摘要:

Experimental studies were performed on simple structural elements subjected to sinusoidal and random noise excitations in both linear and nonlinear response regions. On the basis of results obtained, a theory is formulated to account for the observed nonlinearity and to explain the possible factors causing sudden amplitude changes inherent in skewed response peaks identifiable to nonlinear cases. By using familiar resonance equations of one degree of freedom, an alternative approach is offered and compared with current understandings of acoustically induced stresses under high level excitation. Sample results will be employed to illustrate the feasibility of applying these findings to fatigue life expectancy calculations for random loading. The methods used in determining damping coefficient ratio will also be discussed.

ISSN:0001-4966    

DOI:10.1121/1.1936935

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

We were recently presented with the opportunity of making a series of noise and vibration measurements on a 25‐hp ventilating fan located above an occupied floor in an office building. The measurements were carried out during the process of trying to diagnose the cause of excessive noise levels in the office floor beneath the fan. Vibration levels at various parts of the fan base and noise levels in the office area below are presented for various degrees of isolation of the fan on its mounting.

ISSN:0001-4966    

DOI:10.1121/1.1936946

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP

摘要:

Stroboscopic lights and cameras are utilized to photograph the excitation and motion of piano, violin, and harp strings; high speed pictures of which will be shown. Fingers after plucking harp strings are not hit by the string, the shape of which may be easily computed. The wave character may be easily seen from the persistence of waveshape. Piano hammers hitting wound strings oscillate in the plane of the shank and hammer. The contact time (2–7 msec) is relatively independent of the speed of depression and frequency of the note (C1–C5). The piano action itself works much faster than it could be played. Very slight painting of a wound string greatly damps the sound. Terminal hammer speeds vary from 30 to 600 msec. The bow pulls the string aside without slipping. The return of the previously created pulse, reflected and inverted at the nut, snaps the string away from the bow in15of a period. The string deflects an equal and opposite amount before being picked up and replucked by the bow again. (This work was performed in Professor Harold Edgerton's laboratory and was supported by the National Association of Music Merchants.)

ISSN:0001-4966    

DOI:10.1121/1.1936950

出版商:Acoustical Society of America    

年代:1961

数据来源: AIP