摘要:

In this Letter the problem of sound propagation in ducts lined with bulk reacting material in the presence of laminar mean flow is considered. The boundary conditions appropriate for the cases of circular and two‐dimensional rectangular ducts with bulk reacting linings are formulated by making use of the analytical solutions of the sheared flow wave equations presented by the authors in their earlier work. These are then solved numerically. Results showing the effect of sheared mean flow on the attenuation of the lowest mode, and the comparison of locally reacting and bulk reacting linings are presented.

ISSN:0001-4966    

DOI:10.1121/1.414701

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

By extending the definition of the covariance matrix, an algorithm is proposed for active matched‐field tracking. The new algorithm is similar to matched‐field tracking in that data is first collected over an extended period of time (∼3–5 min in the underwater problem). Then the algorithm sorts through the data to find possible source tracks that are mostly defined by their end points, A and B.

ISSN:0001-4966    

DOI:10.1121/1.414702

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

The recent article by Burdisso and Fuller [‘‘Design of active structural acoustic control systems by eigenproperty assignment,’’ J. Acoust. Soc. Am.96, 1582–1591 (1994)] does not fully illuminate the contributions of a number of prior authors for a crucial part of the work, that is, the development of weak radiator modes. This comment places the subject development of Burdisso and Fuller in context with the prior art. Further, it demonstrates the similarities of the subject development to prior work published by K. A. Cunefare [‘‘The minimum multimodal radiation efficiency of baffled finite beams,’’ J. Acoust. Soc. Am.90, 2521–2529 (1991)]. The authors recognize and acknowledge that Burdisso and Fuller’s implementation of the concept, through eigenproperty assignment, is unique and valuable.

ISSN:0001-4966    

DOI:10.1121/1.414703

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

The authors thank Professor Cunefare for his interest in our paper on the design of active structural acoustic control systems. This Letter is to clarify questions raised in his Comments.

ISSN:0001-4966    

DOI:10.1121/1.414704

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

In their recent paper, Orrisetal. (OMK) [J. Acoust. Soc. Am.96, 3499–3503 (1995)] present the ‘‘matched‐phase noise reduction’’ technique, which they characterize as a ‘‘method for improving signal‐to‐noise ratios in noise dominated data, given the shape of the noise spectrum.’’ They derive an optimum ‘‘filter,’’ analyze its properties, provide ‘‘an example in which a signal can be retrieved from noise at a level more than 100 dB higher than the signal,’’ and suggest practical applications for the method in underwater acoustics scenarios ‘‘where the frequency spectrum is known approximately.’’ The present paper analyzes the OMK technique in terms of estimators that best approximate the unknown signal and noise and arrives at conclusions which differ from those of OMK. The demonstration of signal recovery reported by OMK is shown to result from their synthesis of an atypical noise realization. Limitations of their technique under more typical conditions are derived.

ISSN:0001-4966    

DOI:10.1121/1.414681

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP

摘要:

In the paper under discussion, the authors conducted a survey on several qualities of resonant wood, particularly conifer, in view of their suitability for violin top plates and piano soundboards. They reported their experiments with several agents, especially with formaldehyde to improve certain physical properties. It will be shown that the discussion about acoustical magnitudes of resonant wood, although detailed, should be complete and that some results do not correspond to previous knowledge.

ISSN:0001-4966    

DOI:10.1121/1.414705

出版商:Acoustical Society of America    

年代:1996

数据来源: AIP