Papers by Keyword: Sound Pressure

Abstract: This paper discusses the development of an in-situ, real-time tool wear monitoring system using the cutting sound that occurs during machining. In this study, the turning of carbon steel was implemented to examine the relationship between tool wear and the waveform of the cutting sound. Characteristic waveforms were extracted by fast Fourier transform (FFT) analysis of the cutting sound. The results indicated that the sound pressure of a specific frequency range increased during the progress of cutting-tool wear. In addition, it was possible to monitor the progress of tool wear by measuring the spectrum of a specific frequency range, even if the shape of the tool rest and the shapes of the work material were different, under certain cutting conditions.

Abstract: A semi-analytical and semi-numerical method is presented for analyzing the acoustics radiation characteristics of a rotational shell. Combining the dynamics control equation and the sound pressure expression, the vibro-acoustics equation of the rotational shell is formulated firstly. Then, a semi-analytical method is developed based on the superposition principle. The comparisons with the document show that the proposed method is accurate and efficient.

Abstract: In view of the traditional methods can not accurately identify the far field of the problem of sound source location,Sound pressure and sound intensity combination technique is proposed for identifying environmental noise source. Using the method of sound pressure can test the size of the noise sound pressure and sound intensity method can identify the noise source bearing characteristics identify the noise source. The technology of this noise identification is applied to identify Noise of boundary of a factory and then finds out the main noise source. Test results showed that: Causing the plant boundary noise source are the 3rd, 5th, 6th, 7th sound source, therefore the solution of reducing noise at boundary is developed.

Abstract: How to locate accurately positioning of underwater noise source is the most important link of underwater vehicle fault detection and diagnosis. In this paper, Near-field Acoustic Holography technique is applied to detection and location of noise sources of underwater vehicle, to collect radiated noise information of noise source. A LABVIEW-based underwater vehicle sound pressure measurement system is designed, which has capacity to detect and locate noise sources of the underwater vehicle, so that the fault positioning of underwater target can be located and excluded easily.

Abstract: The vibration and sound radiation characteristics of laminated composite flat-panel sound radiators are studied via both theoretical and experimental approaches. In the theoretical study, a finite element model is presented to formulate the forced vibration of the sound radiators. The first Rayleigh integral is used to construct the sound pressure level curve of the sound radiators. In the experimental study, a laminated composite sound radiator was subjected to sweep sine excitation to determine the frequency response spectrum from which the natural frequencies of the sound radiator were identified. The sound radiator with salt powder distributed on its top surface was excited to generate the vibration shapes of the sound radiator at several selected frequencies. The SPL curve of the sound radiator was also measured experimentally. The experimental results are then used to verify the feasibility and accuracy of the proposed finite element model.

Abstract: A high-precision marine ambient noise sound pressure monitoring system is developed based on the Michelson interference, a method of improving the measurement accuracy is presented by signal modulation and compensation. Experiments show that the monitoring system has a wide dynamic range and high accuracy especially in low-frequency.

Abstract: A computer-aided engineering (CAE) model was developed to analyze the acoustic characteristics of a car cabin. Pro/Engineer Wildfire 4.0 was used to three-dimensionally represent the geometry of the cabin. The CAE, using COMSOL Multiphysics 4.2a, was performed to investigate the distribution of sound pressure fields at natural frequencies. The principle mode indices were (2, 1, 1), (2, 1, 1), (1, 1, 1), and (2, 2, 2), corresponding to the modal coefficients 1, 2, 3, and 4 and the natural frequencies of 179.691, 139.276, 221.620, and 231.386 Hz, respectively. The results of the analysis provided insight into the car cabin design to suppress exterior and interior noise.

Abstract: Abstract. To realize the sound pressure unit directly, the method of sound pressure measurement based on acoustic particle velocity was described. In order to get a simple acoustic field, a travelling wave tube was designed. The sound pressure distribution obtained by microphone along the tube was measured. The result showed the acoustic field inside the tube could be considered as travelling wave and the sound pressure is equal to the product of the air density, sound speed and the particle velocity. The laser Doppler Anemometry was used to measure the particle velocity in the acoustic field. The modulated Doppler signal was obtained by measurement system. With the spectral analysis of Doppler signal and the signal model, the particle velocity was obtained with the Bessel function analysis. The comparison of sound pressure measured by microphone and the value deduced from the velocity measured by laser Doppler system shows that deviations between two methods were 0.04 dB at 650 Hz and discrepancies were less than 0.34 dB at frequencies from 300 Hz to 1k Hz.

Abstract: Vibration characteristics of 5μm- thick Ni film were investigated with applying acoustic wave to the Ni diaphragm of 2mm x 2mm unit size. In the modal analysis, the first resonance mode of the diaphragm showed an out-of-plane piston-like movement and the first natural frequency was 1,643 Hz, whereas in this experiment, the first natural frequency appears at about 1,300 Hz under sound pressure of 0.2 Pa. The amplitudes of diaphragm increase with increase of sound pressure level in the applied frequency range from 300 Hz to 1,000 Hz, indicating that area of diaphragm influences directly the amplitude.