摘要:

Progress in modeling the mechanical response of man exposed to various environmental forces is discussed. Starting with a mathematical description of the mechanical and physical characteristics of the integument, soft and hard tissue, the numerous approaches taken and the results obtained from modeling various integrated elements such as the human vertebral column under vibration and impact loads, the chest and respiratory system under vibratory and blast loads and of the whole body system for selected force input conditions and locations are reviewed. Generalized (five‐degree and more) freedom models are best suited to understand the correlation between the models derived to understand anatomical and physiological mechanical events and models used to explain the various injury mechanisms under environmental biodynamic loads (impact, blast, vibration, and noise). To derive a capability of modeling specific injury modes or experimentally observed probabilities of injury curves for various parenchymatous and hollow organs as a function of the force input variables, more detailed and specialized models are being used such as, for example, the lumped parameter, discrete parameter, and continuum model of the spine or models considering nonlinear tissue behavior. The status and value of these models for studying the body's physical and physiological response, for understanding and predicting injury mechanisms and probability of injury, for scaling the results of animal experiments, and for applying the models in protection engineering, such as escape and restraint systems design are demonstrated. There is need for further experimental as well as theoretical work in support of these practical biomedical as well as hardware requirements.

ISSN:0001-4966    

DOI:10.1121/1.1912782

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

An expression relating the normalized impact sound level (Ln) and the sound transmission loss (TL) of a floor is derived. It takes into account both the resonant and the forced response of the floor, thus extending the utility of the formulas derived previously by Heckl and Rathe into the frequency range below the critical frequency. This relation between normalized impact sound level and sound transmission loss permits an experimental evaluation of the potential TL of a floor partition in the presence of certain types of flanking.

ISSN:0001-4966    

DOI:10.1121/1.1912783

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

An investigation is made of the sound attenuation in a rectangular duct with two sides lined and with a uniform steady flow. It is found in the study of modal attenuation that the fundamental mode is not necessarily the least attenuated in lined ducts. It is shown that sound attenuation is influenced by the fluid flow; tuning frequency shifts to higher frequency with decreasing peak attenuation for downstream propagation and to lower frequency with increasing peak attenuation for upstream propagation. The effect of acoustic impedance on sound attenuation for a given duct geometry is presented as well as the effect of duct geometry on sound attenuation for a given acoustic impedance. Theoretically predicted attenuation spectra are compared with experimental results (test data for both rectangular flow duct and Boeing 747/JT9D engine). The predicted attenuation spectra are in very good agreement with the experimental results for downstream propagation. However, the present theory overpredicts the sound attenuation for upstream propagation.

ISSN:0001-4966    

DOI:10.1121/1.1912784

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

The multipath acoustic impulse response of the deep ocean has been measured over a 250‐NM propagation distance and has been used in an attempt to remove the multipath distortion of a broad‐band signal propagated over the same range interval. The process can be considered a coherent recombination of multipath arrivals, or a deconvolving of the received signal from the ocean impulse response. The measured impulse response is cross correlated with the distorted received signal to produce an estimate of the transmitted signal. Cross correlating this estimate with a replica of the original signal, and comparing this result to a cross correlation of the distorted received signal with the replica, shows a significant improvement in the former. Sidelobes due to undesired arrivals have been reduced to the point that, with a suitably chosen threshold, the message resolution time can approach the system inverse bandwidth rather than the multipath spread time, an improvement in resolution time of more than an order of magnitude. The experiment also demonstrates short‐term (e.g., 6‐sec) stability of the ocean impulse response, without establishing an upper limit for this stability.

ISSN:0001-4966    

DOI:10.1121/1.1912785

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

A two‐dimensional acoustic analog to gravity water waves traveling over constant depth is suggested as an experimental approach to problems of water‐wave scattering, harbor resonance, etc. The advantages of an acoustic model over the present water tank models are many, including a factor of 20–50 in cost, shortened time scale of experiments, sensitive readily available measuring equipment, etc.

ISSN:0001-4966    

DOI:10.1121/1.1912786

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

In the course of a study of the basic properties of acoustic linings for ducts transmitting air at high speeds, experimental evidence indicated that aerodynamic noise generated by the flowing air could limit the magnitude of noise attenuation inside the duct achievable by means of linings. A discussion of the matter leads to the conclusion that aerodynamic noise generated by the fluid flow could limit the maximum attenuation achievable.

ISSN:0001-4966    

DOI:10.1121/1.1912787

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

摘要:

This paper describes a simplified hooked‐wire electrode insertion procedure for laryngeal electromyography. Percutaneous and peroral implantation techniques are combined with an effective anesthesia routine to provide a technically straightforward and medically safe means for obtaining electromyographic data from the five intrinsic laryngeal muscles, simultaneously.

ISSN:0001-4966    

DOI:10.1121/1.1912788

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912790

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912794

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP

ISSN:0001-4966    

DOI:10.1121/1.1912799

出版商:Acoustical Society of America    

年代:1971

数据来源: AIP