Browsing Reprints by Subject "Underwater acoustics"
Now showing items 2140 of 46

Highfrequency normalmode calculations in deep water
(NATO. SACLANTCEN, 1982/10)A method has been developed to perform highfrequency deepwater normalmode calculations in the multikilohertz region in water depths of the order of 5 km. The results from this technique agree with fast field program ... 
Intensity calculations along a single ray
(NATO. SACLANTCEN, 1974/02)A method is presented for the calculation of sound intensity using only one ray. The soundvelocity profile is assumed to be continuous up to the second derivative and it is supposed that the ray equations are solved ... 
Is power averaging the best estimator for undersea acoustic data?
(NATO. SACLANTCEN, 1982/06)The power average is the statistic which is commonly used in all types of acoustic data processing. It is an excellent estimator for "well behaved" Gaussian distributions when the central or average value is desired. ... 
Measurement and interpretation of angular spreading from multiple boundary interactions in a shallow water channel
(NATO. SACLANTCEN, 1997)The problem of angular spreading of sound that has undergone multiple boundary scattering (both sea surface and sea bed) in a shallow water channel is discussed. Measurements made of the horizontal spatial coherence along ... 
Measurement of the bubble population in coastal waters using combination frequencies of MHz order
(NATO. SACLANTCEN, 1997)This paper describes the use of a combinatron frequency technique to measure the size distribution of oceanic bubbles. Written between two sea trials, the paper describes how the apparatus cart be adapted to design tests ... 
Methods used in France for the calculation of sound fields
(NATO. SACLANTCEN, 1971/12) 
Noise sources in the ocean  part 1
(NATO. SACLANTCEN, 1975/10)Following a brief historical survey of the development of our knowledge of the origins and characteristics of ambient noise in the ocean, the principal known sources of noise are described. These are: environmental origin, ... 
Noise sources in the ocean  part 2
(NATO. SACLANTCEN, 1975/10)Following a brief historical survey of the development of our knowledge of the origins and characteristics of ambient noise in the ocean, the principal known sources of noise are described. These are: environmental origin, ... 
The ocean noise coherence matrix and its rank
(CMRE, 2019/05)An expression for the crossspectral density matrix of ocean noise naturally separates into a Toeplitz part and a Hankel part [Harrison (2017). J. Acoust. Soc. Am. 141, 2812?2820]. The Toeplitz part is shown to be substantially ... 
Processing of broadband acoustic signals
(NATO. SACLANTCEN, 1972/05) 
Ray convergence in a fluxlike propagation formulation
(CMRE, 2014/01)The energy flux formulation of waveguide propagation is closely related to the incoherent mode sum, and its simplicity has led to development of efficient computational algorithms for reverberation and target echo strength, ... 
Review of numerical models in underwater acoustics including recently developed fastfield program
(NATO. SACLANTCEN, 1984/12)Two papers given by SACLANTCEN personnel at the NATO Advanced Research Workshop on Hybrid Formulation of Wave Propagation and Scattering at Castel Gandolfo, Rome, Italy on 30 August to 3 September 1983 are published as a ... 
Riverine environmental acoustics at an ocean estuary
(NATO. SACLANTCEN, 1997)The purpose of these studies was to investigate some of the more important geoacoustrc parameters that might govern the use of high frequency sonar in muddy rivers, where they flow into the sea. Both environmental and ... 
Secure underwater acoustic networks: current and future research directions
(CMRE, 2019/06)Underwater Acoustic Networks (UANs) are widely used in various applications such as climate change monitoring, pollution control and tracking, tactical surveillance and offshore exploration. However, limited consideration ... 
Separation of measured noise coherence matrix into Toeplitz and Hankel parts
(CMRE, 2017/08)The crossspectral density of ocean ambient noise is usually estimated from the product of the complex hydrophone signals, each of which already corresponds to the summed responses of sources from all angles. The true ... 
Simultaneous analysis in real time
(NATO. SACLANTCEN, 1972/05) 
Status of ray theory development of Naval Undersea Research and Development Center
(NATO. SACLANTCEN, 1971/12)The first part of this paper discusses NUC (Naval Undersea Research and Development Center) work on the accuracy and validity of ray theory. By comparing the range to convergence zones as indicated by experiment and by ... 
Subcritical penetration of narrow Gaussian beams into sediments
(NATO. SACLANTCEN, 1988/03)Complete wavetheory solutions have been obtained numerically for both the reflected and the transmitted fields associated with a narrow Gaussian beam incident on a watersediment interface near the critical grazing angle. ... 
Summary and recommendations
(NATO. SACLANTCEN, 1971/12)An unfortunate first impression might be that ray tracing is dull, simply because the idea is a very old one. In fact, ray tracing is the single most powerful method available to us for understanding the complexities of ... 
The effect of gravityforced oscillations at the base of the duct on its effective depth as a channel for acoustic rays
(NATO. SACLANTCEN, 1971/12)