ISSN:0001-4966    

DOI:10.1121/1.1906509

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1906510

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1906511

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1906512

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1906513

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

摘要:

A small load on a bell usually changes the rapidity of beats and shifts the positions of nodal meridians. A study of the first three partials of one bell leads to the following conclusions. If the antinodal meridian nearest the position at which the load is to be applied is associated with the lower [higher] pitched of two beating components, the addition of the load increases [decreases]the rapidity of the beats, and also shifts the nearest antinodal meridian of the lower component toward the position of the load. Small increases in the load increase these effects.

ISSN:0001-4966    

DOI:10.1121/1.1906514

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

摘要:

An ideally stiff string has overtones νn, which are sharper than multiples of the fundamental, the inharmonicity being proportional to(n2 − 1). This well known theoretical result has been verified by Schuck and Young [J. Acous. Soc. Am.15, 1, (1943)] for typical strings. It is proposed to improve the tone of a piano string by attaching a small mass, thus lowering the frequency of each normal mode except those for which the mass is at a node. It turns out that for an ideally stiff string, approximate correction of a large number of overtones can be obtained with a single mass suitably located. In the limit of a large mass near the end of the string, the correction is exact for all overtones. A mass of the order of 0.1 g placed a few cm from the end of a typical string adjusts the first eight overtones to within a few hundredths of a semitone, a negligible inharmonicity. Improved tone is expected since the subjective fundamentals derived from difference tones between adjacent partials will show greatly reduced dispersion. The effect of the loading upon tuning would reduced the observed stretching of the octaves to a negligible amount. Deviations from ideal stiffness and the effect of adding two masses are also considered.

ISSN:0001-4966    

DOI:10.1121/1.1906515

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

摘要:

Webster's equation for the approximate formulation of the propagation of sound waves in horns is solved using two methods of approach. The first method considers a transmission line with variable parameters as the electrical analogue of the horn. This approach is specially useful in yielding generalized solutions for horns of finite length. The second method, based on an investigation of the singularities of Webster's differential equation, leads to the discovery of a great number of new families of horns.

ISSN:0001-4966    

DOI:10.1121/1.1906516

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

摘要:

The near and distant diffraction fields of a circular disk of zero thickness are plotted according to an exact theory. The results are compared with the Kirchhoff approximation and recent experimental data.

ISSN:0001-4966    

DOI:10.1121/1.1906517

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP

摘要:

A rigid circular plate was exposed to an essentially plane progressive sound wave, and the sound pressurepat various points on the surface measured relative to the free‐field pressurep0in the undisturbed incident wave by means of a small probe microphone. The diffraction effect |p/p0| was determined as a function of angle of incidence over a range of frequencies beginning with “long” wave‐lengths and extending into the region where the radiusaof the obstacle approximately equals the wave‐length. Expressed in customary notation,14 < ka < 8, wherekis the wave number of the incident wave. Data were obtained for angles of incidence θ = 0, 45, 135, and 180 degrees, where θ is measured with respect to the axis of the obstacle. Similar measurements for θ = 0 and 180° were made for a rigid square plate with side 2a.Approximate contour maps of the quantity |p/p0| in decibels have been prepared from the experimental data portraying the pressure distribution on the surface of the plates.The experimental results are compared with computed values of |p/p0| obtained from an approximate theory in which an attempt is made to solve the problem in terms of a scattered potential calculated as if the face of the obstacle were surrounded by an infinite baffle. The agreement is quite good on the “illuminated” side of the plates, i.e., for θ = 0 and 45° and on the “shadow” side for θ = 180°. The agreement for 135 degree incidence is generally poor, although the computed values show the trends of the experimental data in many instances. At low frequencies the theory gives values which are somewhat too high on the illuminated side and too low on the shaded side.The values of |p/p0| obtained from the exact expression of the diffraction of a plane wave by a disk of zero thickness and for perpendicular incidence are found to be in good agreement with experiment and the approximate theory on the illuminated side (θ = 0) and they agree reasonably well on the shaded side (θ = 180°) for 1⩽ka⩽5. The region near the edge shows discrepancies which are to be expected from the finite thickness of the circular plate (approx.a/12).It is concluded that the approximate theory mentioned above is capable of predicting the diffraction effect |p/p0| on the illuminated side of the obstacles in the frequency range covered by this study for the angles of incidence investigated. On the shadow side the theory can be expected to yield usably approximate answers only for θ = 180°. There are reasonable grounds for the assumption that similar predictions can be made for points on or “near” the surface of “thin” plane obstacles of arbitrary shape and for other acute angles of incidence not too close to θ = 90°.

ISSN:0001-4966    

DOI:10.1121/1.1906518

出版商:Acoustical Society of America    

年代:1949

数据来源: AIP