Acoustic Design of Naval Structures

Abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.

Non resonant transmission modelling with statistical modal energy distribution analysis

“…For the purposes of validation, in Fig. 13 we compare the ENR predicted by SmEdA (51-53) and DMF (14)(15)(16)(17)(18) for two calculations: one taking the NR modes into account and the other one considering only the R modes. Generally good agreement between the two models can be observed for both the R and NR paths.…”

“…The harmonic response is obtained by direct analysis (SOL108 in NASTRAN code) and the subsystem energies are estimated from the node responses using a homemade MATLAB code. For the present test case, the subsystem modal information required in the DMF equations (16)(17)(18) can be calculated analytically for both the natural frequencies and the interaction modal works (see [31]). Two DMF calculations are performed to estimate the response in the 500 Hz octave band: only the resonant modes of the three subsystems are considered in the first while the second also considers the low frequency non resonant modes of the plate.…”

“…For the last 1/3 octave bands, the numbers of Resonant cavity modes are prohibitive but the DMF calculations were performed despite that fact that the total number of modes was greater than 400 000 as the resolution proposed with Eq. (16)(17)(18) only requires the numerical inversion of a square matrix whose dimension is the number of plate modes. The ENR results are proposed in Fig.…”

“…The Patch Transfer Function approach [14] was used to evaluate the sound insulation of a finite size double wall partition [4] and the influence of room characteristics on acoustic transmission was again pointed out. The sound transmission of stiffened panels for the naval and railway sectors was studied in [15][16][17][18]. In [18] the authors used the space harmonic expansion method to show that the spacing and mechanical properties of stiffeners can significantly influence the acoustic performance of stiffened panels.…”

The development of measuring system for studying the dynamic processes of the main brake components in operation

“…Since the stiffness characteristics of the wheel-block contact and the joints in the hinges are generally nonlinear, it is advisable to experimentally determine the frequency range of dynamic processes, which will indirectly indicate the accuracy of setting these parameters in mathematical models and the correctness of the models` structure. As a result, the task of experimental research is to determine the frequency range and analyze the spectrum of dynamic processes occurring in the braking gear during braking [1][2][3][4][5][6][7][8][9][10][11][12].…”