Dimensional Sound Field Research Articles

2.5 dimensional sound field reproduction based on mode matching and equivalent sources considering primary reflections

Many sound field reproduction methods using many loudspeakers (secondary sources) have been studied to reproduce a physically-accurate sound field. In our previous research, we proposed a pressure matching method using the modeled transfer functions of the secondary sources based on the sparse equivalent source method (ESM). By modeling the sound field emitted from the loudspeaker, the number of measurement points required for pressure matching can be significantly reduced. Moreover, another well-known method of sound field reproduction is Mode Matching (MM). In the MM method, the driving functions are derived such that the weight coefficients of the spherical harmonics are matched between the desired and reproduced sound fields. In this study, we proposed an implementation of the MM method based on the ESM considering the sound reflections and loudspeakers' directivity. We estimate the spherical harmonic coefficients of the loudspeakers and sound reflections based on the superposition of equivalent sources. In the simulation experiments, we evaluate the reproduction accuracy achieved with the first-order sound reflections.

On Relation between Similarity Ratio and Acoustic Damping Ratio in One Dimensional Sound Field Partitioned by Perforated Plate with Geometric Similarity

On Relation between Similarity Ratio and Acoustic Damping Ratio in One Dimensional Sound Field Partitioned by Perforated Plate with Geometric Similarity

Multiple Circular Arrays of Vector Sensors for Real-Time Sound Field Analysis

This article proposes multiple circular arrays of vector sensors for analyzing the three dimensional sound field. By exploiting the fact that a finite number of spatial basis functions can represent the sound field within a region, the designed arrays allow the analysis of the sound field around the arrays sequentially by either a frequency-domain method or a time-domain method. The arrays are compact and thus are suitable for integrating with small-sized devices. The time-domain method is of low latency and computationally simple, and thus are suitable for providing the devices with spatial acoustic features in real-time. The effectiveness of the proposed arrays and the sound field analysis methods are confirmed by simulations, and compared with another array.

Consideration of Natural Acoustic Frequency of One Dimensional Sound Field Partitioned with Perforated Plate

Consideration of Natural Acoustic Frequency of One Dimensional Sound Field Partitioned with Perforated Plate

Study on Acoustic Damping Ratio of One Dimensional Sound Field Partitioned with Perforated Plate

Study on Acoustic Damping Ratio of One Dimensional Sound Field Partitioned with Perforated Plate

Study on sound pressure level and acoustic damping ratio of one dimensional sound field partitioned by perforated plate with geometric similarity

Study on sound pressure level and acoustic damping ratio of one dimensional sound field partitioned by perforated plate with geometric similarity

Relation between peak value and acoustic damping of sound pressure level of one dimensional sound field partitioned with perforated plates

Relation between peak value and acoustic damping of sound pressure level of one dimensional sound field partitioned with perforated plates

Bearing Fault Diagnosis Based on Spatial Features of 2.5 Dimensional Sound Field

The traditional acoustic‐based diagnosis (ABD) technique based on single‐channel testing has a significant engineering value. Since its diagnosis robustness is sensitive to sound signal acquisition location, it develops slowly. To solve this problem, the 2‐dimensional (2D) sound field variation near the machine is adopted for diagnosis by the near‐field acoustic holography (NAH)‐ based fault diagnosis method with array measurement. However, its performance is limited due to the neglect of the sound field normal change information. To dig the sound field fault information further, a 2.5‐dimensional (2.5D) acoustic field diagnosis method is presented in this paper and its performance compared with the 2D technology is verified by the bearing diagnostic test. Different from the 2D technique with only one source image, the 2.5D acoustic field model consists of source image, holographic sound image, and the differences between them, and its effective feature model is constructed by Gabor wavelet feature extraction and random forest feature reduction algorithm. The diagnostic effect of the 2.5D technique compared with the 2D technique increases more than 11% in the bearing diagnostic test. It provides new ideas for the development of the NAH‐based fault diagnosis method, and further improves the ABD technique‐based array measurement.

Relation between peak value and acoustic damping of sound pressure level of one dimensional sound field partitioned by perforated plates

Relation between peak value and acoustic damping of sound pressure level of one dimensional sound field partitioned by perforated plates

Study on a method for estimating acoustic natural frequency of one dimensional sound field partitioned by perforated plate

Study on a method for estimating acoustic natural frequency of one dimensional sound field partitioned by perforated plate

Effect of perforated plates on sound pressure level of one dimensional sound field partitioned by perforated plates

Effect of perforated plates on sound pressure level of one dimensional sound field partitioned by perforated plates

Study on acoustic natural frequency of one dimensional sound field partitioned by perforated plate

Study on acoustic natural frequency of one dimensional sound field partitioned by perforated plate

On sound pressure level of one dimensional sound field partitioned by perforated plate

On sound pressure level of one dimensional sound field partitioned by perforated plate

Study on acoustic natural frequency of one dimensional sound field partitioned by perforated plate

Study on acoustic natural frequency of one dimensional sound field partitioned by perforated plate

A planar array of differential microphones for 3D sound capture

Three dimensional soundfield decomposition based on spherical harmonic analysis is becoming an integral part of 3D audio for virtual and augmented reality systems. Spherical harmonic analysis reveals the underlying characteristics of the soundfield, thus allowing high accuracy manipulation and analysis of the soundfield. This requires a microphone array with 3D pick up capability to detect the soundfield. A well-studied type of such array configuration is the spherical array. Since its geometry coincides with the spherical harmonics, the sound signal captured by a spherical microphone array is well-suited for the spherical harmonic transform. The placement of microphones on a spherical array has to follow a strict rule of orthogonality of the spherical harmonics which limits the flexibility of the array configuration. The spherical shape of the array also pose difficulties on implementation as well as practical usage. Recently, the authors presented the theory and design of a compact hybrid microphone array distributed on a 2D plane for three dimensional soundfield analysis. The proposed array uses a combination of omnidirectional microphones and differential microphones placed along multiple circles on the X-Y plane. In this paper, we present the practical implementation of a prototype array based on the above design.

穴あき板で仕切られた１次元音場の共鳴周波数と音圧モードに関する研究

Karman vortex shedding occurs when the gas passes through the duct with tube bank of the heat exchangers, such as gas heaters and boilers. Very high level sound in called “self-sustained tones” occurs due to the interference of the vortex and the sound field in the duct. In general, baffle plates are used to suppress the self-sustained tone. However, it is difficult to use them effectively, because insertion conditions have not been established. Then, perforated plates are installed in both sides of the duct to suppress the self-sustained tones. As a result, it was clarified that the perforated plate could suppress the self-sustained tone as expected. The perforated plates are generally used with a cavity to obtain the suppression effect effectively. However the perforated plates change the acoustic natural frequency of the sound field of the duct. In previous paper, this was not referred. This paper aims to clarify the role of the perforated plates when it changes the acoustic natural frequency of the duct. In this study, one dimensional duct will be used for simplicity and the relationship between the aperture ratio and the acoustic natural frequency will be obtained analytically and experimentally. As a result, it was clarified that the analytical results are in good agreement with the experimental ones and the plates with holes had a role of acoustic damping in calculation of the acoustic natural frequency of the one dimensional sound field like a duct with plates with holes.

Effect of set position of perforated plate on acoustic natural frequency of one dimensional sound field

Effect of set position of perforated plate on acoustic natural frequency of one dimensional sound field

Effect of perforated plate on acoustic natural frequency of one dimensional sound field partitioned by perforated plate

Effect of perforated plate on acoustic natural frequency of one dimensional sound field partitioned by perforated plate

Acoustic natural frequency of one dimensional sound field partitioned by perforated plate

Acoustic natural frequency of one dimensional sound field partitioned by perforated plate

Consideration of acoustic natural frequency of one dimensional sound field partitioned by perforated plate

Consideration of acoustic natural frequency of one dimensional sound field partitioned by perforated plate