The Analysis of Mechanical Vibrations and Acoustic Pressure Level οf a Transformer Model

European Directives 2002/44/EC and 2003/10/EC establish the exposure limit values for preventing operators’ risks to vibration and noise transmitted by machines. Few studies studied noise and vibration of agricultural backpack powered machines (as mist blowers and blowers), but nobody critically studied them. This work analyzed the field back vibration, hand-arm vibration (HAV), and noise transmitted to ten operators by eight blowers and mist blowers. Unweighted and weighted vibration were analyzed, using the standards ISO 2631-1 (back), and ISO 5349-1 and ISO/TR 18570 (hand-arm system). The noise was evaluated by recording the acoustic pressure level at the operators’ ears using the ISO 9612. With the ISO 2631-1, the vibration to the operators’ back was low (0.38 ms−2), but the unweighted vibration measured along y and z-axes (not used by the ISO 2631-1) were high (>11 ms−2). HAV were also low when using the ISO 5349-1 (the highest value was 2.51 ms−2 in mist blowers), but high with the ISO/TR 18570 for the onset of vibration white finger (1446 ms−1.5 in blowers). Noise levels were always high: more than 100 dB(A), excluding the blower with the exhaust inside the blower hose. This last machine had noise levels lower than 86 dB(A), but its specific feature could increase environmental pollution.

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Acoustic distribution study inside centrifugal pump impeller under different blade outlet angles using the Powell vortex sound theory

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406220908732 ◽

2020 ◽

Vol 234 (13) ◽

pp. 2595-2609

Author(s):

Chang Guo ◽

Ming Gao ◽

Jingying Wang

Keyword(s):

Acoustic Pressure ◽

Weighted Average ◽

Pressure Level ◽

Acoustic Source ◽

Pump Impeller ◽

Outlet Angle ◽

Sound Theory ◽

Impeller Outlet ◽

Acoustic Pressure Level ◽

Centrifugal Pump Impeller

The acoustic distribution characteristics inside centrifugal pump impeller under different blade outlet angles are explored based on the Powell vortex sound theory. It is shown that the increase in the blade outlet angle narrows the fluctuation ranges of the acoustic source and acoustic pressure perturbation at the impeller outlet far away from the tongue, while extends those near the tongue. The total acoustic source intensity and total acoustic pressure level at the impeller outlet far away from the tongue decrease by 1.23% and 1.17%, respectively, while those near the tongue increase by 0.64% and 0.94% when the angle increases from 15° to 35°, respectively. Additionally, under different blade outlet angles, the total acoustic source intensity and total acoustic pressure level on the streamline far away from the tongue increase rapidly first, then increase slowly from inlet to outlet of the impeller. On the streamline near the tongue, a mutation of total acoustic source intensity and total acoustic pressure level appears near the impeller outlet, and the mutation range moves towards the middle section of the impeller with increasing blade outlet angle and rotational speed. In addition, the A-weighted average acoustic source intensity level and A-weighted average acoustic pressure level increase by 0.4% and 1.22% when the angle increases from 15° to 35°, respectively. The study reveals the rotor–stator interaction intensity evolution characteristics, and provides a reference for the optimization design of centrifugal pumps.

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Signal transfer through the hearing protectors with the regulation of damping in the presence of the impulse noise

Occupational Safety – Science and Practice ◽

10.5604/01.3001.0013.3200 ◽

2019 ◽

Vol 575 (8) ◽

pp. 22-25

Author(s):

Rafał Młyński ◽

Emil Kozłowski

Keyword(s):

Impulse Noise ◽

Acoustic Pressure ◽

Blocking Effect ◽

Pressure Level ◽

Signal Source ◽

Signal Transfer ◽

Hearing Protectors ◽

The Mean ◽

Definition Of ◽

Acoustic Pressure Level

Hearing protectors with the regulation of damping are used ever so more frequently to protect the hearing of persons endangered with the presence of impulse noise. A clear advantage coming from the use of this type of hearing protectors, compared to other types, lies in the improvement of the perception of useful signals. However, in spite of such advantages it is during their use one can observe the effect of “blocking” of the sound transfer underneath the protectors (meaning the limitation of the signal transfer through the protectors), occurring directly after the appearance of the acoustic impulse. The article presents an analysis of the acoustic signal transfer underneath the hearing protectors with the regulation of damping in the situation of the acoustic impulse appearance. The analysis aimed at the definition of the time of the “blocking” of noise transfer underneath the protectors effect as well as the decrease of the acoustic pressure level resulting from the mentioned effect. Towards that goal a special work stand was prepared, consisting of impulse signal source, a set noise and an acoustic tester (artificial head). The research had shown the time of the “blocking” effect during the use of the protectors with the regulation of damping to be reaching 1.2 seconds and the decrease in the value of the mean acoustic pressure level, resulting from such effect, to be exceeding even 16 dB.

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Exhaust Noise Reduction by Application of Expanded Collecting System in Pneumatic Tools and Machines

Energies ◽

10.3390/en14061592 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1592

Author(s):

Dominik Gryboś ◽

Jacek S. Leszczyński ◽

Dorota Czopek ◽

Jerzy Wiciak

Keyword(s):

Experimental Data ◽

Mathematical Model ◽

Noise Reduction ◽

Sound Pressure ◽

Acoustic Pressure ◽

Pressure Level ◽

Computational Results ◽

Noise Measurements ◽

Exhaust Noise ◽

Collecting System

In this paper, we demonstrate how to reduce the noise level of expanded air from pneumatic tools. Instead of a muffler, we propose the expanded collecting system, where the air expands through the pneumatic tube and expansion collector. We have elaborated a mathematical model which illustrates the dynamics of the air flow, as well as the acoustic pressure at the end of the tube. The computational results were compared with experimental data to check the air dynamics and sound pressure. Moreover, the study presents the methodology of noise measurement generated in a pneumatic screwdriver in a quiet back room and on a window-fitting stand in a production hall. In addition, we have performed noise measurements for the pneumatic screwdriver and the pneumatic screwdriver on an industrial scale. These measurements prove the noise reduction of the pneumatic tools when the expanded collecting system is used. When the expanded collecting system was applied to the screwdriver, the measured Sound Pressure Level (SPL) decreased from 87 to 80 dB(A).

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Aeroacoustics of [s]

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2004.1405 ◽

2005 ◽

Vol 461 (2056) ◽

pp. 1005-1028 ◽

Cited By ~ 36

Author(s):

M.S Howe ◽

R.S McGowan

Keyword(s):

Sound Pressure ◽

Acoustic Pressure ◽

Vocal Tract ◽

Mathematical Problem ◽

Pressure Fluctuations ◽

Pressure Level ◽

Correct Prediction ◽

Oral Pressure ◽

Spectral Peaks ◽

Principal Source

The theory of the sibilant fricative [s] is formulated and solved as a mathematical problem of aeroacoustics. Air is forced through the constriction between the tongue blade and the hard palate by intra-oral pressure, forming a jet that strikes the upper incisors and leaves the mouth through a gap between the upper and lower incisors. The principal source of sound is the ‘diffraction’ of jet turbulence pressure fluctuations by the incisors. The spectrum of these pressure fluctuations incident on the teeth is modelled analytically using an empirical formula adapted from turbulent boundary-layer theory. Predictions are made about the far field acoustic pressure spectrum with reference to measured and estimated values of vocal tract dimensions and intra-oral pressure. Predicted spectra compare well with observations. The principal spectral peaks are determined by vocal tract physiology anterior to the tongue–palate constriction. The theory furnishes the first correct prediction of the dependence of the overall sound pressure level on the intra-oral pressure.

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Contributions of Voice and Nonverbal Communication to Perceived Masculinity–Femininity for Cisgender and Transgender Communicators

Journal of Speech Language and Hearing Research ◽

10.1044/2019_jslhr-19-00387 ◽

2020 ◽

Vol 63 (4) ◽

pp. 931-947

Author(s):

Teresa L. D. Hardy ◽

Carol A. Boliek ◽

Daniel Aalto ◽

Justin Lewicke ◽

Kristopher Wells ◽

...

Keyword(s):

Fundamental Frequency ◽

Sound Pressure Level ◽

Sound Pressure ◽

Vocal Tract ◽

Presentation Mode ◽

Pressure Level ◽

Presentation Modes ◽

Audiovisual Stimuli ◽

Vocal Tract Resonance ◽

Point Light

Purpose The purpose of this study was twofold: (a) to identify a set of communication-based predictors (including both acoustic and gestural variables) of masculinity–femininity ratings and (b) to explore differences in ratings between audio and audiovisual presentation modes for transgender and cisgender communicators. Method The voices and gestures of a group of cisgender men and women ( n = 10 of each) and transgender women ( n = 20) communicators were recorded while they recounted the story of a cartoon using acoustic and motion capture recording systems. A total of 17 acoustic and gestural variables were measured from these recordings. A group of observers ( n = 20) rated each communicator's masculinity–femininity based on 30- to 45-s samples of the cartoon description presented in three modes: audio, visual, and audio visual. Visual and audiovisual stimuli contained point light displays standardized for size. Ratings were made using a direct magnitude estimation scale without modulus. Communication-based predictors of masculinity–femininity ratings were identified using multiple regression, and analysis of variance was used to determine the effect of presentation mode on perceptual ratings. Results Fundamental frequency, average vowel formant, and sound pressure level were identified as significant predictors of masculinity–femininity ratings for these communicators. Communicators were rated significantly more feminine in the audio than the audiovisual mode and unreliably in the visual-only mode. Conclusions Both study purposes were met. Results support continued emphasis on fundamental frequency and vocal tract resonance in voice and communication modification training with transgender individuals and provide evidence for the potential benefit of modifying sound pressure level, especially when a masculine presentation is desired.

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Influence of the Acoustic Reflex on Vowel Recognition

Journal of Speech Language and Hearing Research ◽

10.1044/jshr.2903.420 ◽

1986 ◽

Vol 29 (3) ◽

pp. 420-424 ◽

Cited By ~ 4

Author(s):

Michael Dorman ◽

Ingrid Cedar ◽

Maureen Hannley ◽

Marjorie Leek ◽

Julie Mapes Lindholm

Keyword(s):

Auditory System ◽

Sound Pressure ◽

Dynamic Range ◽

Recognition Accuracy ◽

Pressure Level ◽

Acoustic Reflex ◽

The Poor ◽

Stapedial Reflex ◽

Vowel Recognition ◽

High Sound

Computer synthesized vowels of 50- and 300-ms duration were presented to normal-hearing listeners at a moderate and high sound pressure level (SPL). Presentation at the high SPL resulted in poor recognition accuracy for vowels of a duration (50 ms) shorter than the latency of the acoustic stapedial reflex. Presentation level had no effect on recognition accuracy for vowels of sufficient duration (300 ms) to elicit the reflex. The poor recognition accuracy for the brief, high intensity vowels was significantly improved when the reflex was preactivated. These results demonstrate the importance of the acoustic reflex in extending the dynamic range of the auditory system for speech recognition.

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Computers and Electronics in Agriculture The sensor to estimate the sound pressure level in eggs

Qeios ◽

10.32388/7x11uf ◽

2020 ◽

Author(s):

Iran Oliveira Silva

Keyword(s):

Sound Pressure Level ◽

Sound Pressure ◽

Pressure Level

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Kekuatan Sambungan AL/CFRP Menggunakan Adhesif Epoksi/Serbuk-AL dengan Variasi Pressure Level

JEECAE (Journal of Electrical, Electronics, Control, and Automotive Engineering) ◽

10.32486/jeecae.v1i1.14 ◽

2017 ◽

Vol 1 (1) ◽

Author(s):

Bi Asngali

Keyword(s):

Pressure Level ◽

Lap Joint ◽

Single Lap Joint ◽

Al 2024

Penelitian ini bertujuan untuk menyelidiki pengaruh pressure level terhadap kekuatan geser sambungan single lap joint (SLJ) antara Al 2024 dan CFRP dengan adesif epoksi/serbuk Al. Variasi pressure level yang digunakan adalah 0,6; 0,7; 0,8; 0,9 dan 1 MPa. Pembuatan dan pengujian spesimen uji geser mengacu pada ASTM D 1002. Hasil penelitian menunjukkan bahwa pressure level dapat meningkatkan kekuatan geser sambungan. Pada variabel pressure level terbaiknya yaitu 0,9 MPa menghasilkan kekuatan geser tertinggi (8,59 MPa). Pada kondisi tersebut, penampang patahan menunjukkan jenis kegagalan kombinasi antara kegagalan cohesive, light fiber tear dan fiber-tear.Kata kunci— pressure level; epoksi/serbuk-Al; kekuatan geser; single lap joint .

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