Software for Acoustic Design

We present the СATEС software, which implements the solution to the problems of computational acoustics. The software is based on the use of the superelement method and finite element modeling algorithms, in-cluding hydrodynamic noise. The paper presents the main possibilities of software for solving acoustic design problems. .

Optimization Design for the Sandwich Piezoelectric Transmitters in Acoustic Logging

An optimized transducer prototype with a sandwich structure vibrated longitudinally is proposed for a transmitter in acoustic logging, especially in acoustic logging while drilling, 5y taking account of drilling environments with high temperature and pressure, as well as strong collar drilling vibration during the drilling process. Aimed to improve the transmitting performance, numerical and experimental studies for the transducer optimization are conducted. The impact of location and length of the piezoelectric stack on resonance characteristics arid effective electromeehanical coupling coefficient is calculated and analyzed. Admittance and transmitting performance of the proposed transducer are measured in laboratory experiments, and the results are compared with simulated ones. It is shown that the newly proposed transducer has higher transmitting performance with lower resonance frequencies. This work provides theoretical and experimental bases for transducer designing and acoustic wave measurements in acoustic logging, especially in acoustic logging while drilling.

Experimental and Numerical Study on Vibration of the Full-Revolving Propulsion Ship Stern

In order to solve the severe vibration problems of an ocean engineering ship with a full-revolving propulsion system, the navigation tests, including forced vibration response test and modal test, are carded out in its stem. It is concluded from the comparison of the time-domain waveform and spectrum from different measurement points that three main factors lead to a high-level stern vibration. Firstly, the specific dynamic stiffness of a water tank is relatively small compared with its neighbor hold, which makes it act like a vibration isolator preventing vibrational energy transmitting to the main hold. Secondly, there exists high-density local modes in the working frequency range of the main engine and thus the local resonance occurs. Thirdly, the abnormal engagement of gears caused by the large deflection of the shaft bearing due to its low mounting rigidity leads to violent extra impulse excitations at high speeds. Then the modification against the dynamic defects is given by simply improving the specific stiffness of the water tanks. And the effect is validated by the FEM calculation. Some important experience is obtained with the problems being solved, which is useful in the design of ships with the same propulsion system. It is also believed that the dynamic consideration is as important as the static analysis for the ships, and that most of the vibration problems may be avoided with a proper acoustic design.

Acoustic design and research on the auditorium of Shanghai Grand Theatre

Shanghai Grand Theatre is a great modern theatre with the largest formula, the highest investment, the most advanced technique and excellent acoustic quality in China. This article mainly introduced Shanghai Grand Theatre's characteristics of formula, technical requirements of acoustic design of Auditorium, characteristics of figure design, reverberation control, acoustic simulation research, acoustic performance and subjective evaluation.

A subspace fitting algorithm of acoustic vector sensor array and corresponding matrix pre-filter design

In order to ease the pass-band response distortion of the matrix pre-filter,a simple approach for designing matrix spatial filter is proposed,which minimizes the sum of the k maximal distortion norm（k is the number of the constraint points）within the pass-band,while constraining the filter response within the stop-band.Considering the costly amount of calculation of the high-resolution methods,an algorithm with small amount of calculation based on matrix pre-filtering and subspace fitting using acoustic vector array（MF-VSSF）is proposed.Through joint processing of signal subspace of both pressure and particle velocity,the pre-filtering matrix and the signal subspace is decreased to M-dimensional（M is the number of array-element）,hence reduces the time-consumption of the matrix pre-filter design and DOA searching.Simulation results show that,the method offers the same performance as MUSIC with pre-filtering,but has much lesser amount of calculation.Moreover,the designed prefilter can efficiently suppress the interference in the stop-band and improve the estimation and resolution performance of successive DOA estimators.

Acoustic design of Beijing Theater

Beijing Theater, with a capacity of 1,000 seats, is a multipurpose theater mainly for dramatic performances. To meet the acoustic criteria of different kinds of performances, adjustable sound absorption structures are installed in the hall. Special consideration has been given to the sound diffusion for gratifying natural sound effect of mustic performance. In addition, a movable orchestra shell and a lifting orchestra pit have also been employed. In this paper, the authors discuss the acoustic design of the Theater and the success achieved to testify the necessity and possibility of multi-purpose utilization in acoustics in an auditorium .

Acoustic design of the Gymnasium and Natatorium of Chinese National Olympic Sports Center

The proper control over the reverberation times is of vital importance to acoustic design of large-sized gymnasium. In the projects discussed in this paper gratifying reverberation times have been obtained by employing space absorbers suspended under the exposed space frame and strong absorbing structures mounted on the side walls. Some suggestions concerning acoustic design of large-sized gymnasia and natatoria are made on the basis of the practical experience gained from the projects.

The design and experimental investigation of control system for acoustic liner with adjustable impedance

A kind of new acoustic liner with adjustable impedance has been proposed. At the same time, a set of control system has been designed for this kind of liner. Many experimental results have been obtained based on this control system. In fact, the present investigation shows the possibi1ity of active control of sound absorption coefficient or impedance of a liner according to external sound source condition by means of a standing wave tube. The experimental results show that the sound absorption coefficient of the liner can keep optimal under any sound source condition by controlling the cavity depth and the flow rate through the perforated plate of the liner. In addition, hoth the resistance and the reactance of the liner can also be controlled independently corresponding to any given condition. which is necessary to control unsteady How in turbomachinery.