Application of compact silencers as a noise barrier to a naturally ventilated double-skin façade

2021 ◽  
Vol 69 (3) ◽  
pp. 220-228
Author(s):  
Jeehwan Lee ◽  
Jae D. Chang ◽  
Robert Coffeen
Keyword(s):  
Noise Reduction ◽  
Surface Area ◽  
Natural Ventilation ◽  
Experimental Investigations ◽  
Test Case ◽  
Open Surface ◽  
Low Frequencies ◽  
Noise Barrier ◽  
Double Skin ◽  
Air Vent

A prior study of the acoustical performance of a double-skin facade (DSF) as a noise barrier was carried out based on the percentage of the air vent open surface area, shading louver configurations, and shading louver surface materials. Earlier research findings led to experimental investigations of the acoustical performance capabilities of compact silencers to replace DSF air vents as both noise barriers and air channels because DSF air cavities, which contribute to natural ventilation performance (e.g., wind-driven or buoyancy-driven performance), are acoustically vulnerable to noise transmitted through the air vents. This experimental investigation aims to explore noise reduction (NR) through compact silencers applied to DSF air vents. Double-skin facade mock-up test cases were designed based on three test scenarios of a ventilation open surface area: (1) a 100%air vent open surface area (open mode), (2) a 0% air vent open surface area (closed mode), and (3) a compact silencer. From a data analysis of DSF mock-up test results, the overall NR values of a DSFmock-up ranged from20 to 37 dB(A) depending on the number of compact silencers and the shading louver orientation used. Configurations of compact silencers and shading louvers helped the DSF mock-up achieve additionalNR values of 5 to 10 dB(A) depending on the test case. Moreover, applying compact silencers to a naturally ventilated DSF mock-up led to significant noise reduction at low frequencies (125Hz).

scholarly journals AN EXPERIMENTAL STUDY OF THE HERSCHEL-QUINCLE (HQ) TUBE NOISE ATTENUATION PERFORMANCE

2019 ◽  
Vol 2 (1) ◽  
pp. 71-84
Author(s):  
Abdul-Hafid El-Majani ◽  
Mohamed S. Oun ◽  
Salem A. Farhat
Keyword(s):  
Noise Reduction ◽  
Passive Control ◽  
Power Transmission ◽  
Plane Waves ◽  
Acoustic Power ◽  
Tube Length ◽  
Experimental Investigations ◽  
Low Frequencies ◽  
Labview Software ◽  
Cylindrical Duct

The work presented in this paper summarize both analytical and experimental investigations of the Herschel-Quincke (HQ) concept for reducing known radiated inlet noise using signal generating system.  The analytical part of this work involves one-dimensional plane wave propagate in a cylindrical duct. In this paper adaptive HQ tube is used to reduce tonal noise propagating as plane waves in closed end duct. The effect of HQ tube length on the noise reduction, induced by a loudspeaker at various frequencies, is investigated experimentally in an acoustically cylindrical duct with and without HQ. Five HQ tubes with different lengths are investigated. The distance between the HQ tube ends is kept constant (l=20 cm), (  = 1.5, 2.5, 3, 3.5, and 4). Two Microphones system was used to measure the net acoustic power transmission in the duct. One microphone is located just before the HQ tube in the duct, and the other is at the closed end of the duct where it is always anti-node pressure. Data acquisition, monitoring and analysis are done using National Instrument DAQ card and LabVIEW software.  A LabVIEW vi code is developed to interface and process the two microphones system signals. Results showed that the length of the HQ tube is very important for a passive control of the noise reduction. While long HQ tube was effective in noise reduction in low frequencies, short HQ tube was more effective for high frequencies.

PRACTICAL METHODS OF ACOUSTIC MATERIALS PATTERNING FOR INCREASE OF THEIR EFFECTIVENESS

Akustika ◽  
2021 ◽  
pp. 107-111
Author(s):  
Aleksandr Krasnov ◽  
Igor Deryabin
Keyword(s):  
Noise Reduction ◽  
Laboratory Scale ◽  
Experimental Investigations ◽  
Passenger Cars

This article includes the results of experimental investigations of patterned noise-reducing materials and components, carried out using special-purpose laboratory-scale bench plants (Alpha Cabin, Torre di Pisa, RTC-3, Oberst). Illustrative examples of constructive-technological structurization of the components (gaskets, panels and upholstery) providing noise reduction of passenger cars are given.

Optimization of spiral-shaped piezoelectric energy harvester using Taguchi method

2017 ◽  
Vol 24 (19) ◽  
pp. 4484-4491 ◽  
Author(s):  
R Tikani ◽  
L Torfenezhad ◽  
M Mousavi ◽  
S Ziaei-Rad
Keyword(s):  
Taguchi Method ◽  
Energy Harvester ◽  
Piezoelectric Materials ◽  
Mechanical Energy ◽  
Experimental Investigations ◽  
Optimum Level ◽  
Low Frequencies ◽  
Piezoelectric Energy ◽  
Resonance Frequencies ◽  
Design Values

Nowadays, environmental energy resources, especially mechanical vibrations, have attracted the attention of researchers to provide energy for low-power electronic circuits. A common method for environmental mechanical energy harvesting involves using piezoelectric materials. In this study, a spiral multimode piezoelectric energy harvester was designed and fabricated. To achieve wide bandwidth in low frequencies (below 15 Hz), the first three resonance frequencies of the beam were designed to be close to each other. To do this, the five lengths of the substrate layer were optimized by the Taguchi method, using an L27 orthogonal array. Each experiment of the Taguchi method was then simulated in ANSYS software. Next, the optimum level of each design variable was obtained. A test rig was then constructed based on the optimum design values and some experimental investigations were conducted. A good correlation was observed between measured and the finite element results.

scholarly journals Fire safety case study of a railway tunnel: Smoke evacuation

2007 ◽  
Vol 11 (2) ◽  
pp. 207-222 ◽  
Author(s):  
Maele van ◽  
Bart Merci
Keyword(s):  
Fire Safety ◽  
Large Scale ◽  
Natural Ventilation ◽  
Real Life ◽  
Test Case ◽  
Fire Dynamics ◽  
Railway Tunnel ◽  
Tunnel Section ◽  
Safety Case ◽  
Smoke Evacuation

When a fire occurs in a tunnel, it is of great importance to assure the safety of the occupants of the tunnel. This is achieved by creating smoke-free spaces in the tunnel through control of the smoke gases. In this paper, results are presented of a study concerning the fire safety in a real scale railway tunnel test case. Numerical simulations are performed in order to examine the possibility of natural ventilation of smoke in inclined tunnels. Several aspects are taken into account: the length of the simulated tunnel section, the slope of the tunnel and the possible effects of external wind at one portal of the tunnel. The Fire Dynamics Simulator of the National Institute of Standards and Technology, USA, is applied to perform the simulations. The simulations show that for the local behavior of the smoke during the early stages of the fire, the slope of the tunnel is of little importance. Secondly, the results show that external wind and/or pressure conditions have a large effect on the smoke gases inside the tunnel. Finally, some idea for the value of the critical ventilation velocity is given. The study also shows that computational fluid dynamics calculations are a valuable tool for large scale, real life complex fire cases. .

Noise reduction of enhanced acoustic balconies on a high-rise building block

2021 ◽  
Vol 263 (1) ◽  
pp. 5327-5334
Author(s):  
SK Tang ◽  
Rudolf YC Lee
Keyword(s):  
Noise Reduction ◽  
Natural Ventilation ◽  
Traffic Noise ◽  
Elevation Angle ◽  
Noise Levels ◽  
Indoor Space ◽  
New Device ◽  
Air Inlet ◽  
The Difference ◽  
The Impact

A new device called 'enhanced acoustic balcony' is installed in a new housing estate in Hong Kong. It is intended to help reduce the impact of traffic noise on the residents. This balcony is basically an enlarged form of a plenum window and with three openings. Apart from the outdoor air inlet, there is the balcony door and a side-hung window on the interior balcony wall for natural ventilation of the indoor space. Sound absorption of NRC 0.7 is installed on the balcony ceiling and its sidewall facing the incoming traffic noise and an inclined panel is installed outside the balcony to provide noise screening. A site measurement of its noise reduction is carried out in the present study in a newly completed housing block. A 28 m long loudspeaker array is used as the sound source. The indoor noise levels are measured according to ISO standard. The results show that the difference between indoor and outdoor noise levels in the presence of this balcony form varies over a relatively narrow range between 10 to 13 dBA for an elevation angle from 25 to 60 deg. There is a weak increase of the noise level difference with elevation angle.

Additional noise reduction with diffracting elements on barriers: experimental testing

2021 ◽  
Vol 263 (4) ◽  
pp. 2654-2664
Author(s):  
Wout Schwanen ◽  
Mark Mertens ◽  
Ysbrand Wijnant ◽  
Willem Jan van Vliet
Keyword(s):  
Noise Reduction ◽  
Experimental Testing ◽  
Low Noise ◽  
Motor Vehicles ◽  
Additional Element ◽  
High Noise ◽  
Quarter Wavelength ◽  
Noise Barrier ◽  
Sound Reduction ◽  
Development And Validation

The noise reduction of a (low) noise barrier can be enhanced by using an additional element with quarter-wavelength resonators with varying depths. The so-called WHISwall or WHIStop deflects sound upwards for specific frequencies creating an additional sound reduction. Different experiments on the WHISwall and WHIStop are performed as input for model validation. The development and validation of the model are described in a separate paper. In this paper the measurement campaign and its results are presented. We performed measurements on two setups. The first setup consists of a 1.1 meter high WHISwall, a 1.1m high noise barrier and a reference section (without noise measure). Measurements have been conducted with both an artificial sound source and pass by measurements with light and heavy motor vehicles. In a second test setup, the WHIStop was placed on top of a 4 meter high noise barrier and the diffraction was determined according the European standard EN 1793-4.

scholarly journals An analytical and experimental investigation of aerofoil–turbulence interaction noise for plates with spanwise-varying leading edges

2019 ◽  
Vol 865 ◽  
pp. 137-168 ◽  
Author(s):  
Lorna J. Ayton ◽  
Paruchuri Chaitanya
Keyword(s):  
Noise Reduction ◽  
Analytic Solution ◽  
Piecewise Linear ◽  
Separation Of Variables ◽  
Leading Edge ◽  
Test Case ◽  
Far Field ◽  
Mean Flow ◽  
Flat Plates ◽  
Leading Edges

This paper presents an analytic solution for gust–aerofoil interaction noise for flat plates with spanwise-varying periodic leading edges in uniform mean flow. The solution is obtained by solving the linear inviscid equations via separation of variables and the Wiener–Hopf technique, and is suitable for calculating the far-field noise generated by any leading edge with a single-valued piecewise linear periodic spanwise geometry. Acoustic results for homogeneous isotropic turbulent flow are calculated by integrating the single-gust solution over a wavenumber spectrum. The far-sound pressure level is calculated for five test-case geometries; sawtooth serration, slitted $v$-root, slitted $u$-root, chopped peak and square wave, and compared to experimental measurements. Good agreement is seen over a range of frequencies and tip-to-root ratios (varying the sharpness of the serration). The analytic solution is then used to calculate the propagating pressure along the leading edge of the serration for fixed spanwise wavenumbers, i.e. only the contribution to the surface pressure which propagates to the far field. Using these results, two primary mechanisms for noise reduction are discussed; tip and root interference, and a redistribution of energy from cuton modes to cutoff modes. A secondary noise-reduction mechanism due to nonlinear features is also discussed and seen to be particularly important for leading edges with very narrow slits.

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