A Likelihood-Maximizing Framework for Enhanced In-Car Speech Recognition Based on Speech Dialog System Interaction

Speech recognition in car environments has been identified as a valuable means for reducing driver distraction when operating noncritical in-car systems. Under such conditions, however, speech recognition accuracy degrades significantly, and techniques such as speech enhancement are required to improve these accuracies. Likelihood-maximizing (LIMA) frameworks optimize speech enhancement algorithms based on recognized state sequences rather than traditional signal-level criteria such as maximizing signal-to-noise ratio. LIMA frameworks typically require calibration utterances to generate optimized enhancement parameters that are used for all subsequent utterances. Under such a scheme, suboptimal recognition performance occurs in noise conditions that are significantly different from that present during the calibration session – a serious problem in rapidly changing noise environments out on the open road. In this chapter, we propose a dialog-based design that allows regular optimization iterations in order to track the ever-changing noise conditions. Experiments using Mel-filterbank noise subtraction (MFNS) are performed to determine the optimization requirements for vehicular environments and show that minimal optimization is required to improve speech recognition, avoid over-optimization, and ultimately assist with semireal-time operation. It is also shown that the proposed design is able to provide improved recognition performance over frameworks incorporating a calibration session only.

Competitive advantage through safety compliance : smaller firm responses to changes in the Australian occupational health and safety regulatory context

Smaller firms are often viewed as resistant to regulation due to cost burdens. However, evidence indicates that for some compliance is beneficial under certain conditions. Drawing on data on attitudes and responses of smaller firm owner-managers to changes in Australia’s harmonising work health and safety context we report on smaller firms’ responses to these changes. Despite uncertainty due to incomplete harmonisation, many owner-managers viewed safety compliance as important and necessary to do business. Those with negative views still linked positive safety performance to business outcomes. We categorise smaller firms’ responses and in this sample most are Positive Responders. We suggest ways forward for policy-makers to support smaller firms in complying with occupational health and safety regulation.

Estimating the mean critical gap

The estimation of the critical gap has been an issue since the 1970s, when gap acceptance was introduced to evaluate the capacity of unsignalized intersections. The critical gap is the shortest gap that a driver is assumed to accept. A driver’s critical gap cannot be measured directly and a number of techniques have been developed to estimate the mean critical gaps of a sample of drivers. This paper reviews the ability of the Maximum Likelihood technique and the Probability Equilibrium Method to predict the mean and standard deviation of the critical gap with a simulation of 100 drivers, repeated 100 times for each flow condition. The Maximum Likelihood method gave consistent and unbiased estimates of the mean critical gap. Whereas the probability equilibrium method had a significant bias that was dependent on the flow in the priority stream. Both methods were reasonably consistent, although the Maximum Likelihood Method was slightly better. If drivers are inconsistent, then again the Maximum Likelihood method is superior. A criticism levelled at the Maximum Likelihood method is that a distribution of the critical gap has to be assumed. It was shown that this does not significantly affect its ability to predict the mean and standard deviation of the critical gaps. Finally, the Maximum Likelihood method can predict reasonable estimates with observations for 25 to 30 drivers. A spreadsheet procedure for using the Maximum Likelihood method is provided in this paper. The PEM can be improved if the maximum rejected gap is used.

Development of a flexible design approach for the deflection zone behind road safety barriers

Flexible design practices broadly permit that design values outside the normal range can be accepted as appropriate for a site-specific context providing that the risk is evaluated and is tolerable. Execution of flexible design demands some evaluation of risk. In restoration projects, it may be the case that an immovable object exists within the zone of the expected deflection of a road safety barrier system. Only by design exception can the situation be determined to be acceptable. However, the notion of using flexible design for road safety barrier design is not well developed. The existence of a diminishing return relationship between safety benefits and provision of increased clear zone has been established previously. This paper proposes that a similar rationale might reasonably apply for the deflection zone behind road safety barriers and describes how the risk associated with road safety barriers might be quantified in order that defensible road safety barrier design can exist below the lower bounds of normal design standards. As such, the methodology described in this paper may provide some basis to enable road authorities to make informed design decisions, particularly for restoration, or “Brownfield”, projects.

Keeping international visitors safe on Australian beaches : informing the content of surf safety messages

In Australia, international tourists/visitors are one of the highest risk groups for drowning at beaches. Swimming in patrolled areas, between the flags, reduces the risk of drowning with most drownings occuring outside these areas. There is a need to understand beliefs which influence the extent to which international tourists/visitors intend to swim between the flags. The theory of planned behaviour (TPB) and, in particular, the indirect beliefs which underpin constructs in the model, represent a means of determining what factors influence this intention. The current study compared international visitors/tourists as having either low or high intentions to swim between the flags on a range of behavioural, normative, and control beliefs. A series of MANOVAs revealed significant differences between the groups in all three of the beliefs. The findings provide insight into potential foci for message content for use in educational campaigns aimed at keeping international visitors safe on Australian beaches.