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Developing Structural Health Monitoring (SHM) techniques for monitoring and evaluation in civil, mechanical and aerospace applications has a direct impact on public safety, primarily because it is related to reduced downtime and life extension of critical aging components and structures. Such trends are further fueled by the observed shift in modern inspection from "time-based" to "condition-based" maintenance approaches, which promise targeted evaluations when and exactly where they are needed. In this context, the objective of this dissertation is to develop a novel cross-validated framework of using acoustics-based methods for non-destructive testing & evaluation (NDT&E) with the ultimate goal to improve infrastructure condition assessment related primarily to the aerospace industry. This framework is called cross-validated as the primary NDT method of interest, the Acoustic Emission (AE) method, is used in conjunction with several other NDT methods including Guided Ultrasonic Waves (GUW), Digital Image Correlation (DIC) and Infrared Thermography (IRT). The proposed work is built therefore upon the idea of implementing a multimodal NDE approach including both novel hardware integration and data processing techniques that can mitigate existing challenges in reliably using AE in SHM applications. The advantage of designing reliable damage detectors is realized by integrating acoustic features with heterogeneous features that can provide complementary information on the initiation and development of damage. Several demonstrations in static and dynamic conditions of the proposed framework ranging from fundamental plasticity investigations to applied structural analysis are described to demonstrate the efficacy of the novel approach.