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Journal of the Acoustical Society of America

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Apr 1938

Volume 9, Issue 4, pp. 275-354


Loudness, Masking and Their Relation to the Hearing Process and the Problem of Noise Measurement

Harvey Fletcher

J. Acoust. Soc. Am. Volume 9, Issue 4, pp. 275-293 (1938); (19 pages) | Cited 3 times

Online Publication Date: 15 Jun 2005

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Limits of Audition for Bone Conduction

Norman A. Watson

J. Acoust. Soc. Am. Volume 9, Issue 4, pp. 294-300 (1938); (7 pages)

Online Publication Date: 15 Jun 2005

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The laboratory facilities and apparatus described in an earlier paper were used to study the normal intensity and frequency limits of audition for bone conduction. The condition of the observer's head to give greatest acuity for pure tones, and the optimal total force of application and area of the vibrator button were found to be essentially the same as for speech sounds. Acuity was found to vary with the position of application of the vibrator; for example, the maximum variation with position of the 1000‐cycle threshold was 18 db. A threshold for open canals was determined for the frequency range 80–2000 cycles, without interference from stray air radiation (18 normal observers). Above 2000 cycles air radiation interfered with open canal tests to such an extent that a special technique was devised to obviate its effects. The occluded threshold curve, for a single normal individual, lay below his open canal curve over the range 80–2000 cycles, and also at 10,000 cycles. The usable intensity range for open canals was tentatively determined; it is a maximum of 80–90 db at 1000–2000 cycles. The total audible frequency range for open canals was found to be at least 25–17,000 cycles.

Periods of Longitudinal Vibration of Steel Cones and Truncated Cones

G. W. Pierce and Atherton Noyes, Jr.

J. Acoust. Soc. Am. Volume 9, Issue 4, pp. 301-307 (1938); (7 pages)

Online Publication Date: 15 Jun 2005

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The Role of the Speaker Impedance in Resonance in a Closed Pipe

William D. Phelps

J. Acoust. Soc. Am. Volume 9, Issue 4, pp. 308-311 (1938); (4 pages)

Online Publication Date: 15 Jun 2005

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An analysis is made of a standing wave resonance system consisting of an eight‐foot iron pipe with an eight‐inch dynamic speaker at one end and a movable iron piston at the other. Considering the speaker both as a source and as an impedance, expressions are derived for the phase shift, φ1, of the pressure wave at the speaker, and for the pressure amplitude in the tube. The relation connecting l and λ at resonance is found to be l  =  (n + φ/2π)λ/2, placing the speaker at a distance (φ/4π)λ from the first particle velocity node. (Contrast this equation with the relation l  =  nλ/2 for a tube rigidly closed at both ends.) Initial resonance frequencies and a pressure‐frequency curve are computed for comparison with experimental data. The possibility of using the resonance conditions for measuring the impedance of diaphragms is pointed out.

Absolute Sound Intensity in Liquids by Spherical Torsion Pendula

Elias Klein

J. Acoust. Soc. Am. Volume 9, Issue 4, pp. 312-320 (1938); (9 pages) | Cited 1 time

Online Publication Date: 15 Jun 2005

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These experiments demonstrate the use of spherical radiometers to determine the energy density in an acoustic field. It is shown that the theoretical work of King is applicable to the measurement of radiation pressure in liquids. Considering the torsion pendulum as an absolute instrument, pressure microphones are calibrated as secondary standards.

Tones Produced by a Wire Placed in an Ignited Gas Jet

J. J. Coop

J. Acoust. Soc. Am. Volume 9, Issue 4, pp. 321-330 (1938); (10 pages)

Online Publication Date: 15 Jun 2005

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It was found that a wire placed in an ignited gas jet would produce a tone when the velocity of the gas reached a critical value. The tone was amplified by use of a second wire and by use of a photoelectric cell. The relation between the diameter D of the wire, the diameter O of the orifice, the distance d of the wire from the orifice and the critical velocity Ui for the initiation of the tone was found to be of the form OUi  =  kd/D + C, where k and C are constants. This equation is not linear for values of d less than one centimeter. It appears that a similar relation exists for the critical velocity Uf at which “flaring” starts. The products OUi/ν, where ν is the kinematic viscosity, were found to be nearly the same for the two gases used. At any distance of a wire from the orifice the frequency of the tone was found to be a linear function of the efflux velocity of the gas. The expression for the frequency was found to be of the form N  =  k/D(U − U0), where k is a constant and U0 is the velocity intercept. The quantity D(dN/dU) has an average value of about 0.047 for wire diameters between 0.04 and 0.1 cm. For a constant frequency the relation between the orifice velocity and the distance was found to be of the form U  =  Kdn, where n is approximately ½; nO½ is a constant and KO½ nearly constant. An approximate relation between frequency, velocity, and distance is given by N  =  kU/d½ + C, where k and C are constants. A thin metallic sheet placed against the wire on the downstream side prevents the production of the tone. As the distance between this sheet and the wire is varied the tone ceases at a critical distance, which is a function of the velocity and the diameter of the wire. For a fixed velocity this critical distance is proportional to the square root of the diameter of the wire. It was concluded that the tone is an Aeolian tone modified by the flow of one stream into a similar fluid at rest. An equation of the form N  =  kU/D was derived on the basis of the Bernard‐Karman vortex theory. By comparing experimental with theoretical results it was concluded that for an ignited jet the density varies inversely as the distance from the orifice.

Sound Absorption and Attenuation by the Flue Method

Hawley O. Taylor and Chalmers W. Sherwin

J. Acoust. Soc. Am. Volume 9, Issue 4, pp. 331-335 (1938); (5 pages)

Online Publication Date: 15 Jun 2005

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The M.K.S. System of Units Applied to Electroacoustics

A. E. Kennelly and Jackson H. Cook

J. Acoust. Soc. Am. Volume 9, Issue 4, pp. 336-340 (1938); (5 pages)

Online Publication Date: 15 Jun 2005

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The Position of the Vibrator in the Experiments of Melde and Kundt

B. J. Miller and L. O. Olsen

J. Acoust. Soc. Am. Volume 9, Issue 4, pp. 341-343 (1938); (3 pages)

Online Publication Date: 15 Jun 2005

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It is shown that the point of application of the obligatory motion in the experiments of Melde and Kundt is at a displacement “node” in the driven medium. The word “node” means a point of minimum amplitude in the standing wave in the tube or string. This result agrees with that of Rayleigh but is obtained in a simpler manner. The discussion is presented briefly to make the results more available as current textbooks indicate a nearly universal misunderstanding of these two well‐known experiments.

The Sound of Bells

Jan Arts

J. Acoust. Soc. Am. Volume 9, Issue 4, pp. 344-347 (1938); (4 pages)

Online Publication Date: 15 Jun 2005

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The Velocity of Sound in Single Crystals of Bismuth

A. B. Focke, R. B. Lindsay, and C. R. Wilks

J. Acoust. Soc. Am. Volume 9, Issue 4, pp. 348-351 (1938); (4 pages)

Online Publication Date: 15 Jun 2005

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The velocity of compressional waves in single crystals of bismuth of two orientations (P1 and P3) of the principal axis has been measured. The specimen to be tested (around 10 cm in length) is inserted between two longer steel rods, one of which is driven by a loudspeaker coil while the other has a free end. The velocity is computed from the observed distance between two nodes when all or part of the crystal is included between them. For the P1 and P3 orientations the velocities are found to be 2028 meters/sec. and 1541 meters/sec., respectively, and the corresponding Young's moduli come out to be 4.043 × 1011 dynes/cm2 and 2.245 × 1011 dynes/cm2.

An Improved Method for Obtaining Photographs of Ripple Wave Actions

M. E. Raquet and F. R. Watson

J. Acoust. Soc. Am. Volume 9, Issue 4, pp. 352-353 (1938); (2 pages)

Online Publication Date: 15 Jun 2005

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A “Foaming Tone” Obtained from Vibrating Strings and Rods

Tai Chung‐Ling

J. Acoust. Soc. Am. Volume 9, Issue 4, pp. 354-354 (1938); (1 page)

Online Publication Date: 15 Jun 2005

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