The Effect of Sound Pressure on the Aeroacoustic Sources Around Two Ducted Tandem Cylinders

2010 ◽  
Author(s):  
Shane Leslie Finnegan ◽  
Craig Meskell ◽  
Samir Ziada
Keyword(s):  
Flow Velocity ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Acoustic Resonance ◽  
Pressure Level ◽  
Acoustic Energy ◽  
Source Distribution ◽  
Main Stream ◽  
Tandem Cylinders ◽  
Mainstream Flow

An empirical investigation of the spatial distribution of aeroacoustic sources around two tandem cylinders subject to ducted flow and forced transverse acoustic resonance is described. The work builds on a previous investigation by the authors and utilises Howe’s theory of aerodynamic sound. The influence of the sound pressure level in the duct on the strength and location of the aeroacoustic sources in the flow was the main focus of the investigation and experiments to resolve the aeroacoustic source distribution were concentrated at a low main-stream flow velocity (before acoustic-Strouhal coincidence), at a medium mainstream flow velocity (just after acoustic-Strouhal coincidence) and at a high mainstream flow velocity (substantially higher than acoustic-Strouhal coincidence). The sound pressure level was found to have a considerable effect on the “lock-in”’ range of the cylinders which widened as the sound pressure level increased. A proposed normalisation of the net acoustic energy transfer per spanwise location appears to show good metric for the distribution of the aeroacoustic sources in the flow field. Using this, it was found that the amplitude of the sound pressure had a negligible influence on the aeroacoustic sources in the wake and the gap region for all the tested cases apart from the lowest flow velocity. This particular case showed indications that the aeroacoustic source strength and location could be altered for certain changes in sound pressure level.

Interaction Between Acoustic Resonance and Fluidelastic Instability in a Normal Triangular Tube Array

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
John Mahon ◽  
Craig Meskell
Keyword(s):  
Flow Velocity ◽  
Acoustic Field ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Acoustic Resonance ◽  
Pressure Level ◽  
Structural Damping ◽  
Duct Acoustics ◽  
Fluidelastic Instability ◽  
Independent Parameters

The interaction between acoustic resonance and damping controlled fluidelastic instability (FEI) in a normal triangular tube array (P∕d=1.32) has been investigated. The duct acoustics were excited with speakers placed adjacent to the tube array to artificially replicate flow-induced acoustic resonance. The paper deals with the effect on the rms level of tube vibration of three independent parameters: imposed acoustic sound pressure level, freestream flow velocity, and structural damping. A fall in the FEI vibration amplitude with increasing sound pressure level in the tube array has been observed. In addition, the imposed acoustic field delays the onset of damping controlled fluidelastic instability. The effects of flow velocity and structural damping in conjunction with acoustic resonance on the rms of tube displacement are discussed. While the current study has clearly captured the phenomenon of interaction between the fluidelastic motion at approximately 10Hz and the acoustic field at approximately 1kHz, it is not apparent what the physical mechanism at work might be.

Analysis of the Noise Level Generated by Axial Flow Fan Composed of Radial-Bladed Centrifugal Rotor

2014 ◽  
Author(s):  
S. S. Borges ◽  
R. Barbieri ◽  
P. S. B. Zdanski
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Axial Flow ◽  
Acoustic Resonance ◽  
Pressure Level ◽  
Resonance Mode ◽  
Numerical Techniques ◽  
Cooling Systems ◽  
Centrifugal Fans ◽  
Motor Cooling

The objective of this work is to present, by means of experimental, analytical and numerical techniques that sound pressure level generated by radial-bladed centrifugal fans of electric motor cooling systems may be expressed by a logarithmical ratio of the peripheral velocity of rotor, volumetric flow and efficiency of the fan. The proposed methodology proved to be efficient and simple in the prediction of generated noise by radial-bladed centrifugal fans of TEFC motors with accuracy of ± 3 dB. In addition, the acoustic resonance mode of the fan cavity were determined by means of numerical simulations, which its results were validated through experiments using waterfall spectrum.

Noise Reduction of Blade-Passing Frequency Components in a Centrifugal Blower

2004 ◽  
Author(s):  
Yutaka Ohta ◽  
Eisuke Outa
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Noise Source ◽  
Higher Order ◽  
Pressure Level ◽  
Source Distribution ◽  
Centrifugal Blower ◽  
Blade Passing Frequency ◽  
Active Cancellation ◽  
Frequency Components

A hybrid-type noise control method is applied to fundamental and higher-order blade-passing frequency components, abbreviated to BPF components, radiated from a centrifugal blower. An active cancellation of the BPF noise source is conducted based on a detailed investigation of the noise source distribution by using correlation analysis. The sound pressure level of 2nd- and/or 3rd-order BPF can be reduced by more than 15 decibels and discrete tones almost eliminate from the power spectra of blower-radiated noise. On the other hand, the sound pressure level of the fundamental BPF is difficult to reduce effectively by the active cancellation method because of the large amplitude of the noise source fluctuation. However, the fundamental BPF is largely influenced by the frequency-response characteristics of the noise transmission passage, and is passively reduced by appropriate adjusting of the inlet duct length. Simultaneous reduction of BPF noise, therefore, can be easily made possible by applying passive and active control methods on the fundamental and higher-order BPF noise, respectively. We also discuss the distribution pattern of BPF noise sources by numerical simulation of flow fields around the scroll cutoff.

scholarly journals Pengujian Alat Pemanen Energi Akustik Berbasis Loudspeaker Dengan Sumber Kebisingan Acak Dari Mesin Kendaraan Bermotor

2019 ◽  
Vol 4 ◽  
pp. 152
Author(s):  
Untung Adi Santosa ◽  
Ikhsan Setiawan ◽  
B.S. Utomo
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Random Noise ◽  
Electrical Power ◽  
Dominant Frequency ◽  
Pressure Level ◽  
Acoustic Energy ◽  
Noise Sources ◽  
Quarter Wavelength ◽  
The Impact

<p class="AbstractEnglish"><strong>Abstract: </strong>This paper reports the test results of a loudspeaker-based acoustic energy harvester with acoustic random noise sources from a motorcycle. The harvester consists of a quarter wavelength resonator and a subwoofer type loudspeaker with a nominal diameter of 6 inches. The motorcycle used in this experiment is 135 cc Bajaj Pulsar motorsport with modified exhaust from the GBS-Motosport Jakarta. The motor engine is operated at 3000 rpm, resulting in noise with a fluctuating Sound Pressure Level (SPL) in the range of (90-93) dB. Six variations of resonator lengths are used, those are 21 cm, 31 cm, 58 cm, 85 cm, 112 cm, and 139 cm. In this test, data of dominant frequency, SPL, and output rms voltage were taken for 15 minutes. The rms voltage is measured at 100 Ω load resistor. The results show that the 112 cm resonator produces the highest average rms electrical power, that is (0.21 ± 0.01) mW, which is obtained at frequency that fluctuates within (95-120) Hz. In addition, with random sound sources, SPL and its dominant frequency fluctuate greatly, so it will greatly affect the generated electric power. Further research is needed to enhance the output electrical power and anticipate the impact of frequency fluctuation which exists in random noise sources.</p><p class="AbstractEnglish"><strong>Abstrak: </strong>Paper ini memaparkan hasil pengujian alat pemanen energi akustik berbasis <em>loudspeaker </em>dengan sumber kebisingan acak dari mesin kendaraan bermotor. Alat pemanen energi akustik ini terdiri dari resonator seperempat panjang gelombang dan <em>loudspeaker</em> jenis <em>subwoofer</em> dengan diameter nominal 6 inci. Sumber kebisingan yang digunakan adalah motor Bajaj Pulsar 135 cc dengan knalpot modifikasi dari GBS-Motosport Jakarta. Mesin motor dioperasikan pada laju putaran tetap 3000 rpm, sehingga menghasilkan kebisingan dengan <em>SPL</em> (<em>sound pressure level</em>) yang berfluktuasi dalam interval (90-93) dB. Digunakan enam variasi panjang resonator, yaitu 21 cm, 31 cm, 58 cm, 85 cm, 112 cm, dan 139 cm. Dalam pengujian ini, data frekuensi dominan kebisingan, <em>SPL</em> kebisingan, dan tegangan keluaran alat pemanen energi akustik diambil selama 15 menit. Tegangan <em>rms</em> keluaran diukur pada resistor beban 100 Ω. Hasil eksperimen menunjukkan bahwa resonator dengan panjang 112 cm menghasilkan daya listrik <em>rms</em> rata-rata tertinggi yaitu sebesar (0,21 ± 0,01) mW, diperoleh pada frekuensi yang berfluktuasi antara 95 Hz sampai 120 Hz. Selain itu, hasil eksperimen ini menunjukkan bahwa dengan sumber bunyi acak, <em>SPL</em> kebisingan dan frekuensi dominannya sangat berfluktuasi, sehingga akan sangat berpengaruh terhadap daya listrik yang dihasilkan. Penelitian lebih lanjut diperlukan untuk meningkatkan daya listrik keluaran dan mengantisipasi dampak fluktuasi frekuensi sumber kebisingan acak.</p>

PZT Acoustic Energy Harvester Arrays with Dual Top Electrodes

2013 ◽  
Vol 300-301 ◽  
pp. 912-915
Author(s):  
Yusuke Uchida ◽  
Satoshi Iizumi ◽  
Syungo Tomioka ◽  
Kyohei Tsujimoto ◽  
Kazuki Tomii ◽  
...  
Keyword(s):  
Power Generation ◽  
Lead Zirconate Titanate ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Energy Harvester ◽  
Lead Zirconate ◽  
Pressure Level ◽  
Acoustic Energy ◽  
Microelectromechanical System ◽  
Energy Harvesters

This paper presents the power generation performances of an array of three microelectromechanical system (MEMS) acoustic energy harvesters equiped with lead–zirconate–titanate (PZT) capacitors. The PZT acoustic energy harvesters had a diaphragm with a　diameter of 2 mm consisting of Al (0.1 μm) / PZT (1 μm) / Pt (0.1 μm) / Ti (0.1 μm) / SiO2 (1.5 μm), and the diaphragm vibrations were excited by sound pressure. The arrayed peripheral energy harvester generated a maximum power of 2.26 × 10-10 W at a sound pressure level (SPL) of 100 dB at 5 kHz. The output power of three arraying devices was about 3 times larger than that of the single devices.

scholarly journals Noise Reduction Mechanisms of an Airfoil with Trailing Edge Serrations at Low Mach Number

2019 ◽  
Vol 9 (18) ◽  
pp. 3784 ◽  
Author(s):  
Hui Tang ◽  
Yulong Lei ◽  
Yao Fu
Keyword(s):  
Noise Reduction ◽  
Sound Pressure Level ◽  
Sound Source ◽  
Sound Pressure ◽  
Pressure Level ◽  
Source Distribution ◽  
Noise Mitigation ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Trailing Edge Serrations

Trailing-edge serrations have proven to be valid applications of trailing edge noise mitigation for an airfoil, while the physical noise reduction mechanism has not been adequately studied. We performed simulations employing Large-eddy simulation and the Lighthill–Curle method to reveal the variation in the hydrodynamic field and sound source due to the trailing edge serrations. The grid resolution and computational results were validated against experimental data. The simulation results show that: the trailing edge serrations impede the growth of spanwise vortices and promote the development of streamwise vortices near the trailing edge and the wake; the velocity fluctuations in the vertical cross-section of the streamwise direction near the trailing edge are reduced for the serrated airfoil, thereby obviously reducing the strength of the pressure fluctuations near the trailing edge; and the trailing edge serrations decrease the distribution of the sound source near the trailing edge and reduce the local peak value of sound pressure level in a specific frequency range as well as the overall sound pressure level. Moreover, we observed that, in the flow around the NACA0012 airfoil, the location where the strong sound source distribution begins to appear is in good agreement with the location where the separated boundary layer reattaches. It is therefore effective to reduce trailing edge noise by applying serrations on the upstream of the reattachment point.

Aeroacoustic Source Distribution Around Four Cylinders Orientated in a Square

2010 ◽  
Author(s):  
Shane Leslie Finnegan ◽  
Craig Meskell ◽  
Peter Oshkai
Keyword(s):  
Flow Field ◽  
Vortex Shedding ◽  
Sound Pressure Level ◽  
Sound Pressure ◽  
Acoustic Resonance ◽  
Pressure Level ◽  
Field Conditions ◽  
Acoustic Sources ◽  
Four Cylinders ◽  
Flow Velocities

An experimental investigation of the flow-acoustic coupling of four cylinders arranged in a square configuration with a spacing ratio in the proximity interference range subject to forced acoustic resonance is presented. The aeroacoustic characteristics and the flow field structures are investigated at various sound pressure levels to study its influence on the “lock-in” behaviour of the separated flow and the corresponding distribution of the resonant acoustic sources. Two mainstream flow velocities were selected for testing that corresponded to flow field conditions before acoustic-Strouhal coincidence of the vortex shedding frequency with the natural acoustic frequency of the duct and to flow field conditions after acoustic-Strouhal coincidence. Increasing the sound pressure level was found to slightly increase the range of flow velocities with which the acoustics could entrain the vortex shedding regime. Increasing the sound pressure level was also found to shorten the length of the most intense vortical structures in the shear layers emanating from the upstream cylinders and hence also shifted the dominant acoustic sources upstream. Spatial distributions of the net acoustic energy suggests that the mechanism triggering acoustic resonance of the four cylinders is shear layer instability, which is similar to that observed for two tandem cylinders.

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

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.

Case study: Theoretical calculation model and variable condition analysis research on the water-splashing noise for natural draft wet cooling towers

2020 ◽  
Vol 68 (2) ◽  
pp. 137-145
Author(s):  
Yang Zhouo ◽  
Ming Gao ◽  
Suoying He ◽  
Yuetao Shi ◽  
Fengzhong Sun
Keyword(s):  
Theoretical Model ◽  
Sound Pressure Level ◽  
Water Droplet ◽  
Water Distribution ◽  
Sound Pressure ◽  
Cooling Tower ◽  
Distribution Patterns ◽  
Calculation Model ◽  
Pressure Level ◽  
Cooling Towers

Based on the basic theory of water droplets impact noise, the generation mechanism and calculation model of the water-splashing noise for natural draft wet cooling towers were established in this study, and then by means of the custom software, the water-splashing noise was studied under different water droplet diameters and water-spraying densities as well as partition water distribution patterns conditions. Comparedwith the water-splashing noise of the field test, the average difference of the theoretical and the measured value is 0.82 dB, which validates the accuracy of the established theoretical model. The results based on theoretical model showed that, when the water droplet diameters are smaller in cooling tower, the attenuation of total sound pressure level of the water-splashing noise is greater. From 0 m to 8 m away from the cooling tower, the sound pressure level of the watersplashing noise of 3 mm and 6 mm water droplets decreases by 8.20 dB and 4.36 dB, respectively. Additionally, when the water-spraying density becomes twice of the designed value, the sound pressure level of water-splashing noise all increases by 3.01 dB for the cooling towers of 300 MW, 600 MW and 1000 MW units. Finally, under the partition water distribution patterns, the change of the sound pressure level is small. For the R s/2 and Rs/3 partition radius (Rs is the radius of water-spraying area), when the water-spraying density ratio between the outer and inner zone increases from 1 to 3, the sound pressure level of water-splashing noise increases by 0.7 dB and 0.3 dB, respectively.

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