It is well known that some auditory sensation is caused by ultrasound through bone conduction. In order to understand the mechanism of the perception of ultrasound and its effects on man, we investigated its pitch, loudness, temporary threshold shift and masking caused by ultrasound, including its threshold. Some interesting facts are found from these experiments. Namely, we can clearly perceive the pitch of ultrasound and it slightly varies with the frequency of stimulus, loudness level of ultrasound whose SPL is 2 dB above the threshold level becomes60phon, and recruitment appears in judgment of loudness. Moreover ultrasound can mask the sound in audio frequency range and TTS is observed in that range. From these results, we assume ultrasound is perceived by the vibration of around the basal end of basilar membrane and the distribution of excited position varies more or less with the ultrasonic frequency. And there exists a possibility that hearing damage will occur when we hear the ultrasound from some equipments or instruments.

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This paper presents a new method for calculating the velocity potential Ø of scattered ultrasonic waves from a rigid sphere placed freely in the nearfield of a circular piston in an infinite baffle. The solution Ø is given in the form of an infinite series of spherical surface harmonics as a function of reduced quantities ka, kr₀, kR, kr, etc., where k is the wavenumber, a is the radius of the sphere, r₀ is the distance from the piston to the center of the sphere, and R is the radius of the piston. The theoretical framework has the advantages that it includes neither approximations nor numerical integrations, and that it is applicable to elastic or compressible sphere cases with slight modifications of the boundary conditions.

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An ultrasonic resonator equipped with the piezoelectric polymer film was constructed for the measurement of velocity and absorption in liquids. The pair of transducers composing the resonator cavity was made of PVDF sheet, 30μm thick, which was coated by aluminum electrode on both surfaces. Some preliminary experiments were made in ethanol as a standard liquid at 25°C over the frequency range from 100 kHz to 2 MHz to examine performance of the resonator and also to determine the instrumental cavity loss. The results suggested that the PVDF can make an almost ideal transducer for the ultrasonic resonator method after some minor technical problems are solved.

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Modifying ink-jet techniques used for character displays, an atomizer with a multipinhole plate is trial-made. The pinhole plate with seven pinholes of 80μm in diameter is piezoelectrically driven at 34.4 kHz by a bimorph structure. Due to the intrinsic nature of the technique, important merits such as the uniform diameter of the atomized droplets, easiness of changing the diameter and of control of the atomizing rate may be expected. Employing the trial-made atomizer, the principle and physical properties of the ultrasonic atomization are experimentally studied. The displacement amplitude distribution of the plate, threshold pressure of atomization, phase of ejection, diameter and amount of droplets as a function of applied voltage are measured to make clear the physical properties of the technique. As a result of experiments, it is made clear that the surface tension of the liquid acts as a valve and that the atomizer has a self-acting liquid supply itself and does not need any pumping apparatus.

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Ultrasound focusing transducers with a conical or a toroidal radiating surface are studied theoretically and experimentally, and it is shown that these non-spherical transducers have high capability in converging the sound beam over a long range along the axis. The axial and lateral field distributions are calculated for toroidal transducers as well as for conical transducers, and the focusing properties are evaluated for various aperture geometries. To facilitate the transducer fabrication, quasi-toroidal transducers are proposed, which are composed of a few conical or several cylindrical segments. Experimental examinations using flexible piezoelectric polymer sheets show that the conical and quasi-toroidal transducers of 1-inch diameter operating at a frequency of 3.6 MH2 produce the sound beam with the full-width at half-maximum of6to10wavelengths in the range of70mm to 220 mm.

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It has been shown that echoes obtained in conventional pulse echo systems can be expressed by an integral which contains the velocity potential of thefield in the integrand. In order to perform the integral it is necessary to expand the velocity potential into a series of functions which include no integrations. The series expansions which have been reported so far converge rather slowly and one of them requires different forms of the series depending on the position in the field. Consequently they are not adequate to our purpose. In this paper the velocity potential of a circular concavetransducer is expanded into a series of the functions J_n (x)/x (n=1, 3, 5, …). This series is not a rigorous one and holds for far field, but it converges very fast and for most cases first several terms are sufficient to express the velocity potential approximately.

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The SAW energy is concentrated into the SAW waveguide and is propagating along it without radiation. However the energy can radiate from the waveguide if there are corrugations at waveguide edges. This paper described the radiation characteristics from the rectangular edge corrugations of SAW Δν/ν waveguide on YZ-LiNb0₃. The theoretical characteristics is derived from the perturbation method and it is found that the SAW energy radiates toward only one side of the waveguide, if the corrugation size and position at the both edges of the waveguide are suitably designed. The experimental results are qualitatively in agreement with theoretical predication.

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