bluuebunny/crossref_metadata_2025 huggingface dataset:
Hand-made sound absorber using familiar materials for nursery facilities
Authors: Toyoda Emi , Sugie Satoshi
Published: December 2023

We have been proposing a hand-made sound absorber using familiar materials to develop a comfortable sound environment for children. By installing the hand-made absorber, anyone can easily add sound absorption to nursery rooms. In this study, as one of the familiar materials, we focused
on bubble wrap, which is used as a packaging material. We measured the normal incidence absorption coefficient of bubble wrap arranged in layers and found that bubble wrap had reasonable sound absorption. As an example of a hand-made absorber, we created round-shaped fabric balls filling bubble
wrap and measured the sound absorption performance in a reverberation room. As a result, the fabric ball absorber had sufficiently high sound absorption performance. Additionally, we clarified the sound absorption mechanism of bubble wrap by predicting based on simple assumptions. Therefore,
it could be possible to design sound absorbers with higher sound absorption performance at low frequencies by stacking bubble wrap horizontally or vertically.
Further improvements of the measurement method for sound absorption characteristics using the ensemble averaging technique
Authors: Otsuru Toru , Tomiku Reiji , Okamoto Noriko
Published: December 2023

In the authors' former papers, an in-situ measurement method using the ensemble averaging technique for sound absorption characteristics, surface normal impedance and absorption coefficient, was proposed and the method's reproducibility as well as the robustness have been examined.
We call the method EA method, for short. In the EA method, two kinds of sensor types have been employed: one is two-microphone and the other is pressure-velocity sensor (PU sensor). Field measurements, however, frequently encounter difficulties due to practical complexities existing in/around
the measurements, e.g. sensor-sensitivity-mismatching, material non-uniformity, etc. In this paper, a summary of the EA method is described, first. Next, detailed investigations on the sensor calibration procedure and statistical techniques are presented using an improved mathematical model
for the EA method. Then, the outline of practical measurements conducted at several field environments including sports-arenas are given to discuss the model's plausibility.
Noise Regulations in Japan
Authors: Mizuhara Kensuke , Ozaki Tetsuya , Shoji Daisuke , Tatsuta Yasunori , Fujii Yusuke
Published: December 2023

For noise regulations in Japan, environmental quality standards as noise-related administrative targets are provided under the Basic Environment Law and various measures are put in place under the Noise Regulation Law which was legislated as a law for the implementation of the Basic
Environment Law. Environmental quality standards for general ambient noise are established by certain land-use types and time divisions, while separate environmental quality standards are specifically set for aircraft and Shinkansen Superexpress Railway noise. The Noise Regulation Law controls
noise from factories and business that have specified facilities and sit in designated areas as well as noise from specified types of construction operations, with proper demarcation of regulation roles among national and local governments. Also, rationalization of Noise Regulation Low and
Vibration Regulation Low were considered from 2021 to 2022. In recent years, new types of noise problems that are not well controlled by the Noise Regulation Law or the application of environmental quality standards, including complaints against noise from facilities not regulated under the
Noise Regulation Law and against low-frequency noise, calling for responses to these problems.
1D Convolutional Neural Network-based Signal Tracking Algorithm with Feature Extraction and System Diagnosis
Authors: Hong Dongwoo , Kim Byeongil
Published: December 2023

Diverse adaptive algorithms have been investigated and developed in an effort to mitigate the vibration and noise produced by mechanical systems. A reference signal plays a crucial role in adaptive algorithms for monitoring the target signal, however it is difficult to identify the
reference signal when its spectrum is relatively complex. In addition, if the state of a mechanical system changes due to a disturbance or malfunction, signal tracking may not perform as well if the reference signal for the changing condition has not been redefined. This work focuses on constructing
a signal tracking mechanism based on deep learning to increase tracking performance. The suggested algorithm consists of the following two parts: 1) automatically defining the reference signal segment and 2) system state feedback segment. These portions are managed by convolutional neural
networks in one dimension. The Case Western Reserve University (CWRU) bearing dataset was used for training and testing to validate the proposed technique. In addition, a neural network-based approach for signal tracking is applied to validate the signal tracking performance. The suggested
approach demonstrates that the signal tracking performance is great regardless of the system's state.
Experimental evaluation of feedforward active noise control system with optical laser microphone and proportional-integral-differential filter
Authors: Naiki Shota , Iwai Kenta , Nishiura Takanobu , Soeta Yoshiharu
Published: December 2023

In this paper, we propose a feedforward active noise control (ANC) system with an optical laser microphone utilizing a proportional-integral-differential (PID) filter. The feedforward ANC system with the optical laser microphone has been proposed to relax the causality constraint. This
system adopts a first-order differentiator to modify the velocity picked up by the optical laser microphone. This modification achieves the improvement of the coherence between the velocity as the reference signal and the unwanted noise as the sound pressure. However, the frequency response
of the first-order differentiator is similar to the high-pass filter and attenuates the reference signal at low frequencies. This causes the degradation of the noise reduction performance of the conventional ANC system. To solve this problem, the proposed ANC system adopts the PID filter instead
of the first-order differentiator. By adjusting the coefficients of the PID filter, the proposed system avoids the attenuation of the reference signal at low frequencies. Then, the noise reduction performance can be improved. Experimental results show that the proposed ANC system reduces the
unwanted noise compared to the conventional ANC system and relaxes the causality constraint compared to the basic ANC system in the real-time operation.
Demodulated sound enhancement based on virtual multi-boosted amplitude modulation with parametric array loudspeaker
Authors: Ikezaki Yoto , Geng Yuting , Nakayama Masato , Nishiura Takanobu
Published: December 2023

A parametric array loudspeaker can achieve sharp directivity in the audible band by utilizing ultrasounds. Ultrasounds are emitted intensely from the parametric array loudspeaker and the difference frequency component self-demodulates due to the nonlinear interactions in the air. Therefore,
the sound pressure of the audible sound reproduced by the parametric array loudspeaker is lower than that reproduced by the conventional electro-dynamic loudspeaker. This makes it difficult to use the parametric loudspeaker in a noisy environment. To solve this problem, we modify conventional
modulations to improve the demodulated sound pressure. When modulated waves are emitted as primary waves, various components containing the audible sound are generated as secondary and tertiary waves. Conventional modulations are difficult to utilize these components of the ultrasonic band
effectively. Therefore, we propose the demodulated sound enhancement based on virtual multi-boosted amplitude modulation. In the proposed method, the modulated wave is designed so that frequency components of carrier waves and demodulated sound are generated as the secondary and tertiary waves.
Secondary and tertiary waves boost the carrier waves and the demodulated sound, and the demodulated sound pressure can be enhanced. Theoretical value evaluation in the demodulated sound pressure demonstrated the effectiveness of the proposed method.
Detection of Arc Discharge through Sound Event Detection Techniques and Public Datasets
Authors: Ko Byeong-Yun , Nam Hyeonuk , Min Deokki , Lee Gyeong-Tae , Park Yong-Hwa
Published: December 2023

Arc discharge in switchboard is a potential fire hazard and caused by short-circuits in power supply cords with damaged electrical insulation. Arc detection based on electric current and resistance can be destructed while arc discharge occurs due to circuit contact, and humidity condition
of switchboard affects the detection performance of optical signal-based arc detection. This paper proposes a deep learning-based arc discharge detection that uses sound event detection (SED) method. The neural network was trained on public datasets to exclude the processfor obtainingsound
dataset of arc discharge. Filter-augmentation techniques were applied to account for the acoustical differences between the public dataset and target environments. The network uses cepstrum in addition to STFT as network input feature for effective extraction of harmonic spectral patterns
of arc discharge. The results show that the proposed neural network achieved an F1 score of 0.83 and accuracy of 0.89 when tested on a test-bed with arc discharge generator based on UL1699.
Designing of ultrasonic reactor using machine learning
Authors: Kanchanapradit Kamin , Thida Worakrit , Danworaphong Sorasak
Published: December 2023

Ultrasonic reactors consist of transducers that emit high-frequency acoustic waves, with designs varying based on their intended application. One such application is extraction, achieved through the cavitation effect generated by the pressure gradients produced by the ultrasound field
within the medium. The cavitation effect depends on several physical parameters of the ultrasonic reactor, such as the driving frequency, acoustic energy, liquid medium, transducer attachment locations, and size and shape of the reactor. The proper design of an ultrasonic reactor is complex
due to the numerous parameters that affect the distribution of ultrasonic energy, which must be concentrated and distributed in a specific way to extract effectively. To simplify the design process, this study utilizes an artificial neural network (ANN) to predict the physical dimensions and
transducer locations of a square duct-shaped ultrasonic reactor with transducers attached to its sides based on the desired spatial energy distribution. The algorithm was developed using data from 1365 reactor configurations, which were numerically generated using COMSOL Multiphysics. The
study tested two main models of ANNs, one using intensity profile as input and the other using power profile as input, and the results showed that each ANN had its advantages.
A unidirectional secondary sound source for local active noise control in enclosures
Authors: Chen Ruoyan , Tao Jiancheng , Qiu Xiaojun
Published: December 2023

Directional secondary sources are beneficial for local active noise control in cabins with multiple seats. In this paper, a method of designing a unidirectional compound sound source composed of two units is introduced. A prototype was implemented using two closed-box speakers and an
analog circuit, and the directivity of the compound source was measured in the anechoic chamber to verify the effectiveness of the proposed design method. Furthermore, the sound radiation characteristics of the compound sound source in a car cabin are reported and analyzed. The average sound
pressure level at the driver's seat and rear seats is reduced by over 3.5 dB and 8.3 dB respectively in the frequency range from 125 Hz and 500 Hz when a single loudspeaker box located at the front passenger's seat is replaced by the compound sound source.
Indonesian users' active sound design preference for armored electric SUV interior
Authors: Gunawan Timothy Nathaniel , Sarwono Joko , Nitidara Ni Putu Amanda , Sudarsono Anugrah Sabdono
Published: December 2023

This paper explores the potential of Active Sound Design (ASD) in the Indonesian electric vehicle (EV) market, where there are a projected 2 million EV users by 2030. While ASD is a crucial aspect in addressing the lack of engine sound in EV, it is still developing and mainly focused
on certain regions. The ASD approach includes active noise control (ANC) to reduce unwanted noise inside the cabin and engine sound enhancement by inserting additional engine sound through the speakers. The study evaluates the original EV stimulus, ANC stimulus, and two ASD stimuli (ICE and
futuristic) of an armored electric SUV using an audiovisual car cabin soundscape simulator. The results show that the ANC technology (improved EV with noise filter) is the most preferred stimulus with the highest comfort value perceived by the participants. These insights can help EV manufacturers
optimize their sound design solutions for future EV productions in Indonesia.
Practical calculation methods for ground noise correction factors in airport noise prediction model
Authors: Sugawara Masayuki , Nakazawa Toshiyasu , Shinohara Naoaki , Hanaka Kazuyuki , Yokota Takatoshi
Published: December 2023

This paper describes the results of a study to improve the calculation method for predicting aircraft noise around Japanese airports using our prediction model. The model limited the calculation frequency for the insertion loss caused by noise barriers and buildings to a single 250
Hz, which does not reflect the actual frequency spectrum of aircraft. Therefore, to simulate more realistic conditions, we calculated a synthetic attenuation chart from the frequency spectra of several representative aircraft models and included the chart in our model. We then compared the
calculated values with the measured values to verify the validity and discussed the influence of this change on the airport noise contours. In addition, for noise propagation of engines and auxiliary power units on the ground, an improved calculation formula for ground surface attenuation,
taking into account the ground condition, has already been reported. In this paper, we report on the implementation of this calculation formula in our model and discussion of the calculation results.
A model-based approach for gear train whine noise reduction by mesh phasing modification
Authors: Battarra Mattia , Pizzolante Francesco , Frulli Alberto , Meleti Stefano , Mucchi Emiliano
Published: December 2023

Heavily loaded gear trains are known to produce a characteristic whine noise and vibration signature, which radiates through the bearings producing an undesired noise emission affecting the NVH behavior of the overall machine. This phenomenon is generated by the variable mesh stiffness
and the static transmission error of the gear pairs in mesh within the gear train, but its magnitude strongly depends on how the meshing processes combine between each others. In this context, the present work proposes an analytical methodology to predict amplitude and direction of the variable
loads applied on the bearings of idle gears, assuming quasi-static conditions. The dissertation demonstrates that the multiple mesh forces produce a variable load on idle gear bearings describing an ellipse whose shape depends on various geometrical parameters of the system. Numerical examples
are shown to assess the potentials of the method and highlight how gear train spatial layout and phasing between different meshings may be used during gearbox design projects to limit the emitted noise of the gear train.
A standardized approach to identify nonlinearity in fighter jet noise during ground run-ups
Authors: Billot Guido , Marinus Benoît G. , Expeels Xavier , Harri Kristof , Moiny Francis
Published: December 2023

High-intensity military sources (explosions, gunfire, fighter jet noise. . . ) fall out of the scope of linearity-based commercial software and international standards. On top of its intrinsic complexity (high temperature supersonic jet, shocks, turbulent eddies, etc), fighter jet engine
noise bears additional challenges: turbulent surrounding flow, airframe interference, directionality and tonal components typical of rotating equipment. The absence of a suitable metric to determine the boundary of the nonlinear propagation region can lead to costly mispredictions in the exposure
levels for noise abatement procedures and the personnel's safety. The derivative skewness of the time domain signal used as an indicator of spectral reshaping proved effective in setting a threshold to the generation of acoustic nonlinearity for seven firearms. Its application to aircraft
noise is here discussed, in order to verify the claim of persistence of nonlinear behaviour at large distances and set the foundations for a common framework contemplating the peculiarities of each military noise source. The experimental data was collected during a series of static ground
run-ups of an F-16 military jet aircraft. The results from five engine regimes and two propagation paths are compared with the findings from firearms, existing literature and the solution of a nonlinear acoustic propagation solver.
Status of the revision of ISO 1996-1 standard on the assessment of environmental noise
Authors: Douglas Manvell , Kaliski Kenneth
Published: December 2023

The international standard on "Description, measurement and assessment of environmental noise - basic quantities and assessment procedures" ISO 1996 Part 1 is a major international reference document that both inspires and is inspired by regional and national standards on
noise assessment. It is supplemented by a number of standards including ISO 1996 Part 2 which deals with the determination of sound pressure levels, Part 1 defines the basic quantities to be used for the description of noise in community environments and describes basic assessment procedures.
It specifies methods to assess environmental noise and gives guidance on predicting the potential annoyance response of a community to long-term exposure from various types of environmental noises. The current edition from 2016 is under revision, as an ISO "preliminary work item."
This paper will explain why it was decided to revise the standard, what comments were submitted during the standard's systematic review, and the topics under discussion in the working group assigned by ISO to revise it. In addition, it will describe the process of revision within the ISO structure
including the current development framework, the status of the revision and the planned next steps.
Condition Monitoring of Ball Bearing Using MEMS-based Accelerometer
Authors: Gaikwad Mahesh , Shakya Piyush , Devadula Sivasrinivasu
Published: December 2023

Industry 4.0 has attracted a lot of attention in recent times. Intelligent machines are at the heart of Industry 4.0. Condition monitoring and predictive maintenance of critical components in rotating machines are crucial for intelligent machines. This paper studies the use of a commercially
available Micro Electro Mechanical System (MEMS) accelerometer for the condition monitoring of ball bearings. Embedding the sensor in the housing reduces the transmission path between the sensor and the fault providing efficient condition monitoring for low-speed applications. A comparison
between MEMS and piezoelectric accelerometers has been made. Defects are induced artificially into the bearing and fault classification of the bearing has been done using a machine learning algorithm.
The measurement and practical effectiveness of noise attenuation kits for mobile equipment
Authors: McNamara Joe , Liu Yang
Published: December 2023

The control of noise emissions from mobile equipment in quarry and mine sites plays a critical role in mitigating noise impacts to meet project noise limits while maximizing production capacity. To meet stringent noise limits, sites are commonly required to reduce noise emissions from
mobile plants. This is typically achieved through the implementation of retrofit noise attenuation kits. This paper explores a number of case studies in which noise attenuation kits are installed, comparing sound power level measurement methodologies and assessing the effectiveness of attenuation
kits through the analysis of resulting reductions in sound power level. Case studies involve the application of sound power tests in accordance with ISO test standards, and the comparison of practical results against theoretical predictions to assess the true effectiveness of attenuation kits.
A mini review of the Chinese literature on noise maps
Authors: Ni Ke , Huang Yu , Yan Li , Jiang Weikang
Published: December 2023

According to the recently published 'Noise pollution prevention and control action plan' by the Chinese government, all the prefecture-level cities should achieve acoustic environmental quality monitoring for the functional areas. The noise map is essential for noise monitoring, evaluation
and regulation. This paper reviews the Chinese literature on noise maps in the past three decades, particularly concerning noise indexes. Most studies adopted A-weighted equivalent sound pressure level (LAeq), whereas a few investigated noise pollution index (NPI), noise impact index (NII),
and index of noise evaluation model (ANEM) by considering the influence of different functional areas, the distribution of people, and both, respectively. However, studies are mostly based on sound energy parameters and rarely have considered the differences in subjective discomfort for the
dynamic evolvement of changing populations among different areas and periods. The appropriate noise evaluation index for noise maps, which can reasonably reflect the influence of noise on people in various functional areas, merits further research. Recommendations for future work in this area
are presented.
An investigation of the noise characteristics of a small-scale rotor in axial descent
Authors: LI Yuhong , LI Xiangtian , ZHOU Peng , ZHANG Xin , HUANG Xun
Published: December 2023

In this work, the acoustic characteristics of a small-scale drone rotor in axial descent are numerically investigated. Various descent speeds covering different working states are tested, and the corresponding effects on the noise are analysed. The turbulent flow fields are obtained
using delayed detached eddy simulations and an acoustic-wave preserved artificial compressibility method. The far-field noise is obtained by an integral solution of the Ffowcs-Williams and Hawkings equation. The aerodynamic force and the noise features are also evaluated experimentally in
anechoic wind tunnel tests, and test data are used to validate the numerical simulations. The results show that the increase in descent speed leads to a reduction in the mean thrust. Significant thrust fluctuations are also observed when the rotor approaches the vortex ring state. Consequently,
a substantial increase in sound pressure level in the low to medium frequency range is found in the far-field noise spectra, while the high-frequency sound pressure level shows a slight decrease. Furthermore, a noise source analysis is performed on the blade surface to help understand the
corresponding noise mechanism.
Anechoic wind tunnel noise tests for high-speed train bogie aerodynamic noise characterization
Authors: Iglesias Eduardo Latorre , Tonai Tatsuya , Uda Toki , Paniagua Jorge Muñoz
Published: December 2023

At speeds normally reached by high-speed trains (above 300 km/h), aerodynamic noise becomes significant. The bogie region is one of the main sources of aerodynamic noise in high-speed trains due to incoming flow impinging the bogie components and the cavity steps. Noise tests were performed
in the Railway Technical Research Institute's anechoic wind tunnel placed in Tokyo, Japan, for different flow speeds from 100 km/h up to 250 km/h using simple shapes representing bogie components, and a 1:5 scale simplified bogie installed in a cavity. The noise spectra radiated by the simple
shapes placed at different heights relative to the upstream cavity step are presented, showing the relation between the component geometry and position in the cavity with the produced noise. In addition, the measured noise spectra are shown for different configurations of the 1:5 scale simplified
bogie: bare, only with front motor and gearbox, only with rear motor and gearbox and with all of them. The presented results aim to provide a better understanding of how the aerodynamic noise is produced in the bogie region of a high-speed train, and to be used for the prediction models adjustment
or validation.
Combination of a 3D-printed microperforated panel and a Helmholtz resonators array for low-frequency sound absorption
Authors: Iglesias Eduardo Latorre , Heredero Sergio Martín , Martín Henar Redondo , Bernalte David Fuentes , Gil-Barba Marta , Aznar-Ballesta Francisco
Published: December 2023

The application of solutions based on conventional porous materials for low-frequency sound absorption is often limited to the available space for their installation, as these require a significant thickness to be efficient. A system combining of a microperforated panel with an array
of Helmholtz resonators, properly designed, can provide effective noise absorption at low- and mid-frequencies with a limited thickness. In this work, the sound absorption coefficient of several systems of this type was assessed by analytical calculations, numerical simulations and experiments
carried out in an impedance tube according to the standard ISO 10534-1:1996. The prototypes were 3-D printed using recycled materials. The absorption coefficient, analytically obtained, was significantly higher than that measured. However, the results from numerical simulations are in good
agreement with measurements, showing that the numerical model carried out can be used for further studies to optimize the system design. An example is given by increasing of the number of Helmholtz resonators in the array, that yields an increase in the sound absorption. Results show the potential
of this type of solutions to be used for low-frequency noise absorption in applications where the available space is limited.
Noise Prediction of an Open Fan Using Acoustic Analogy Approaches
Authors: Sugiyama Masakazu , Falissard Fabrice , Reboul Gabriel , Jaouani Nassim , Gloerfelt Xavier
Published: December 2023

The purpose of this study is to evaluate numerical aero-acoustic methods for the noise prediction of an open fan, which is expected to reduce CO2 emissions for the next generation of aircraft engines. The far-field noise is computed using a CFD/CAA approach. The unsteady Reynolds Averaged
Navier-Stokes (uRANS) and the Ffowcs Williams-Hawkings (FWH) analogy using solid and permeable surfaces are applied. The phase-lag method (single-blade passage) is used for the purpose of calculation for aerodynamic flow and noise sources with ONERA elsA finite volume solver. The sensitivities
to the numerical CFD setup as well as the position and formulation of FWH permeable surface for noise computation are discussed in this paper. The present noise prediction strategy is evaluated for approach and take-off operating conditions. In particular, several spatial discretization schemes
and FWH surface locations are tested and compared to evaluate their influence on the noise levels and directivity.
Shin-Sound Quality Evaluation: Image recognition AI for sound quality evaluation
Authors: Kubo Norio
Published: December 2023

Sound quality evaluation are historically based on psychoacoustical parameters, namely loudness, sharpness and so on. From awake of massive progress of Artificial Intelligence, analysis of sound should be affected by this novel technology. Therefore, in this paper the author introduces
an approach with image recognition AI into sound quality evaluation. It results in showing advantages over complex and non-linear sound evaluation. Thus, the idea of "eyes to ears" could lead new application to this type of solutions.
Least-squares approach for improving the accuracy of bulk acoustic property measurements using an impedance tube
Authors: Kimura Masateru
Published: December 2023

The bulk acoustic property (characteristic impedance, propagation wave number, or propagation constant) of porous acoustic material with an impedance tube is generally calculated by the two-cavity method, which is calculated from the specific acoustic impedance obtained by the two-microphone
transfer function method (ASTM E1050, ISO 10534-2) or from the transfer matrix measured by the four-microphone transfer matrix method (ASTM E2611). These methods can obtain the bulk acoustic property from the results of up to two measurements with different termination conditions. However,
the bulk acoustic property may not be obtained correctly due to calculation singularities caused by the test specimen and/or measurement conditions, and calculation errors caused by setting errors regarding the dimensions or environmental conditions of the tube nd/or test specimen. As a result,
to reduce the errors in the bulk acoustic property, workarounds such as measuring the specific acoustic impedance or transfer matrix under multiple termination conditions (n conditions) and averaging the bulk acoustic properties obtained for all combinations of two termination conditions have
sometimes been used. Therefore, to improve the error in the bulk acoustic properties, a new calculation method based on the least squares method using all the data measured under multiple termination conditions is proposed.
The sound insulation across the plenum window with staggered sound scatter arrays
Authors: Li Xiao-Long , Tang S.K.
Published: December 2023

In this study, experiments and simulations were carried out by a scaled-down model in a semi-anechoic chamber to investigate the acoustic effect of the staggered sound scatter array on the sound insulation of a plenum window. The 1/4 scaled-down plenum window has a gap of 98 mm and
the diameter of the sound scatter cylinder is 19 mm. Firstly, the reverberation times of the verified case and reference case were presented to explore the possible effect of the installment of the sound scatter array on the reverberation of the room model. Next, the effect of four sound scatter
array arrangements on the sound insulation of the plenum window was analyzed experimentally and numerically. Results show that the installment of the staggered sound scatter array can enhance the sound insulation of the plenum window. Below 600 Hz, enhancement of the staggered sound scatter
array on the sound insulation of the plenum window is lower than 2.2 dB. Beyond 600 Hz, the extra transmission loss increases with the frequency and is up to around 6.0 dB. In addition, the trapped mode was observed inside the window cavity and it excited a second higher gap mode which helps
improve the sound insulation of the plenum window.
Vibro-acoustic responses of coupled pump-jet-hull model under duct excitation and the influence of shafting support modes
Authors: Zhang Junyue , Zhang Zhenhua , Rao Zhiqiang , Hua Hongxing
Published: December 2023

The vibro-acoustic characteristics of coupled pump-jet-hull system under excitations on the wall of duct are investigated. The fluid excitation of duct is simulated using computational fluid dynamics. The different vibro-acoustic characteristics for excitations on inner and outer wall
of duct are contrastively investigated through establishing a finite element model and boundary element model of coupled pump-jet-hull system. Meanwhile, the influence of shafting support modes on vibro-acoustic responses is discussed. The results show that the source of excitation forces
on inner and outer wall is different. The force spectra of inner wall exhibit a line spectrum characteristic, reflected in blade passing frequency, while the force spectra of outer wall show a broadband characteristic. The vibration response as well as sound radiation are mainly contributed
by hull modes. The acoustic radiation power excited by forces on inner wall is slightly dominant in the low frequency range. The duct excitation can cause a coupling resonance of the shafting system and it is insensitive to the shafting support modes.
Vibration reduction technology using modal energy propagation analysis method
Authors: Yamashita Koki , Utsunomiya Akinori , Nakagawa Kohya , Yamada Daisuke , Matsumoto Kenji , Kurata Miho , Honda Iwao
Published: December 2023

Since the noise generated by mechanical structures affects the merchantability, it is important to predict the noise and vibratory characteristics at the first design stage. The frames and panels or trim parts in automobiles are coupled systems of the rigid and flexible substructure.
In these systems, vibration of the flexible structures often becomes one of the major noise sources when the excitation force is applied to the rigid structure. FEM and modal analysis technique are not sufficient to carry out the effective low noise design in higher frequency because of high
modal density and complexity of mode shape. Modal energy propagation method, proposed in this paper, is based on the mode synthesis method and the vibration power flow between the eigen modes of the rigid and flexible structures. Previous studies have verified that the vibration level can
be reduced by extracting modes that contribute highly to the vibration power flow between subsystems and changing their characteristics. In this report, we present the results of applying this method to a coupled system of a body and panel structures in automobiles and verifying its validity.
The structural modifications obtained from this analysis method were verified for their effectiveness in decreasing vibration.
Study of drone self-noise estimation for low frequency noise measurement by multicopter drone
Authors: Kitamura Toshiya , Onuki Atsuya , Inomata Koki , Hayashi Yoshinari , Nishio Koji , Oshima Norio
Published: December 2023

We are developing low-frequency noise measurement system with multi-copter type drone. The biggest obstacle to measurements is drone self-noise. Therefor the system records environment noise and propeller rotation timing signal and removes the self-noise from the recording offline.
For a high cancellation performance, accurate self-noise estimation is very important to remove self-noise from recordings. Focusing on the reproducibility of the self-noise for each rotation, we proposed a method for estimating self-noise at arbitrary rotations during flight from prerecording
self-noise data. When the proposed system was mounted on a toy drone and its self-noise cancellation performance was evaluated, high cancellation performance was obtained in the low frequency region. In the study, In this paper, we report a method and its evaluation for estimating the self-noise
of the propeller 1 axis from the rotation signal of the propeller axis of the drone.
Spatiotemporal principal component analysis for event-related potentials in three oddball paradigms under meaningful noise
Authors: Tamesue Takahiro
Published: December 2023

Open offices that make effective use of limited space and encourage dialogue, interaction, and collaboration among employees, are becoming an increasingly. However, productive work-related conversation might actually decrease the performance of other employees within earshot more so
than other random, meaningless noises. It is well known that the eventrelated potentials (ERPs) in the brain wave elicited by internal or external stimuli are related to the operation of selective attention. The presence of noise during the performance of cognitive tasks involving such as
memory, commonly causes a subjective experience of annoyance, which can lead to a decline in performance. This tendency is stronger in response to meaningful noise, such as music and conversation, than for meaningless noise, such as the sound of traffic, and heating ventilating and air-conditioning
noise. The present experiment was designed to determine the effects of meaningfulness of the external noise on the ERPs in the auditory three odd-ball paradigms. Multivariate analysis such as the spatiotemporal Principal Component Analysis (PCA) for components of ERPs was performed.
Numerical Analysis and Measurement Techniques for Aircraft Cabin Noise Using JAXA's Jet-FTB "HISHO"
Authors: Takahashi Takashi , Ura Hiroki , Hayashi Kensuke
Published: December 2023

The reduction of aircraft cabin noise is one of the important issues not only to increase passenger comfort but also to strengthen international competitiveness in aircraft development. JAXA has been conducting research activities on numerical and experimental prediction techniques
of aircraft cabin noise. This paper focuses on the development of our cabin noise prediction tool using the Finite-Difference Time-Domain method, and in-flight noise measurement in the JAXA's Jet-Flying Test Bed (Jet-FTB) "HISHO" with the aim of grasping the cabin noise characteristics.
The measurement data include the noise level near interior walls using the near-field acoustic holography method, the wall impedance, and structural vibrations, acquired through some flight test / ground test campaigns. The authors also explain validation results of our numerical prediction
tool using microphone data measured in the Jet-FTB.
On a recording method for ambient sounds with a confidential speech
Authors: Koyama Yumi , Toyotani Jun , Morinaga Makoto , Lee Hyojin , Shimizu Yasushi
Published: December 2023

There are many reports that environmental noise in healthcare facilities affects patients and healthcare workers both physically and psychologically. To study the sound environment in hospital wards, it is necessary to analyze live sounds (conversations, sounds of daily life, alarms,
etc.) generated by human activities. Recording in hospital wards, as in all healthcare facilities, requires the protection of personal information. Sound recorded in healthcare facilities may include conversations that people do not want to hear. Therefore, it is necessary to develop a recording
method that solves confidentiality issues. We have already confirmed that by fragmenting recorded sounds at short time intervals, the time-averaged sound pressure level of 1/3 octave band frequency of the sounds does not change. This time we developed a new PC application that fragments and
then stores the data without storing original sound data. We analyzed the time-averaged sound pressure level of 1/3 octave band frequency of fragmented speech and alarm sounds using this new application. The results showed that the time-averaged sound pressure levels of fragmented and non-fragmented
sounds were almost the same.
On the multiple tones in trailing edge noise of an aerofoil at low-to-moderate Reynolds number flows
Authors: Li Xiangtian , Zhou Peng , Zhang Xin , Chen Wangqiao , Zhong Siyang , Huang Xun
Published: December 2023

In this work, the aeroacoustics of a NACA 0012 airfoil are studied at the Reynolds number ranges from 3.2×10^4 to 3.2×10^5, in which region there are controversies of tonal noise generation, especially for multiple tones. Particle image velocimetry and acoustic measurements
are simultaneously performed in an anechoic wind tunnel. A dynamic acoustic feedback loop in different flow regimes is proposed to explain the noise generation mechanism. At the low Reynolds number, the existing tonal noise acts as an external force, trigging the upstream flow structures that
will interact with the shedding vortices aft the trailing edge. Consequently, this vortex interaction at the hydrodynamic region can modulate the tonal noise amplitude, resulting in the observed secondary tonal noise. Intermittency of vortex dynamics occurs due to tonal noise amplitudes variation.
With the increase of Reynolds number, the boundary-layer transition on the suction side leads to a weak tonal noise. If the Reynolds number is higher, the boundary-layer flow on the suction side is turbulent, leading to the dominance of broadband noise. However, flow instability on the pressure
side is triggered by the acoustic waves such that the modulation process takes place again. The quantitative measurements of the boundary layer flow and acoustic signals provide insight into understanding the aeroacoustics of airfoils at low-to-moderate Reynolds number.
A literature review of floor impact noise characteristics in wooden apartment buildings using cross-laminated timber slab
Authors: Won Dae-Gwan , Kim Yong-Hee
Published: December 2023

In this study, the floor impact noise characteristics of wooden apartment buildings made of cross-laminated timber (CLT) slabs were analyzed through a literature review. Data on heavy-weight impact noise performance was gathered, including information on floor components such as floor
topping materials and ceiling finishes. The collected data was primarily analyzed in terms of CLT slab thickness. The results showed that 150 mm-thick bare CLT slabs had a single number rating of 70 to 77 dB when tested with a rubber ball, but this decreased to 64 dB for a 210 mm-thick bare
slab. The addition of lower ceiling finishes and floor-topping materials could reduce the heavy-weight impact noise level to around 50 dB. However, results using a bang machine indicated 5 dB higher levels than those obtained with the rubber ball. The floor impact noise characteristics of
CLT structures were also compared to those of concrete structures. The paper concludes by discussing directions for improving the floor impact noise isolation performance of CLT buildings.
An acoustic metasurface by applying planar periodic arrays of resonators with a multiple folded long neck for broadband sound absorption
Authors: Nakanishi Shinsuke
Published: December 2023

An acoustic metasurface gives a broadband sound absorption by a planar periodic array combining small resonant modules tuned at different frequencies. The resonant module is often applied by a Helmholtz resonator, a membrane backed by an airtight cavity and a quarter wavelength closed
tube, which have equivalent small area to a fraction of the wavelength. The author has studied the sound absorption of resonators by applying a multiple folded long neck and an airtight cavity for a thin sound-absorbing structure with high sound absorption at low frequencies below 100 Hz.
In this paper, the author prototypes an acoustic metasurface by planar periodic array of Helmholtz resonators at various resonant frequency tuned by this neck and cavity of the resonator as a unit cell, and discusses the sound absorption characteristics. The prototyped acoustic metasurface
gives a 40 % - 70 % sound absorption from 125 Hz to 250 Hz when it is combined with a 6.4 mm thickness of top plate including a 24 mm - 96 mm length of the multiple folded long neck and a 43.2 mm depth of the airtight cavity. And, more broadband sound absorption will be discussed by a theoretical
analysis.
A study on the evaluation structure of urban soundscape using the Extended Caption Evaluation Method
Authors: Nishizawa Keiichiro , Akita Takeshi , Yu Hanui , Sano Naoko , Hirate Kotaroh
Published: December 2023

This study aimed to understand the impression evaluation of the soundscape of urban streets easily. For the purpose of the present investigation, a new method that is named Extended Caption Evaluation Method (ECEM) was used to extract the structure of the individual's evaluation of
the soundscape. In the ECEM, the Caption Evaluation Method was supplemented by the 'Node-kara' method which enables subjects to make evaluation decisions easily by using standardized free-form descriptions. Sound walks were carried out with smartphones so that evaluation data by ECEM can be
linked with location information. Therefore, results of the sound walk can be shown on a map. The survey was conducted with 20 students in two cities, Marunouchi and Kitasenju in Tokyo. As a result, almost three times as many responses were obtained for sounds rated as 'good' than for sounds
rated as 'bad' or 'neither' in each city. More 'good' sounds were cognized near the parks, whereas in the city blocks, more 'bad' and 'neither' sounds were perceived. On the other hand, it was suggested that the evaluation structure of soundscape which differs from individual to individual
and from city to city.
Estimation of seafloor burrow length and inclination using underwater ultrasound
Authors: Fujimaru Teruki , Hirasawa Haruki , Tachiki Hajime , Asakura Takumi , Mizuno Katsunori , Seike Koji
Published: December 2023

There are many benthic organisms on the seafloor. Then, Some benthic organisms form burrows beneath the seafloor. These burrows have a considerable influence on the surrounding environment providing shelter for symbionts other than the main organisms and promoting water circulation
in seafloor sediments. Therefore, the investigation of the burrow morphology of benthic organisms can be valid for marine environment conservation. Several methods already exist that can estimate the burrow shape and the organisms within the burrows. However, there is a need for a method suitable
for screening surveys to measure many burrows. In this study, a novel method to estimate the morphology of the burrow interior, such as the total length and slope, using underwater ultrasound was proposed. By using this method, it is expected to enable quick and nondestructive measurement
of the internal conditions of a burrow. This paper discusses the feasibility of using the proposed method to estimate the length and inclination of the burrow based on the results of laboratory experiments and field surveys. It was confirmed that the inclination angle and the length of the
actual burrow can be accurately estimated on the order of 4 deg. and up to 18 cm, respectively.
Simulation of aeroacoustic pressure on a vehicle glass with turbulent inflow
Authors: Miyazawa Masashi
Published: December 2023

Cabin noise of a C-segment hatchback vehicle was measured with an inflow velocity in a proving ground at 120km/h and 160km/h. The recorded data is cut and classified into loud and quiet parts of 10 seconds by a subjective and specific loudness evaluations. In 120km/h case, time-averaged
inflow velocity is about 10km/h higher in the loud section than in the quiet section, and the turbulence intensity is higher by 2%. Hydrodynamic and acoustic pressure on glass surfaces are calculated by a CFD and acoustic simulation with and without inflow turbulence in order to evaluate increase
in aeroacoustic input due to fluctuation in the inflow velocity. Fluctuation in pressure on glass surfaces increases with the inflow turbulence.
Floor vibration reduction using damping pad and composed of metal recycling materials
Authors: Kim Wanseung , Lee Donghyeon , Kim Narae , Park Junhong
Published: December 2023

The reduction of floor noise is important issue to improve quality of the life. The flexural vibration by heavy impact is the main cause of noise in building. The purpose of this study is to reduce the floor vibration of the building using environmentally friendly material. A damping
pad composed of metal recycling materials was suggested. The properties of the pad was measured using transfer function method. The constrained layer damping analysis was used to investigate the effect of the pad on floating floor structure. The performance of the pad was estimated by the
experiment in the building. The pad showed higher performance compared to the existing vibration reduction methods. The result of experiment was compared with the vibration analysis.