Properties of Beam-Noise Fluctuations for Horizontal Arrays in Ship-Induced Noise Fields
Abstract
The beam-noise distribution is determined using a Poisson shipping noise model and related to the system characteristics and the noise environment through six physical parameters: the directivity, the sidelobe degradation, the sidelobe/mainlobe power ratio, the noise anisotropy, the isotropic shipping level and the shipping anisotropy. The results indicate that the beam-noise distribution function takes two different forms depending on the extent to which the noise contributions from individual ships are resolved. For highly resolved shipping, the distribution function describes fluctuations that range from very low values to very high values. The low noise values are characterized by a 'noise floor' which represents the lowest noise value that is visible a significant percentage of the time regardless of the extent of the shipping resolution. The value of the noise floor increases linearly with the sidelobe/ mainlobe power ratio and the sidelobe degradation and decreases linearly with the noise anisotropy. The percentage of time that the noise floor is visible increases with the directivity and decreases with the shipping anisotropy and the logarithm of the isotropic shipping level. For weakly resolved shipping, and the distribution function describes comparatively small beam-noise fluctuations. The range of low noise values that are visible, as determined by the lower tail of the distribution, increases with the directivity and decreases with the shipping anisotropy and the shipping level and is essentially independent of the sidelobe degradation and the noise anisotropy. NATO furnished.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1988
- Accession Number
- ADA197248
Entities
People
- R. Heitmeyer
Organizations
- SACLANT ASW Research Centre