Volume 14, Issue 2, October 1942
Index of content:
14(1942); http://dx.doi.org/10.1121/1.1916208View Description Hide Description
Edge tones are produced when wind from a slit strikes an opposed edge under suitable conditions. Two types of such tones are here distinguished. The first type is the one that has hitherto been most investigated. In it a gradual change of either wind pressure or distance from slit to edge gives several “stages” of tone, in each of which the pitch changes gradually, separated by sudden “jumps” from one pitch to another. The second type occurs at higher pressures, where the sheet of air that escapes from the slit is probably turbulent, and in this type the jumps in pitch are absent. In the first type the ranges of pitch between jumps are never much in excess of an octave, whereas in the second type there may be a continuous range over several octaves. Most of the tones now investigated were obtained with a brass wedge above a slit 0.7–0.8 mm wide. The wind escaped from the slit at velocities up to about 50 m/sec. The higher pitched tones were not studied, but only those running up to about 1900∼/sec. Tones of the first type are less simple than has usually been indicated, and they are described. Tones of the second type become practically simple as they fall toward inaudibility. A number of equations are tested to see which expresses best the relation between frequency N, slit‐edge distance h, and the velocity U with which the wind escapes from the slit. It is concluded that the most satisfactory equation is , where s has, respectively, the values 1.00, 1.14, 1.22, 1.43, and j the values 3.9, 11.8, 24.0, 6.8, for stage I, stage II, stage III, and the second type of edge tones. In this equationh is in mm, and U in cm/sec. Various edge tone phenomena are given qualitative explanation on the basis of the pressure caused alternately on the two sides of the wedge by the injected air, together with the Bernoullieffect on the transverse velocity in the constriction between slit and edge. The velocity of the wind from the windway of one c 2organ pipe is measured, and found to be about 26 m/sec.
14(1942); http://dx.doi.org/10.1121/1.1916209View Description Hide Description
An analysis with friction shows that the mobility for a Haskell organ pipe is not exactly equal to that for a simple open pipe. The inclusion of friction probably explains the observation that a Haskell pipe and a simple open pipe blown in exactly the same way show substantial differences in harmonic structure.
14(1942); http://dx.doi.org/10.1121/1.1916211View Description Hide Description
The effect of humidity on the velocity of sound waves is investigated (Eq. (5), Table I). The radius of curvature for a ray of sound which is propagated in the direction of the wind is given [Eq. (13)] and discussed. The amplitudes of sound waves as a function of the distance are given [Eq. (17)], and the relative importance of the quantities involved is discussed.
14(1942); http://dx.doi.org/10.1121/1.1916212View Description Hide Description
14(1942); http://dx.doi.org/10.1121/1.1916213View Description Hide Description
Quantitative measurements are reported on the intensities of subjective tones produced within the human ear under single and dual tone excitation. The measurements are made by the exploring tone method. The even and odd subjective harmonics show some differences, indicating that the organ, or set of organs, producing non‐linearity is not the same as the source of asymmetry. The intensities at which these two distorting effects first appear are not the same. The subjective summation tones are, in general, weaker than the corresponding difference tones of the same order. These differences are to be expected if auditory masking is a process occurring within the hearing mechanism.