet. The difficulties of making measurements of the underwater Radiated Noise of a quiet submerged vehicle are discussed and suggestions are made for improvements in techniques.

Gwyn Griffiths - One of the best experts on this subject based on the ideXlab platform.

  • On the Radiated Noise of the autosub autonomous underwater vehicle
    ICES Journal of Marine Science, 2001
    Co-Authors: Gwyn Griffiths, Peter Enoch, N.w. Millard
    Abstract:

    Autonomous Underwater Vehicles (AUVs) can be very quiet platforms from which to make observations of marine living resources. With few moving parts and very low propulsion power they should have a very low underwater Radiated Noise signature. The purpose of this paper is to describe measurements on Autosub to test this assumption. The measured Noise level and spectrum are compared to the ICES proposal for the Radiated Noise of fisheries research vessels. Integrated over the band 100 Hz to 5000 Hz the AUV source level, at 124 dB relative to 1mPa at 1 m, was about 39 dB below of the ICES specification and about 30 dB quieter than the Noise-reduced vessel "Scotia". Autosub is in fact exceedingly quiet. The difficulties of making measurements of the underwater Radiated Noise of a quiet submerged vehicle are discussed and suggestions are made for improvements in techniques.

Li Gui-juan - One of the best experts on this subject based on the ideXlab platform.

  • Spatial directivity of ship Radiated Noise at far field
    Journal of the Harbin Institute of Technology, 2010
    Co-Authors: Li Gui-juan
    Abstract:

    In order to obtain the spatial directivity of ship Radiated Noise at far field in shallow water,a new method is presented to compute the corresponding sound field distribution at far field.Firstly the sound pressure data measured by hydrophone array at near field was used to obtain the equivalent intensity and positions of multi-pole structure model for ship Radiated Noise,then the spatial directivity of far field Radiated Noise is computed by normal modes.A comparison between simulation results of far field spatial directivity of ship Noise obtained by this method and the result obtained from direct computation using assumed data of sound sources show that the method presented in this paper can give an acceptable spatial directivity of far field.

  • Validity test of Radiated Noise sources model of ship
    Journal of Vibration and Shock, 2009
    Co-Authors: Li Gui-juan
    Abstract:

    Usually the Radiated Noise of the ship is measured only at near distance to ensure enough signal to Noise ratio.So it is highly important to study the modeling of the volume source of ship.In order to show the validity of the suggested model of Radiated Noise sources of ship at shallow wave guide,the Radiated Noise of a fishery ship was measured.Experimental results show that the established model is effective,which means that the ship Noise sources can be described as some distributed multi-poles along the ship.The conclusion is helpful to understand the internal characteristics of ship.

  • On near field distribution of warship Radiated Noise
    Journal of Naval University of Engineering, 2008
    Co-Authors: Li Gui-juan
    Abstract:

    In order to modify the measuring method of warship Radiated Noise which has been widely used in our country,a physical model of warship Radiated Noise model with some spatial distribution was provided.The sound pressure at near distance under free field was computed by using the wave number integration and the basic characteristics of the Radiated Noise were analyzes.The simulation results are in accordance with the characteristics of the Radiated Noise at near distance in the foreign literature,which thus validates the physical model of warship Radiated Noise.

  • A SIMPLIFIED MODEL FOR SHIP'S Radiated Noise SOURCES
    Journal of Vibration and Shock, 2008
    Co-Authors: Li Gui-juan
    Abstract:

    Underwater Radiated Noise of a ship possesses complex spatial intensity distribution.In order to accurately analyze the characteristic of underwater Radiated Noise of a ship,a simplified model of the ships' Noise sources composed of several multi-pole sources is established.After proving the validity of the model,the target's source parameters are inversed using an optimized algorithm through processing the Noise data of the ship in different trips,then the sound pressure in another trip is calculated using multi-pole coefficients obtained from inversions.A comparison between the simulation results of the sound pressure of the ship Noise using this method and the theoretical results shows that this simplified model is effective.

Peter Enoch - One of the best experts on this subject based on the ideXlab platform.

  • On the Radiated Noise of the autosub autonomous underwater vehicle
    ICES Journal of Marine Science, 2001
    Co-Authors: Gwyn Griffiths, Peter Enoch, N.w. Millard
    Abstract:

    Autonomous Underwater Vehicles (AUVs) can be very quiet platforms from which to make observations of marine living resources. With few moving parts and very low propulsion power they should have a very low underwater Radiated Noise signature. The purpose of this paper is to describe measurements on Autosub to test this assumption. The measured Noise level and spectrum are compared to the ICES proposal for the Radiated Noise of fisheries research vessels. Integrated over the band 100 Hz to 5000 Hz the AUV source level, at 124 dB relative to 1mPa at 1 m, was about 39 dB below of the ICES specification and about 30 dB quieter than the Noise-reduced vessel "Scotia". Autosub is in fact exceedingly quiet. The difficulties of making measurements of the underwater Radiated Noise of a quiet submerged vehicle are discussed and suggestions are made for improvements in techniques.

Li Yao-bo - One of the best experts on this subject based on the ideXlab platform.

  • A Method for Modulation Feature Extraction of Underwater Target Radiated Noise
    Torpedo Technology, 2006
    Co-Authors: Li Yao-bo
    Abstract:

    Modulated signal of underwater target Radiated Noise contains much important feature information.According to modern signal processing theory,a method for modulation feature extraction of the Radiated Noise is discussed.First,by using wavelet transform and multiresolution analyses,the modulated envelop of underwater target Radiated Noise is extracted.Then,the dynamic modulation is analyzed by one and a half dimensional spectrum and the harmonic information is obtained.The method can simultaneously make use of the Noise elimination performance of wavelet and the natural restraint to Gaussian Noise of higher order spectrum.The simulation result of real Radiated Noise data indicates that the method can extract the dynamic modulated feature from Radiated Noise effectively with an excellent anti-Noise property.

  • Study on underwater target Radiated Noise modulated information extraction method
    Journal of Naval University of Engineering, 2006
    Co-Authors: Li Yao-bo
    Abstract:

    This paper deals with the modulated information extraction based on the wavelet transform.First,the modulated information is separated from Radiated Noise by means of multi-resolution analysis.Second,the separated modulated information envelopment is extracted and the power spectrum is estimated by using the continuous wavelet transform.On the basis of the above research,the real data of Radiated Noise is simulated.The result indicates that the method is an effective way to extract the modulated information from Radiated Noise.