Sound Properties Research Articles

Adding Glass Fibers to 3D Printable Mortar: Effects on Printability and Material Anisotropy

Adding fibers is an effective way to enhance the printability and mechanical performance of 3D printable cementitious materials. Glass fibers are commonly used owing to their sound mechanical properties, high durability and affordable price. However, there is still a lack of systematic and in-depth research on the effects of adding glass fibers to cementitious materials. In this study, a series of 3D printable mortars with varying glass fiber content and water/cement (W/C) ratio were produced to evaluate their printability, flexural strength and compressive strength. The results showed that decreasing the W/C ratio generally has positive effects on printability and mechanical performance, whereas increasing the glass fiber content from 0% to 1% would substantially improve the extrudability, dimensional stability and buildability; increase the flexural strength by up to 82%; but decrease the compressive strength by up to 35%. Such large differences in the effects of glass fibers on the flexural and compressive strengths indicate significant material anisotropy. In fact, comparison of the strength results of printed specimens to those of un-printed specimens reveals that the printing process could increase the flexural strength by 98% but decrease the compressive strength by 47%.

Theoretical study of sound absorption performance for Al2O3-polyurethane foam composite

To reveal the sound absorption property and mechanisms of Al2O3-polyurethane (Al2O3-PU) composite materials in theory, the impedance tube model is established by using the finite element method in this paper. Meantime, the theoretical modal and the calculation method adopt the Johnson-Champoux-Allard (JCA) modal and the standing wave ratio method, respectively. By comparing the experimental and simulation values of PU and Al2O3-PU composites from 0 to 1250 Hz, the results prove that the JCA predicted values can match the actual measured values. To further predict the sound property of Al2O3-PU composites in the medium and high frequency, the diameter of 29 mm and length of 600 mm for the impedance tube is installed. Finally, the sound pressure distribution diagram of the impedance tube is obtained.

Glass Microspheres Thermo-Deformation Sintering Processes in the Technologies of Obtaining Materials for Underwater Technical Equipment

Abstract In this work, the important scientific and technical problem of creating multifunctional composite materials for shipbuilding and ocean engineering was solved. The work aimed to study the thermal deformation processes of sintering glass microspheres to obtain lightweight glass composites with a cellular structure that provides positive buoyancy and sound insulation properties. For this purpose, glass microspheres of Na2O‒SiO2 and Na2O‒B2O3‒SiO2 composition with a dispersion of 10 to 60 μm were used as raw materials. They were sintered to form a closed, porous structure. The theoretical substantiation of technological parameters is based on the concepts of solid state and glassy state chemistry and physicochemical concepts of glass softening processes. The process of hot-pressing glass microspheres without plasticisers and additives was investigated. The author’s own laboratory equipment was used for the experiments. The sintering intensity was determined from the results of shrinkage processes; the kinetic shrinkage curves were constructed in semilogarithmic coordinates. The glass composite samples were examined by optical and electron microscopy. As a criterion, the storage of spherical microspheres under the influence of simultaneous heating to 700 °C with the application of pressure in the range of 0,5 to 1,5 MPa was chosen. It was established that the formation of a predominantly closed-porous structure of glass composites with a density of 350...600 kg/m3 occurs by the mechanisms of viscous glass phase flow through liquefaction processes in the walls of microspheres. At the same time, shrinkage processes in the linear direction reach up to 50%. The acoustic properties were investigated by measuring the differences in sound pressure levels in octave frequency bands using a Kundt pipe. The water absorption of the glass composite samples was determined at hydrostatic pressures up to 20 MPa. The research results were compared with the characteristics of analogue composites, such as syntactic foams and foam glass. The developed materials can be used in the design and manufacture of technical equipment for research and maintenance of underwater infrastructure. The prospects for further research are related to the feasibility study and marketing research on implementing the developed glass composites.

The language of sound: events and meaning multitasking of words

Abstract The focus of much sensory language research has been on vocabulary and codability, not how language is used in communication of sensory perceptions. We make a case for discourse-oriented research about sensory language as an alternative to the prevailing vocabulary orientation. To consider the language of sound in authentic textual data, we presented participants with 20 everyday sounds of unknown sources and asked them to describe the sounds in as much detail as possible, as if describing them to someone who could not hear them. We explored how the participants use language to describe these sounds. Do they describe their listening experiences (stressful), sound properties (intermittent beeping), and/or the events that caused the sounds (eating an apple)? The results show that out of these three soundscape elements, events are the most frequent and most indispensable element. We let the results from the study illustrate the need for more discursive data in studies of sensory language and argue that there is no designated language of sound. Our study highlights that in order to account for sensory language use, we need an analytical framework that accommodates discursive language in a non-trivial way beyond stable couplings between individual words and meanings.

Enhancing the sound and thermal insulation properties of polypropylene foam by preparing high melt strength polypropylene.

High-performance polypropylene (PP) foam is a vital polymer product in industrial areas. However, the poor melt strength of ordinary PP homopolymer limits its foaming molding. In this work, high melt strength polypropylene (HMSPP) was prepared by using styrene (St) and tripropylene glycol diacrylate (TPGDA) as comonomers, and then PP foams were prepared by mold foaming method. The results showed that adding St in the grafting process of TPGDA will obviously improve the melt strength of the PP matrix, and its melt strength (28184Pa.s) is 7.4 times higher than that of pure PP. HMSPP foam has more regular and uniform cells and higher cell density, which significantly improves the sound and thermal insulation properties of PP foam. Compared with pure PP foam, the average sound transmission loss (52.9dB) of HMSPP foam with a low foaming ratio increased by 64%, and the thermal conductivity (0.0867W/mK) decreased by 46%. Therefore, the obtained HMSPP foam can be used in sound insulation or thermal insulation area. This work provides an available route for the high-performance utilization of PP foam. This article is protected by copyright. All rights reserved.

"Please say what this word is": Linguistic experience and acoustic context interact in vowel categorization .

Ladefoged and Broadbent [(1957). J. Acoust. Soc. Am. 29(1), 98-104] is a foundational study in speech perception research, demonstrating that acoustic properties of earlier sounds alter perception of subsequent sounds: a context sentence with a lowered first formant (F1) frequency promotes perception of a raised F1 in a target word, and vice versa. The present study replicated the original with U.K. and U.S. listeners. While the direction of the perceptual shift was consistent with the original study, neither sample replicated the large effect sizes. This invites consideration of how linguistic experience relates to the magnitudes of these context effects.

Sound attenuation enhancement of acoustic meta-atoms via coupling.

Arrangements of acoustic meta-atoms, better known as acoustic metamaterials, are commonly applied in acoustic cloaking, for the attenuation of acoustic fields or for acoustic focusing. A precise design of single meta-atoms is required for these purposes. Understanding the details of their interaction allows improvement of the collective performance of the meta-atoms as a system, for example, in sound attenuation. Destructive interference of their scattered fields, for example, can be mitigated by adjusting the coupling or tuning of individual meta-atoms. Comprehensive numerical studies of various configurations of a resonator pair show that the coupling can lead to degenerate modes at periodic distances between the resonators. We show how the resonators' separation and relative orientation influence the coupling and thereby tunes the sound attenuation. The simulation results are supported by experiments using a two-dimensional parallel-plate waveguide. It is shown that coupling parameters like distance, orientation, detuning, and radiation loss provide additional degrees of freedom for efficient acoustic meta-atom tuning to achieve unprecedented interactions with excellent sound attenuation properties.

Sound properties affect measurement of vocal consistency in birdsong: Validation of the spectrogram cross correlation method (SPCC).

In songbirds, singing with precision (vocal consistency) has been proposed to reflect whole-organism performance. Vocal consistency is measured using spectrogram cross correlation (SPCC) to assess the acoustic similarity between subsequent renditions of the same note. To quantify how SPCC is sensitive to the acoustic discrepancies found in birdsong, we created a set of 40 000 synthetic sounds that were designed based on the songs of 345 species. This set included 10 000 reference sounds and 30 000 inexact variants with quantified differences in frequency, bandwidth, or duration with respect to the reference sounds. We found that SPCC is sensitive to acoustic discrepancies within the natural range of vocal consistency, supporting the use of this method as a tool to assess vocal consistency in songbirds. Importantly, the sensitivity of SPCC was significantly affected by the bandwidth of sounds. The predictions derived from the analysis of synthetic sounds were then validated using 954 song recordings from 345 species (20 families). Based on psychoacoustic studies from birds and humans, we propose that the sensitivity of SPCC to acoustic discrepancies mirrors a perceptual bias in sound discrimination. Nevertheless, we suggest the tool be used with care, since sound bandwidth varies considerably between singing styles and therefore, SPCC scores may not be comparable.

Sex-specific difference in agonistic sounds depends on size of sonic organs in fishes: Testing the hypothesis in the croaking gourami (Labyrinth fishes).

In most vocal fish species, females possess smaller sound-generating organs and vocalize less than males. In certain cases females lack sonic organs, in others differences between sexes are unknown. This study analyzes in detail the relationship between sexual dimorphism of sonic organs and the characteristics of agonistic behavior and of sounds recorded under the same behavioral conditions in a vocal fish species, the croaking gourami Trichopsis vittata. During agonistic contests both sexes stretch and pluck two enhanced (sonic) tendons when beating pectoral fins alternately, resulting in a series of double-pulsed bursts, termed croaking sound. The following anatomical, behavioral, and acoustic variables were analyzed: diameter of enhanced tendons in each specimen, duration of same-sex dyadic contests, number and duration of lateral display bouts and of sounds, number of single- and double-pulsed bursts, burst period, peak-to-peak amplitudes of pulses, dominant frequency and sound pressure level (SPLrms). Female sonic tendons were approximately one-fifth smaller than male's of the same size. Six out of seven behavioral variables did not differ between sexes. Sound characteristics were similar in both sexes except for SPLs, which were on average 5 dB lower in females. The degree of sexual dimorphisms in sonic organs may explain differences in sound characteristics. Sounds differ only in one sound characteristic (SPLrms) in T.vittata, in contrast with the congeneric Trichopsispumila which possesses a more pronounced sexual dimorphism in sonic organs and in which agonistic sounds differ in all sound properties between sexes.

Effects of Carbon Nanotubes on Thermal Behavior of Epoxy Resin Composites

Human society’s need to build low-weight, high-strength and durable structures has increased the demand for composite materials. In this case, composites are used where high mechanical strength, low weight, sound and thermal insulation properties are required. One of the most important issues now is designing materials and coatings aimed at reducing heat loss and resisting high temperatures. One way to address this problem is to develop a technique for preparing and applying composite materials that slow down their heating applied to a surface. In this study, carbon nanotubes (CNTs) reinforced composites were fabricated using silicone molding to be applied to honeycomb sandwich structures. To determine the effect of CNTs on the thermal behavior of the sandwich panels, different weight percentages of this material (0.025, 0.05. 0.075 wt.%) were added to the epoxy resin. The results showed that the thermal stability of the epoxy composites was directly related to the increase in the percentage of CNTs as the CNT content increased to 0.075 wt.%, and the thermal degradation temperature of the epoxy composites increased by 14 °C. In addition, the energy absorption increased by 4.6% with an increase in CNTs up to 0.075 wt.%. Density measurements showed that the density of the nanocomposite samples increased by adding CNTs to pure epoxy resin. The actual densities of the samples reinforced with 0.025, 0.05, and 0.075 wt.% CNTs are 0.925, 0.926, and 0.927 of the theoretical density, respectively. Since the CNT dispersion uniformity in the epoxy matrix can significantly affect the properties of the composites, in this study, a new method of dispersing CNTs in the epoxy resin matrix resulted in higher thermal conductivity while using lower amounts of CNTs compared to other studies. The storage modulus of the epoxy matrix composites reinforced with 0.05 wt.% in this study was 25.9% and 6.9% higher than that from the previous study reinforced with 0.1 wt.% and 0.25 wt.% CNTs, respectively. Furthermore, the tanδ and loss modulus of the composite reinforced with 0.05 wt.% CNTs in this study were 52% and 54.5% higher than that from the previous study with 0.1 wt.% CNTs, respectively. This study provided an optimal approach for designers and engineers who want to effectively design their composite honeycomb sandwich structure with better thermal properties.

Airborne sound transmission loss of ship bulkheads: A new methodological approach for in-laboratory assessment by including low frequencies

Current standard laboratory measurements of sound transmission loss properties of ship bulkheads at low frequencies, below 100 Hz, are not accurate enough due to the non-diffuse acoustic field of typical laboratory volumes. However, what has been recently observed in non-diffuse field conditions is the transmission of source modes into the receiving room through the partition. On the basis of this, in this paper, a novel procedure to determine the laboratory airborne sound transmission loss properties of ship bulkheads at low frequencies through the airborne modal sound transmission loss is investigated. It is defined as the difference between the average sound pressure levels of source room modes peaks that occur in both source and receiving rooms. A correction method is proposed to suppress the influence of natural receiving room modes. Normalization terms related to receiving room volume and modal damping are introduced, and an envelope method is applied to extend the results in third octave bands. Measurements on five different ship bulkheads show that the standard transmission loss in the low frequency range provides unlikely results, whereas the proposed descriptor follows the expected theoretical curve. This evidence confirms the validity of the proposed method, at least for comparison purposes in marine applications.

Sound Transmission Through a Thin Plate with Shaped Frequency Response

Thin plates, in the form of individual panels or whole device casings, often separate the noise source from its recipients. It would be very desirable if the panels could effectively block the sound transmission preventing noise from further propagation. This is especially challenging to achieve at low frequencies. A promising approach, intensively developed in the recent years, is to employ active control methods by adding sensors and actuators, and running a control algorithm. However, if the noise is narrow-band, an alternative passive solution originally developed by the authors can be applied. It is based on appropriately located passive elements which can be used to alter the frequency response of the vibrating structure thus improving its sound insulation properties. Such an approach is referred to as the frequency response shaping method. The purpose of this paper is to further develop this method and apply it to a device casing panel. The efficiency of the method is evaluated by simulation and real experiments. Appropriate cost functions and mathematical models are formulated and used to optimise the arrangement of passive elements mounted to the plate, enhancing its sound insulation properties at the given frequency range. The results are reported, and advantages and limits of the method are pointed out and discussed.

Voice Traces of Anxiety: Acoustic Parameters Affected by Anxiety Disorder

Although the emotions and learning based on emotional reaction are individual-specific, the main features are consistent among all people. Depending on the emotional states of the persons, various physical and physiological changes can be observed in pulse and breathing, blood flow velocity, hormonal balance, sound properties, face expression and hand movements. The diversity, size and grade of these changes are shaped by different emotional states. Acoustic analysis, which is an objective evaluation method, is used to determine the emotional state of people’s voice characteristics. In this study, the reflection of anxiety disorder in people’s voices was investigated through acoustic parameters. The study is a case-control study in cross-sectional quality. Voice recordings were obtained from healthy people and patients. With acoustic analysis, 122 acoustic parameters were obtained from these voice recordings. The relation of these parameters to anxious state was investigated statistically. According to the results obtained, 42 acoustic parameters are variable in the anxious state. In the anxious state, the subglottic pressure increases and the vocalization of the vowels decreases. The MFCC parameter, which changes in the anxious state, indicates that people can perceive this situation while listening to the speech. It has also been shown that text reading is also effective in triggering the emotions. These findings show that there is a change in the voice in the anxious state and that the acoustic parameters are influenced by the anxious state. For this reason, acoustic analysis can be used as an expert decision support system for the diagnosis of anxiety.

Influence of Geometric Structure, Convection, and Eddy on Sound Propagation in Acoustic Metamaterials with Turbulent Flow

The problem of reducing noise in the transportation is an important research field to prevent accidents and to provide a civilized environment for people. A material that has recently attracted attention in research to reduce noise is acoustic metamaterial, and most of the research projects so far have been limited to the case of static media without flow. We have studied the sound transmission properties of acoustic metamaterial with turbulent flow to develop acoustic metamaterial that be used in transportation. In this paper, the effect of geometrical structure, the convective effect, and the eddy effect on sound propagation in acoustic metamaterial with turbulent flow are investigated, and the relationships between them are analyzed. The convective effect and the eddy effect both reduce the resonant strength of sound transmission loss resulting from the unique geometry of the acoustic crystal, but shift the resonant frequencies in opposite directions. In addition, when the convective effect and the eddy effect of the airflow, as well as the intrinsic interaction effect generated from the unique geometrical structure of the acoustic metamaterial cannot be ignored, they exhibit competition phenomena with each other, resulting in a widening of the resonance peak. As a result, these three effects cause the shift of the resonance frequency of the sound transmission loss and the widening of the resonance peak. The results of this study show that even in the case of turbulent flow, acoustic metamaterial can be used for transportation by properly controlling the geometric size and shape of the acoustic metamaterial.

Preparation and sound absorption properties of multi-layer composites formed by waste polyphenylene sulfide filters

Composite materials with multi-layer structure were prepared by combining polyurethane film and waste polyphenylene sulfide filters by hot melting, which could be used as sound-absorbing materials to contribute to the noise control and reutilization of industrial waste. The structure, mechanical property, pore size distribution and stability of waste polyphenylene sulfide filters were investigated and could directly affect the quality of recycled products. The effects of layer numbers, layering sequence and polyurethane film thickness on sound absorption and insulation properties were also analyzed using an impedance tube absorption test system. The results showed that multi-layer materials had a better sound absorption effect than single-layer polyphenylene sulfide filters at low frequency. The sound absorption coefficients of the single-layer sample was only 0.081 at 1000 Hz, while the sound absorption coefficients of the five-layer sample could reach 0.26. The sound absorption properties of multi-layer materials were slightly affected by layering sequence, but polyurethane film thickness had a significant effect on sound absorption properties. The α of the SUS1 and USU1 samples were 0.151 and 0.170, while the α of the SUS3 and USU3 samples were only 0.076 and 0.056, respectively. Meanwhile, the sound insulation properties of multi-layer materials could be significantly influenced by the polyurethane film position. The sound transmission loss of the SUSUSU3 sample was just 32.83 dB, whereas that of the USUSU3 sample could reach 47.94 dB. Moreover, when polyurethane film was located on the sound facing side of multi-layer materials, the increase in polyurethane film thickness could cause the average sound reduction index of the USUSU sample to increase from 28.76 dB to 47.94 dB.

Comparative Study to Assess the Thermal Behaviour of Sandwich Roof Panels with Coconut Fibre as an Alternative Core Material to Polyurethane

Sandwich panels (modular panels) promote optimal solutions to some major issues prevailing in the construction industry such as increased energy consumption by building elements, excessive disposal of constructional waste and unproductive time spent during construction. Hence, the inclination towards sandwich elements has been increased vastly deviating from conventional building construction materials and methods. However, the potentiality of using locally available natural materials for the development of sandwich panels is a salient sustainable approach that needs to be addressed. This study evaluates the current and potential materials used in modular panels and key properties of sandwich panels including mechanical, thermal insulation, and sound insulation properties. Moreover, various test methods followed, and standards specified to investigate the mechanical, thermal and acoustic insulation properties are also discussed. The possibility of using coconut fibre as a locally available natural alternative core material to polyurethane core of sandwich panels has been evaluated using simulations based on the material properties obtained from literature. The study identifies coconut fibre as a potential alternative core material for sandwich roof panels as it reflects nearly similar thermal behaviour to polyurethane.

Less is More: A Novel Feature Extraction Method for Heart Sound Classification via Fractal Transformation.

Cardiovascular diseases (CVDs) are the leading cause of death globally. Heart sound signal analysis plays an important role in clinical detection and physical examination of CVDs. In recent years, auxiliary diagnosis technology of CVDs based on the detection of heart sound signals has become a research hotspot. The detection of abnormal heart sounds can provide important clinical information to help doctors diagnose and treat heart disease. We propose a new set of fractal features - fractal dimension (FD) - as the representation for classification and a Support Vector Machine (SVM) as the classification model. The whole process of the method includes cutting heart sounds, feature extraction, and classification of abnormal heart sounds. We compare the classification results of the heart sound waveform (time domain) and the spectrum (frequency domain) based on fractal features. Finally, according to the better classification results, we choose the fractal features that are most conducive for classification to obtain better classification performance. The features we propose outperform the widely used features significantly (p < .05 by one-tailed z-test) with a much lower dimension.Clinical relevance-The heart sound classification model based on fractal provides a new time-frequency analysis method for heart sound signals. A new effective mechanism is proposed to explore the relationship between the heart sound acoustic properties and the pathology of CVDs. As a non-invasive diagnostic method, this work could supply an idea for the preliminary screening of cardiac abnormalities through heart sounds.

Vibration and structure-borne sound isolation properties of silica aerogels

Vibration reduction and structure-borne sound insulation create a healthy environment in housing by reducing the exposure of the habitants from sources outside or inside the building (railway and road traffic, neighbors). Current solutions include textiles, polymer foams, rubber mats and metal springs, but for many applications, highly sought after. Although thermal insulation drives the silica aerogel market, acoustic applications are increasingly gaining attention. Most acoustic studies focus on airborne sound absorption, but structure-borne sound and vibration isolation remain unexplored. In this paper, we compare the vibroacoustic properties of silica aerogel granules to those of recycled rubber and expanded cork to assess the suitability for vibration damping or vibration isolation. With a remarkably low resonance frequency (<12 Hz) and dynamic stiffness (<0.1 N/mm3), silica aerogels provide superior vibration isolation performance compared to recycled rubber (by 8 dB) over a wide range of static loads (0.02–0.12 MPa), and silica aerogel may become a viable solution for vibration isolation in construction.

Development and evaluation of the Norwegian Fatigue Characteristics and Interference Measure (FCIM) for stroke survivors: cognitive interviews and Rasch analysis

PurposeThere is need for a comprehensive measure of post-stroke fatigue with sound measurement properties. This study aimed to develop the Norwegian Fatigue Characteristics and Interference Measure (FCIM) and assess its content validity, structural validity, and internal consistency.MethodThis study consisted of three steps: (1) an expert panel developed version 1.0 of the Norwegian FCIM, (2) its content validity was assessed in cognitive interviews with stroke patients (N = 15), (3) a convenience sample of stroke patients (N = 169) completed an online questionnaire with the FCIM, Fatigue Severity Scale, and sociodemographic information; validity and reliability were assessed using Rasch analysis.ResultsFCIM version 1.0 included a 10-item characteristics subscale, a 20-item interference subscale, and two pre-stroke fatigue items. The cognitive interviews revealed content validity issues, resulting in two interference items being removed and five items being flagged but retained for Rasch analysis (version 2.0). Rasch analysis led to removal of four items from the characteristics subscale and six more from the interference subscale. The final six-item characteristics subscale and 12-item interference subscale (version 3.0) both showed adequate fit to the Rasch model with indications of unidimensionality and local independence. The interference subscale had a high person separation index. No significant differential item function (DIF) was found in relation to gender, but one item demonstrated DIF in relation to age.ConclusionThe cognitive interviews and Rasch analysis demonstrated that the Norwegian version of the FCIM has high content validity, structural validity, and internal consistency. Future research should assess its construct validity, reliability, and responsiveness.

Sound transmission properties of a porous meta-material with periodically embedded Helmholtz resonators

The main scope of this work is to study the effect of embedding a periodic pattern inside a porous material, in order to passively improving its acoustic performance in terms of sound transmission loss. A contemplated application is the improvement of classical aeronautical soundproofing packages. In order to reach this goal, numerical models of an acoustic package including periodic patterns are implemented using the finite element method and the Transfer Matrix Method. Firstly, some of the proposed configurations are experimentally tested, providing a comparison and validation of the obtained numerical results. Afterwards, several configurations of inclusions are numerically studied, and incorporate hollow cylindrical inclusions, half-cut hollow cylindrical inclusions and cylindrical Helmholtz resonators. The improvements in terms of transmission loss, essentially brought by a periodicity peak, are evaluated under plane wave excitation with various incidence angles. The main novelties of the present work are represented by an experimental validation of the proposed acoustic meta-materials that were only numerically studied in previous works. The effect of the inclusion of a periodic pattern of Helmholtz resonators inside the foam core is also considered. The presented numerical results are also evaluated for different incidence angles of an exciting acoustic plane wave.