Noise and vibration data

1977 ◽  
Vol 8 (1) ◽  
pp. 49
2021 ◽  
Vol 263 (6) ◽  
pp. 407-417
Author(s):  
Paul Bollard

Bollard Acoustical Consultants, Inc. was retained by the Placer County Planning Dept. to quantify noise and vibration levels resulting from the Gazex avalanche control system usage during the winter of 2018-2019. The primary objective of the monitoring program was to obtain a statistically representative sample of noise and vibration data during Gazex usage for comparison against criteria for potential damage to structures and human hearing. During the survey period, 75 discrete discharges of Gazex cannons occurred. Each discharge was monitored at five fixed monitoring sites in the Alpine Meadows residential community. At the completion of the survey, 1,079 of the possible 1,125 possible data points of interest had successfully been captured. The results of the surveys indicated that, although noise and vibration levels generated by the Gazex system were elevated to the point of being considered highly annoying to local residents, criteria for damage to hearing and structures were not exceeded during the survey period.


1963 ◽  
Vol 35 (11) ◽  
pp. 1886-1886
Author(s):  
Peter A. Franken ◽  
David N. Keast

2019 ◽  
Vol 11 (9) ◽  
pp. 168781401987830
Author(s):  
Md Shakhawat Hossen ◽  
Christopher Kappes ◽  
Mohamed Trabia ◽  
Brendan Morris ◽  
JeeWoong Park ◽  
...  

Transverse rumble strips are common practice to alert drivers by engaging their auditory and tactile senses in addition to visual senses by traffic signals. However, continuous exposure to noise and vibration by transverse rumble strips often results in diminished effectiveness and erratic behaviors, leading to additional safety challenges. In response, demand-responsive transverse rumble strips were developed as traffic safety countermeasures that reduce unnecessary noise and vibration associated with transverse rumble strips by incorporating active control of the rumble strips. Rather than staying static, demand-responsive transverse rumble strips are activated based on the presence of pedestrians, at predesignated times, or in response to abrupt changes in traffic flow. To evaluate the effectiveness of demand-responsive transverse rumble strips, the research team assessed noise and vibration data, both inside the vehicles and on the roadside, for various types of vehicles traveling at different speeds. The test data indicate that demand-responsive transverse rumble strips produced noticeable in-vehicle noise and vibration that could alert drivers to downstream events. Furthermore, demand-responsive transverse rumble strips generated sufficient noise to alert roadside pedestrians to vehicle presence but at low enough level to be considered as acceptable for a residential neighborhood use. Accordingly, demand-responsive transverse rumble strips could address the challenges that static transverse rumble strips face, by providing a design with relatively limited noise while enhancing safety.


2019 ◽  
Author(s):  
E M Fay

The issues of noise and vibration related to the propulsion system of vessels shines a bright light over the present day operation of sea going vessels. Some of the principal issues coming to the front are not new and are concerned with passenger and crew comfort which has been a touchstone for a decade or more. The most recent, more ominous issue is transmission of noise from transiting vessels and how this noise affects marine mammals. The tools used to analyse and define the expected levels of vibration and noise in the design phase are becoming more and more robust. The paper describes the use of computational fluid dynamics to predict the noise and vibration generated by hydrodynamic flow over the hull and the propeller(s) of the vessel. The analysis is carried out using the program OpenFOAM comparing the operating propeller performance coefficients with the open water propeller coefficients. The paper also looks at the effects of cavitation, vessel trim and propeller loading on a 140 meter car ferry. The loading, noise and vibration data will be quantified and compared to full scale vessel data.


Author(s):  
M. F. Aladdin ◽  
N. A. A. Jalil ◽  
N. Y. Guan ◽  
K. A. M. Rezali ◽  
S. A. Adam

Exposure to noise and whole-body vibration (WBV) has been a key element in determining comfort levels in transportation systems. In the automotive industry, researchers and engineers continuously work on reducing noise and vibration levels to minimize discomfort. Noise annoyance in vehicles results from structure-borne as well as air-borne noise from vehicle powertrain, tires and aeroacoustics. Whole-body vibration affects vehicle passenger comfort at the seat pan, back rest and feet. The objective of this research is to evaluate the comfort level of seated passengers in a vehicle from noise and whole-body vibration by considering both separate and combined modality. The noise and vibration data were recorded and analysed in two vehicles on the same highway road with four different speeds. The vibration exposure in vehicle were evaluated based on ISO2631-1:1997. Noise exposure was based on A-weighted sound pressure level. The combined discomfort on noise and vibration were quantified. The vibration results identified clear dominant of z-axis vertical vibration on seat pan, backrest and feet in both vehicles. The discomfort of combined noise and vibration showed that vehicle B caused a higher discomfort level at the high vehicle speed of 90 km/h and 110 km/h. The Relative Discomfort Indicator (RDI) were introduced to compare levels of discomfort from noise and vibration in different vehicles with varying speeds. The result suggests that the RDI value for vehicle A relative to vehicle B is negative at higher vehicle speed which further indicates that at higher speed, vehicle B have a higher discomfort level compared to vehicle A. The RDI value is expected to be useful for automotive Noise, vibration and harshness (NVH) improvement.


Author(s):  
Zheji Liu ◽  
Raymond Smith

Centrifugal compressors used in gas transmission produce strong pressure pulsations, piping vibration, and noise. These are undesirable by-products of the compressor operation that is inherently an unsteady process. This is particularly true for compressors that use a vane diffuser, rather than a vaneless scroll type of diffuser. High vibration levels can potentially cause structural damage in the piping, particularly instrumentation connections, which can cause unnecessary machine down-time and production loss, and is a potential safety hazard. This paper discusses a unique technique to reduce centrifugal compressor piping vibration. This technique reduces aeroacoustics excitation by mounting a duct resonator array inside a compressor diffuser. The effectiveness of this technique is demonstrated by a recent field application to address a noise and vibration concern of a compressor installed in a pipeline station. This compressor had run successfully for several years with a high (but not excessive) level of high frequency vibration in the unit piping. Recent changes in pipeline operating conditions resulted in a significant increase in vibration and associated problems including failure of thermowells and resistance temperature detectors (RTDs). A preliminary measurement of gas pressure pulsations and piping vibration revealed a severe level of high frequency vibration that could lead to a fatigue failure of the unit piping, if operation continued under these conditions. Additional vibration data were measured from the compressor to characterize the noise and vibration and to establish the baseline for future comparison. The baseline vibration data are characterized with a dominant component at the blade passing frequency that makes the duct resonator array an ideal solution. Consequently, a resonator array was designed, manufactured, and installed to reduce the compressor piping vibration and noise. A final test was conducted to verify the effectiveness of the resonator array. Comparing the data acquired before and after the resonator array shows that the dominant vibration level at the blade passing frequency was reduced by 93% on average. The compressor is now able to operate safely at the new pipeline conditions, and it runs much quieter over the full operating range.


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