Time filter

Source Type

Hirao Y.,Kobayasi Institute of Physical Research | Kunimatsu S.,Japan National Institute of Advanced Industrial Science and Technology | Hamamoto T.,Tokyo City University
Mapan - Journal of Metrology Society of India | Year: 2012

The environmental impact on residents of buildings, such as adverse effect on sleep and physical discomfort is caused by ground-borne vibration sources such as rail transit systems, road traffic, construction sites, and industrial plants. To estimate the impact of these vibrations on the residents, it is necessary to measure the tri-axial vibrations in the vertical and horizontal directions of the buildings as specified in the international standard regulated by ISO 2631-2:2003. A wireless measurement system for simple and accurate measurement of building vibration was developed. Five wireless vibration measurement devices (installed together with a data recorder in the building) are controlled simultaneously by an outdoor mobile PC or a laboratory PC via wireless local area network and an Internet connection. It sends the vibration acceleration waveforms recorded in buildings over the wider internet communication system to the laboratory PC. The wireless measurement system was used for measuring vibration in two- and three-story detached houses of wooden or steel construction. The impact on the residents may be caused by the vibration amplifications associated with building structural resonances. The vibration amplifications in 120 houses were evaluated as ratios and level differences in 1/3 octave band vibration accelerations measured at the ground near the substructure and floors. © 2012 Metrology Society of India.

Sato H.,Japan National Institute of Advanced Industrial Science and Technology | Yoshimura J.,Kobayasi Institute of Physical Research
INTERNOISE 2014 - 43rd International Congress on Noise Control Engineering: Improving the World Through Noise Control | Year: 2014

This study presents results of subjective judgments to simulated floor impact sound to create classification scheme of heavy weight impact sound with standardized rubber ball. The floor impact sound samples were recorded in a wood-frame test house with different floor configurations and were reproduced in an anechoic chamber. Using the relationship between subjective rating and physical indices, an example of classification scheme for rubber ball impact sound measurement will be presented.

Yasuno Y.,Kobayasi Institute of Physical Research
Proceedings of Meetings on Acoustics | Year: 2010

The electret condenser microphone (ECM) has become an important component for various consumer equipment systems because of its stable sensitivity and frequency characteristics and its success in achieving small size and high sensitivity. A previous report described the method to design a microphone with stable temperature characteristics. The quality of the silicon material for the diaphragm was pointed out as important for improving robustness. Recently, microphones using micro-electro-mechanical systems (MEMS) have been practically applied and widely used for mobile equipment, such as cellular phones. The major reason for adopting MEMS is that a re-flow soldering process can be used in production, in addition to having desirable features such as being small and thin. However, almost no electret types have been commercialized since a guaranteed 300-degree C heat resistance is required. This report presents a new trial electret silicone microphone that contains a SiO2 thin-film electret. The report also evaluates the heat resistance of a SiO2 electret, the temperature stability of a silicon diaphragm, and the temperature change of sensitivity and frequency characteristics compared with those of a conventional ECM and the microphone for measurement. © 2010 Acoustical Society of America.

Iwanaga K.,Kobayasi Institute of Physical Research | Doi T.,Kobayasi Institute of Physical Research
INTER-NOISE 2015 - 44th International Congress and Exposition on Noise Control Engineering | Year: 2015

In Japan, a serious environmental noise problem such as the window rattling has been caused by infrasound. It is difficult to reduce exposure of infrasound by passive mechanisms such as noise barriers, porous materials, acoustic resonators, and so on. On the other hand, active noise control (ANC) technique has not been applied to the infrasound, since it is not easy to generate the infrasound at high sound pressure level. We have developed transportable low frequency sound generators (LFSGs) driven by pneumatic servo actuators. LFSGs can reproduce the arbitrary waveform, in which the frequency range is 5 to 20 Hz. For pure tones, sound pressure level of generated sound reaches over 100 dB at a front of the source in the free-field. To investigate the applicability of ANC technique to the infrasound, two field experiments were performed. One is an experiment that ANC technique was applied to reducing pure tones of 5 Hz by using LFSGs. As the result, it was confirmed that sound pressure level at an observation point was reduced by over 25 dB. The other is a field experiment to apply ANC to an actual sound was performed. Using LFSG, window displacement due to a helicopter passing could be reduced by one-third. © 2015 by ASME.

Ishii H.,Tokyo University of Science | Nakajima T.,Tokyo University of Science | Takahashi Y.,Tokyo University of Science | Furukawa T.,Tokyo University of Science | Furukawa T.,Kobayasi Institute of Physical Research
Applied Physics Express | Year: 2011

Polarization switching dynamics at extremely high electric fields were measured for a 50-nm-thick ferroelectric vinylidene fluoride/trifluoroethylene copolymer film. Using a fast-rise voltage pulse with minimal duration, we obtained a switching time of as fast as 2 ns at an electric field of 800 MV/m without electrical breakdown. Departure from an exponential law toward a power law was detected above 300 MV/m. Distorted switching curves due to limited voltage rise time were shown to be reproducible by means of nonlinear superposition © 2011 The Japan Society of Applied Physics.

Yoshimura J.,Kobayasi Institute of Physical Research
40th International Congress and Exposition on Noise Control Engineering 2011, INTER-NOISE 2011 | Year: 2011

The sound reduction index of a solid glass pane depends strongly on boundary conditions attributable to a low internal loss factor. The sound reduction index can be calculated precisely using Cremer's theory and the total loss factor of the system (estimated experimentally or theoretically) at and above the critical frequency. Below the critical frequency, Sewell's mass law accounts for the effects of panel size on forced-wave transmission. The internal loss factor and bending stiffness of laminated glass vary with temperature, and they also have frequency dependence. Generally, the sound reduction index is calculated using Cremer's expression: the theta (angle of incidence) from 0 to 78° is integrated under the assumption of field incidence. However, there are discrepancies in the critical frequency region, especially in the case of a small thick glass pane. At and above the critical frequency, the incidence at the grazing angle to the system has to be taken into account. The incident angle limitation for an ISO test opening was estimated by the calculations comparison between experimental data and predicted the sound reduction index using them for laminated glass panes at various temperatures.

Mabuchi Y.,Tokyo University of Science | Nakajima T.,Tokyo University of Science | Furukawa T.,Tokyo University of Science | Furukawa T.,Kobayasi Institute of Physical Research | Okamura S.,Tokyo University of Science
Applied Physics Express | Year: 2011

We investigated the polarization enhancement in 60-nm-thick vinylidene fluoride/trifluoroethylene (VDF/TrFE) films without thermal annealing by applying repeated bipolar electric pulses. The remnant polarization was 8.4mC/m2 in as-spin-coated films and increased to up to 45mC/m 2 when 105 pulses were applied. Although the remnant polarization was half and the coercive field twice those of annealed films, the electrically treated film had a markedly smoother surface than the annealed film. Finally, a 15-nm-thick ferroelectric VDF/TrFE film with low conductivity was fabricated by electric treatment; annealed films with the same thickness experienced a severe short-circuit problem originating from the surface roughness. © 2011 The Japan Society of Applied Physics.

Okubo T.,Kobayasi Institute of Physical Research | Yamamoto K.,Kobayasi Institute of Physical Research
Acoustical Science and Technology | Year: 2013

Diffraction-reducing efficiency of a T-profile noise barrier is discussed using boundary element analyses considering a point source against an infinitely long barrier. The efficiency against a fixed point source includes both an increased thickness effect due to the T-profile cap and an interference effect due to phase difference between propagation paths around cranked edges of the cap. The latter interference effect depends on the relationship between wavelength and geometries; the effect disappears for incoherent point sources moving parallel to the barrier. For incoherent line sources such as road traffic noise, the efficiency of the T-profile barrier is almost equivalent to that of a thick barrier, and difference between them is almost less than 1 dB when the T-cap depth is equal to or less than 1m. As a result, reduction in road traffic noise by a T-profile barrier is approximately calculated using a kind of engineering prediction models based on geometrical acoustics. © 2013 The Acoustical Society of Japan.

Sakagami K.,Kobe University | Yairi M.,Kajima Technical Research Institute | Toyoda E.,Kobayasi Institute of Physical Research | Toyoda M.,Kansai University
Acoustics Australia | Year: 2013

A microperforated panel (MPP) is usually placed with a rigid-back wall to form a Helmholtz resonator with its hole and the air-back cavity. However, the authors have so far proposed an MPP space sound absorber without any backing structure. In the previous studies, as a basic form of such an MPP space absorber, multiple-leaf MPP structures without a back wall were proposed, and were theoretically and experimentally examined. In order to provide more unrestricted usage and designs for an MPP space absorber, the authors have also proposed a three-dimensional MPP space absorber, called a cylindrical MPP space absorber (CMSA). The CMSA was shown to exhibit resonance peak absorption and additional low frequency absorption. In this paper, another alternative of a three-dimensional MPP space absorber, a rectangular MPP space absorber (RMSA) is proposed. Its sound absorption performance is discussed using experimentally measured results. The results show sound absorption characteristics similar to a CMSA, and an RMSA can be effectively used if properly designed.

Yoshida K.,Tokyo University of Science | Manabe H.,Tokyo University of Science | Takahashi Y.,Kobayasi Institute of Physical Research | Furukawa T.,Tokyo University of Science
Electrochimica Acta | Year: 2011

Broadband electrical spectroscopy was used to investigate the correlation between ionic conductivity and dielectric relaxation in the liquid state of polyethylene oxide (PEO)/lithium perchlorate (LiClO4) complexes over the broad ranges of salt concentration Li/O, molecular weight of PEO M w, and temperature T. The introduction of LiClO4 induced a split of the dielectric relaxation into fast and slow modes. The fast mode decreased its relaxation strength with increasing Li/O while keeping the frequency constant, whereas the slow mode first increased its strength and then became constant while decreasing the frequency. On the basis of their M w dependences, we concluded that the fast mode is associated with the segmental motion of free PEO and that the slow mode arises from the slowed segmental motion due to the cation coordination of ether oxygens. The molar conductivity first increased and then decreased with increasing Li/O in parallel with the slow-mode relaxation frequency showing a plateau near Li/O = 3%. The ionic diffusion coefficient was shown to be proportional to the slow-mode relaxation frequency, with the coefficient of proportionality being independent of Li/O, Mw, and T. The use of a random walk scheme yielded a microscopic feature in which ions hop for a distance of 0.3 nm at the rate of the slowed relaxation frequency. Discussions are extended to the conduction mechanisms in the partially crystallized states. © 2011 Elsevier Ltd. All rights reserved.

Loading Kobayasi Institute of Physical Research collaborators
Loading Kobayasi Institute of Physical Research collaborators