For decades noise control engineers have urged manufacturers to publish the acoustical noise levels of the products they develop and sell. Yet, it is fair to say that typical consumers walking into a retail store today filled with noise-making products (leaf blowers, hair dryers, power tools, humidifiers, exhaust fans, portable fans and heaters, and hundreds of other product types) will find very little information about the noise levels of these products. Nor will they find much information when shopping online. Yes, they may see terms like “whisper quiet” or “noise only 35 dB,” but these are essentially meaningless for comparing one product to another objectively or for making informed purchasing decisions with respect to noise. The availability of noise level information will ultimately help drive demand for quieter products, not only from consumers but also from large organizations, corporate purchasing groups, and regulatory agencies. With the recent publication of ASA/ANSI S12.3-2023, “Declaration of Product Noise Emission Values” and ASA/ANSI S12.61-2024, “Declaration and Verification of Noise Emission Values of Machinery, Equipment, and Products,” product manufacturers now have clear instructions and procedures for how to go about publishing meaningful and uniform noise level information to the general public for the products they put on the market. This paper will provide background for the technical aspects and underlying statistics of these standards.
This paper investigates the effect of sound insulation on the acoustic behavior of bus interior cavities in three areas: the driver's head, the middle passenger's head, and the rear passenger's head cavities. For this purpose, which has been done at high frequencies, the VA One (R) engineering software, which is based on the Statistical Energy Analysis (SEA) method, has been used. After extracting all the equations of the SEA method, all the structural and acoustic subsystems of the bus, as well as the connections between them, have been modeled. Aerodynamic loads at the speed of 80 km/h, airborne engine noise, fan, and exhaust manifold at the back, and airborne tire/road noise as noise sources have been applied separately to the roof, body, and windscreen of the bus. Finally, by using the Response Surface Methodology (RSM), considering the minimum weight and maximum noise reduction, the panels have been optimized to improve the interior sound quality. The results show that using optimized panels reduces overall sound transmission within the bus and specifically improves noise reduction at the driver's head, middle passenger's head, and rear passenger's head cavities by 47.8%, 51.6%, and 69.8%, respectively.
All rotating machinery has vibrations by nature, and appropriate balancing can frequently solve 80% of the vibration problems. Mass unbalance, coupling misalignment, and mechanical looseness are some of the problems that can cause vibrations in rotating machinery. An imbalanced rotor is usually the main cause of machine vibration. This causes too much force in the bearing area, which shortens the machine’s working life. This study investigates the balance condition of a rotor-bearing assembly utilising the Machinery Fault Simulator-Lite (MFS-Lite) through a combination of experimental and analytical methodologies. Experiments were carried out to analyze vibration responses under different imbalance conditions, applying several balancing techniques, namely the Influence Coefficient Method, Four-Run Method, and Phase-Only Balancing. The experimental data acquired from the MFS-Lite configuration were compared with analytical outcomes to confirm the accuracy of the employed dynamic correction methodologies. The results show that MFS-Lite can accurately model real rotor-bearing dynamics and that theoretical predictions and experimental observations are quite near to each other.
Low-voltage induction motors are widely used in industry and commercial settings, where reliable operation and early fault detection are crucial to prevent downtime. Past detection methods often rely only on electrical signals, overlooking complex electromechanical interactions that affect fault signatures, especially in vibration signals. This paper introduces a fully coupled electromechanical interaction (F-EMI) model designed for fault detection in low-voltage three-phase squirrel cage induction motors. The model integrates electromagnetic forces, bearing dynamics, and structural deformation to simulate motor behavior under healthy and faulty conditions. The model captures ten key interaction pathways between mechanical and electrical parts and generates realistic fault vibration signals. Validation experiments cover four conditions: healthy, mechanical looseness, stator open-circuit, and bearing outer-race faults. Comparisons of simulated and measured vibration spectra show that the F-EMI model accurately reproduces fault-specific frequencies and broadband levels. These results demonstrate the model’s value for predictive maintenance and fault diagnosis in low-voltage motor applications requiring accurate, system-level interaction modeling.
In recent years, acoustic black hole (ABH) has developed rapidly in vibration acoustics as a wave manipulation technology. It is currently being tried to be applied to the vibration control of industrial pipes. Usually, the ABH structure has an obvious vibration suppression ability in the middle and high frequency range, but the vibration suppression is insufficient in the low frequency range; at the same time, the embedded ABH structure leads to structural weakening. Considering the advantages of low-frequency control of local resonance (LR), this paper proposes an acoustic black hole-local resonance coupling structure (ABH-LR), which is used in pipe vibration control, by combining the theory of ABH and local resonance. It consists of a one-dimensional ABH structure, damping layers, and oscillators (several for local resonance) attached to the pipe. The results show that at low frequencies such as 190Hz and 440Hz (<500 Hz), vibration amplitude decreases significantly through the local resonance effect and anti-resonance matching in the periodic structure. In the middle and high frequency range (>500 Hz), the vibration energy in the pipe is captured by the ABH and dissipated through the damping layer attached to the central region of the ABH. ABH-LR realizes broadband vibration attenuation. The study reveals the wave blocking mechanism of the local resonance effect and the energy accumulation effect of the ABH structure, through the influence analysis of the material parameters, boundary conditions, and periodical arrangements of the ABH-LR pipe. With the increase of the damping layer thickness and loss factor, the equivalent modal loss factor of the system shows a nonlinear jump feature, with a maximum increase of 5 times. Compared with the single ABH-LR unit model, three-unit models attached to the pipe have better vibration suppression on the pipe. When the boundary conditions change, ABH-LR can still suppress the vibration of the pipe.
