A two step viscothermal acoustic FE method
Previously, the authors presented a finite element for viscothermal acoustics. This element has the velocity vector, the temperature and the pressure as degrees of freedom. It can be used, for example, to model sound propagation in miniature acoustical transducers. Unfortunately, the large number of coupled degrees of freedom can make the models big and time consuming to solve. A method with reduced calculation time has been developed. It is possible to partially decouple the temperature degree of freedom, as result of the differences in the characteristic length scales of acoustics and heat conduction. This leads to a method that uses two sequential steps. In the first step, a scalar field containing information about the thermal effects is calculated (not the temperature). This is a relatively small FE calculation. In the second step, the actual viscothermal acoustical equations are solved. This calculation uses the field calculated in the first step and has the velocity vector and the pressure as the degrees of freedom. The temperature is not a degree of freedom anymore, but it can be easily calculated in a post processing step. The required computational effort is reduced significantly, while the difference in the results, compared to the fully coupled method, is negligible. Along with the theoretical basis for the method, a specific FE calculation is presented to illustrate its accuracy and improvement in calculation time.
Modelling of acoustic viscothermal losses using the Boundary Element Method: From method to optimization
A range of acoustic engineering problems require the inclusion of viscous and thermal dissipation to be modelled accurately. The dissipative effects are especially relevant when the geometric dimensions of the acoustic domain become small which is the case in acoustic transducers and hearing aids. Computer-based numerical tools such as the Finite Element Method can be used to model and investigate the performance of acoustic devices without expensive prototyping. Directly including acoustic dissipation into the Finite Element Method comes at a significant computational cost, sometimes making simulations on modest hardware problematic. An interesting alternative to the Finite Element Method, is the Boundary Element Method that is capable of including dissipation and at the same time avoid so-called boundary layer meshing. However, a potential shortcoming of the existing boundary element implementation is its use of tangential derivative finite difference coupling terms, that may lead to undesirable inaccuracies. This work presents two new coupling strategies that avoid the use of finite difference by either using boundary element itself or the shape functions to estimate the tangential derivatives. Numerical experiments demonstrate increased stability and error reduction when using the new coupling strategies. Furthermore, based on the improved viscothermal Boundary Element Method, a gradient-based shape optimization technique is developed. The shape optimization technique is used to optimize the absorption coefficient of two-dimensional quartewave and Helmholtz resonators located at an impedance tube termination. Shape optimization results show that high absorption coefficients are only obtained when viscous and thermal dissipation is modelled accurately. The shape optimization technique has the future potential of improving the design of acoustic devices which require the inclusion of viscous and thermal dissipation.
Understanding the broader implications of strategic evidence disclosure in police interviews with suspects
Police around the world present evidence to suspects at different points during the interview. Some psychologists suggest that police should strategically delay disclosing evidence and test the truthfulness of a suspect’s account by comparing it with the evidence. Moreover, psychologists suggest interviewers who plan strategic evidence disclosure might be less guilt-presumptive about the suspect because they must consider alternative explanations of the evidence as part of their planning. In contrast, many lawyers argue that police should not strategically disclose evidence as it undermines a suspect’s fair trial rights and prevents lawyers from advising suspects effectively before the interview. 
 
To address these conflicting perspectives from the domains of psychology and law, this thesis takes an interdisciplinary approach and considers strategic evidence disclosure within the broader legal context of a suspect’s custodial detention. First, a field study of police disclosure briefings with lawyers, lawyer-client consultations, and police interviews, and a survey of lawyers highlights how lawyers rely upon the police’s evidence to advise suspects in custody. When police strategically disclose evidence, lawyers cannot provide informed legal advice and tend to advise suspects to not answer police questions. Second, three experiments and a mini meta-analysis show that generating alternative evidential explanations for criminal cases, as interviewers planning strategic evidence disclosure might do, has a very small effect, or plausibly no effect, on people’s beliefs about the suspect’s guilt. Finally, a mock crime experiment shows that, even two months after a crime, truthful suspects’ accounts fit evidence that was strategically withheld more than deceptive suspects’ accounts did. Independent laypeople from a follow-up experiment could distinguish between these truthful and deceptive accounts. Together, these findings suggest that strategic evidence disclosure could help deception detection even months after a crime, but it also impinges upon suspects’ legal rights and is unlikely to make interviewers less guilt-presumptive.