Index of content:
Volume 120, Issue 2, August 2006
- STRUCTURAL ACOUSTICS AND VIBRATION 
120(2006); http://dx.doi.org/10.1121/1.2217371View Description Hide Description
The acoustic signature of a footstep is one of several signatures that can be exploited for human recognition. Early research showed the maximum value for the force of multiple footsteps to be in the frequency band of . This paper reports on the broadband frequency-dependent vibrations and sound pressure responses of human footsteps in buildings. Past studies have shown that the low-frequency band (below ) is well known in the literature, and generated by the force normal to the ground/floor. The seismic particle velocity response to footsteps was shown to be site specific and the characteristic frequency band was . In this paper, the high-frequency band (above ) is investigated. The high-frequency band of the vibration and sound of a human footstep is shown to be generated by the tangential force to the floor and the floor reaction, or friction force. The vibration signals, as a function of floor coverings and walking style, were studied in a broadband frequency range. Different walking styles result in different vibration signatures in the low-frequency range. However, for the walking styles tested, the magnitudes in the high-frequency range are comparable and independent of walking style.
120(2006); http://dx.doi.org/10.1121/1.2211567View Description Hide Description
This investigation deals with the vibration of and the acoustic radiation from a simply supported rectangular plate with elastic restraints against edge rotations. The displacement of the plate is first sought as a series expansion in terms of the beam functions. Each of the beam functions is then expressed as the linear combination of a Fourier sine series and a complementary sufficiently smooth function that is introduced to ensure and improve the convergence of the Fourier series expansion. To facilitate the acoustic analysis, the plate displacement is eventually simplified to a standard Fourier sine series. The modal and acoustic characteristics of square plates are studied for different restraining stiffnesses and configurations. It is shown that the modes of the restrained plates can be considerably different from those in the simply supported case, so are the corresponding modal radiation efficiencies. The proposed method is generally applicable to rectangular plates elastically restrained along any edge(s), and the acoustic calculations are valid for an arbitrary acoustic or structural (modal) wave number.