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The First Biennial International Conference on Acoustic and Vibration (ANV 2020) is the first international conference held every two years on a regular basis in Indonesia. The scope of the conference includes acoustics, vibration, and their applications. The ANV 2020 was originally set in Denpasar, Bali. However, due to the COVID-19 pandemic with increasing travel restrictions from Indonesia authority and around the world, the Organizing Committee decided to move to all virtual platforms on November 23^rd – 24^th 2020. We had full support from DPTSI, our university directorate who is in charge of allocating necessary internet bandwidth to virtual room served as main for plenary with 500 attendees' capacity and two breakouts for parallel presentations.

In the plenary session, there were 5 invited distinguished speakers namely Profs. Lily M. Wang of University of Nebraska-Lincoln, Weidong Zhu of University of Maryland, Valtteri Hongisto of Helsinki University of Technology; and two of our keynote speakers were from industry Mr. Mahesh Kavinda of Ganther Instruments GmbH, Mr. Senthil Vel RS of SKF Group. The time for the keynote was about 40 minutes for presentation and 20 minutes for discussion. For parallel sessions, each presentation had 15 minutes including Q&A. The audience had two ways to ask a question to the presenter, either raise hand then the moderator will unmute to allow direct interaction, or by typing the question in the chatbox and the presenter answered verbally. There were lively discussions at both in plenary and parallel sessions. We arranged the time slot accordingly to suit the presenters' time zone relative to Jakarta time zone, from US it was around after dinner time, and about afternoon in the EU.

The success and prosperity of the conference is reflected at a high level of the paper received, and the attendees at this conference were numerous. The ANV 2020 was a communication platform for exchanging ideas on acoustic and vibration with more than 300 participants, either as presenters or as attendees at the event. They were from Indonesia, Malaysia, India, Austria, Bangladesh, Morocco, France, Japan, and more; 11 countries in total.

We would like to express our gratitude to all committees who have worked hard so that this event can run successfully. We also would like to thank for our keynote speakers, participants, and sponsors as well as to the reviewers that has worked very hard in reviewing papers and making valuable suggestions for the authors.

ANV 2020 was organized by IoT Research Center and Defense Technology, Directorate of Research and Community Service in cooperation with the Vibration and Acoustic Laboratory of Institut Teknologi Sepuluh Nopember Surabaya (ITS). The theme of the Conference is "Sound of Indonesia". The conference also supports the International Year of Sound 2020. We wish all the attendees of ANV 2020 and their respective community in safety and healthy.

We look forwards to your participation in the forthcoming ANV 2022!

Dhany Arifianto, Chairman of ANV 2020

List of COMMITTEE, Contact Us are available in this pdf.

All conference organisers/editors are required to declare details about their peer review. Therefore, please provide the following information:

• Type of peer review: Single-blind

• Conference submission management system: web-based system operating

• Number of submissions received: 53

• Number of submissions sent for review: 49

• Number of submissions accepted: 28

• Acceptance Rate (Number of Submissions Accepted / Number of Submissions Received X 100): 0.00528

• Average number of reviews per paper: 3.5 (5: excellent, 1: poor)

• Total number of reviewers involved: 10 reviewers

• Any additional info on review process: 7 papers have been withdrawn by the authors since they could not complete revisions from reviewers.

• Contact person for queries: Ainun Nadiroh (ainun.nadiroh@gmail.com)

Please submit this form along with the rest of your files on the submission date written in your publishing agreement.

The information you provide will be published as part of your proceedings.

We report the result of infrasound observation applied to microbaroms between peak winter and summer season of 2018, obtained from ambient noise. For our study several infrasound sensor over Shikoku island was used, which had been installed since 2015. Observation of our microbaroms shows regular pressure variations of a few milliPascals at around 0.2 Hz produced by the incoming of infrasound arrived from the ocean fields. As the result, their amplitudes show prominent greatly in winter time expect to depend on the appearance of the atmospheric sound ducts between the surface and the level at certain altitudes. These ducts depend on the wind structure and vertical temperature of the atmosphere. For our station close to the ocean, sound ducting from the oscillation wave of the ocean surface, requires strong contribution westerly winds at certain upper reflection point. With a global reanalysis horizontal wind assimilation, the seasonal wind structure at our geographical study, near 33° N, is shown to distinguish and to account for the observed profiles of microbaroms. Finally, we suggest that use of our network of infrasound sensors would provide a global complementary result to monitor the upper atmosphere conditions in the middle latitude regions.

Humans' auditory system can separate mixed sounds based on their sources easily. However, mimicking this ability by computer algorithm is not an easy task. Some approaches have been developed, particularly based on the statistical approach and binaural modeling. From statistical methods, independent component analysis (ICA) grows fast to mimics sound separation and localization by human auditory processing. On the other side, mathematical modeling to model binaural hearing has been built block by block. This paper is a comparative study of both approaches, a statistical method represented by FastICA and binaural modeling represented by the frequency domain binaural model. The task is to mimic how to binaural processing works to separate sound sources. The result of the comparison was given by the perceptual evaluation of speech quality (PESQ) and Itakura-Saito (IS) distortion measurement. PESQ scores ICA method obtains better performance than the binaural model while, in contrast, IS scores the binaural model better than ICA.

The choice of a loss function is a critical part in machine learning. This paper evaluates two different loss functions commonly used in regression-task dimensional speech emotion recognition — error-based and correlation-based loss functions. We found that using correlation-based loss function with concordance correlation coefficient (CCC) loss resulted in better performance than error-based loss functions with mean squared error (MSE) and mean absolute error (MAE). The evaluations were measured in averaged CCC among three emotional attributes. The results are consistent with two input feature sets and two datasets. The scatter plots of test prediction by those two loss functions also confirmed the results measured by CCC scores.

Woven Fabrics are potentially developed as a sound absorber system because of the presence of micro perforation on their surface. By introducing air cavity backing the woven fabrics up, such system can undergo Helmholtz resonator mechanism as found in micro-perforated panel (MPP) absorber system. The micro perforations in a woven fabric are formed by yarn in x (weft) and y (warp) direction. The perforations can create a viscos-inertial effect when interact with sound fields that is useful as a basis for sound absorption mechanism. In this study, the works are focused on investigating the relationship of micro hole of woven fabric material to sound absorption characteristics. For this, micro holes are developed by controlling weft density. Meanwhile, the sound absorption coefficients are evaluated by measurement using impedance tube. From this study, it can be concluded that the sound absorption coefficients of woven fabric are affected by weft density variation by which the perforation parameter can be varied. Moreover, the performance of woven fabrics are promising as indicated by absorption coefficients that is ranging from 0.71-1.00 with absorption bandwidth of 3 kHz-5 kHz.

To create a comfortable acoustic environment both indoor and outdoor, we need to control the noise. In the room, noise comes from both outside and inside the room for example is flatter echo. Installation of acoustic material such as absorber, resonator, or diffuser is an example of indoor noise control. QRD is one of diffuser consider of wells with different depth to diffuse the reflected sound. The depth of the wells is calculated by DR. Manfred Schroeder formula. In this research, a combination of Skyline QRD and Helmholtz resonator is given, we call it SQRD-R. This SQRDR follows the design from Wes Lachot Design but using a Helmholtz resonator as the cell. The examination of its characteristic is built using both of impedance tube test and calculation. The purposes of this research are learning about the effect of holes position on its sound impedance and sound absorption coefficient. The highest impedance value is –j(3.5 x 107) acoustic ohm. The highest absorption coefficient is 0.9. By controlling the SQRD-R dimension, we can control noise at specific frequency.

Indeterminacy in music, a well known neo-avant-garde approach of composing sound where some features of a musical work are left open to chance or to the interpreter's free choice, became noticeable among some American music composers such as John Cage, Earle Brown, Morton Feldman and Christian Wolff in the mid 20th century. Simultaneously, a group of artists from the West created "abstract expressionism" in visual arts, which showed a strong resemblance with this "indeterminate music", both using two kinds of abstract languages. The commonality among these two art forms is the free improvisation of creative activity. The correspondence between the indeterminate music induced emotions and the depicted emotional contents in paintings is a relevant area which is still scientifically unexplored. To investigate the same, we conducted a case study where a visual artist listened to four music clips composed by the above mentioned musicians and created four paintings. The visual artist is strongly inspired by the abstract expressionist methods and these methods lend well to inspirational work based on listening to indeterminate music.To understand the nature of intermediality, if any, that exists between "indeterminate music" and "evoked abstraction" in paintings, the artist's phenomenological interpretations of the process was compared with detailed semiotic analysis of specific musical and visual elements and the nature of their relatedness. Fractal analysis in the form of Detrended Fluctuation Analysis (DFA) was also done on both the acoustic waveforms of the chosen music clips and the corresponding paintings to explore possible correlations. Some unique findings yielded from the analysis, which hint toward strong correlation between the prominent musical features of indeterminate music and the prominent visual features of the paintings inspired by them. This novel study has the potential to offer both new methodology as well as better understanding the features of intermediality between "indeterminate music" and visual art.

Acoustic monitoring has always been a niche area in the field of monitoring applications compared to other modalities, such as computer vision. Over the last decades, the number of applications for acoustic monitoring has been growing and ranges from predictive maintenance within the industrial sector to acoustic scene classification and security monitoring in traffic and urban scenarios. With the rise of the internet-of-things (IoT) and artificial intelligence (AI) in recent years, smart consumer products and devices have pushed forward using different sensor technologies to enhance the user experience. To this end, acoustic monitoring is still an underestimated discipline with great potential to serve as a missing link in smart sensing within environments where other modalities face difficulties. In this paper, we present PyzoFlex^®, a printable sensor technology which facilitates accurate measurement of pressure and temperature changes in objects and their environment, as a sensor interface for acoustic monitoring applications. In contrast to microphones or acceleration sensors, PyzoFlex may be printed onto any curved or textured surface. To demonstrate the possibilities, we present a case study in which we equip a coffee machine with PyzoFlex to acoustically monitor the machine states in real-time using a machine learning model.

A split tube resonator (STR) is one of the typical base structures in many previous acoustic metamaterial structures. This paper introduces a brand new approach to designing the tunable concentric wall resonating structure to look like a similar shape but with a different response and performance to STR. The central concept is a planar resonator folded outward and inward direction. We found that the proposing approach gives the possibility for a single geometrical dimension tunable sonic crystal element that could not occur in a single degree of freedom conventional STR. The test model made of stiff paper and the sound absorption performance test conducted experimentally with impedance tube refers to ASTM E-150-98 standard.

This paper emphasized the tuning local resonance approach for proposing folded planar resonator-based sonic crystal scatterers. The folded inward design gives similar performance to the conventional single degree of freedom split tube resonator (STR). The sound absorption performance shifted to a lower frequency band according to the enlarging total volume of the resulting structure's volume without any significant effect from its inner wall thickness. Contrary to the folded outward direction design, which is resulting in multi-degree of freedom response. As the planar resonator folded in an outward direction, the resonator depth became a thin slit connecting the two separated cavities. The test model is made of stiff paper, as mentioned in part one. The entire laboratory test also conducted with a similar procedure refers to ASTM E-1050-98.

Lack of speech privacy is a significant problem in open-plan offices. Sound masking, which essentially covers the target speech with the competing speech simultaneously (masker), can increase speech privacy. However, a conversation takes place in a reverberant room at which will reduce speech intelligibility. This study observed the effectiveness of reverberation time on the sound masking to the target. In this early study, three conditions of stimuli were used, namely clean, 0.3 s and 0.6 s reverberation time added to both target and masker, respectively. The STI and subjective measure were used with twenty-five volunteers. As expected, the results suggest that the longer the reverberation time, the lower the effectiveness of the masker strength. The STI agrees with the subjective measure.

Petrol driven motorboat engine consisted of direct handle-engine mounting mechanism which exposed the operators to the high level of vibration and can lead to the Hand-arm Vibration syndrome (HAVs). The transmitted vibration from the engine to the handle with natural frequency excitation making the transmitted vibration worsen. This study is focusing on the vibration analysis of the 3.3 HP motorboat engine and the transmitted vibration to the operator handle in specific directions and frequency ranges. A lab-scale experimental rig with motorboat engine is set-up to represent the actual operation of the motorboat engine. Experimental Modal Analysis (EMA) is conducted at the motorboat handle to obtain the natural frequencies in y and z axis directions. Two levels of engine speed (Speed 1: Low and Speed 2: High) are taken into consideration for the vibration measurement of both engine and handle in x, y and z axis directions. From this study, the natural frequencies of the handle are determined within 75 – 80 Hz. For the vibration spectral measurement, the engine has produced high vibration in x and y axis directions, whereby the transmitted vibration to the handle is worst in y axis direction. At Speed 1, the engine excited the vibration within frequency range of 45 – 50 Hz while by increasing the engine to Speed 2, the vibration peak shifted to 95 – 100 Hz with higher vibration amplitude. In overall, the vibration transmissibility at the handle are significant between the frequency range of 0 – 100 Hz (above 1) which can result the HAVs among the operators if no necessary action been taken.

The open-plan office is one of the most popular and preferred workspace arrangement options for employers today. The results of research in western countries show that listeners' perceptions of the soundscape in open-plan offices are negative, due to reduced visual and acoustic privacy and uncontrolled sound levels. This can cause a significant decrease in work comfort and productivity. Several researchers have provided acoustic design solutions by performing adequate speech control through several solutions such as creating spacing between workstations, the use of acoustic dampening materials, insulation between workstations, and application of a noise masking system. The phenomenon of adopting an open-plan office has also hit offices in big cities in the world, including in Indonesia. The purpose of this paper is to further examine listeners' perceptions of the soundscape in the case of open-plan offices in the local environment because the results are indicated to be different from similar cases in western countries, given the peculiarities of employee work behaviour which are influenced by individual experiences and social effects in the local environment are also different. For this reason, a comprehensive literature review method is needed that aims to investigate the relationship between soundscape perceptions and working behaviour in open-plan offices in the local environment and then to create an integrated conceptual model so that further researchers can evaluate the research related to these problems.

Raga characterization in Indian classical music is an important aspect of music learning in this country. But the methods usually followed are mostly qualitative. In this study, we intend to quantify such abstractness using measurable parameters. To study musical information congregation quantifiably, we introduce methods based on well-known concepts used in Statistical Physics, namely Maxwell-Boltzmann (MB) and Bose-Einstein (BE) distribution. In this present study, these distributions have been applied on the chosen acoustic signals to find new parameters (equivalent to 'temperature' in physical systems) which can distinguish between different features of different ragas (containing the same notes) in Indian classical music. Music clips chosen were the 'Alap' part of these three different ragas (Marwa, Puriya, Sohini) sung by a legendary classical music maestro. All of the chosen three ragas are based on the following same note structure: Sa, komal Re, shuddh Ga, tivra Ma, shuddh Dha, shuddh Ni. To apply MB statistics to music, it is assumed that different notes with different occurrence frequencies are at different energy levels, the distribution of which follows the MB distribution pattern. In case of BE statistics, a rank-frequency distribution of the time durations of various notes of different ragas is studied. The resulting analysis gives rise to a number of parameters that help to categorize the individual characteristics of ragas. The methods studied here are novel in the music research field and can prove to be useful in the fields of music and speech as quantifying parameters for style identification.

Nowadays, the demand of sustainable and eco- friendly absorber is increasing. Non-woven fabrics made of textile waste can be a good candidate to address such a demand. From measurement results, absorption capability of this kind of material is evident. However, most of non-woven fabrics are manufactured on the basis of density only rather than targeted acoustic parameter to meet particular absorption performance. This work is focused on investigation of non-woven fabrics sound absorption performance characteristics. For this, surface morphology of non-woven fabrics with different density is evaluated by which detail geometrical properties of fiber can be observed. Experimental works on similar material system with variation in density and thickness are also conducted to obtain sound absorption coefficients. It is found that fiber size affects the absorption performance for the same thickness by which flow resistivity can be determined. For thickness of 10-50 mm, fibre size of 15-23 µm can produce sound absorption greater than 0.7 while the thickness and flow resistivity are inter-play to determine overall absorption characteristics.

A perfect complementary relationship between the lyric and the melody can give birth to a beautiful song. The melodic expression of a song is universal but the lyrical expression is not – lyric is culture specific because of its language dependence. Can melody itself communicate the core emotions of a song? Or does the addition of a lyrical sense significantly change its emotional experience? This study looks for the answers focusing on a unique subgenre of Indian Classical Music – Ragashroyi compositions, where the melodic movements sincerely follow the Raga pathways but the lyrics explore a much deeper and wider variety of emotions compared to Raga bandishes. Recordings were collected from two eminent vocalists (1 male, 1 female), each of whom was asked to sing (with proper lyrics) and hum (without meaningful lyrics) any two Bengali Ragashroyi compositions of two opposite emotions – happiness and sadness. Hurst Exponents, obtained from robust non-linear Detrended Fluctuation Analysis (DFA) of the recorded acoustic waveforms, were compared for each song-humming pair having same melodic structure to understand the acoustic contribution of the lyrics in a song quantitatively. A comparative audience response study was also conducted where several humming and song clips were played randomly and two groups (one which understands Bengali, the other which does not), each having 30 participants, were asked to mark the emotions and the characteristic features corresponding to each clip on 5 point Likert scale, and their responses were compared for each song-humming pair. This pilot study on Ragashroyi Indian music explores in depth the contribution of lyrics in vocal music from both the perspectives of computational acoustics and audience psychology.

Modern smartphones have been equipped with MEMS sensors allowing them to be used for advanced purposes. A MEMS accelerometer is embedded in the smartphone to sense motion and vibration. Recently, many smartphone-based vibration-meter applications software employed the embedded accelerometer and used them for vibration monitoring and field measurement. However, the accuracy of this kind of vibration meter has not known yet. In this paper, we discuss about the evaluation of smartphone-based vibration meter using the standard method for vibration meter calibration described in the ISO 16063-21. A vibration measurement by the smartphone-based vibration meter is compared to the reading of the reference accelerometer type B&K 8305. The evaluation was conducted in a frequency range of 10 Hz to 50 Hz with the amplitude of 0.1 G to 1 G. This study showed that the accuracy of the smartphone-based vibration meter is decreased in the higher frequency range.

It has been known that woven fabrics and nonwoven fabrics exhibit absorption capability. Despite this, both have different characteristics in absorption. The absorption of woven fabrics occurs due to resonance system which has a narrow absorption bandwidth but it is tunable for low frequency absorption. Meanwhile, that of nonwoven fabrics is present due to mainly visco-thermal effect of porous media so that the wide absorption bandwidth can be obtained at mid-high frequency. This works is focused to investigate the possibility to combine features of each fabrics in order to have a better performance of textile-based absorber. Experimental works on some configurations of combined woven fabrics and non-woven fabrics are conducted. It is found that some absorption enhancements are observed compared to original performance of each material. Hence, both materials are complementary to produce a better performance in overall. However, such a combination should be realized with a great care as absorption performance at mid-high frequency can be deteriorated or lead to poor results.

A large number of industrial needs to the sound level meter (SLM) calibration has encouraged the laboratory to develop a qualified calibration system. As one of the SLM calibration methods required by the standard, the coupler method is considered as the most convenient to be implemented, especially for the secondary laboratory. Therefore, the aim of this work is to compare the SLM calibration for the frequency weighting parameter by this method using the instrument standards that comprise of a multifunction acoustic calibrator and a working standard of pressure microphone (WS2-P Microphone). Moreover, the result of frequency weighting calibration using these standards, therefore, is compared to the reference value required by IEC 61672-1. From the result, the deviation values of these standards are obtained relative to the reference. At the low to middle frequencies, the deviation values are slight relatively, while at the higher frequency, it tends to bigger. In addition, these methods also support the development system of noise dosimeter and sound level meter calibration that still under research through the scheme of Incentive Research Program for the National Innovation System in 2020.

The world is full of events, and events are construed. One of the major research questions, therefore, seeks to understand the way events are construed through language. Event construals involve the syntacto-semantic properties of certain linguistic categories such as Verb, Tense, Aspect, Modality, etc. Serial Verb Constructions (SVC) and Complex Predicate Constructions (CPC) are no exception to this very fact. In this work, we look forward to compare both linear and non linear acoustical features generated from SVC and CPC events found in sentences of Bengali language. For this, we recorded 60 common utterances of Bengali language containing SVC and CPC events individually (around 36 of them belong to SV category while the rest belong to CP category), from 1 male and 1 female native Bengali speakers. The serial verb construction in these utterances may contain two (2) serial verbs in either simultaneous or sequential order, while few sentences are such that they can be interpreted both as SV or CP events. The main objective is to look for robust acoustic features which lead to perceptual categorization of events as SV or CP with a particular linguistic background. Various linear features like MFCC (Mel frequency Cepstral Coefficients), spectral skewness/energy, pause duration, pitch profile and nonlinear features like Fractal Dimension (FD) have been employed for the classification purpose. This work is a pilot study of an ongoing project which looks to explore the concept integrating capacity of human brain in terms of Syntactic Compositionality or Semantic Combinatorics in a complex sentence. This preliminary acoustic study reveals interesting new results in terms of perceptual linguistic representation of the event construals.

The purpose of this work is to investigate the geometrical non-linearity in free vibrations of the Euler-Bernoulli shallow arch with clamped ends. The nonlinear governing equilibrium equation of the shallow arch is obtained after the Euler Bernoulli theory and Won Karman geometrical nonlinearity assumptions. The initial curvature of the arch is not due to the axial displacement of the beam but is due to the geometric of the beam itself. Taking into account a harmonic motion, the kinetic and total strain energy are discretized into a series of finite functions, which are a combination of the linear modes calculated before and the coefficients of contribution. The discretized expressions are derived by applying a Hamilton principle energy and spectral analysis. A cubic nonlinear algebraic system is obtained and solved numerically using an approximation method (the so-called second formulation) is applied to resolve various nonlinear vibration problems. To illustrate the effect of the curvature on the fundamental nonlinear mode and nonlinear frequency, the corresponding backbone curves, nonlinear amplitude vibration, and curvature of the arch are presented for the first modes shapes.

Use of the FRF decoupling method can be used to determine joint parameters for connected systems. The method has been verified to determine stiffness parameter for lumped mass systems and beam elements by the author in his earlier publication. Modal coupling method used to verify generated FRF in a coupled system for simple mass damper system. Sensitivity modes can be used for identifying the most accurate values for stiffness. In this paper, the method is extended to determine the stiffness parameter for a solid element. Though solid elements have only translational degree of freedoms (DOFs), this method can be used to determine rotational stiffness apart from translational stiffness for joint parameter.

The objective of this research is to study geometrically non-linear free vibrations and forced vibrations subjected to harmonic excitations of laminated composite beams. On the basis of Euler Bernoulli's beam theory and Green-Lagrange's hypothesis of geometric non-linearity, the theoretical model has been established. Taking into account the harmonic response, the transverse displacement function of the non-linear beam determined by applying Hamilton's principle, the problem is reduced to a non-linear algebraic system solved by an approximate method. In order to verify this method, numerical examples for carbon/epoxy materials, under two boundary conditions, i.e. clamped-free and clamped- clamped, have been performed and the results are very consistent with those obtained in the literature. In addition, based on the approximate multimode method in the vicinity of the predominant mode, a nonlinear forced response was performed for a wide range of vibration amplitudes. It should also be noted that the effects on the non-linear forced dynamic response of the fiber orientation and number of layers, the excitation frequency and the level of the applied harmonic force have been studied and illustrated by various examples.

Non-destructive testing (NDT) methods nowadays are essential in materials and structures control due to their capability to not affect the integrity of material. These methods are particularly efficient for the monitoring of resin or composites formation. In particular, ultrasonic technics can be used to evaluate mechanical properties of materials by measuring acoustic waves characteristics. In general classical characterization techniques, based on linear measurements, give local information's of medium. Reverberation methods, classically used in room acoustics, allow global characterization. This approach is not so common in NDT or structure monitoring. The reverberation signals which contain global information about propagation media properties, are highly dependent on the boundary conditions. Sabine's formula gives the relationship between reverberation time RT and wall attenuation coefficient can be adapted in many acoustic applications. Previous studies established a relation between RT and solid interfaces absorption. In the case of a sol-gel material, the reverberation time measured in a metallic block can be linked to the material properties such as density or viscosity. The RT will vary during the phase transition of our material from liquid to solid state. Hence, our motivation is to derive the equation of the acoustic intensity for solid interface absorption considering the shear and the longitudinal waves. Furthermore, to estimate the reverberation time from the determined acoustic intensity (simulation part) and to compare the results with the experimental part. For this reason, experiments were performed to validate the simulation part. Measurements are preformed in an aluminium mold using five piezoelectric (PZT) patches, one being used as emitter and the others as receivers has been studied and it's evolution is shown to lead to a good estimation of the phase transition time.

A silencer model was designed for application to HVAC systems, specifically for noise control in ducts. The goal was to see how the perforation of the silencer affected the resonant frequency and Insertion Loss (IL), as well as analyse physical phenomena that occurred in system. The materials used were 1/2-inch PVC pipes 5 cm in length and acrylic with a thickness of 2 mm used as the silencer frame. The varied parameters were the amount of PVC pipes (percentage of silencer perforation) from 0 holes (no perforation) to 10 holes. It is concluded that perforation affects the resonant frequency through changes in acoustic mass and affects the IL through acoustic resistance. It is inconclusive whether the resonant frequencies generated affected IL. It is assumed that negative valued IL observed at lower frequencies occurred due to resonance between the sound and duct (structure-borne sound) which increased sound pressure level, or that these may be the actual resonant frequencies generated. Further research is needed to study the generation of resonant frequencies and structure-borne sound in the system, study airflow and thermal performance of a HVAC system when the silencer is applied, the transmission loss (TL) of the silencer and optimisation of the design to improve low-frequency sound attenuation.

The number of smartphone-based application software for noise measurement has been increasing recently. Some application software has complete features of the sound level meter such as frequency weighting and time averaging. They have been used for field noise measurement. However, the reliability of the smartphone-based sound level meter as a measurement instrument has not known yet. In this paper, we tested the smartphone-based sound level meter application software according to the international standard for sound level meter calibration IEC 61672. The parameter of self-generating noise, frequency weighting, and long-term stability in a fully anechoic chamber was measured. We evaluated the class of the smartphone-based sound level meter from the deviation of the measured parameter with the tolerance value described in the standard. The practical implementation of the calibration method is also discussed.

The sparse method or better known as compressed sensing (CS), is a method often used for the signal reconstruction process. This method had considered better than conventional methods because it can reconstruct a signal with a smaller amount of data. Many algorithms had used for signal reconstruction using the CS method, including l₁-minimization and orthogonal matching pursuit (OMP). In this study, the two algorithms were used for signal reconstruction of underwater objects and then compared to find out which algorithm is better for the signal reconstruction of underwater objects. Comparing the two algorithms had based on parameters in the form of PSNR and RMSE against sparsity. Based on the simulations that had been doing, known that the l₁-minimization algorithm can reconstruct signal up to 40% sparsity. Whereas the OMP algorithm can only reconstruct signals up to 30% sparsity. PSNR and RMSE generated from the l₁-minimization algorithm show that this algorithm provides better reconstruction results than OMP for underwater object signals. The results obtained show that the best tracking process is at an angle of incidence of 90°.

When an earthquake occurs tectonically and volcanically, it is preceded by the emergence of sound wave propagation that cannot be heard by the human ear because it has a low frequency, called infrasound. These infrasound waves are difficult to detect because they are much weaker than earthquake waves and other natural sound waves in nature. The Hilbert-Huang transform method (HHT) is proposed, which in principle decomposes a wave into several simpler sinusoidal harmonic waves so as to separate the low-frequency infrasound waves from the other waves. Once separated, the envelope frequency can be determined which represents the frequency of the earthquake occurrence, then the amplitude represents the predicted earthquake strength, and the wave propagation phase that represents the location of the earthquake source. From the comparison of secondary data, it was obtained that HHT was able to obtain all three information faster than the data from seismographs so that it had the potential to increase the evacuation time which in turn reduced the potential for greater casualties and losses.

Speaker Forensic is a process to determine the identity between a person's voice (known speaker) and the investigated voice (suspect speaker). To improve accuracy in speaker forensic analysis is used a combination of 2 forensic methods, joint factor analysis and i-vector methods. The forensic approach by adding noise signal with SNR value as a representation of a tapping situation to measure speaker identification performance. Classification on verification using i-vector is done by comparing i-vector model tests and targets. Both models calculated vector similarities using cosine similarity score. Verification is done with compare the same speaker and verification between different speakers The testing process on the program performance is indicated by an equal rate error value. While the system's sensibility is indicated by the threshold value. The results showed that the EER value of the Graz dataset (1.87%) compared to the Indonesia dataset (10%).