Field Of Noise Control Research Articles

Designing, constructing and testing of a new generation of sound barriers.

Nowadays, noise pollution is considered a major environmental problem which has affected the health and comfort of millions of people around the world. Solving the mentioned problems need to design a new generation of acoustic barriers. Acoustics experts believe that stopping and absorbing the low-frequency sound is difficult. The aims of this study were to remove the harmful frequency in industries and cities. This study concentrates on the reduction of the noise level and increasing the mass law and resonance at low frequencies. Sound measurement and frequency analysis did to fix the harmful frequency in the Shiraz city and in the Shiraz Gas Power Plant. COMSOL 5.3a software used for simulation. Suitable material chose for the manufacture of the sound barrier through the Cambridge engineering selection software 2013. The meta-material sound barrier made and tested in the acoustic room and in the free space. Results analyzed and optimized by Design of Experiment (DOE) and Response Surface Methodology (RSM) software. Mini Tab. 18.1 software used for Statistical Calculations. New sound barriers manufactured with adding new strategies to previous studies to improve the performance of meta-materials like beautification inspired from the flowers of nature and increasing of resonance in internal pipes. Three mechanisms used in this scatterer model which included, resonance phenomenon, Band Gap (BG) without absorption mechanism and inner-fractal-like structure. Our technique showed an advantage to reduce at frequencies below 100Hz without adsorbent usage. The results showed that reduced noise exposures about 17.8dB at frequency 50Hz, about 9.1dB within the range of 250Hz according to EN 1793-2 standard (Lab Test for Airborne Sound Insulation). The sound barrier reported in this work provides the best and updated solution in the field of noise control. A novel generation of sound barriers introduced. We called this structure Interior Quasi-Fractal Sonic Crystal Acoustic Barrier (IQFSCAB). In this study, several different gaps used to remove various frequencies. It could be concluded that the outcomes of the meta-material models based on the Sonic Crystal (SC) could be used for the purpose of noise control system and could be helpful for decision-makers on the noise control legislations. Graphical abstractInteraction of waves with noise barriers and wave propagation inside periodic media is a hot topic in many branches of science and technology. The acoustic metamaterial can create green environments by reducing the low frequencies of industrial noise or traffic jam. New barrier have added a number of new strategies to previous studies in order to improve the performance of meta-materials. Our technique shows a clear advantage over to absorb at frequencies below 100Hz without adsorbent usage. Innovative use of several different gaps and diameters for to remove various frequencies was done in this study. We called this structure IQFSACB due to fractal like interior pipes as those seen in some of the flowers in nature.

Comparison of acoustic absorption characteristics of coir and date palm fibers: experimental and analytical study of green composites

The use of natural biodegradable fibers in manufacturing of porous sound absorbers is an environmental-friendly approach employed by many researchers in the field of noise control and acoustics. The present study aimed to determine and compare the sound absorption coefficients of samples fabricated from fibers of coir and date palm by experimental and analytical methods. Experimental measurements of the sound absorption coefficients were performed in an impedance tube by modifying several parameters (thickness and air gap) of the samples. Prediction of sound absorption coefficient was determined by Delany–Bazley, Miki and Johnson–Champoux–Allard models along with differential evolution algorithm in MATLAB software and data from the experiments. The correlation between the sound absorption coefficients obtained from the experiments and the ones predicted by the existing models was examined by the Pearson correlation test. Samples from both type of fibers showed a poor and almost similar sound absorption in low-frequency range. In intermediate range (1000–3000 Hz), the sound absorption significantly increased to the maximum levels of 0.81 and 0.84 at 2000 Hz for the thickness of 40 mm. An increase in the samples thickness led to a fair agreement between values of sound absorption coefficient obtained from experimental and analytical methods. Correlation analysis showed that there was a significant and strong correlation between the outputs from the existing models and the experiments. The values approximated by Johnson–Champoux–Allard model demonstrated a better fit with the ones determined by the experimental tests.

Pressure calibration of a digital microelectromechanical system microphone by comparison.

In the field of noise control and monitoring, a new generation of small and low-cost microelectro-mechanical system (MEMS) microphones is nowadays widely adopted. MEMS microphones, after recognition as traceable measurement instruments, could open up promising measurements based on wireless sensor networks. Current standards do not apply specifically to digital microphones. In this work, a pressure calibration procedure by comparison is carried out for a digital MEMS microphone and a sensitivity parameter suitable for metrological purposes is proposed. Measurement procedure and results between 20 Hz and 20 kHz are presented along with uncertainty contributions.

Study on the Acoustical Properties of Natural Jute Material by Theoretical and Experimental Methods for Building Acoustics Applications

Noise control treatment is essential to maintain a quiet and comfortable environment in buildings. In order to control noise, sound absorbing materials play a significant role. Nowadays, natural materials have gained importance in noise control field. In this study, acoustical characterization of a natural material jute is performed using experimental and numerical techniques. Normal incidence sound absorption coefficient and sound transmission loss of building materials using jute are predicted using the transfer matrix method. The theoretical and numerical predictions show a good match with the experimental data in the mid and high-frequency range of interest.

Improving low-frequency sound absorption of micro-perforated panel absorbers by using mechanical impedance plate combined with Helmholtz resonators

The traditional Micro-perforated plate (MPP) is a kind of clean and non-polluting absorption structure in the middle and high frequency and has been widely used in the field of noise control. However, the sound absorption performance is dissatisfied at low frequencies when the air-cavity depth is restricted. In this paper, a mechanical impedance plate (MIP) is introduced into the traditional MPP structure and a Helmholtz resonator is attached to the MIP. Mechanical impedance plate (MIP) provides a good absorption at low frequency by using mechanism of mechanical resonance and the acoustic energy is dissipated in the form of heat with viscoelastic material. Helmholtz resonator can fill in the defect of the poor absorption effect between the Micro-perforated plate (MPP) and the mechanical impedance plate (MIP). The acoustic impedance of the proposed sound absorber is investigated by using acoustic electric analogy method and impedance transfer method. The influence of the tube’s length of Helmholtz resonator and the number of Helmholtz resonator on the sound absorption is studied. The corresponding results are in agreement with the theoretical calculation and prove that the composite structure has the characteristics of improving the low frequency sound absorption property.

The Effect of Occupational Noise Exposure on Blood and Biochemical Parameters: A Case Study of an Insulator Manufacturer in Iran.

IntroductionOccupational noise is among the most critical occupational hazards, which, in addition to hearing loss, can cause other adverse consequences on an individual’s physical and mental health. Long-term exposure to noise can affect blood and biochemical parameters and subsequently lead to increased risk of cardiovascular disease. This study investigated the effect of occupational exposure to noise on blood and biochemical parameters of workers in an insulator manufacturing plant.MethodsThis case-control study was conducted on workers in the production section (49 people as a case group) and the administrative staff (10 people as a control group) in one insulator manufacturing plant from 2010 to 2014. To assess individual exposure of workers to noise, the noise dosimeter model TES-1355 was used. Noise dosimetry testing was done based on the exposure pattern of workers to noise in compliance with the Iranian national standard (the criterion level of 85 dBA and the exchange rate of Q = 3 dBA). Blood parameters such as blood glucose, cholesterol, red blood cells (RBC), white blood cells (WBC), hemoglobin (Hb), and hematocrit (Hct) were studied in production workers (case) and administrative staff (control) over five consecutive years. The data were analyzed by software (SPSS-22) using the t-test, Mann-Whitney test, Fisher exact test, and Greenhouse-Geisser test.ResultsNo significant difference was found among the demographic data of the two groups (p > 0.05). Average of glucose and cholesterol levels in the two groups was statistically significant (p < 0.05) and blood glucose levels in the case group significantly reduced over time and cholesterol increased (p < 0.001). Mean difference of RBC number, WBC number, and serum levels of Hb and Hct was statistically significant between the two groups (p < 0.05). In addition, these hematological parameters increased among workers during these years.ConclusionOccupational exposure to noise may have a significant effect on an individual’s blood parameters, which will cause harmful effects on worker health. Therefore, industrialists must take preventive measures in the field of noise control.

Open Noise Barriers Based on Sonic Crystals. Advances in Noise Control in Transport Infrastructures

Noise control is an environmental problem of first magnitude nowadays. In this work, we present a new concept of acoustic screen designed to control the specific noise generated by transport infrastructures, based on new materials called sonic crystals. These materials are formed by arrangements of acoustic scatterers in air, and provide a new and different mechanism in the fight against noise from those of the classical screens. This mechanism is usually called multiple scattering and is due to their structuring in addition to their physical properties. Due to the separation between scatterers, these barriers are transparent to air and water allowing a reduction on their foundations. Tests carried out in a wind tunnel show a reduction of 42% in the overturning momentum compared to classical barriers. The acoustical performance of these barriers is shown in this work, explaining the new characteristics provided in the control of noise. Finally, an example of these barriers is presented and classified according to acoustic standardization tests. The acoustic barrier reported in this work provides a high technological solution in the field of noise control.

Requirements for low-frequency reverberation in spaces for music: Part 2: Auditoria for performances and recordings.

(ProQuest: ... denotes formulae omitted)A large number of contemporary concert and assembly halls are criticized for their mediocre acoustics, although most elaborate model tests and computer simulations are at our disposal for the large-scale planning and small-scale interior design of an enclosure. On the other hand, we have inherited numerous spaces with excellent acoustics that were built without any powerful prediction and calculation tools. Acousticians or sound engineers may complain that nowadays, architects almost exclusively consider the visual of a structure. Only rarely do they consider the acoustic aspects (Blesser & Salter, 2007, p. 1). But are we able to provide the builders with a firm and generally applicable guideline for achieving acoustical quality and comfort in a room for a specific musical or lingual destination?Concerning the less concrete, more complicated sonic processes such as hearing (meaning, the detection of sound) and listening (as active attention or reaction to the meaning, emotions, and symbolism contained within sound), one may refer to Blesser and Salter (2007) for a profound synopsis of the various of architects, interior designers, and sound engineers. As an acoustician, one may retreat to the standard International Organization for Standardization (ISO 3382, 1997) on p. 2: This standard continues to specify room acoustic quality by reverberation time T alone . . . T measurements are important in the field of noise control (e.g., in public buildings, libraries, swimming halls or work places) as well as for the assessment of rooms for speech and with... (1)where V is the room volume in m3 and both T in s and the equivalent absorption area A in m2 of the room are strongly frequency dependent in the range between (at least) f 63 Hz and 8,000 Hz relevant for room acoustics in general. ISO 3382-1997 in its Note 17 states, The frequency range should include the octave bands from 125 Hz to 4 kHz or the one-third octave bands from 100 Hz to 5 kHz. In concert halls the 63 Hz octave band should be added. When it comes to additional quantities, meant to be subjectively important according to ISO 3382-1997, Annex A, like early decay time, strength (G), clarity (C80), definition (C50), center time TS, and lateral energy fraction (LF), however, the focus is only on a much more restricted mid-frequency (mf) spectrum between 500 Hz and 1 or 2 kHz (also for the averaged singlenumber ratings that prevail in practice) intended to summarize measurement results, see Beranek (1996, Appendix 1). As a result, one rarely finds acoustics criteria for the complete frequency spectrum. Instead, standard recommendations usually just refer to a correspondingly averaged Tm as a function of room volume.In this context, Beranek et al. (2010) may be cited:I am convinced that we need to work with the whole spectrum of human hearing-we must not ignore the universes of very high and very low frequency sound that are presently unattended in our data gathering and analysis. Half the instruments of our orchestra have their fundamental pitches below 125 Hz. We need to design for strength in the fundamental sounds of those instruments. Fundamental pitches of low frequency instruments support intonation and bloom for the full orchestral sound. Fundamentals are fundamental! (p. 7)At the same meeting, Bradley (2010) stated that there is not much evidence to support the idea that mid-frequency values are most representative of the perceived broadband changes of all measures (p. 7). Burkowitz (2011), an experienced sound engineer, suggests that recognizing the musical structure and architecture in the contra- and sub-contra ranges is just as important as doing it for the formants (p. 279).The present authors recognize and deal with the prominent role that the performance spaces play in all music making and listening. Hundreds of venues of different size and use have taught them that the complete reverberation characteristic has an enormous impact on any type of music performances, well knowing that modern recording equipment may, to a certain extent, help to cope with adverse acoustics. …

Loudness and noise rating: How may standardization bridge the gap between science and engineering?

Current noise regulations and standards, in Europe and to some extent also elsewhere, are primarily based on A-weighted sound levels. Most perceptual aspects are—if at all—taken into account by additional correction levels, for example, punishing tonality or impulsive content. On the contrary, instrumental loudness-prediction methods have been available for more than half a century and were first standardized 40 years ago. Against this background, the question arises why loudness—regardless of being calculated according to Zwicker or Moore and Glasberg—has not yet been accepted more widely in the field of noise control and related standardization. This contribution attempts to raise some possibly influential aspects, and to discuss them in the light of next-generation loudness standards. Advantages of stationary and time-varying loudness predictions over corrected weighted levels will be discussed and contrasted with potentially contradicting arguments. The discussion is primarily intended to provide arguments for the selection of future loudness-prediction standards. However, also a broader perspective is taken, looking at interrelations with other standards, algorithmically and regarding limiting values.

Sound absorption of a flexible micro-perforated panel absorber based on PVDF piezoelectric film

Micro-perforated panel (MPP) has been widely used in the noise control field. However, the performance at low frequencies is relatively poor due to the restricted space limitations in actual applications. Hence in this paper a flexible micro-perforated panel absorber (PVDF-MPPA) based on Polyvinylidene fluoride (PVDF) piezoelectric film is proposed, which is composed of a perforated aluminum-electrode PVDF piezoelectric film and a small air cavity. Its sound absorption at low frequency can be improved by employing panel vibration effect and shunting the electrodes of piezoelectric film with some electrical impedance. The corresponding structure of the PVDF-MPPA was designed and fabricated. Experiments were performed under different shunting cases such as open circuit, short circuit, and resonant circuit in an impedance tube with the testing frequency range from 100Hz to 1600Hz. The results demonstrated that the PVDF-MPPA with shunt circuits had a wider absorption bandwidth compared with a rigid MPP absorber with the same structural parameters. When compared with the open circuit and short circuit cases, the PVDF-MPPA with resonant circuit definitely has a better low frequency absorption performance if the shunting parameters have been carefully tuned. By using shunt-damping technology, the PVDF-MPPA has a potential to be widely used as an efficient sound absorber in practical situations because of its simple structure and good absorption performance at low frequencies.

Psychometric properties of the Bulgarian translation of noise sensitivity scale short form (NSS-SF): implementation in the field of noise control.

The Noise Sensitivity Scale Short Form (NSS-SF), developed in English as a more practical form of the classical Weinstein NSS, has not to date been validated in other cultures, and its validity and reliability have not yet been confirmed. This study aimed to validate NSS-SF in Bulgarian and to demonstrate its applicability. The study comprised test-retest (n = 115) and a field-testing (n = 71) of the newly validated scale. Its construct validity was examined with confirmatory factor analysis, and very good model-fit was observed. Temporal stability was assessed in a test-retest (r = 0.990), convergent validity was examined with single-item susceptibility to the noise scale (r = 0.906) and discriminant validity was confirmed with single-item noise annoyance scale (r = 0.718). The lowest observed McDonald's omega across the studies was 0.923. The cross-cultural validation of NSS-SF was successful but it proved to be somewhat problematic with respect to its annoyance-based items.

Design, Manufacture and Characterization of an Acoustic Barrier Made of Multi-Phenomena Cylindrical Scatterers Arranged in a Fractal-Based Geometry

Abstract In this work we present the design and the manufacturing processes, as well as the acoustics standardization tests, of an acoustic barrier formed by a set of multi-phenomena cylindrical scatterers. Periodic arrangements of acoustic scatterers embedded in a fluid medium with different physical properties are usually called Sonic Crystals. The multiple scattering of waves inside these structures leads to attenuation bands related to the periodicity of the structure by means of Bragg scattering. In order to design the acoustic barrier, two strategies have been used: First, the arrangement of scatterers is based on fractal geometries to maximize the Bragg scattering; second, multi-phenomena scatterers with several noise control mechanisms, as resonances or absorption, are designed and used to construct the periodic array. The acoustic barrier reported in this work provides a high technological solution in the field of noise control.

Enclosure Active Structure Acoustic Control Based on Multi-Agent System

For enclosure noise reduction, limited discrete distributed control is an ideal choice when it is difficult to understand sound-structure coupling characteristics accurately. An enclosure medel of two flexible plates is established in this paper. Two secondary control channels are constructed by applying distributed force on flexible plate. In the basis of control problem decomposition a multi-agent system (MAS) structure is established and the coordination relationship between agents is regulated. The simulaition resultes show the Active Structure Acoustic Control based on MAS is effective. The MAS control method improves the extension of noise control system and can be used in “plug-and–play” control field to realize noise reduction. MAS is a better effective tool to realize the divide-and-conquer approach in enclosure noise control field.

Propagation of Longitudinal Waves in Microporous Slab Sandwiched between Elastic Half-Spaces

A granular composite that consists of stiff inclusions embedded in a weaker matrix produces a well defined micro-structure. This composite is extensively used in the passive noise control field in sound absorbers. In classical continuum mechanics, the basic assumption is that the micro-structure of a material does not govern the mechanical behavior. However, classical theory and experimental results have some discrepancies, revealing the potential importance of the micro-structure. For instance, acoustic waves are characterized by high frequencies and small wavelengths, particularly in microporous materials with various stiffness values. Consequently, unlike for a homogeneous isotropic elastic medium with only two elastic constants, linear elastic micropolar theory utilizes 6 degrees of freedom and its results can hence be regarded as being a function of the micro-structure. This investigation explores the reflected and transmitted wave fields of an incident longitudinal plane wave that propagates in elastic–microporous–elastic interfaces. The numerical study demonstrates a through transmission in the sandwiched problem in situation of interest. This property of the half-wave microporous layer allows it to be regarded as a frequency or direction filter. Two sets of the forward and backward transverse plane waves are present in the sandwiched microporous layer. The specified work frequency and the width of the intermediate microporous layer affect all of the described phenomena.

Propagation of Transverse Waves in Elastic-Micropolar Porous Semispaces

Porous materials are widely used in the passive noise control field as sound absorbers. Conventional models of porous materials are assumed to have a rigid frame and show finite bulk elasticity. However, in the case of acoustical waves – characterized by high frequencies and small wavelengths – the effect of microstructure becomes significant. This effect of microstructure has resulted in the development of new types of waves, not found in the classical theory of elasticity. Generalized continuum theories include the construction of the linear theory of micropolar elasticity that consists of deformation and microrotation with six degrees of freedom, and hence can be used to study the acoustical characteristics of composites with a granular structure. In this study, we investigated transverse wave propagation and its reflection and transmission from a plane interface between two different elastic-micropolar porous interfaces in perfect contact. The micropolar porous composite was constructed using hollow glass microbubbles embedded in an epoxy matrix with six material constants that can be used as the acoustical absorbers. It was found that there are different wave types in a micropolar porous material for the incident SV (vertical transverse) or SH (horizontal transverse) wave. It was also found that these two coupled sets of transverse waves, when traveling with different velocities, are dominated by the critical value of microinertia, showing the influence of the micropolar porous characteristics.

Longitudinal Plane Wave Propagation in Elastic-Micropolar Porous Media

Porous materials are widely used in the passive noise control field as sound absorbers. Conventional models of porous materials are assumed to have a rigid frame and to satisfy finite bulk elasticity. However, it may be the case that when high-frequency sound is applied to porous materials for nanotechnology applications, the classical theory of elasticity cannot be satisfied. Generalized continuum theories, such as coupled stress theory and micropolar theory, have additional degrees of freedom compared with classical elasticity. It is hence assumed that such theories are applicable to composites with granular structure. In this study, two of the six material constants are obtained from experimental results on micropolar porous solids by Lakes. At the same time, a theoretical analysis concerning reflected and transmitted fields of an incident longitudinal plane wave propagating in elastic-micropolar porous media has been investigated. The results show that two fields are affected by micropolar porous characteristics. The boundary value problem of micro elasticity is also investigated in this paper.

Sound insulation of a rectangular thin membrane with additional weights

As a result of experiments on sound insulation under conditions of normal incidence, it has been confirmed that attaching small weights to a membrane improves the sound insulation efficiency in a frequency range from natural frequency of the whole membrane to that of the partial area divided by the additional weights. This effect is due to the interfering mode mixing of the fundamental normal mode of the membrane and the divided mode with the same phases formed by attaching the additional weights to the membrane, and not due to mass law. In the present paper this mechanism is studied and revealed through both experiments and numerical analyses. This method is simple, lightweight, possible to tune and effective in a lower frequency range, and hence it is thought that this method has the possibility of being developed into a useful one in the field of noise control.

Uses of sound intensity in architectural acoustics practice

Sound intensity has received significant attention over the past five years in the fields of noise control and product noise analysis. Yet, at this date, it is an infrequently used technique in consulting acoustics in general. Standards have been slow in developing and thus have not increased its use, and the most fundamental reason for its use is still the utility of its results rather than any existing standard. The benefit of intensity measurement in architecture is principally in its ability to indicate source direction, and this benefit is particularly important in a number of fields now being studied. The first of these is the open plan office, and the current work in intensity is based on an interest in the performance of acoustical dividers and absorbers. The second field, for which intensity seems to be the only measurement technique that is easily used, is the analysis of compound element building facades. This analysis is aimed at developing field transmission loss values for facade elements, such as windows, doors, and wall sections.

Two probabilistic evaluation methods for single and double walls type sound insulation systems with arbitrary random noise excitation.

In the practical engineering field of noise control, it is as important as the sound source countermeasure to improve the sound propagation characteristics by newly setting a sound insulation system. On the other hand, the noise statistics like an Lx (x=5, 10, 50, 90, ) defined as a (100 -x) percentage point of the sound level distribution are very important as well as the lower order energy moment statistics like an Leq in the actual noise evaluation and regulation problems. In this paper, two kinds of probabilistic evaluation methods for sound insulation systems are theoretically proposed from typically different points of view for the probability distribution of the transmitted sound intensity, when a general stationary random noise having an arbitrary distributionform and frequency characteristics is insulated by a wall. To evaluate its sound transmission coefficient, a somewhat modified statistical energy analysis method has been used.The validity of the theoretical results is experimentally confirmed by applying it to the actually observed data on the output response fluctuation of single and double walls type insulation systems inserted between two reverberation rooms.

The role of professional societies in noise‐control education

Although societies of technical professions are not chartered to provide studies for certified credit (in the sense of educational institutions), each society has addressed the matter of education in its respective field. Such concerns are manifested in various forms: society‐sponsored workshops, seminars, special sessions, topical conferences, and even selected certification of individual technical qualifications. Additional society contributions include directories of accredited course offerings by educational institutions within selected fields of special concern and information on job opportunities and advanced degree graduates produced by educational institutions within selected subfields of specialization. Thus, even though professional societies do not offer accredited courses of study, they tend to be an active partner in education‐related functions. During the past decade, noise‐related studies have received increased attention by both educational and professional institutions, resulting in a marked upturn of events relating to educational activities by professional societies. Specific education‐related activities by professional societies have been selected for abbreviated description of the important role they play in the total educational process in the field of noise control.