scholarly journals Optimization of Shunted Loudspeaker for Sound Absorption by Fully Exhaustive and Backtracking Algorithm

2021 ◽  
Vol 11 (12) ◽  
pp. 5574
Author(s):  
Zihao Li ◽  
Xin Li ◽  
Bilong Liu
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Sound Absorption Coefficient ◽  
Moving Mass ◽  
Frequency Range ◽  
Force Factor ◽  
Coil Inductance ◽  
Specific Frequency ◽  
Circuit Resistance ◽  
Good Agreement

The shunted loudspeaker with a negative impedance converter is a physical system with multiple influencing parameters. In this paper, a fully exhaustive backtracking algorithm was used to optimize these parameters, such as moving mass, total stiffness, damping, coil inductance, force factor, circuit resistance, inductance and capacitance, in order to obtain the best sound absorption in a specific frequency range. Taking the maximum average sound absorption coefficient in the range of 100–450 Hz as the objective function, the optimized parameters of the shunted loudspeaker were analyzed. Simulation results indicated that the force factor and moving mass can be sufficiently reduced in comparison with that of a typical four-inch loudspeaker available on the market. For a given loudspeaker from the market as an example, the four optimized parameters of the shunted loudspeaker were given, and the sound absorption coefficient was measured for verification. The measured results were in good agreement with the predicted results, demonstrating the applicability of the algorithm.

scholarly journals Acoustic Panels Made of Paper Sludge and Clay Composites

2021 ◽  
Vol 13 (2) ◽  
pp. 637
Author(s):  
Tomas Astrauskas ◽  
Tomas Januševičius ◽  
Raimondas Grubliauskas
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Composite Panel ◽  
Sound Absorption Coefficient ◽  
Core Material ◽  
Paper Sludge ◽  
Frequency Range ◽  
Absorption Properties ◽  
Air Gaps ◽  
The Core

Studies on recycled materials emerged during recent years. This paper investigates samples’ sound absorption properties for panels fabricated of a mixture of paper sludge (PS) and clay mixture. PS was the core material. The sound absorption was measured. We also consider the influence of an air gap between panels and rigid backing. Different air gaps (50, 100, 150, 200 mm) simulate existing acoustic panel systems. Finally, the PS and clay composite panel sound absorption coefficients are compared to those for a typical commercial absorptive ceiling panel. The average sound absorption coefficient of PS-clay composite panels (αavg. in the frequency range from 250 to 1600 Hz) was up to 0.55. The resulting average sound absorption coefficient of panels made of recycled (but unfinished) materials is even somewhat higher than for the finished commercial (finished) acoustic panel (αavg. = 0.51).

Broadening of the Sound Absorption Bandwidth of the Perforated Panel Using a Membrane-Type Resonator

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Xuezhi Zhu ◽  
Zhaobo Chen ◽  
Yinghou Jiao ◽  
Yanpeng Wang
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Degrees Of Freedom ◽  
Low Frequency ◽  
Absorption Capacity ◽  
Sound Absorption Coefficient ◽  
Sound Waves ◽  
Frequency Range ◽  
Absorption Bandwidth ◽  
Membrane Type

In order to broaden the sound absorption bandwidth of a perforated panel in the low frequency range, a lightweight membrane-type resonator is installed in the back cavity of the perforated panel to combine into a compound sound absorber (CSA). Because of the great flexibility, the membrane-type resonator can be vibrated easily by the incident sound waves passing through the holes of the perforated panel. In the low frequency range, the membrane-type resonator and the perforated panel constitute a two degrees-of-freedom (DOF)-resonant type sound absorption system, which generates two sound absorption peaks. By tuning the parameters of the membrane type resonator, a wide frequency band having a large sound absorption coefficient can be obtained. In this paper, the sound absorption coefficient of CSA is derived analytically by combining the vibration equation of the membrane-type resonator with the acoustic impedance equation of the perforated panel. The influences of the parameters of the membrane-type resonator on the sound absorption performance of the CSA are numerically analyzed. Finally, the wide band sound absorption capacity of the CSA is validated by the experimental test.

scholarly journals Elucidating the Sound Absorption Characteristics of Foxtail Millet (Setariaitalica) Husk

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5126
Author(s):  
Dhayalini Balasubramanian ◽  
Senthil Rajendran ◽  
Bhuvanesh Srinivasan ◽  
Nirmalakumari Angamuthu
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Foxtail Millet ◽  
Air Gap ◽  
Composite Panel ◽  
Sound Absorption Coefficient ◽  
Mass Content ◽  
Frequency Range ◽  
Backing Material ◽  
Absorption Characteristics

The current study deals with the analysis of sound absorption characteristics of foxtail millet husk powder. Noise is one the most persistent pollutants which has to be dealt seriously. Foxtail millet is a small seeded cereal cultivated across the world and its husk is less explored for its utilization in polymer composites. The husk is the outer protective covering of the seed, rich in silica and lingo-cellulose content making it suitable for sound insulation. The acoustic characterization is done for treated foxtail millet husk powder and polypropylene composite panels. The physical parameters like fiber mass content, density, and thickness of the composite panel were varied and their influence over sound absorption was mapped. The influence of porosity, airflow resistance, and tortuosity was also studied. The experimental result shows that 30-mm thick foxtail millet husk powder composite panel with 40% fiber mass content, 320 kg/m3 density showed promising sound absorption for sound frequency range above 1000 Hz. We achieved noise reduction coefficient (NRC) value of 0.54. In view to improve the performance of the panel in low-frequency range, we studied the efficiency of incorporating air gap and rigid backing material to the designed panel. We used foxtail millet husk powder panel of density 850 kg/m3 as rigid backing material with varying air gap thickness. Thus the composite of 320 kg/m3 density, 30-mm thick when provided with 35-mm air gap and backing material improved the composite’s performance in sound frequency range 250 Hz to 1000 Hz. The overall sound absorption performance was improved and the NRC value and average sound absorption coefficient (SAC) were increased to 0.7 and 0.63 respectively comparable with the commercial acoustic panels made out of the synthetic fibers. We have calculated the sound absorption coefficient values using Delany and Bezlay model (D&B model) and Johnson–Champoux–Allard model (JCA model) and compared them with the measured sound absorption values.

Sound absorption of textile curtains – theoretical models and validations by experiments and simulations

2016 ◽  
Vol 88 (1) ◽  
pp. 36-48 ◽  
Author(s):  
Reto Pieren ◽  
Beat Schäffer ◽  
Stefan Schoenwald ◽  
Kurt Eggenschwiler
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Planning Process ◽  
Measurement Data ◽  
Theoretical Models ◽  
Sound Absorption Coefficient ◽  
Absorption Coefficients ◽  
Semi Empirical ◽  
Field Sound ◽  
Good Agreement

Textile curtains can be designed to be good sound absorbers. Their acoustical performance, as usually described by the sound absorption coefficient, not only depends on the textile itself but also on the drapery fullness and the backing condition, that is, the spacing between the fabric and a rigid backing wall, or the absence of a backing in the case of a freely hanging curtain. This article reviews existing models to predict the diffuse-field sound absorption coefficient, which to date can only predict the case of flat curtains. A set of existing models is extended to the case of curtains with drapery fullness using a semi-empirical approach. The models consider different backing conditions, including freely hanging curtains. The existing and new models are validated by comparing predicted sound absorption coefficients with data measured in a reverberation room. Hereby, curtains consisting of different fabrics and with different degrees of fullness are considered. Besides situations with rigid backing, also the measurement data of textiles hung freely in space are included in this study. Comparisons reveal a very good agreement between measured and predicted sound absorption coefficients. Compared to currently available commercial sound absorption prediction software that can only handle the situation of flat textiles with rigid backing, the results of the presented models not only show a better agreement with measured data, but also cover a broader range of situations. The presented models are thus well applicable in the design and development of new textiles as well as in the room acoustical planning process.

Exploration and optimization on the usage of micro-perforated panels as trim panels in commercial aircrafts

2020 ◽  
Vol 68 (1) ◽  
pp. 87-100
Author(s):  
L.I. Chenxi ◽  
H.U. Ying ◽  
H.E. Liyan
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Sound Absorption Coefficient ◽  
Aviation Industry ◽  
Sound Insulation ◽  
Aircraft Cabins ◽  
Aircraft Cabin ◽  
Specific Frequency ◽  
Trim Panel

Micro-perforated panels (MPPs), as an alternative to porous materials for sound absorption, have been commonly used in electronic industries and aircraft engines but are barely used in aircraft cabins. The effect of MPPs on the sound insulation and absorption properties of aircraft cabin panels has been investigated in this article. Theoretical modeling has been conducted on an aircraft cabin panel structure with a trim panel replaced by an MPP trim panel, using the transfer matrix method and the classic MPP theory. It is indicated by the theoretical results that, although the sound transmission loss (STL) of the cabin panel with an MPP trim panel is lower than that with an un-perforated panel, the MPP trim panel can significantly enhance the sound absorption coefficient of the entire cabin panel structure. Based on the well-developed MPP theory, the sound absorption coefficient of an aircraft cabin panel with an MPP trim panel can be improved by optimizing the MPP's parameters at a specific frequency. Taking an engine frequency 273 Hz as an example, the optimization can increase the sound absorption coefficient to 1 by using the doublelayered MPPs. When the thermal acoustic insulation blanket is considered, although the STL of the proposed structure with double-layered MPP trim panels in a diffuse field is lower than those without MPP trim panels, the sound absorption in the cabin is significantly enhanced due to the double-layer MPP trim panel at the specific engine frequency and across all frequencies. The STL of the structure with double-layered MPP trim panels and TAIB can be higher than 40 dB from 880 Hz in a diffuse field, which implies its effectiveness as sound insulation structure in aviation industry. MPP trim panels provide a new idea for the design of aircraft cabin panels and areworthy of further research

scholarly journals Synthesis and Evaluation of Polyurethane Foam Composites for Enhanced Sound Absorption at Low Frequency

2019 ◽  
Vol 8 (3) ◽  
pp. 6815-6818
Keyword(s):  
Absorption Coefficient ◽  
Polyurethane Foam ◽  
Sound Absorption ◽  
Low Frequency ◽  
Weight Fraction ◽  
Crumb Rubber ◽  
Polyurethane Foams ◽  
Sound Absorption Coefficient ◽  
Filler Materials ◽  
Frequency Range

Polyurethane foams are extensively used as sound absorbing materials in various automobile parts. However, the sound absorption capability of polyurethane foam ispoorin low frequency range. The advancement of technologies to develop newerpolymer composites, provide scope to develop composite polyurethane foam with better sound absorption coefficient in low frequency range. Composite foams are made with two different filler materials as crumb rubber and coconut fiber, in varying weight fraction of up to 2.0%. Density, Sound absorption coefficient, and Noise reduction, measurements were done on all polyurethane foams. The effect offiller additionsto polyurethane foams ondensity and sound absorption coefficient at low frequency are discussed.The 1.4 % crumb rubber polyurethane foam offers the best combination of low density, improved sound absorption coefficient value and noise absorption at low frequency.

scholarly journals Effect of Porous Materials Combination in Layers on Sound Absorption Characteristics

2015 ◽  
Vol 773-774 ◽  
pp. 210-215
Author(s):  
Muhd Hafeez Zainulabidin ◽  
M.H.M. Yusuff ◽  
Al Emran Ismail ◽  
M.Z. Kasron ◽  
A.S.M. Kassim
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Low Frequency ◽  
Sound Absorption Coefficient ◽  
Frequency Range ◽  
Sound Absorber ◽  
Number Of Layers ◽  
Combination Number ◽  
Impedance Tubes ◽  
Absorption Characteristics

This paper describes the investigation and analysis on two materials in which one material is a relatively good sound absorber at low frequency range and another is a relatively good sound absorber at high frequency range, combined together in layers to form a better sound absorber for a wider range of frequencies. The layer combinations of the materials are varied and the values of Sound Absorption Coefficient, α are measured experimentally by using impedance tubes with two microphones transfer function method according to ISO 10534-2 standard. The results obtained are compared in terms of the order of material and the number of layer combinations of materials for each sample. The orders of combinations and number of layers of combinations have significant influence on the sound absorption characteristics. The order of materials has reversed effect on Sound Absorption Coefficient, α as the number of layer combination is increased. Increase in the combination number will make the specimen performed relatively better at a wider frequency range.

scholarly journals Acoustic Properties of Composite Synthesized from Activated Zeolite and Fibre

2018 ◽  
Author(s):  
Hidjan Hidjan ◽  
Sutanto Sutanto ◽  
Nanang Rohadi
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Acoustic Properties ◽  
Sound Absorption Coefficient ◽  
Frequency Range ◽  
Porous Crystal ◽  
High Flexibility ◽  
And Shifts ◽  
Frequency Area ◽  
Banana Stem

The unique porous crystal structure of zeolite offers various important utilizations, it is one of the considerations in selecting zeolite at this study as component of composite for restraining noise. It so happens, previous experiments show that banana stem has porous structure, fibrous, high flexibility and can be applied as material for many various products including as component of acoustic material. The combination of both is alleged that it has capability in absorbing noise. This paper presents an investigation on the composite that it was synthesized of Activated Zeolite and Banana Stem Fibre in various weight for determining its sound absorption coefficient alpha (a). Activating natural zeolite was conducted by using 6M HCl in order for enlarging zeolite pores. The sound absorption coefficient was measured in the frequency range between 125 Hz up to 6000 Hz. The results show that the different weight of banana stem fibre as component of the synthesized composite affects the value of alpha and shifts the frequency area.

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