In situ control of therapy parameters based on real time monitoring of ablation targets is a promising strategy to improve the safety and efficacy of extracorporeal high-intensity focused ultrasound (HIFU). In this work, we present an approach to evaluate the accuracy of acoustic monitoring techniques using computational fluid dynamics simulation. In the numerical setup, computed tomography images are used to model anatomical structures that can scatter and dissipate therapy waves in the body of the patient, including fat, bone, tissues, and organs. An in-house, compressible flow solver is used to simulate ultrasound generation from a transducer, nonlinear focusing of the wave toward therapy targets in the body, and backscattering toward the body surface. The simulation also captures excitation of cavitation bubbles in the focal region and their influence on the pressure fields in the body. Sensing and processing of the scattered signals provide for acoustic monitoring. For demonstration, we apply this approach to HIFU-based lithotripsy that uses burst waves with a focal pressure of O(1) MPa and frequency of O(100) kHz. Accuracies of acoustic monitoring are compared for various sensing and signal processing methods in quantifying the effects of anatomical structures and cavitation on ultrasound irradiation into targeted kidney stones. Finally, we discuss the use of these numerical experiments for control and optimization of therapy parameters. [Work supported by NIH P01-DK043881.]