Evaluation of Hydrophone Spatial Averaging Effect in Near Field Measurement for Determining Mechanical Index

Yoshioka, Masahiro; Kikuchi, Tsuneo

doi:10.1143/jjap.51.07gb03

Cited by 2 publications

(1 citation statement)

References 15 publications

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“…Therefore, we used the Rayleigh integral to calculate the sound pressure at any observation point. [21][22][23] Figure 8 shows the position of the vibrating plate of the proposed acoustic transducer on the xy-plane and the calculation area of the sound pressure level at the far field. The length L of the vibrating plate was 200 mm.…”

Section: Calculation Of Sound Pressure Level At Far Field Of Vibratinmentioning

confidence: 99%

Suppression of sound radiation to far field of near-field acoustic communication system using evanescent sound field

Fujii

Wakatsuki

Mizutani

2015

Jpn. J. Appl. Phys.

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A method of suppressing sound radiation to the far field of a near-field acoustic communication system using an evanescent sound field is proposed. The amplitude of the evanescent sound field generated from an infinite vibrating plate attenuates exponentially with increasing a distance from the surface of the vibrating plate. However, a discontinuity of the sound field exists at the edge of the finite vibrating plate in practice, which broadens the wavenumber spectrum. A sound wave radiates over the evanescent sound field because of broadening of the wavenumber spectrum. Therefore, we calculated the optimum distribution of the particle velocity on the vibrating plate to reduce the broadening of the wavenumber spectrum. We focused on a window function that is utilized in the field of signal analysis for reducing the broadening of the frequency spectrum. The optimization calculation is necessary for the design of window function suitable for suppressing sound radiation and securing a spatial area for data communication. In addition, a wide frequency bandwidth is required to increase the data transmission speed. Therefore, we investigated a suitable method for calculating the sound pressure level at the far field to confirm the variation of the distribution of sound pressure level determined on the basis of the window shape and frequency. The distribution of the sound pressure level at a finite distance was in good agreement with that obtained at an infinite far field under the condition generating the evanescent sound field. Consequently, the window function was optimized by the method used to calculate the distribution of the sound pressure level at an infinite far field using the wavenumber spectrum on the vibrating plate. According to the result of comparing the distributions of the 1/40 Japanese Journal of Applied Physics REGULAR PAPER sound pressure level in the cases with and without the window function, it was confirmed that the area whose sound pressure level was reduced from the maximum level to-50 dB was extended. Additionally, we designed a sound insulator so as to realize a similar distribution of the particle velocity to that obtained using the optimized window function. Sound radiation was suppressed using a sound insulator put above the vibrating surface in the simulation using the three-dimensional finite element method. On the basis of this finding, it was suggested that near-field acoustic communication which suppressed sound radiation can be realized by applying the optimized window function to the particle velocity field.

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Section: Calculation Of Sound Pressure Level At Far Field Of Vibratinmentioning

confidence: 99%

Suppression of sound radiation to far field of near-field acoustic communication system using evanescent sound field

Fujii

Wakatsuki

Mizutani

2015

Jpn. J. Appl. Phys.

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Effect of methods for determining the frequency dependency of hydrophone sensitivity phase on instantaneous acoustic pressure of diagnostic ultrasound

Chiba¹,

Yoshioka²,

Horiuchi³

2020

Jpn. J. Appl. Phys.

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Ultrasonic diagnostic equipment must balance advanced performance and the safety of patients. Precise techniques have been investigated for determining instantaneous acoustic pressure of broadband ultrasound radiated from the equipment. These techniques require frequency dependency of the amplitude and phase in a hydrophone sensitivity. Phase response can be a constant value or determined by methods such as theoretical calculation and calibration. However, few studies have focused on quantitative evaluation of the difference among the methods in terms of the instantaneous acoustic pressure. In the present study, we investigated the effect of each method on the negative peak value of the instantaneous acoustic pressure using several sound sources and hydrophones. The results revealed that the quantitative effect of each method for determining the sensitivity phase depends on the combination of sound sources and hydrophones due to the frequency dependency of the spectrum of the ultrasonic pulse and the sensitivity of the hydrophone.

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Evaluation of Hydrophone Spatial Averaging Effect in Near Field Measurement for Determining Mechanical Index

Cited by 2 publications

References 15 publications

Suppression of sound radiation to far field of near-field acoustic communication system using evanescent sound field

Suppression of sound radiation to far field of near-field acoustic communication system using evanescent sound field

Effect of methods for determining the frequency dependency of hydrophone sensitivity phase on instantaneous acoustic pressure of diagnostic ultrasound

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