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Volume 11 (1955)
- Issue 4 Pages 213-
- Issue 3 Pages 149-
- Issue 2 Pages 83-
- Issue 1 Pages 1-
Volume 11, Issue 4
Displaying 1-8 of 8 articles from this issue
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Kenjiro Owada, Keijiro Koga, Yoshiko NakamuraArticle type: Article
1955 Volume 11 Issue 4 Pages 213-218
Published: December 30, 1955
Released on J-STAGE: June 02, 2017
JOURNAL FREE ACCESSMeasurements for determining the normal persons' threshold of audibility by air and bone conduction were made. For the calibration of sound pressure on the ear-piece (receiver), a similar apparatus to that of National Bureau of Standard's 9A Coupler was used here. All the threshold values in this paper are indicated by db unit with 0 db as one per sq. cm at each of the frequencies indicated below. The average threshold by air conduction for 50 normal ear per respective frequencies were as follows; -13. 0 at 125 c/s, -37. 2 at 250 c/s, -53. 3 at 500 c/s, -60. 8 at 1000 c/s, -60. 0 at 2000 c/s, -61. 5 at 4000 c/s, and -56. 3 at 8000 c/s. The threshold of audibility by bone conduction was measured in pressure by applying the bone conduction ear-piece (receiver) equipped with BaTio_3 ceramic element on the mastoid process. The values below represent the pressure in decibels with 0 db as one dyne. The average values for 30 normal ears were as follows: 22. 0 at 250 c/s, 18. 6 at 500 c/s, 3. 4 at 1000 c/s, -0. 7 at 2000 c/s and 11. 4 at 4000 c/s. "Normal ears" were defined in this paper as those having threshold values of within ±15db of the mean value in case of air conduction, and as those with threshold value of within ±20 db of the mean value in case of bone conduction.View full abstractDownload PDF (587K) -
Toshio Hayasaka, Kenro Masuzawa, Masayuki MurakamiArticle type: Article
1955 Volume 11 Issue 4 Pages 218-221
Published: December 30, 1955
Released on J-STAGE: June 02, 2017
JOURNAL FREE ACCESSWhen a loudspeaker is used as the laboratory standard, following characteristics are required: 1) The response-frequency characteristics is to be monotone. 2) Response is not to be affected by temperature and humidity. 3) Amplitude distortion is to be small. Since the response of a paper-cone speaker fluctuates by the variation of temperature and humidity of the room, it cannot be used as a laboratory standard. Therefore, a loudspeaker for laboratory use, was designed employing metallic titanium as the diaphragm material. The fluctuation of response due to the variation of temperature and humidity was very small and the response-frequency characteristics was flat over the range of 50 c/s to 10000 c/s. In designing the cone, calculations were made so as to make the frequency characteristics of sound pressure on the front axis to be flat when a constant driving force is applied to a mass-controlled piston diaphragm.View full abstractDownload PDF (438K) -
Kiyoshi Awaya, Isao Yokoyama, Masayuki MatsuiArticle type: Article
1955 Volume 11 Issue 4 Pages 222-231
Published: December 30, 1955
Released on J-STAGE: June 02, 2017
JOURNAL FREE ACCESSAlthough it is known in the measurements of electromagnetic wave that the directional coupler is a useful means in separating an incident wave from a reflected wave at a fixes position, the utilization of the directional coupler in this form has not yet being introduced in acoustics. Authors are suggesting the application of the acoustic coupler in the two new phases in acoustics, namely; in measuring of amplitude reflection coefficients (complex quantity) and in directional microphones. The purpose of this paper is to explain their advantages and the prospection extensive usage in the future. The directional coupler when applied for measuring amplitude reflection coefficients, the system as a whole is a stationary equipment having no movable components, so it would be free from errors causable from mechanical looseness, thus enabling a practical accuracy at higher frequencies together with the virture of shortening the time considerably for its operation. A directional microphone of this type is simply composed of a single metal or a plastic tube, terminated with a non-reflective material at one end and a microphone at the other end and having a row of small holes on its side. The dimension of this microphone being small, handling would be easy. By incorporating acoustic networks inside the tube various characteristics will be available.View full abstractDownload PDF (896K) -
Isao Yokoyama, Kiyoshi AwayaArticle type: Article
1955 Volume 11 Issue 4 Pages 232-238
Published: December 30, 1955
Released on J-STAGE: June 02, 2017
JOURNAL FREE ACCESSWhen acoustic impedances are measured by the standing wave method, scattered waves generated at the movable microphone in the acoustic tube cause errors in measured values of acoustic impedances. Since these errors are complicatedly affected by reflections from the both ends of the tube, it is very difficult to correct these errors directly and to acquire the true value of the acoustic impedance. The correction will be made much more easily if another fixed microphone is added at the test piece end of the standing wave tube. The standing wave is then measured as the ratio of output of the movable microphone to that of the fixed microphone. It could be proved theoretically that the ratio of the true value to the measured value of reflection coefficients depends solely upon the four-terminals coefficients of the movable microphone. Following the method described above, the error caused by the scattered waves can easily be corrected by comparison with the measured value of a standard sample, or by calculation involving four-terminals coefficients of the movable microphone.View full abstractDownload PDF (660K) -
Eiji MoriArticle type: Article
1955 Volume 11 Issue 4 Pages 238-247
Published: December 30, 1955
Released on J-STAGE: June 02, 2017
JOURNAL FREE ACCESSTheoretical and experimental methods have been established for measuring mechanical load impedance at the tool tip surface in ultrasonic machining. Expression formulas of the mechanical load impedance were derived from the electrical equivalent circuit of the mechanical vibrating system, consisting of a magnetostriction transducer, a metallic horn and a tool. Mechanical load impedance was calculated by the previous formulas in measuring the free impedance of the transducer with no load and with load. The free impedance of the transducer at high power level was obtained by measuring the terminal voltage, current and electric power by a special high frequency wattmeter. The magnetostriction transducer was made of nickel, and the natural frequency was 20. 2 kc/s. Two types of exponential horns, (rectangular and circular section), two tools (rectangular thin plate and circular rod) and two kinds of abrasives (green carborandum of 200 and 1000 mesh) were used fir the experiments. It was found out that the mechanical load impedance consists of mechanical resistance and stiffness reactance, and that it takes different values by the shape and vibration amplitude of the tool tip, even when the other conditions (static contact pressure, machined depth and kinds of abrasive, etc. ) were the same. When static contact pressure and vibration amplitude of the tool tip were increased, the mechanical resistance and stiffness were also increased, but the variation of the resonance frequency of the mechanical vibration system were only 1〜2%. In the case of the tool of circular section, mechanical resistance and stiffness were 3x10^2 dyne/kine/mm^2 and 3x10^7 dyne/cm/mm^2 respectively at 250 gr/mm^2 for steatite and 3x10^3 dyne/kine/mm^2 and 5x10^7 dyne/cm/mm^2 respectively at 400 gr/mm^2 for super hardness alloy. The effects of grain size of the abrasive on the value of the mechanical load impedance were found to be very sligit.View full abstractDownload PDF (996K) -
[in Japanese]Article type: Article
1955 Volume 11 Issue 4 Pages 248-254
Published: December 30, 1955
Released on J-STAGE: June 02, 2017
JOURNAL FREE ACCESSDownload PDF (733K) -
[in Japanese]Article type: Article
1955 Volume 11 Issue 4 Pages 255-263
Published: December 30, 1955
Released on J-STAGE: June 02, 2017
JOURNAL FREE ACCESSDownload PDF (959K) -
[in Japanese], [in Japanese]Article type: Article
1955 Volume 11 Issue 4 Pages 264-271
Published: December 30, 1955
Released on J-STAGE: June 02, 2017
JOURNAL FREE ACCESSDownload PDF (920K)
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