In:
The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 94, No. 3 ( 1993-09-01), p. 1510-1516
Kurzfassung:
Surface ducts are formed by wind mixing at the sea surface and are a common feature in many of the world’s oceans. These surface ducts have the effect of channeling acoustic energy for long ranges. This paper, however, focuses on the energy that leaks out of the surface duct—paths that are typically neglected by ray models. It is found that the leakage energy at lower frequencies can be surprisingly strong so that a receiver in a ray-theory shadow zone is actually well insonified. Furthermore, the leakage energy is refracted back into the duct where it may dominate the ducted paths. Inside the duct, these two arrivals add up constructively or destructively resulting in anomalously high or low acoustic levels in the surface duct relative to a prediction that neglects the leaky arrival. Thus, a full-wave model is needed; however, certain types of parabolic equations (PEs) fail for these problems because they scramble the phases of the two dominant arrivals. The same mechanism that causes the PEs to fail makes the problem very sensitive to environmental data. For instance, a change in the mean duct speed of 0.5 m/s can also produce large changes in the acoustic levels.
Materialart:
Online-Ressource
ISSN:
0001-4966
,
1520-8524
Sprache:
Englisch
Verlag:
Acoustical Society of America (ASA)
Publikationsdatum:
1993
ZDB Id:
1461063-2
