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The role of phase in ultrasonic measurements of phase aberrating media using piezoelectric receivers.

机译：相位在使用压电接收器超声测量相差介质中的作用。

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摘要

This dissertation is the product of experiments designed to utilize the phase-sensitive characteristics of ultrasonic piezoelectric transducers to study and characterize the effects magnitude and phase aberrating media have on the propagation of ultrasonic waves. Two specific measurement artifacts were addressed resulting from propagation through magnitude and phase distorting paths: the spatial overlap and therefore interference of two or more ultrasonic waves and phase cancellation occurring at the surface of a phase sensitive receiver.;The study of magnitude and phase distorting media naturally lends itself to Kramers-Kronig analysis. The ultrasonic Kramers-Kronig relations couple the frequency dependent ultrasonic attenuation coefficient and the phase velocity through the fundamental notions of causality, linearity, and finite energy. Experiments demonstrated that even in the presence of phase cancellation artifacts, measurements of apparent attenuation and apparent phase velocity appear to remain causally consistent. A number of forms of the Kramers-Kronig relations found in the acoustics literature are derived, clarified, and related in this dissertation, and are applied to specific data sets to illustrate the utility and the limitations of the individual forms.;Measurements of the attenuation coefficient of cancellous bone have been shown to correlate well with bone mineral density, and ultimately with osteoporotic fracture risk. However, in the context of the Kramers-Kronig relations, published data reporting the attenuation coefficient of cancellous bone do not appear to be causally consistent with the measured dispersion. The cause of this disagreement might, in part, be due to the detection of multiple waves. In this dissertation it was experimentally shown, using a simple phantom capable of supporting multiple waves, that the effects of phase cancellation might be a potential source of the anomalous dispersion observed in studies of cancellous bone.;Artifacts due to phase cancellation at the surface of a phase sensitive receiver can be avoided if one is able to collect data phase insensitively. However, artifacts due to interference in the ultrasonic field can plague both phase sensitive and phase insensitive measurements systems. It was demonstrated that the largest possible phase insensitive receiving transducer should be implemented in order to supress the effects of interference on experimental data.
机译：本文是利用超声压电换能器的相敏特性研究和表征幅度和相差介质对超声波传播的影响的实验产品。解决了通过幅度和相位失真路径传播而导致的两个特定的测量伪影：空间重叠以及两个或多个超声波的干扰以及在相敏接收器表面发生的相位抵消。;幅度和相位失真介质的研究自然地适合进行Kramers-Kronig分析。超声Kramers-Kronig关系通过因果关系，线性和有限能量的基本概念将取决于频率的超声衰减系数和相速度耦合在一起。实验证明，即使在存在相位抵消伪像的情况下，表观衰减和表观相速度的测量也似乎保持因果一致。在本文中，得出，阐明和关联了声学文献中发现的多种形式的Kramers-Kronig关系，并将其应用于特定的数据集，以说明各个形式的效用和局限性。松质骨的骨密度已经显示出与骨矿物质密度，并最终与骨质疏松性骨折风险良好相关。但是，在Kramers-Kronig关系的上下文中，公开的数据报告了松质骨的衰减系数似乎与所测得的色散在因果上不相符。引起这种分歧的部分原因可能是由于检测到多个波浪。本文通过实验证明，使用能够支持多波的简单体模，相消除的影响可能是在松质骨研究中观察到的异常色散的潜在来源。如果一个相位敏感的接收机能够不敏感地收集数据，则可以避免这种情况。然而，由于超声场中的干扰造成的伪影会困扰相位敏感和相位不敏感的测量系统。事实证明，应采用最大可能的相位不敏感接收转换器，以抑制干扰对实验数据的影响。

著录项

  • 作者

    Bauer, Adam Quentin.;

  • 作者单位

    Washington University in St. Louis.;

  • 授予单位 Washington University in St. Louis.;
  • 学科 Physics Acoustics.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 200 p.
  • 总页数 200
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 声学;
  • 关键词

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