Basic Flow Analyses Used in the Study of Broad-Band Noise in Compressors

1976 ◽  
Vol 98 (1) ◽  
pp. 23-28
Author(s):  
F. Buckens
Keyword(s):  
Broad Band ◽  
Wave Number ◽  
Frequency Noise ◽  
Noise Generation ◽  
Noise Sources ◽  
Left Hand ◽  
Dispersive Effect ◽  
Band Noise ◽  
Axisymmetrical Flow ◽  
The Right

The propagation of sound in a moving compressible fluid displays interesting features which are important in the problem of noise generation in compressors. Without considering the discrete frequency noise generated by interacting rotating blades and stationary parts, a perturbation method applied to the equations of flow motion in an idealized continuous medium leads to an equation of density waves propagation in a nonhomogeneous moving fluid. The right-hand side is considered as describing distributed noise sources which involve velocity fluctuations. On the left-hand side there appears a negative diffusive effect due to a negative divergence of the velocity field, which downstream entails a streamwise amplification of the intensity of the sound generated upstream. Further, there is a dispersive effect entailing, for a given wave number, a group velocity which in a simple example is shown to be larger than the phase velocity and to become imaginary for a velocity divergence sufficiently high in absolute value. This, together with the amplification effect, may explain the relative importance of the high frequency band in the actual noise spectra of compressors. An attempt at determining the coefficients of the acoustical equation for compressors is made in the schematic Beltrami-Gromeka case of a helicoidal axisymmetrical flow. With simplified assumptions on the behavior of density, depending either solely on the axial coordinate or only on the radial one, both types of axial and radial compressors are considered simultaneously and the method of analytical solution applied. It is emphasized that this treatment is restricted to the mechanical aspect of the broad-band noise generation.

Annoyance and Discomfort during Exposure to High-Frequency Noise from an Ultrasonic Washer

1995 ◽  
Vol 81 (3) ◽  
pp. 819-827 ◽  
Author(s):  
Kjell Holmberg ◽  
Ulf Landström ◽  
Bertil Nordström
Keyword(s):  
High Frequency ◽  
Broad Band ◽  
Short Exposure ◽  
Frequency Noise ◽  
High Frequency Noise ◽  
High Frequency Sound ◽  
Band Noise ◽  
Significant Difference ◽  
Exposure Levels ◽  
Different Levels

Annoyance and discomfort during exposure to high-frequency noise from an ultrasonic washer have been examined in the experiments carried out with 10 subjects. After a short exposure during which the subjects rated their annoyance and discomfort, a broad-band noise was matched to the ultrasound. The subjects were exposed to three different levels of ultrasound on three different occasions. Analyses showed that ultrasound causes considerable annoyance and discomfort even for the lowest exposure levels. No significant difference between annoyance and discomfort was observed. The matchings indicated, however, that the A-weighting, i.e., the traditional rating technique used for noise evaluations, overestimated the high-frequency sound when evaluating annoyance and discomfort.

Noise Sources and Transmission in Piping Systems

2002 ◽  
Author(s):  
Stephen A. Hambric ◽  
Yun Fan Hwang ◽  
Thomas S. Chyczewski
Keyword(s):  
Vibrational Energy ◽  
Broad Band ◽  
Computational Cost ◽  
Piping System ◽  
Frequency Noise ◽  
Energy Propagation ◽  
Acoustic Attenuation ◽  
Noise Sources ◽  
Band Frequency ◽  
Piping Systems

An overview of the vibro-acoustic behavior of fluid-filled piping systems is given, summarizing noise sources, how piping structures and fluids accept energy from noise sources, and how the energy is then transmitted and exchanged by wavetypes throughout the piping. Discrete and broad-band frequency noise sources from active components, such as pumps, and passive components, such as valves and flow over piping, are described, and scale on flow velocities and operating speeds. The turbulence in the fluid flow contributes to piping system noise and vibration. The turbulence in the core flow impinges on both active and passive devices, causing discrete and broad-band noise sources. Turbulence near pipe walls excites structural piping modes. Techniques for quantifying the turbulence and its effects are described. An overview of the mechanisms of acoustic and vibrational energy propagation in piping walls and fluids is given, along with a discussion of various tools used to model the propagation, such as finite element (FE) and boundary element (BE) analysis, transfer matrix (TM) analysis, and statistical energy analysis (SEA). FE and BE models may be used to model high levels of complexity in both structural-acoustic systems and noise sources, but require large model sizes at high frequencies. TM and SEA models sacrifice modeling generality, but can represent high frequency behavior at low computational cost. Finally, means of mitigating acoustic and vibration energy transmission, such as narrow-band acoustic attenuation devices (quarter wavelength silencers and Quincke tubes), broad-band acoustic attenuation devices (mufflers and acoustic filters), and broad-band structural vibration attenuation devices (isolators and rubber piping), are outlined.

Editorial Note

1946 ◽  
Vol 11 (1) ◽  
pp. 2-2
Keyword(s):  
Editorial Note ◽  
Speech Sounds ◽  
Left Hand ◽  
Hand Column ◽  
Right Hand ◽  
Infant Speech ◽  
The Right

In the article “Infant Speech Sounds and Intelligence” by Orvis C. Irwin and Han Piao Chen, in the December 1945 issue of the Journal, the paragraph which begins at the bottom of the left hand column on page 295 should have been placed immediately below the first paragraph at the top of the right hand column on page 296. To the authors we express our sincere apologies.

Is the Future the Right Time?

2010 ◽  
Vol 57 (4) ◽  
pp. 308-314 ◽  
Author(s):  
Marc Ouellet ◽  
Julio Santiago ◽  
Ziv Israeli ◽  
Shai Gabay
Keyword(s):  
Auditory Task ◽  
English Speakers ◽  
Visual Modality ◽  
Opposite Pattern ◽  
Time Line ◽  
Temporal Reference ◽  
Left Hand ◽  
Reading Direction ◽  
Mental Time Line ◽  
The Right

Spanish and English speakers tend to conceptualize time as running from left to right along a mental line. Previous research suggests that this representational strategy arises from the participants’ exposure to a left-to-right writing system. However, direct evidence supporting this assertion suffers from several limitations and relies only on the visual modality. This study subjected to a direct test the reading hypothesis using an auditory task. Participants from two groups (Spanish and Hebrew) differing in the directionality of their orthographic system had to discriminate temporal reference (past or future) of verbs and adverbs (referring to either past or future) auditorily presented to either the left or right ear by pressing a left or a right key. Spanish participants were faster responding to past words with the left hand and to future words with the right hand, whereas Hebrew participants showed the opposite pattern. Our results demonstrate that the left-right mapping of time is not restricted to the visual modality and that the direction of reading accounts for the preferred directionality of the mental time line. These results are discussed in the context of a possible mechanism underlying the effects of reading direction on highly abstract conceptual representations.

Noise source location and scaling of subsonic upper-surface blowing

2020 ◽  
Vol 19 (3-5) ◽  
pp. 191-206
Author(s):  
Trae L Jennette ◽  
Krish K Ahuja
Keyword(s):  
Strouhal Number ◽  
Noise Source ◽  
Low Frequency ◽  
Directivity Pattern ◽  
Source Location ◽  
Dipole Source ◽  
Frequency Noise ◽  
Noise Sources ◽  
Trailing Edge ◽  
Trailing Edge Noise

This paper deals with the topic of upper surface blowing noise. Using a model-scale rectangular nozzle of an aspect ratio of 10 and a sharp trailing edge, detailed noise contours were acquired with and without a subsonic jet blowing over a flat surface to determine the noise source location as a function of frequency. Additionally, velocity scaling of the upper surface blowing noise was carried out. It was found that the upper surface blowing increases the noise significantly. This is a result of both the trailing edge noise and turbulence downstream of the trailing edge, referred to as wake noise in the paper. It was found that low-frequency noise with a peak Strouhal number of 0.02 originates from the trailing edge whereas the high-frequency noise with the peak in the vicinity of Strouhal number of 0.2 originates near the nozzle exit. Low frequency (low Strouhal number) follows a velocity scaling corresponding to a dipole source where as the high Strouhal numbers as quadrupole sources. The culmination of these two effects is a cardioid-shaped directivity pattern. On the shielded side, the most dominant noise sources were at the trailing edge and in the near wake. The trailing edge mounting geometry also created anomalous acoustic diffraction indicating that not only is the geometry of the edge itself important, but also all geometry near the trailing edge.

scholarly journals Hand Preference and Performance in Basketball Tasks

2019 ◽  
Vol 16 (22) ◽  
pp. 4336 ◽  
Author(s):  
Emanuela Gualdi-Russo ◽  
Natascia Rinaldo ◽  
Alba Pasini ◽  
Luciana Zaccagni
Keyword(s):  
Professional Training ◽  
Factor Model ◽  
Hand Preference ◽  
Control Group ◽  
Basketball Players ◽  
Confirmatory Factor Analyses ◽  
Left Hand ◽  
Confirmatory Factor ◽  
And Performance ◽  
The Right

The aims of this study were to develop and validate an instrument to quantitatively assess the handedness of basketballers in basketball tasks (Basketball Handedness Inventory, BaHI) and to compare it with their handedness in daily activities by the Edinburgh Handedness Inventory (EHI). The participants were 111 basketballers and 40 controls. All subjects completed the EHI and only basketballers filled in the BaHI. To validate the BaHI, a voluntary subsample of basketballers repeated the BaHI. Exploratory and confirmatory factor analyses supported a two-factor model. Our results show that: (i) Handedness score (R) in daily actions did not differ between basketball players (R by EHI = 69.3 ± 44.6) and the control group (R by EHI = 64.5 ± 58.6); (ii) basketballers more frequently favored performing certain sport tasks with the left hand or mixed hands (as highlighted by R by BaHI = 50.1 ± 47.1), although their choice was primarily the right hand in everyday gestures; and (iii) this preference was especially true for athletes at the highest levels of performance (R by BaHI of A1 league = 38.6 ± 58.3) and for those playing in selected roles (point guard’s R = 29.4 ± 67.4). Our findings suggest that professional training induces handedness changes in basketball tasks. The BaHI provides a valid and reliable measure of the skilled hand in basketball. This will allow coaches to assess mastery of the ball according to the hand used by the athlete in the different tasks and roles.

scholarly journals Digit Variability in Carotenoid Scores Obtained with the Veggie Meter: A Pilot Study (P02-001-19)

2019 ◽  
Vol 3 (Supplement_1) ◽  
Author(s):  
Velarie Ansu ◽  
Stephanie Dickinson ◽  
Alyce Fly
Keyword(s):  
Indiana University ◽  
Left Hand ◽  
Funding Sources ◽  
Right Hand ◽  
Period Data ◽  
The Mean ◽  
The Right ◽  
Post Hoc ◽  
Main Effects ◽  
Mean Square Errors

Abstract Objectives To determine which digit and hand have the highest and lowest skin carotenoid scores, to compare inter-and-intra-hand variability of digits, and to determine if results are consistent with another subject. Methods Two subjects’ first(F1), second(F2), third(F3) and fifth(F5) digits on both hands were measured for skin carotenoids with a Veggie Meter, for 3 times on each of 18 days over a 37-day period. Data were subjected to ANOVA in a factorial treatment design to determine main effects for hand (2 levels), digits (4), and days (18) along with interactions. Differences between digits were determined by Tukey's post hoc test. Results There were significant hand x digit, hand x day, digit x day, and hand x digit x day interactions and significant simple main effects for hand, digit, and day (all P < 0.001). Mean square errors were 143.67 and 195.62 for subject A and B, respectively, which were smaller than mean squares for all main effects and interactions. The mean scores ± SD for F1, F2, F3, and F5 digits for the right vs left hands for subject A were F1:357.13 ± 45.97 vs 363.74 ± 46.94, F2:403.17 ± 44.77 vs. 353.20 ± 44.13, F3:406.76 ± 43.10 vs. 357.11 ± 45.13, and F5:374.95 ± 53.00 vs. 377.90 ± 47.38. For subject B, the mean scores ± SD for digits for the right vs left hands were F1:294.72 ± 61.63 vs 280.71 ± 52.48, F2:285.85 ± 66.92 vs 252.67 ± 67.56, F3:268.56 ± 57.03 vs 283.22 ± 45.87, and F5:288.18 ± 34.46 vs 307.54 ± 40.04. The digits on the right hand of both subjects had higher carotenoid scores than those on the left hands, even though subjects had different dominant hands. Subject A had higher skin carotenoid scores on the F3 and F2 digits for the right hand and F5 on the left hand. Subject B had higher skin carotenoid scores on F5 (right) and F1 (left) digits. Conclusions The variability due to hand, digit, and day were all greater than that of the 3 replicates within the digit-day for both volunteers. This indicates that data were not completely random across the readings when remeasuring the same finger. Different fingers displayed higher carotenoid scores for each volunteer. There is a need to conduct a larger study with more subjects and a range of skin tones to determine whether the reliability of measurements among digits of both hands is similar across the population. Funding Sources Indiana University.

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