The authors had conducted a series of questionnaire surveys on the acoustical quality of concert halls in the Tokyo metropolitan area approximately 30 years ago, and now they have reexamined these data in light of current knowledge. In the surveys, eight to ten musical experts served as listeners at 12 orchestral concerts, judging the subjective impression in terms of reverberance, clarity, perceived sound strength, spatial impression (LEV), and overall quality. The surveys consisted of two rounds, each with slightly different sets of subjective attributes. Regression analyses were conducted to investigate the relationships between the subjective attributes and their corresponding physical parameters. In the first round, the relationships between subjective attributes and physical parameters differed from those observed today, when relatively low reverberant spaces were evaluated more favorably. In the second round, the relationships approached those currently recognized as such. This shift is likely attributable to historical context. That is, during the first round, concerts were typically held in multipurpose halls, while around the time of the second round, music-dedicated concert halls began to open.

Optical music recognition technology has significantly enhanced the efficiency and accuracy of computational score transcription through deep learning methodologies. Although current techniques demonstrate strong performance in processing monophonic and single-voice scores, they struggle to achieve comparable accuracy when handling complex scores containing harmonic intervals, chords, polyphony, or multivoice compositions. In this paper, we propose ConvNeXt-Transformer Fusion (CNTF), an autoregressive end-to-end neural network framework employing an image-to-sequence architecture specifically optimized for automated transcription of intricate musical scores. The model integrates a ConvNeXt-based encoder for sheet music feature extraction and a Transformer-based decoder that generates transcription sequences through autoregressive prediction. To address class imbalance during training, we implement Focal Loss optimization. Experimental results demonstrate that the CNTF model achieves state-of-the-art performance in polyphony-rich score recognition, exhibiting superior character, symbol, and line error rates to existing baseline systems.

Previous studies reported that, when two identical sounds are presented from different directions in the median plane, the sound image perception differs from that in the horizontal plane. The current study performed a psychoacoustical experiment to explore the summing localization occurring in the median plane. The results coincide with the literature, showing weaker summing localization in the median plane than in the horizontal plane. Furthermore, the results indicate an upper-lower asymmetricity and inter-individual variability in the summing localization in the median plane. These results also hold for the case without time delay between the two sounds, namely, the amplitude panning.

Advancements in determined blind source separation (BSS) have been achieved through two approaches: design of better source models and derivation of better optimization algorithms. This paper proposes novel BSS algorithms based on alternating direction method of multipliers (ADMM) to easily incorporate additional constraints and regularization terms into a source model, which provides more flexibility for the source model design. In addition, the structure of spatially whitened signals is effectively utilized to simplify the computation and speed up the ADMM algorithm. In experiments, we applied the proposed ADMM algorithm to the source model of independent vector analysis and compared it with the majorization-minimization (MM) algorithms. Experimental results showed that the proposed ADMM algorithm with the speeding up technique can achieve performance and convergence speed comparable to the state-of-the-art MM algorithm. Our MATLAB codes are available at https://github.com/WATARAI-Hiroko/ADMM-IVA.

This study proposes a non-destructive testing method that combines air-coupled ultrasound and nonlinear harmonic techniques with frequency compounding. The frequency compounding process utilizes nonlinear phenomena observed in air-coupled ultrasound to enhance defect detection capability. The objective of this research is to achieve accurate localization and sizing of defects.To validate the proposed method, experiments were conducted using a 400 mm × 400 mm × 3 mm aluminum plate with a 5 mm square artificial thinning area to simulate wall-thinning defects. The effectiveness of the method was evaluated in terms of the accuracy of defect localization and sizing. As a result, it was confirmed that the proposed frequency compounding method, which selectively combines harmonic components up to the 10th order, maintained localization accuracy comparable to that of conventional methods while achieving an improvement in sizing accuracy of up to 50% in the wave propagation direction and 40% in the direction perpendicular to wave propagation. These findings demonstrate that the proposed method enables reliable estimation of both the position and size of defects.

Several attempts have been made to quantify the diffuseness of a sound field from various perspectives. In this study, we focus on the two diffusion indices determined from incidence directivity: directional diffusion coefficient and isotropy indicator. We revise their definitions in the light of physical comprehensibility and also introduce a normalization procedure. These revisions bring an explicit relationship between the indices, which provides their consistent interpretation. Moreover, we conduct numerical examinations using an existing incidence directivity analysis and determine the behaviors of the revised indices in a room with different absorption conditions.

This article reports on measurements of the near-field head-related transfer functions (HRTFs) of a head and torso simulator (HATS) conducted at NHK Science and Technology Research Laboratories. The measurements included 27 source distances ranging from 0.20 m to 1.50 m at 0.05 m intervals, and 865 directions at each distance. It is desirable to use a sufficiently small sound source that has a wide frequency range such that it approximates a point source with omnidirectional characteristics for the measurements of near-field HRTFs. This article introduces the measurement system constructed in an acoustic anechoic chamber at NHK Science and Technology Research Laboratories and the compact loudspeaker manufactured to meet these requirements. The measurements reveal that, in addition to the overall decrease in the HRTF magnitudes with distance, a sharp attenuation of the low-frequency magnitude could be seen on the ipsilateral side of the sound source, and peaks and notches observed in the spectra varied in their depth and frequencies. These tendencies are consistent with previous reports on the near-field HRTFs.

Neural networks have proven valuable for estimating the Direction-of-Arrival (DoA) of acoustic signals since they are capable of overcoming the accuracy and robustness inherent to conventional estimation methods when dealing with acoustic phenomena. This paper presents a system based on the processing of the acoustic intensity formulated in spherical coordinates. Due to the omnidirectional and spherical structure of this type of features, a spherical convolutional neural network (SCNN) architecture is used to estimate the DoA by means of a regression task. A series of experimental tests based on angular error have been performed to examine the accuracy as a function of reverberation and noise, demonstrating the degree to which the proposed method offers competent robustness compared to some state-of-the-art methods.

We previously proposed a noninvasive and quantitative method for estimating the aggregate size of red blood cells (RBCs) based on ultrasound backscatter characteristics. In this study, we improved the estimation accuracy by appropriately setting the focal-region width of the ultrasound beam used to calculate the reference scattering power spectra. Phantom experiments using blood-mimicking particles demonstrated that a wider focal region yielded an estimate closer to the true value and reduced the root-mean-square error (RMSE) of the spectral fitting compared with the conventional width. This result indicates that an appropriate focal-region size enhances the accuracy of RBC aggregate size estimation.

This study investigates changes in the rhythmic characteristics of Japanese speech induced by delayed auditory feedback (DAF). Ten native speakers read sentences under four DAF conditions (0, 100, 200, and 300 ms), and interval durations (consonant, vowel, and mora) were measured. Speech rhythm indices were evaluated using Mean (average duration), Delta (absolute variability), and Varco (relative variability). DAF increased Mean and Delta in consonant and vowel durations, indicating greater temporal variability at the phoneme level. However, the relative isochrony of morae, measured by VarcoM, remained stable, suggesting mora timing tends to be preserved under feedback perturbations.

Since convolution operators characterize linear time-invariant (LTI) systems, convolution is one of the most fundamental operations in acoustic signal processing. Likewise, the analysis and processing of acoustic signals in the time-frequency domain is commonplace. In this context, LTI systems are often approximated with simple time-frequency domain operations, such as channel-wise multiplicative weights or channel-wise convolution. On the other hand, accurate computation of LTI systems in the time-frequency domain usually requires using crossband filters. However, the algorithms for connecting the LTI systems and the corresponding crossband filters have not been well-established, which has hindered their practical applications. In this paper, we introduce and compare several algorithms for computing the crossband filter representation of a given LTI system. Furthermore, we propose an inverse scheme for converting crossband filters into LTI systems, which is proven to recover the correct LTI system from its crossband filter representation. Efficient algorithms for this conversion are presented. We demonstrate numerically that the conversion of crossband filters into LTI systems is faithful: If the crossband filter represents an LTI system, then the conversion recovers the corresponding impulse response, confirming our theoretical result. Finally, we compare the computation time of forward and inverse conversion for all the presented algorithms.

Emotional responses to forest sounds among young Japanese women were examined by comparing birdsong with sounds produced by a potentially dangerous insect. The birdsong of four distinct species was significantly more pleasant and less arousing than the sound of an Asian giant hornet. Skin blood flow, an indicator of sympathetic nervous activity, decreased during exposure to the hornet sound, whereas no significant change was observed to birdsong. These findings suggest that young women show similarly positive subjective responses to the acoustically distinct songs of forest bird species and exhibit an adaptive physiological response to the hornet sound.

When a planar object with a small through-hole at the center was placed near a vibrating surface, a jet flow from the hole was observed. The objective of this study is to clarify the flow velocity distribution and characteristics of the jet phenomenon through measurement and analysis. The airflow with the jet was visualized using particle smoke, a light sheet, and a high-speed camera. The flow velocity fields produced by the jet were calculated by particle image velocimetry. The jet flow from the hole was considered to occur with suction flow around the hole. The maximum velocity of the jet flow was twenty times higher than that of the airflow without the planar object. The sound pressure fields were analyzed by finite element analysis, and high sound pressure was found in the hole. This pressure was higher than that in the air gap between the vibrating surface and the object. Furthermore, it was confirmed that the airflow around the hole fluctuated with driving frequency. Thus, a breathing-like jet was formed in the hole. The flow velocity was increased by increasing the vibration amplitude and decreasing the air gap.

In this study, the validity of the detection of multiple defects in a billet by time-of-flight (TOF) profile and transmission method with linear scanning are evaluated through simulation and experimentation. Simulation results show that TOF measured using the transmission method has higher lateral resolution than using echoes from the defects. Although distinguishing each defect from the TOF profiles becomes difficult when defects are close together, the size of the defect should not be underestimated. As the TOF profiles are consistent between the simulation and experimental results, it is believed that the verification results of the TOF-linear method by simulation are valid.

Modelling traffic noise propagation behind buildings has been a challenging issue for environmental noise assessment. As a solution, the ASJ RTN-model provides a straight-forward and powerful calculation model of road traffic noise, which includes an effective calculation method for predicting the noise propagation behind buildings with complex conditions. However, the model is limited to fixed frequency characteristics of the noise source. To extend the current model to a frequency-dependent prediction model, in this work, we report an attempt at constructing a prediction model accounting for different frequency bands on the basis of scale model experiments. Furthermore, we establish a parameter synthesis method that enables the prediction model to be applied to the various frequency characteristics of the noise source.

Additive manufacturing (AM) has emerged as a novel fabrication method capable of producing complex geometries. Among metal AM techniques, laser-based powder bed fusion of metals (PBF-LB/M) is particularly effective for creating intricate structures. However, the mechanical properties of AM parts often exhibit anisotropy and spatial variation. In this study, Inconel 718 components were fabricated using PBF-LB/M, and their mechanical properties—specifically, Young’s modulus—were nondestructively evaluated using laser ultrasonics (LU). The results revealed pronounced anisotropy and location-dependent variations in mechanical properties. Because LU enables nondestructive evaluation at the millimeter scale, it is highly effective for investigating the physical characteristics of AM parts. This study demonstrates the potential of LU as a powerful tool for advancing the understanding of AM material behavior and optimizing AM processes.

The introduction of intense pressure waves such as laser-induced stress waves (LISWs) during electroporation is expected to solve the problem encountered in electroporation by either promoting cell membrane permeability or cell growth. In this study, the repeated LISW introduction exceeding 10 MPa at peak intensity into a versatile electroporation cuvette was experimentally demonstrated. For generating the LISWs, circulating black ink and a transparent soft tube was used as an optical absorber and a plasma-confined medium, respectively. From experimental results, the author found that the peak positive pressure of LISWs in the cuvette was dominant; however, the effect of cavitation was relatively weak because of a small negative pressure. Moreover, the stable repeated generation of LISWs was observed in laser irradiation for more than 30 cycles. The effects of repeated LISW introduction on yeast cell growth were also investigated using the present system. The reduction of yeast growth after LISW introduction of 100 cycles was suggested.

Pulsed pressure waves propagating through a narrow air gap surrounded by spherical walls of different diameters were computationally and experimentally investigated to generate an impact force for noncontact and nondestructive testing. It was confirmed that with the proposed model, an impulse-like wave with peak positive pressure exceeding 10 kPa can be obtained with a gap width of 0.9 mm at a laser energy of 35 mJ.

A cellular polypropylene film metallized with gold electrodes is directly glued to the back plate of a commercially available condenser microphone cartridge whose metallic diaphragm is removed, composed of a microphone set with an existing pre-amplifier and power module. Lack of vibration resonance of the diaphragm makes it possible to widen frequency ranges in pressure sensitivity compared with those of commonly used condenser microphones. In fact, it has been experimentally verified that the prototyped microphone has good response to sound waves over the extremely wide range of frequencies from 200 Hz to 400 kHz and is highly acceptable to intense sound pressures of up to several tens of kilo-pascals.

This study investigates strategies to enhance the loading and dispensing capabilities of a droplet in ultrasonic levitation systems through acoustic field optimization. Using a 28.58 kHz transducer, two approaches were evaluated: (1) horizontal standing waves with a 5° angled reflector at first- to third-order resonances, and (2) inclined standing waves at different angles (first-order resonance) under a fixed surface vibration velocity of 0.8 m/s. Results show that the horizontal configurations with the angled reflector required up to 112.5% higher surface vibration velocity to reach comparable levitation performance to that of parallel reflectors, revealing inefficiencies in reflector-angle adjustments. In contrast, tilting the standing wave angle to 45° significantly enhanced stability, enabling reliable levitation of an averaged 1.0 µL droplet with reduced energy input. The inclined-wave method outperformed reflector-angle modifications, achieving precise droplet insertion and dispensing while minimizing acoustic energy consumption.

Liquid crystal (LC) varifocal lenses are characterized by their need for compactness and high-speed response, rendering them well-suited for next-generation optical devices. The focal length can be modulated by reorienting LC molecules through acoustic radiation force. In this study, the influence of the geometrical structure of ultrasonic LC lenses on the optical performance was examined. Two LC lenses with distinct glass substrate thicknesses were fabricated, and their optical characteristics were evaluated. The electro-mechanical parameters were found to be altered by the thickness of the glass substrate, which consequently led to an improvement in the power consumption in focus tunability.

In general, the resonance frequencies of ultrasonic emitters that use bolt-clamped Langevin transducers differ slightly. However, when using these emitters in an arrayed device, the resonance frequencies of each emitter must be matched. In this paper, the arbitrary reduction of the resonance frequency by adding a small amount of mass after fabrication is examined. The resonance frequency was lowered by adding more mass, demonstrating the utility of this method.

The effect of the cylinder with a cavity around the target location on underwater acoustic streaming at 28.2 kHz was investigated. Finite element analysis was performed to optimize the dimensions of the transparent acrylic cylinder by the resonance frequency analysis of the whole structure to increase sound pressure in the cavity. Simulation methods ignoring cavitation bubbles and considering bubbles were used to obtain distributions of sound pressure and acoustic streaming at the initial period and stable state separately. For comparison, particle image velocimetry experiments were conducted using the adjusted and original cylinders. The results showed that when the gap was smaller than 25 mm, the cavity had an obvious enhancement effect on streaming velocity, increasing it to twice the maximum value.