Ryuzo Horiuchi

Final report on key comparison APMP.AUV.A-K1

A regional key comparison APMP.AUV.A-K1 has been carried out for the pressure sensitivity of laboratory standard microphones. The National Metrology Institute of Japan (NMIJ) piloted this project. Two LS1P microphones were circulated through nine national metrology institutes and calibrated in the frequency range from 63 Hz to 8 kHz. Deviations from the mean value are below ? 0.05 dB for all the frequencies. Results have been linked to CIPM key comparison CCAUV.A-K1 by introducing a correction factor. For every participant, the degree of equivalence with a key comparison reference value is within the corresponding expanded uncertainty. Main text. To reach the main text of this paper, click on Final Report. The final report has been peer-reviewed and approved for publication by the CCAUV, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Instability of the voltage transfer function for an MR103 microphone in a coupler calibration technique

Abstract MR103 microphones are commonly used laboratory standard microphones in Japan. When the pressure sensitivity of MR103 is calibrated by using a coupler calibration technique, higher accuracy is difficult to achieve due to deviations in the measured voltage transfer function. These deviations are peculiar to MR103, but not to B&K4160, which is also a commonly used laboratory standard microphone throughout the world. Such deviations occur even when the measurements are done consecutively under the same measurement conditions, such as polarization voltage, temperature, and static pressure. This study experimentally and theoretically considered one of the possible reasons for this deviation. The results reveal that (a) this deviation can be explained by changes in the microphone’s parameters, such as the distance between a microphone’s membrane and back-plate, and the tension of the membrane, (b) grease used to prevent leakage of gas and sound out of the coupler might be one of the reasons for this deviation, and (c) insertion of polished sapphire spacers between the microphones and the coupler might help diminish this deviation.

A new traceability system in Japan

In 1993, the measurement law was revised and enacted in Japan. The old law had provided only the use of legal metrology units and the approval and verification systems for measuring equipment. The new one has added the provision of a traceability system to match the needs for a high accuracy measurement technique and international mutual recognition. In the Electrotechnical Laboratory (ETL), the national standard of sound‐pressure level has been established and maintained in an audible frequency range. The type approval test and verification of sound level meters have been carried out in the Japan Quality Assurance Organization (JQA). Now, in conformity with the law, ETL has started to construct the new traceability system for the acoustical standards in cooperation with JQA. An outline, is made of the traceability system in Japan and of the newly constructed pressure calibration systems for laboratory standard microphones.

Free‐field calibration of 1/4 inch microphones for ultrasound by reciprocity technique

Recently, equipment that radiates ultrasound radiation at frequencies far beyond the audible range is increasing in our environment. Such electronic equipment has switching regulators or inverter circuits, and many devices are unintended sources of ultrasound radiation. However, the effects of airborne ultrasound on human hearing and the human body have not been well investigated. To estimate the potential damage of airborne ultrasound radiation quantitatively, it is necessary to establish an acoustic standard for airborne ultrasound because the standard is a basis of acoustic measurement. With the intention of establishing a standard on airborne ultrasound, a free‐field calibration system with an anechoic chamber was produced. The principle of free‐field calibration techniques is introduced in this presentation. Type WS3 microphones (B&K 4939) were calibrated in the system to examine the calibration ability to be achieved. Results showed that it can calibrate a microphone from 10 to 100 kHz with dispersi...

Study on measurement technique for acoustic cavitation using cavitation bubble signals

Acoustic cavitation shows an excellent effect on ultrasonic cleaning and it also has prospects of application to cancer treatment. However, further study is essential to solve the problems such as low yield ratio and safety for human body because too much cavitation can damage the target. In this respect, quantitative evaluation of the generated cavitation is required. The mechanical index has been used so far but it does not reflect the quantity of the generated cavitation. Thus, we have been studying a new measurement technique by using the signal generated from cavitation bubbles, frequency spectrum of which is composed of broadband noise and subharmonics. We have reported that broadband noise has potential as an index for the amount of the generated cavitation. In this presentation, we experimentally investigated the level change of both broadband noise and subharmonics by increasing the acoustic pressure. We found that these two components are observed at the different level of acoustic pressures, pr...

Development of a laser‐pistonphone for an infrasonic measurement standard

Acoustical standards for audio frequencies are based on pressure sensitivities of laboratory standard microphones calibrated using a coupler reciprocity technique. There is a growing need to extend the frequency range downward for reliable infrasonic measurement. The reciprocity technique, however, has limitations on low‐frequency calibration (1–20 Hz) because signal‐to‐noise ratio deteriorates and a sound leak occurs from capillary tubes that equalize the static pressure inside and outside of the coupler. These factors rapidly increase the measurement uncertainty as the frequency is lowered. NMIJ has therefore recently developed a laser‐pistonphone prototype, which enables precise calibration of microphones at low frequencies. Compared with the reciprocity technique, the laser‐pistonphone produces a higher sound pressure within a cavity by the sinusoidal motion of a piston and has a significantly improved signal‐to‐noise ratio. Sound pressure is calculated from the piston displacement, which is determine...

Analysis of sound generation mechanisms of a Samisen: Comparison between its sound waveform and vibration waveforms of the skin, bridge, and plectrum at the beginning of the sound

A Samisen is one of the typical plucked string instruments in traditional Japanese music. In this work, the sound generation mechanism of the Samisen will be discussed by analyzing how each part of the Samisen works. The Samisen sound is classified into four time regions by considering the characteristics of the waveform. The time–frequency analysis of the vibration waveform of each part in each time region is compared with that of the sound. Furthermore, the sound generation mechanism will be discussed, including the time region by the transient touch of the plectrum to the strings and the skin. It is concluded that both the cause of the vibration of the skin and the generation of the Samisen original sound are mainly due to two mechanisms: the transmission of the continuous vibration of strings through the bridge and the transient and direct touch of the plectrum.