scholarly journals Effects of pipe casing structure on acoustic emission characteristics of underwater pyrotechnic combustion

2019 ◽  
Vol 39 (1) ◽  
pp. 149-157
Author(s):  
Jie Li ◽  
Jun Du ◽  
Xian Chen ◽  
Yanli Wang
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Structural Characteristics ◽  
Bubble Formation ◽  
Pressure Level ◽  
Radiation Characteristics ◽  
Acoustic Testing ◽  
Gas Volume ◽  
Broadband Sound

In order to investigate the acoustic radiation characteristics of underwater, a pipe casing was introduced and the effects of its main structural characteristics on underwater combustion acoustic radiation were studied by acoustic testing. The results show that the addition of the pipe casing significantly increased the sound pressure level of underwater pyrotechnic combustion, especially the peak of sound pressure level that was increased by 15.9 dB from 155.5 to 171.4 dB at the frequency of 125 and 100 Hz. But the addition of the pipe casing had little effect on the frequency. These results indicated that adding a pipe casing is effective for improving sound pressure level in underwater pyrotechnic combustion. An increase in nozzle diameter from 10 to 12.5 mm resulted in an increase of gas volume, so the peak of sound pressure level and broadband sound pressure level is higher. Changing the pipe casing direction to vertical downward will make the bubble formation period shorter, which will generate more bubbles and strong wake; the interaction between bubbles and wake results in a higher intensity of turbulence, which accounts for the coalescence and breakup of bubbles in the fluid. Besides, changing the diameter of pipe casing can be used to lower the frequency of underwater noise.

Application of Hartmann Acoustic Generator in Source of Underwater Pyrotechnic Combustion

2013 ◽  
Vol 787 ◽  
pp. 638-643
Author(s):  
Jie Li ◽  
Hua Guan ◽  
Dong Ming Song ◽  
Qi Wang ◽  
Jun Du ◽  
...  
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Structural Parameters ◽  
Resonant Cavity ◽  
Experimental Studies ◽  
Combustion Products ◽  
Pressure Level ◽  
Radiation Characteristics ◽  
Acoustic Frequency

In order to investigate acoustic radiation characteristics of underwater pyrotechnic combustion, Hartmann acoustic generator was applied and its main structural parameters effecting acoustic radiation characteristics were studied by using underwater acoustic measurement system. Experimental studies have shown that, when Hartmann acoustic generator was applied, the sound pressure level of underwater pyrotechnic combustion increased significantly because of the strengthening of turbulence degree. The distance between the nozzle and the resonant cavity is an important factor of affecting acoustic radiation characteristics of Hartmann acoustic generator. When the resonant cavity was placed in the unstable pressure area, it could stimulate strong sound waves. On account of the resistance of the water, the combustion products speed of reaching resonant cavity drooped and the collision strength between the feedback combustion products and the newly generated products reduced. So when the distance was larger, the SPL(sound pressure level) was smaller. The SPL of underwater pyrotechnic combustion increased and the acoustic frequency moved to the low frequency with the depth of resonant cavity increased, which is consistent with the acoustic characteristics of Hartmann acoustic generator applied in air.

Experimental investigation on noise radiation characteristics of pulse detonation turbine engine

2016 ◽  
Vol 231 (2) ◽  
pp. 254-264
Author(s):  
Xiqiao Huang ◽  
Zhuo Guo ◽  
Kai Liu ◽  
Moqi Li ◽  
Longxi Zheng
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Single Pulse ◽  
Pressure Level ◽  
Radiation Characteristics ◽  
Two Phase ◽  
Turbine Engine ◽  
Noise Radiation ◽  
Pulse Detonation ◽  
Radial Turbine

The noise radiation characteristics of two-phase pulse detonation combustor and pulse detonation turbine engine were investigated under different operating frequencies utilizing gasoline as fuel and air as oxidizer. The sound pressure data of noise radiation were presented for both single-pulse detonation combustor tube and pulse detonation turbine engine. The experimental results implied that the peak sound pressure level of PDTE exit with inner diameter being 60 mm was about 157 dB under the operating frequencies which varied from 5 Hz to 25 Hz, while the peak sound pressure level of single-pulse detonation combustor tube exit was about 170 dB under the same condition. The far-field jet-noise measurements of the pulse detonation turbine engine showed that radial turbine interacting with the pulse detonation combustor could decrease the peak sound pressure level of pulse detonation combustor with the maximum acoustic attenuation being approximately 14.2 dB for the current test conditions, which could be contributed to the energy extraction by the radial turbine from the pulse detonation combustor exhaust flow. The sound pressure level of both pulse detonation combustor and pulse detonation turbine engine exit was function of directivity angle from the exhaust centerline. In all the experiments, the equivalence ratio of gasoline/air mixture and the fill fraction were 1.2 and 1.0, respectively.

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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