Octave Band Technique for Noise Measurement at the Source, Path, and Receiver of Gas Turbines in Oil and Gas Facilities

Noise measurement is essential for industrial usage. However, further attention to preventing noise pollution is needed, especially when working with equipment generating a high noise level, such as gas turbines. This study aims to determine the best way to perform noise measurement and analyze the octave band frequency generated by noise pollution caused by gas turbine equipment. Data from site measurements show that the gas turbines produce more than 85 dB of noise with a Z-weighted measurement. A noise measuring investigation was conducted to obtain the data for the 1/3 octave band. A frequency-domain was used to comprehend the properties of the noise measurement frequency band. The frequency band was classified into three different zones called low, medium, and high frequency, which is useful in noise measurement analysis to identify a viable solution to reduce the noise. On-site sampling was performed at the source, path, and receiver of three separate gas turbine locations within oil and gas operations. The 1/3 octave band data collection results at the sound source, path, and receiver demonstrate the noise level distribution at the perimeter of gas turbine installations in the low and medium frequency ranges. Most of the high noise frequency range is between 250 Hz and 2 kHz for source, path, and receiver. All acquired values are compared to the Department of Safety and Health (Occupational Safety and Health (Noise Exposure) Regulations 2019 in Malaysia. As a result, oil and gas service operators can monitor and take countermeasures to limit noise exposure at oil and gas facilities.

Octave-Band Four-Beam Antenna Arrays with Stable Beam Direction Fed by Broadband 4 × 4 Butler Matrix

A novel concept of four-beam antenna arrays operating in a one-octave frequency range that allows stable beam directions and beamwidths to be achieved is proposed. As shown, such radiation patterns can be obtained when radiating elements are appropriately spaced and fed by a broadband 4 × 4 Butler matrix with directional filters connected to its outputs. In this solution, broadband radiating elements are arranged in such a way that, for the lower and upper frequencies, two separate subarrays can be distinguished, each one consisting of identically arranged radiating elements. The subarrays are fed by a broadband Butler matrix at the output to which an appropriate feeding network based on directional filters is connected. These filters ensure smooth signal switching across the operational bandwidth between elements utilized at lower and higher frequency bands. Therefore, as shown, it is possible to control both beamwidths and beam directions of the resulting multi-beam antenna arrays. Moreover, two different concepts of the feeding network connected in between the Butler matrix and radiating elements for lowering the sidelobes are discussed. The theoretical analyses of the proposed antenna arrays are shown and confirmed by measurements of the developed two-antenna arrays consisting of eight and twelve radiating elements, operating in a 2–4 GHz frequency range.

Using noise control principles when evaluating the acoustic impacts of face coverings during the coronavirus pandemic

Several different combinations of face masks and shields are evaluated for their acoustic performance using a head and torso simulator (HATS). The HATS is used as a controlled and repeatable artificial sound source using white noise in a classroom environment. Sound pressure levels at octave band frequencies due to the face coverings are evaluated at a location of 2.0 meters from the HATS which is within the direct field to reduce the room acoustical effects. The problem is modeled as a barrier separating a source and receiver using fundamental noise control principles. Fabric material properties are used such as thickness, density, stiffness, and damping. The results are compared with experimental tests. The face shield with clear plastic barrier produces a resonance in the 1000 Hz octave band. Analytical models of cavity resonances, standing wave resonances, or plate resonances are calculated and compared with the experimental resonance. The speech interference level is used to determine the frequency content that is most likely to cause hearing difficulties and compared with A-weighted differences between the unmasked condition and masked.

Effect of ceiling and dry-type double floor on heavy-weight floor impact sound in concrete building and CLT building.

The air layer between the interior finishes and the structure is used as piping and wiring space. In many cases, ceilings and dry-type double floors are commonly constructed in Japan. However, the effect of the air layer of ceilings and dry-type double floors on the heavy-weight floor impact sound insulation performance has not yet quantitatively investigated. Therefore, in this study, the same floor and ceiling structures were constructed for concrete and CLT buildings, and the heavy-weight floor impact sound was investigated. As results, it was confirmed that the reduction amount of the heavy-weight floor impact sound by the ceiling tended to be smaller in CLT buildings than in concrete buildings. However, the trends were similar. Due to the dry-type double floor structure, the heavy-weight floor impact sound level was increased in concrete building and decreased in CLT building at 63 Hz in the octave band center frequency band. Therefore, it can be said that the dry-type double floor structure can be used to improve the heavy-weight floor impact sound performance in the CLT building.

Statistical assessment of A-weighted sound power level for printer with electrophotographic engine

Statistical distribution and statistical upper limit (the value which 93.5 % of the batch of new equipment are expected to lie) of A-weighted sound power level for one office printer were experimentally estimated from 10 new samples picked up from market. The printer is capable of A4-size printing with electrophotographic engine which corresponds Annex C.16 Page printers in ECMA74 17th (2019). A-weighted sound power level for continuous printing mode was determined in accordance with noise test code for ITTE (Information Technology and Telecommunications Equipment such as printers and personal computers), ISO 7779:2018 and ECMA-74 Annex C. Sample standard distribution of production of overall A-weighted sound power level (determined from 100-10000 Hz one-third-octave band) is 0.25 dB, whereas individual one-third-octave band has larger distribution. The value obtained is better than reference distribution 1.32 dB set in ISO 9296:2017 which states estimation of statistical upper limit value of the batch of equipment for ITTE.

Use of a transient SEA for calculation of structure-borne interior noise in trains from an induction motor controlled by multi-mode PWM

This paper presents a transient SEA (Statistical Energy Analysis) approach to predict the structure-borne interior noise in trains from an induction motor controlled by multi-mode PWM (Pulse Width Modulation). Most of the induction motors installed in trains are controlled by multi-mode PWM, which switches between asynchronous and synchronous modes according to the speed to reduce switching losses. This control causes the electromagnetic forces of PWM harmonics to change, resulting in a transient interior noise depending on the vehicle's speed. In this paper, we model the bogie using FEM to calculate the transmission of the electromagnetic forces to the vehicle body through traction bars and dampers. Next, we model the vehicle body using a transient SEA to calculate transient energy in a 1/3 octave band excited by the transmitted electromagnetic forces. Finally, we restore the waveform of interior noise by applying the appropriate phase to the transient energy to auralize the analysis result. We obtained reasonable agreement by comparing the analysis results of the interior noise with the actual measurements.

Prediction of one-third-octave band sound and vibration levels from heavy-hard impacts

Noise and vibration due to dropping hard heavy weights is a common source of disturbance and complaint in residential, commercial, and mixed-use building types. The authors and others have worked on developing methodologies to accurately, repeatably, and conveniently measure heavy-hard impact noise and vibration in the field based on a standard weight drop. Separately, systems have been created to measure the force being injected into a building from heavy-hard impact. It has been shown that this force data can be used to successfully predict vibration levels in buildings if in-situ transfer functions are known. In this paper, the authors will present a novel one-third-octave band prediction method using the laboratory force data and a reference impact sheet to predict field performance without the need to measure transfer function. The method is evaluated using both noise and vibration measurements.

Improved Unmanned Aerial Vehicle Noise Direction Finding System

The work is devoted to the development of the acoustic direction of creation of means of detection of unmanned aerial vehicles (UAVs). The work of these tools is based on the principles of noise direction finding with the use of such variable characteristics of the acoustic field as: sound intensity, frequency spectrum and spatial spectrum. The architecture of UAV detection devices on the acoustic field corresponds to the algorithms of reproduction in separate paths of the device of ideology of registration and control of dynamics of change of characteristic of an acoustic field which defines the specified change as the fact of detection. The technical implementation of the above detection devices is to create a path of parallel octave, ½ octave and ⅓ octave filters, a path of narrowband filtering and a path of detection by power (intensity). The ideology of construction of detection devices is based on variability and physical manifestations of changes in such characteristics of acoustic noise as: sound intensity in the space - time interval of observation, broadband filtering, narrowband filtering, correlation characteristics. To ensure the detection of acoustic power (or intensity) with subsequent measurement of the level, the counter-inclusion (by switching or using operational amplifiers) of the elements of the cross-shaped group is used. An important and new feature is that one of the linear discrete acoustic antennas with an enlarged base additionally has two more pressure receivers symmetrically relative to the phase center. For broadband filtration, a comb of ⅓ octave band and semi-octave filters is used. In turn, the path of the narrowband spectrum is an octave band filter and a unit for calculating the fast Fourier transform. The path of the correlation direction-finding method implements the determination of changes in the autocorrelation coefficient and the corresponding electrical parameter (say the current through the display circuit) in the processing path in situations of fixing the direction to the target. Therefore, the proposed system for detecting useful noise signals should contain four paths, the physical implementation of detection in which is performed by software implementation of detection algorithms and, threshold processing and indication of results In order to improve and increase the reliability of detection, the direction finder is supplemented by the path of detection on the mutual spectrum and the path of the correlation method of direction finding. The processing of input acoustic information of the type of specific noise-like signal is carried out by using the instrumental laboratory software package Lab View and Math Lab. We will add that the article contains theoretical and practical results of measurements of noise loading and range of action of a noise direction finder. Experimental studies in terms of detection and measurement of the main characteristics of the device were conducted in laboratory and field conditions. At the same time, the present demonstrates the rapid development of the UAV fleet, which determines the urgency of the work and the development of the device as a means of counteracting small aircraft of various recognitions is its goal.