Acoustic Treatment Research Articles

Определение рациональных параметров акустической обработки с целью активации пивных дрожжей

В бродильных производствах, в частности, в пивоварении актуальными являются задачи повышения бродильной активности дрожжей и/или интенсификация накопления их биомассы. Для ее решения в настоящее время предлагаются различные способы, одним из которых может быть предварительная обработка волновыми или полевыми воздействиями. Ранее в наших исследованиях была показана принципиальная возможность интенсификации развития дрожжевых популяций за счет предварительной обработки звуком слышимого диапазона. Данная статья посвящена изучению влияния параметров акустической обработки на такие характеристики процесса культивирования дрожжей, как прирост общего титра клеток, доля нежизнеспособных клеток, убыль веса среды культивирования. Определяли эффективность обработки засевных дрожжей Saccharomyces cerevisiae (Saflager W34/70) звуком слышимого диапазона, варьируя следующие параметры акустического воздействия: частоту звука, продолжительность обработки, амплитуду, расстояние от источника звука до обрабатываемого объекта (навески сухих дрожжей). Обработанными и необработанными звуком дрожжами засевали модельные среды (стерилизованные 5 %-ные растворы сахарозы) и вели культивирование при комнатной температуре без принудительного перемешивания в течение 4 сут. Сразу после засева и ежедневно в процессе культивирования определяли контролируемые показатели. На основании полученных результатов был сделан вывод о том, что предварительная акустическая обработка, проведенная в рациональных условиях, позволяет увеличить прирост общего титра дрожжевых клеток и степень утилизации компонентов питательной среды при сохранении процента нежизнеспособных клеток на уровне контроля. Это создало предпосылки для апробации предлагаемого способа активации пивных дрожжей в условиях, приближенных к производственным.

Influence of Acoustic Waves on the Shelf Life Quality of Broccoli (Bsassica oleracea var. italic)

Broccoli (Brassica oleracea var. italica) is a high value crop that requires the application of post-harvest techniques to extend its shelf life. Acoustic wave is one of the newest non thermal methods to extend shelf life of fresh produce during storage. The purpose of this study was to test the efficacy of prolonging the shelf life quality of broccoli through acoustic waves treatment. Experimental design includes 4 treatments with 3 replications each. The treatments consisted of varying hours of exposure to acoustic waves (0 hour, 4 hours, 6 hours, and 8 hours). Broccolis were treated with low-frequency acoustic waves at 1 kHz, 100 dB produced by a sound transducer in a sound-proof chamber to prevent extraneous noise. After acoustic waves exposure, broccolis were stored in a refrigerator at 10 °C then monitored the surface color, florets firmness, stalk firmness, and the shelf life which are the quality indicator of broccoli. Results showed that treated broccoli has a significant difference compared to non-treated broccoli. Broccoli treated with acoustic waves exhibits gradual changes in its quality than of non-treated. The most suitable hours of exposure to acoustic waves to extend the shelf life quality of broccoli in terms of surface color and flesh firmness is achieved by treating the broccoli with 1 kHz, 100 dB acoustic waves for 8 hours. The acoustic wave has a potential benefit of extending the shelf life of broccoli up to 22 days at 10 °C delaying the changes in marketable quality.

Application of 3D printed structured materials as the sound absorption panels

The human living standard has been increasing day-by-day. Not only the building energy performance has to meet a high expectation, but the noise quality of a building has to be par with it. Sound absorption is one of the key elements in determining the quality of the acoustics performance in a room. A room with high background noise and high reverberant time will affect the comfort level of the occupants in the room. Hence, a well-designed room with acoustics treatment is required. The sound absorptive materials play an important role in reducing the overall sound pressure level in the room. Conventionally sound absorber materials are porous and resonator. With the advancement of the addictive technology, the sound insulation materials can be further improved and optimized with 3D printed structured materials. Two 3D printed structured designs have been developed in this study and were printed out by using fused deposited modelling in 3D printing technology. The two designs are micro perforated design (MPP) and porous design. The structured materials have been tested for its sound absorption ability using the sound impedance tube. The frequency range tested is between 100 Hz to 6400 Hz. In conclusion, micro perforated design (MPP) model has a very good sound absorptive behavior at the low frequency at 4000Hz and below, whereas the porous model is effective at high frequency at the 2500Hz and above. Through the study, the perforation ratio is found to be closely related to the peak sound absorption coefficient frequency. The peak frequency is reduced with the increase of the perforation ratio. The gap between the 3D printed structured materials and end wall also play the important role. The larger the gap, the lower the peak absorptive frequency.

Group behavior and tolerance of Eurasian minnow (Phoxinus phoxinus) in response to tones of differing pulse repetition rate.

Behavioral guidance systems are commonly used in freshwater fish conservation. The biological relevance of sound to fish and recorded responses to human-generated noise supports the viability of the use of acoustics as an effective stimulus in such technologies. Relatively little information exists on the long-term responses and recovery of fish to repeated acoustic exposures. In a controlled laboratory study, the response and tolerance of Eurasian minnow (Phoxinus phoxinus) shoals to tonal signals (150 Hz of 1 s pulse duration) differing only in temporal characteristics ("continuous," "slow," "intermediate," or "fast" pulse repetition rate) were investigated. In comparison to independent control groups, fish increased their mean group swimming speed, decreased inter-individual distance, and became more aligned in response to the onset of all four acoustic treatments. The magnitude of response, and time taken to develop a tolerance to a treatment differed according to pulse repetition rate. Groups were found to have the greatest and longest lasting response to tone sequences tested in this study when they were pulsed at an intermediate rate of 0.2 s-1. This study illustrates the importance of understanding the response of fish to acoustic signals, and will assist toward the development of longer-term effective acoustic guidance systems.

A Parametric Study of the Acoustic Performance of Resonant Absorbers Made of Micro-perforated Membranes and Perforated Panels

Sound absorbing surfaces are being increasingly requested for the acoustical treatment of spaces, like offices and restaurants, where high aesthetic standards are requested. In these cases, perforated and micro-perforated panels may represent the ideal solution in terms of low maintenance, durability, and mechanical resistance. In addition, such a solution might be conveniently realized while using optically transparent panels, which might offer extra value, as they could ensure visual contact, while remaining neutral in terms of design. The paper first investigates the reliability of prediction models by comparison with measured data. Subsequently, while taking advantage of a parametric optimization algorithm, it is shown how to design an absorber covering three octave bands, from 500 Hz to 2 kHz, with an average sound absorption coefficient of about 0.8.

The Growth Morphology and Yield of Grey Oyster Mushrooms (Pleurotus sajor-caju) Subjected to Different Durations of Acoustic Sound Treatment

Pleurotus sajor-caju (grey oyster mushroom) is a typical edible fleshy fungi. It has fruiting bodies shape like an oyster that contain high nutrient such as carbohydrates, proteins, fats, minerals and multivitamins. Due to its high nutritional values, the demand of grey oyster mushrooms keeps increasing. In this study, the effect of different durations and intervals of acoustic sound treatment on growth morphology, yield enhancement and the quality of the mushroom were studied. Using sound of fire cracker at constant intensity of 75 dB, four different acoustic sound treatments had been applied on the mushroom bags which were 5 pops at 5-day interval, 15 pops at 5-day interval, 5 pops at 10-day interval and 15 pops at 10-day interval and mushroom bags without any sound treatment acted as control. The results showed that the controls had longer time for mycellium to fill-up the bags compared to sound treated bags. Besides, controls also showed lower yield in terms of number of fruiting bodies and biological efficiencies (%) compared to all acoustic sound treated bags. However, 15 pops at 10-day interval had the shortest time taken to complete all the growth stages (mycellium growth, emergence of pinhead and formation of fruiting bodies). For colour of the mushroom, there were significant differences (P<0.05) in L* values for 15 pops at 5-day interval and no significant different (P>0.05) was observed for a* (redness) and b* (yellowness) values. Controls had the highest firmness value compared to mushroom with sound treatment. In summary, 15 pops at 10-day interval was the best treatment duration and interval as it took the shortest time for different growth stages with the greatest yield of mushrooms.

Effect of acoustic treatment on fan flutter stability

This paper presents an investigation of the effect of acoustically treated wall on fan flutter stability. The analysis is based on a three-dimensional analytical model which captures the aerodynamic coupling between oscillating annular rotor and finite-length liner in subsonic flow. With the response function of the entire system constructed as a whole, the perturbed duct field in modal description is determined by a simultaneous solution of the rotor and liner responses. Whether or not the aeroelastic instability occurs under a given wall impedance condition is evaluated through the energy method. Numerical experiments are conducted in the parametric space of inter-blade phase angle, liner distribution and acoustic impedance. The results show that under different conditions the acoustically treated wall can take diverse effects on the fan flutter stability. In the presented cases where the rotor stability is considerably affected, it is found that the aerodynamic interaction between the rotor and the lined section modify the overall distribution of the aerodynamic loadings on blade surface rather than change their magnitudes significantly. Moreover, the aeroelastic response of the oscillating blades turns out to be very susceptive to the reactance variation when the resistance is small, further indicating the important role of the reflections on the liner surface in such aerodynamic interaction. The analysis in general implies that the actual impact of a lined wall on the fan flutter stability depends on the aerodynamic excitation condition mutually determined by duct geometry, rotor state and configurations of liner.

Study about the sonorous impact characterization in singing/instrument classes among music students in Brazil

Background: The undergraduate music course students’ routine involves curricular musical practices and instrumental studies. This practice certainly exposes the students to the so called continuous or intermittent noises. Aims: To establish the sonorous exposure profile among the students of the music course of the UFSJ; describe the eventual differences among the diverse musicians groups; detect the presence of structures to protect against the noise during the musical instrument class; point out potential protective strategies for the exposed students. Subjects and methods: 01student from each of the 11musical instrument emphasis and their respective professors, 02Big Musical Instruments Groups and 02chamber groups were included. There were sonorous impact mediations during the musical instruments classes and rehearsals of the groups through decibel meter. 30-second samples in each of the moments (orientations/speeches; low and high intensity) were used. Results: It was verified that the different moments of the practical activities occupied 1/3 of the activities. Discussion: The results indicated that the majority of the practical activities are within the security levels from the sonorous exposure point of view, although there are certain bordering circumstances that call for a special attention. Conclusion: Despite the acoustic treatment of the building facilities, there can still be a risk due to such exposure. The preventive strategies are extremely important among which the earplugs and orientation to the students are highlighted, preferably in the beginning of the course.

The effects of ceiling height and absorber placement on speech intelligibility in simulated restaurants

The intelligibility of speech was measured in simulated rooms with parametrically manipulated acoustic features. The rectangular rooms were designed to simulate restaurant environments with either three or nine occupied tables, using either speech or noise as interfering sounds. The existence of more detailed acoustic features, such as furniture was also modelled. The measurements revealed that reverberation time was poorly correlated with speech intelligibility. In contrast, a psychoacoustic model of spatial release from masking produced accurate predictions for noise interferers and ordinally correct predictions for speech interferers. It was found that rooms with high ceilings facilitated higher speech intelligibility than rooms with lower ceilings and that acoustic treatment of walls facilitated higher speech intelligibility than equivalent treatment of ceilings. Ground-level acoustic clutter, formed by furniture and the presence of other diners had a substantial beneficial effect. Where acoustic treatment was limited to the ceiling, it was found that continuous acoustic ceilings were more effective than suspended panels, and that the panels were more effective if acoustically absorbent on both sides. The results suggest that the most effective control of reverberation for the purpose of speech intelligibility is provided by absorbers placed vertically and close to the diners.

ТЕХНОЛОГИЯ КОМБИНИРОВАННОЙ ЭЛЕКТРОМЕХАНОУЛЬТРАЗВУКОВОЙ ОБРАБОТКИ ПОВЕРХНОСТНЫХ СЛОЕВ ДЕТАЛЕЙ МАШИН

The technology of combined electro–mechanical–acoustic treatment is presented, which is a combination of electro–mechanical treatment and surface plastic deformation by ultrasonic treatment. Microhardness and residual stresses in strengthened EMUzO surface layer of machine parts investigated.

Universality of the Principle of Sufficiency for Ultrasonic Technologies in Liquid Media

Using an ultrasonic technology as an example, we showed the validity and universality of the principle of sufficiency proposed by Dobatkin for various economics fields. A 25-mm-thick compacted material having no solid granules is fabricated when a stream of a molten grade 1973 alloy with high transition metal contents (0.63% Zr, 0.27% Cr, 0.88% Ni) is subjected to ultrasonic gas spraying at a pressure of 25 MPa and an acoustic treatment level of 164 dB. The layer-by-layer joining of solid–liquid granules takes place at 25–35% liquid phase. No primary transition metal intermetallics are observed in the structure of the compacted material. This structure is homogeneous, the average grain size is 5–10 μm, and the dendritic parameter does not exceed 10 μm. Therefore, a traditional granulation technology can be replaced by ultrasonic gas spraying to solve certain problems, such as the production of thin-walled sheets of high-strength or high-temperature aluminum alloys. A colloidal solution with a ζ potential of –15.4 mV and an average nanoparticle size of 200 nm is fabricated during the action of ultrasound on elemental selenium granules in distilled water by an and-face waveguide at a frequency of 22.4 kHz and a power of 300 W. As a result, we fabricated biologically active selenium-containing substances without chemically synthesized substances for medicine and agriculture purposes.

Effect of the Conditions of Low-Frequency Acoustic Treatment on the Stability of Oil-Water Emulsions of Oil from the Ignyalinskoye Deposit

Effect of the Conditions of Low-Frequency Acoustic Treatment on the Stability of Oil-Water Emulsions of Oil from the Ignyalinskoye Deposit

Effect of the Conditions of Low-Frequency Acoustic Treatment on the Stability of Oil-Water Emulsions of Oil from the Ignyalinskoye Deposit

Effect of the Conditions of Low-Frequency Acoustic Treatment on the Stability of Oil-Water Emulsions of Oil from the Ignyalinskoye Deposit

Parameters for Acoustic Design in Auditorium

The clarity of communication in any auditorium is closely associated to the quality of acoustic treatment of that space. This quality is characterized by various parameters in acoustic designing. This research paper aims to explain the acoustical phenomenon and defects that becomes the basis of acoustical designing and material selection. The paper includes the basic guidelines and techniques for an auditorium acoustics designing, including fundamental thumb rules for selection of materials with respect to NRC values required in a space. The paper attempts to explain the NRC values that are generally considered on various surfaces of an auditorium to achieve the most efficient sound distribution in the space. Recommendations for surface finish have been conferred to achieve the required acoustical effect in an auditorium.

Remediation of soil and water contaminated with petroleum hydrocarbon: A review

Abstract The global use of petroleum hydrocarbons for energy and raw materials in various applications has increased with extensive release of a wide variety of contaminants into the environment, affecting soil, surface water and groundwater. The effect results to numerous health, ecological and environmental issues. However, treatment of contamination and pollution caused by petroleum hydrocarbons is a huge and laborious work. It involves several in situ or ex situ treatments comprising containment, separation and destruction which include biological, chemical, physico-chemical, thermal and heat, electric and electromagnetic, acoustic and ultrasonic treatment methods. These treatment methods involve several other techniques and strategies as listed in this review. The health risks pose by petroleum hydrocarbon pollution have driven scientists to research, develop and implement risk-based remediation strategies for restoration and reclamation of affected environments. To select the best treatment option for remediation, it is important to comprehend the nature, composition, properties, sources of pollution, type of environment, fate, transport and distribution of the pollutants, mechanism of degradation, interaction and relationships with microorganisms, the intrinsic and extrinsic factors affecting remediation. It helps to evaluate and predict the chemical behaviour of the pollutants with the short and long-term effects and mitigate the effects of pollution and limit exposure to the pollutants. Despite the available remediation options for petroleum hydrocarbon management and removal, sufficient and complete remediation can be implemented by adoption of proper approach derived from risk-based management procedure that can be practical, scientifically defensible, widely adapted, sustainable, non-invasive, eco-friendly and cost-efficient. This paper provides an overview of the various remediation and treatment technologies derived from risk-based approaches that are used for isolation, containment, separation, restoration reclamation and remediation of soil, sediments, surface water and groundwater contaminated by petroleum hydrocarbons and organic compounds.

Influence of Wave Activation of Fuel Oil-Biomass Blends on Results of their Gasification

The influence of wave (acoustic and high frequency electromagnetic) treatment of biomass—fuel oil—water three-component suspensions on the results of their gasification is investigated. The influence of gasification process implementation conditions on the yield and composition of the produced syngas was studied.

Influence of acoustic treatment and nature of solvents on viscosity of heavy oils

The article summarizes experimental data on the influence of acoustic treatment and the nature of solvents on the viscosity of oil from the Timan-Pechora and the Volga-Ural oil and gas-bearing basin. A combined treatment of oils, including acoustic exposure to 22 kHz and the addition of a chemical reagent was carried out. It is shown that the introduction of 1.75% wt alkaline solution of isobutyl alcohol leads to a decrease in oil viscosity of the Timan-Pechora oil and gas-bearing basin by 35%. After complex treatment (acoustic exposure for 1 min and the addition of reagent) the viscosity decreased by 60%. The introduction of alkaline chemicals into the oil of the Volga-Ural oil and gas-bearing basin does not lead to a decrease in viscosity. Oil viscosity decreases by 2.1 times after the introduction of 3% wt solvent P-12 (60% toluene, 10% xylene, 30% butyl acetate). Viscosity reduces by further 18% after acoustic exposure. Thus, the maximum viscosity reduction of heavy oils can be achieved by using the combined treatment including of acoustic exposure and addition of the selected chemical reagent.

Room acoustic modeling and auralization at an indoor firing range.

Reverberation time measurements were conducted in the 21-lane indoor firing range at Wright Patterson Air Force Base. Long reverberation times resulted in poor speech transmission indices (STI) which required acoustical treatments within the range. After treatment, reverberation times were significantly reduced and STI was dramatically enhanced. Standard Sabine and Eyring models failed to accurately predict the reverberation times. A computer simulation of the range was developed to predict room acoustic conditions and auralize speech performance for perceptual evaluation in the range.

Three-dimensional reflector localisation and room geometry estimation using a spherical microphone array.

The analysis of room impulse responses to localise reflecting surfaces and estimate room geometry is applicable in numerous aspects of acoustics, including source localisation, acoustic simulation, spatial audio, audio forensics, and room acoustic treatment. Geometry inference is an acoustic analysis problem where information about reflections extracted from impulse responses are used to localise reflective boundaries present in an environment, and thus estimate the geometry of the room. This problem, however, becomes more complex when considering non-convex rooms, as room shape cannot be constrained to a subset of possible convex polygons. This paper presents a geometry inference method for localising reflective boundaries and inferring the room's geometry for convex and non-convex room shapes. The method is tested using simulated room impulse responses for six scenarios, and real-world room impulse responses measured in a cuboid-shaped room, using a spherical microphone array containing multiple spatially distributed channels capable of capturing both time- and direction-of-arrival. Results show that the general shape of the rooms is inferred for each case, with a higher degree of accuracy for convex shaped rooms. However, inaccuracies generally arise as a result of the complexity of the room being inferred, or inaccurate estimation of time- and direction-of-arrival of reflections.

Sound Absorption Characteristics of Polyurethane and Polystyrene Foams as Inexpensive Acoustic Treatments

This work examines the absorption characteristics of two well-known porous materials—polyurethane foam (PUF) and polystyrene foam (PSF)—both of which are locally produced and readily available in Saudi Arabia. Nine samples were selected after a careful investigation of the local markets. The chosen samples were systematically tested in conformance with the ISO 354 and ISO 9613-1 standards in the reverberation chamber. The samples were subjected to three sets of measurements. The first set of measurements was obtained with the samples installed directly against the chamber wall (DOW, Type A mounting). For the second and third sets of measurements, the samples to be tested were installed with an air gap of 50 and 100 mm from the wall using wooden joists of 50 × 50 and 50 × 100 mm, respectively. Results showed that polyurethane foam is an efficient absorber, whereas polystyrene is not. It was also observed that sound absorption improves remarkably in the low-frequency range by increasing the air gap between the tested sample and the solid wall behind it, but this improvement becomes very limited in the mid- and high-frequency range. Adding a polystyrene and/or CF13 layer under the tested material generally improves the absorption characteristics when compared with the case where the material is installed directly against the wall or floor. Nevertheless, the best performance is achieved when the material is installed at least 50 mm from the wall or floor. Furthermore, results showed that the thickness of the material has a stronger effect on the absorption than the density in terms of the “correlation coefficient”. The other factors that affect the sound absorption include air flow resistivity, air permeability, and the microstructure of the tested samples.