Sound Characteristics Research Articles

Evaluating emotionalizing effects of active sound designs

Numerous results in the field of musicological research and traffic psychology research show that emotions can be altered by certain sets of pitches or sound characteristics, and emotions on the other hand influence our driving behaviour. Regardless, there is no research on how different artificial vehicle sounds could influence the driving behaviour via emotions. We want to create an active sound design that can alter the driver's emotions to increase traffic safety in certain driving scenarios. To evaluate which harmonic compositions and sound characteristics could be used as stimuli, we first extracted sound characteristics from different music pieces or sounds that have a proven emotionalizing effect, and generated new sounds based on said characteristics that also could work in the context of an active sound design for electrical vehicles. With these sounds, we conducted a subject study with 45 participants to evaluate if people perceive the intended emotions, and further determine the best sounds to use in future subject studies to evaluate their impact on drivers' behaviour. This paper describes the extracted sounds, their characteristics and psychoacoustical properties. Furthermore, it discusses the correlation between the sound properties and the perception of and emotional effect on the subjects.

Optimal design for a perforated panel absorber combined with Helmholtz-resonance and plate vibration

This study proposes a perforated panel sound absorber combined with Helmholtz-resonance and plate vibration and its optimal design method to broaden the sound absorption characteristics. The proposed perforated absorber has a simple structure consisting of a flexible panel with a hole and an air cavity. The conventional optimal design theory of the dynamic vibration absorber is applied to the perforated absorber. The proposed absorber is designed so that the acoustic impedance density will be equalized and almost minimized at two points independently of the damping of the panel. Optimal parameters are related to the Helmholtz-resonance frequency, the natural frequency of the panel, and the loss factor of the panel. The absorber with the optimal parameters was fabricated, and the sound absorption coefficient was measured using an acoustic impedance tube. The experimental results shows that the proposed method can effectively design the perforated panel absorber with the broadband sound absorption characteristics.

Further improvements of the measurement method for sound absorption characteristics using the ensemble averaging technique

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.

Enhancing the Recognition of Speakers in Different Distances using Voice Features

This paper proposes a method to enhance speaker recognition at varying distances by adjusting the reference voice based on voice features. Speaker recognition is the process of identifying an individual based on their voice. It involves analyzing and comparing various acoustic features of a person's voice with the reference voice in the database. Conventional speaker recognition techniques have limitations of reduced accuracy when speakers are from varying distances. In this work, we found that high-frequency signals tend to decline faster than low-frequency ones with respect to speaker distance. Based on this, we propose a method that utilizes support vector machines (SVM) to classify speaker distance using sound features, such as the amplitude sum of high-frequency signals and the dynamic range. Once the speaker distance is determined, the reference signal in the database is adjusted according to the distance before being used for speaker recognition. Mel-Frequency Cepstral Coefficients (MFCC) and Dynamic Time Warping (DTW) were employed as the recognition algorithm. Experiments were conducted with speakers placed at three distances, 0.1, 1, and 2.5 meters from the microphone. The experimental results reveal that signals with the frequency of 4 kHz and above experience a faster decline in amplitude than lower ones with increasing distance. The recognition results also demonstrate a significant improvement in accuracy.

Evaluation of Psychoacoustic Parameters on Internal Combustion Engine Vehicle and Electric Vehicle: Case Study of Armored Vehicle

In this study, psychoacoustic evaluation was performed to identify the sound characteristics of the armored Internal Combustion Engine Vehicle (ICEV) and Electric Vehicle (EV) based on the loudness, roughness, and sharpness parameters. The evaluation was performed on both static and dynamic conditions such as engine on, engine on with AC, constant speed of 20 km/h on smooth roads, and acceleration. The results showed that under the engine on and acceleration conditions, significant differences were found in loudness (0.7-18.4 sone average difference), roughness (0.035-0.058 asper average difference), and sharpness (0.16-0.28 acum difference on average). Meanwhile, there was no significant difference in the Roughness parameter between ICEV and EV on the condition of the engine on with AC and a constant speed of 20km/hour on a smooth road. Significant differences were found in loudness (1.6-4.2 sones average difference) and sharpness (0.11-0.27 acum average difference). Based on the test results in this study, it can be seen that there are differences in sound characteristics between ICEV and EV so that they can cause different perceptions from users.

Numerical prediction of noise generated from a box fan

The noise generated from a box fan is numerically predicted with two approaches. The first one is the FW-H method that can simulate flow and acoustic together by the flow solver scFLOW but assumes sound propagation in free-space. The second one is the ring of dipoles method that is a hybrid approach between the flow solver scFLOW and the acoustic solver Actran. These approaches are validated for small box fans of two different blade configurations with experimental data available for comparison. An incompressible unsteady LES solver with WALE model is used with a fine mesh to solve unsteady flow fields. The numerical results show quantitatively agreement of the pressure rise performance with the experimental results and that the ring of dipoles method gave closer result to the experiment than the FW-H method especially on the low frequency range. Also, we show that the flow rate dependence of the radiated sound pressure of the experiment can be qualitatively well captured with the ring of dipoles method. Finally, we discuss the causes of the different sound characteristics with different blade configurations.

Augmented-reality visual presentation of sounds for deaf and hard of hearing people

To support deaf and hard of hearing (DHH) people by helping them detect environmental sounds in their dwellings, evaluation experiments on environmental sound recognition using a visualization device were conducted. The current study proposes an augmented reality-based system for presenting household sounds to DHH people as visual information. The effect of displaying both the icons indicating sounds classified by machine learning and a dynamic spectrogram indicating the real-time time-frequency characteristics of the environmental sounds were examined. The results confirmed that the comfort of daily life in residential spaces can be improved by combining not only the classification results of machine learning but also the real-time display of spectrograms.

Motor and bearing multi-fault diagnosis with sound quality metrics

The occurrence of multi-faults is more critical as compared to single faults, and it creates unfavourable working conditions. The number of contact-based sensors and their placement plays a crucial role in diagnosing the multi-faults. The use of non-contact-based acoustic sensors could be a cost-effective potential solution to this problem. In this work, two rotating components, a motor and a separate bearing of a system situated away from the motor, were considered for forming system-level multi-fault conditions. The acoustic signature of various multi-fault conditions was acquired at different rotational speeds. Thereafter, a moving window was employed on the acquired raw acoustic signals to extract statistical and sound quality features. A feature fusion approach was implemented on the extracted features, and a machine learning model was trained with optimised hyperparameters. A comparative study was performed to analyse the model's performance, which was trained with the extracted statistical, sound quality and fused features. It was found that the proposed feature fusion-based methodology was helpful for diagnosing multi-faults with acoustic signatures. The importance of psychoacoustical features on model performance was also observed. It mitigated the complexity of mounting the sensors and showed the potential usage of sound quality metrics for multi-fault diagnosis.

A basic study on sound absorption characteristics of disordered hyperuniform periodic structures

Disordered hyperuniform systems are exotic states of matter that cover the intermediate regime between random and periodic structures. Despite appearing disordered and isotropic, they possess a hidden long-range order. Our study aims to develop disordered hyperuniform microperiodic structures that combine short-scale randomness and long-scale periodicity, making them versatile and useful for sound-absorbing materials, such as wall panels. To construct these structures, we generate a large number of three-dimensionally random waves within a specific frequency range, while applying periodic boundary conditions. Using the finite element method, we analyze the sound absorption of the hyperuniform structures. Compared to simple Gaussian random fluctuations, we observe an increase in surface area, resulting in higher airflow resistivity, and a rise in the sound absorption coefficient within the low to mid frequency range.

Low frequency noise control using coupled loudspeaker and negative impedance circuit

It remains a technical challenge for low-frequency duct noise control devices to combine compact and broadband features at same time. A semi-active noise control approach is introduced to solve this problem. The device consists of a main pipe and two loudspeakers connected by a circuit containing a negative impedance network. Due to the effect of the negative impedance circuit, the virtual bypass is composed of the coupled loudspeaker and the circuit has sound transmission characteristics close to a physical duct in a certain frequency range. The effect of the negative impedance network and circuit on the performance of the silencer is studied by using the transfer matrix method. Through the design of the circuit, the sound transmission process of the virtual bypass can be realized. If the proper circuit network and parameters are selected, the virtual bypass HQ tube can achieve compact broadband noise control at low frequencies. A semi-active noise control device has 10dB noise reduction in the range of 100-300Hz.

Experimental and theoretical basic research on sound absorption characteristics of foam materials with and without membrane

A basic study was conducted to theoretically estimate the acoustic properties of a sound-absorbing foam material. Generally, the lattice of sound-absorbing foam materials contains membranes. Herein, for simplicity, a mathematical model was constructed assuming a cubic frame structure as the basic frame structure of the foam, which included a membrane. Accordingly, the sound absorption coefficient was obtained and compared with the experimental results. In the mathematical model, the clearance in the frame structure (with membrane) was divided into elements and was approximated as a clearance surrounded by two parallel planes, considering the exact shape of each element. Herein, the characteristic impedance and propagation constant of the approximated clearance were obtained and treated as a one-dimensional transfer matrix, and the sound absorption coefficient was calculated using the transfer matrix method. For the experiments, the samples were fabricated using a 3D printer and the sound absorption coefficient was measured using a two-microphone impedance tube. Overall, the experimental and theoretical results exhibited similar trends.

A pilot study on the sound insulation performance of plenum doors

Demands for natural ventilation is inaugurated recently, particularly after the COVID-19 outbreak. Various ventilating windows have been proposed, one of which a plenum window has been studied for these years. Since the COVID outbreak shops and restaurants often leave doors opened for ventilation reasons during their business hours. However, by this, the indoor sound environment is suffered by incoming noises from streets. Therefore, it is desirable that a sound insulation structure enabling natural ventilation is developed. In this study, we propose a door with plenum structure which is an application of the same principle of plenum windows to a door. Doors and windows are of different sizes, and under different conditions. Therefore, in this paper, as a pilot study, we employed finite element method to analyse the sound insulation characteristics of a plenum door. Results show that a plenum door, although its sound insulation is not very high, shows sound insulation performance to a certain extent. Also, a parametric study is given to show the effect of parameters including that of sound absorption linings.

Quadcopter Sound Characterization using a UAV Test Stand

Unmanned Aerial Vehicles (UAVs) generate a complex acoustic field that is not entirely understood. Many components and their interactions contribute to the overall noise level and behavior of the acoustic field. A UAV test stand configured to emulate a small quadcopter with a wheelbase of 61 cm was used to determine the acoustic response of a multicopter. Microflown Technologies Scan & Paint 3D solution was utilized to obtain sound pressure, particle velocity, and sound intensity measurements close to the source, along with propagation planes for three-dimensional visualizations containing both amplitude and direction. Draw away measurements using a PU probe were also completed to analyze the sound field characteristics further from the source. The number of propellers in operation was varied to determine the impact of adding additional sources. Aeroacoustic sources, near and far field behavior, interaction noise, directivity, and the sound field propagation of each case is discussed.

Optimal design of low-frequency sound absorber based on Snake Optimizer

In this work, a low-frequency sound absorber composed of a micro-perforated panel (MPP) and a coiled-up space configured by grooved corrugations is proposed. Due to the intricate interactions caused by the hole diameter and hole separation distance, it is difficult to achieve optimal acoustic performance. Here, a high-efficient meta-heuristic optimization algorithm named Snake Optimizer (SO) is applied to flexibly obtain the prime configuration of acoustic absorbing and structure parameters. The expected sound spectrum characteristics are performed by substituting the optimum into the 3D finite element model (FEM). Good agreement verifies the effectiveness of the proposed method. Our work paves the way for broadening the application of algorithms in the optimal design of acoustic metamaterials.

An acoustic metasurface by applying planar periodic arrays of resonators with a multiple folded long neck for broadband sound absorption

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 fundamental study on the sound insulation characteristic of gyroid

Gyroid is a micro-periodic structure that has been observed in biological structural coloration such as butterfly wind scale. It reflects and interferes with light, producing vivid and complex colors. This study aims to apply this property to control sound waves. In this paper, we focused on its sound insulation characteristics, and performed a basic study through the numerical analysis and experiments. The main findings are as follows: (1) The gyroid has a significant sound insulation performance in a specific frequency range depending on its size. (2) Compressing gyroid in the incident direction further improves the performance. The gyroid samples were fabricated by additive manufacturing and their insertion loss were measured in an anechoic chamber. This result experimentally confirmed the findings explained above.

Consideration on accuracy on road traffic noise prediction model "ASJ RTN-Model 2018" in power level and equivalent noise level

This paper introduces the study on verification of prediction accuracy about road traffic noise prediction model "ASJ RTN-Model 2018" used as standard for prediction of road traffic noise in Japan. The effects of vehicle type classification, traffic volume and regional characteristics on prediction accuracy were examined for the power level LWA representing the sound source characteristics of the traveling vehicle and the equivalent noise level LAeq of the evaluation value used for noise control standards. As a result, it was confirmed that the prediction accuracy of this model was generally good regardless of the traffic volume, regional characteristics and the vehicle type classification.

Practical noise measurement method for confirmation of effectiveness of sound insulation in residential houses around airports

In Japan, at airports with significant noise impact, soundproofing for dwellings is subsidized by the airport administrator in accordance with the law requiring noise mitigation. The compensation areas and zone-types are indicated according to noise impact. For each zone-type, the planned quantity of sound insulation to be achieved through soundproofing and the standard construction specifications are determined. Although noise measurement is not required upon completion of the soundproofing, it may be conducted to confirm the sound insulation effectiveness, if necessary. Methods for the measurement of sound insulation characteristics of the buildings are specified in Japanese standards (JIS), but these methods use artificial noise sources from speakers, which require many manpower and sound level meters or noise source equipment, and also cannot directly determine the quantity of sound insulation against aircraft noise. Thus, in order to examine the practical simplified method for noise measurement, we carried out measurements using aircraft noise in or around a dwelling, in parallel with the method required by the JIS standard. From the results, this paper reports the method by using even in a smaller number of microphones with the appropriate placement, to determine the quantity of sound insulation against aircraft noise in a dwelling.

Assessment of Materials on Covid-19 Spread Prevention in Public Buildings

This research is an attempt to suppress the spread of COVID-19 in public buildings through the application of materials that may prevent the spreading of SARS-CoV-2 while at the same time improving audial comfort in such buildings. Study on the capability of materials to break further spreading of the virus applied by measuring the presence of SARS-CoV-2 RNA on the material based on exposure time (0, 3, 6, and 9 minutes). This RNA tracing procedure is repeated on the surface of aluminum, tiles, carbon steel, glass, gypsum, copper, and painted cement on the wall. The results showed that the CT value (cycle threshold) of all materials was approximately 25, which means that they still have the potential to spread the virus. Slightly different results occur on the gypsum surface where the viral envelope (gene E) is not detected with a CT value of 36, meaning no chance of the virus spreading. The same materials will undergo measurement of sound absorptive characteristics to assess their effect on the audial comfort in the building. The results of the study are expected to be a reference before their application as interior materials in public buildings.

Sound absorption of resonators or perforated panels with multiple folded long tubes crammed in small module by additive manufacturing

Resonators or perforated panels give a large sound absorption at a resonant frequency tuned by opening area of the pores, neck length and a cavity depth behind the neck. The author has studied the sound absorption of thin tile-like resonators tuned at low frequencies by including a folded long neck in its surface panel. The resonators are made by an additive manufacturing with a fused deposition modeling (FDM). This paper makes the resonators or the perforated panels with multiple folded long tubes and discusses its measured sound absorption characteristics. One of the multiple folded long tubes is crammed in 12 mm × 12 mm × 19.2 mm of rectangular module even if the tube has 2 mm × 2 mm of opening area and 288 mm of length. A perforated panel consisted of planar periodic arrays of this module gives a large sound absorption at 69 Hz when a 40 mm depth of cavity behind the perforated panel. Furthermore, when the planar periodic arrays of small Helmholtz resonators applied single module and single cavity tuned at different resonant frequency, it has potential to form an acoustic metasurface with sound absorption at broadband frequencies.