A psychophysiological evaluation of the perceived urgency of auditory warning signals

One significant concern that pilots have about cockpit auditory warnings is that the signals presently used lack a sense of priority. The relationship between auditory warning sound parameters and perceived urgency is, therefore, an important topic of enquiry in aviation psychology. The present investigation examined the relationship among subjective assessments of urgency, reaction time, and brainwave activity with three auditory warning signals. Subjects performed a tracking task involving automated and manual conditions, and were presented with auditory warnings having various levels of perceived and situational urgency. Subjective assessments revealed that subjects were able to rank warnings on an urgency scale, but rankings were altered after warnings were mapped to a situational urgency scale. Reaction times differed between automated and manual tracking task conditions, and physiological data showed attentional differences in response to perceived and situational warning urgency levels. This study shows that the use of physiological measures sensitive to attention and arousal, in conjunction with behavioural and subjective measures, may lead to the design of auditory warnings that produce a sense of urgency in an operator that matches the urgency of the situation.     

Perceived urgency mapping across modalities within a driving context

Hazard mapping is essential to effective driver-vehicle interface (DVI) design. Determining which modality to use for situations of different criticality requires an understanding of the relative impact of signal parameters within each modality on perceptions of urgency and annoyance. Towards this goal we obtained psychometric functions for visual, auditory and tactile interpulse interval (IPI), visual color, signal word, and auditory fundamental frequency on perceptions of urgency, annoyance, and acceptability. Results indicate that manipulation of IPI in the tactile modality, relative to visual and auditory, has greater utility (greater impact on urgency than annoyance). Manipulations of color were generally rated as less annoying and more acceptable than auditory and tactile stimuli; but they were also rated as lower in urgency relative to other modality manipulations. Manipulation of auditory fundamental frequency resulted in high ratings of both urgency and annoyance. Results of the current investigation can be used to guide DVI design and evaluation.     

A user-centred approach to the design and evaluation of auditory warning signals: 1. Methodology

This paper presents a method for the design and evaluation of auditory warning signals modelled on an existing internationally standardized method for evaluating public information systems (ISO/DIS 7001: 1979). The procedure is essentially user-centred, capitalizing upon users' associations between sounds and their meanings. The procedure is presented in a step-by-step manner, from the initial identification of referents for which warnings might be required, through the generation of ideas for warning sounds, an appropriateness ranking test, a learning and confusion test, an urgency mapping test, a recognition test and an operational test. Practical issues are discussed with respect to each of the stages, and suggestions are made as to courses of action that might be taken if problems are encountered. Theory behind the relationship between sound and meaning is discussed with reference to the practical issues addressed.     

Judging the urgency of non-verbal auditory alarms: a case study

When designed correctly, non-verbal auditory alarms can convey different levels of urgency to the aircrew, and thereby permit the operator to establish the appropriate level of priority to address the alarmed condition. The conveyed level of urgency of five non-verbal auditory alarms presently used in the Canadian Forces CH-146 Griffon helicopter was investigated. Pilots of the CH-146 Griffon helicopter and non-pilots rated the perceived urgency of the signals using a rating scale. The pilots also ranked the urgency of the alarms in a post-experiment questionnaire to reflect their assessment of the actual situation that triggers the alarms. The results of this investigation revealed that participants' ratings of perceived urgency appear to be based on the acoustic properties of the alarms which are known to affect the listener's perceived level of urgency. Although for 28% of the pilots the mapping of perceived urgency to the urgency of their perception of the triggering situation was statistically significant for three of the five alarms, the overall data suggest that the triggering situations are not adequately conveyed by the acoustic parameters inherent in the alarms. The pilots' judgement of the triggering situation was intended as a means of evaluating the reliability of the alerting system. These data will subsequently be discussed with respect to proposed enhancements in alerting systems as it relates to addressing the problem of phase of flight. These results call for more serious consideration of incorporating situational awareness in the design and assignment of auditory alarms in aircraft.     

Using voice and print directives and warnings to supplement product manual instructions

The present research investigated the effect of supplemental messages on compliance with and recall of product manual instructions. During the unpacking of a computer disk drive supplemental messages were presented that concerned procedures to prevent product damage during installation. The supplemental messages were either presented by digitized voice (auditory) or by printed placard (visual). Two types of message were presented. Either the message gave specific warning instructions or directed users to a specific location in the product manual where the instructions were printed. Results show that the supplemental voice and print messages increased compliance behavior compared to the manual only. The voice message produced the greatest recall compared to print or no supplement. There was no effect of the warning vs directive manipulation. The results support the use of supplemental messages to communicate particularly important information. Implications for the delivery of warning instructions in product manuals are discussed.

Relevance to industry

Manufacturers are responsible for warning users about hazards associated with foreseeable use or misuse of their products. The present study shows that a supplemental print or voice message combined with a typical product manual produces significantly higher compliance than the manual alone.     

On the hazard of quiet vehicles to pedestrians and drivers

The need to produce more efficient and less polluting vehicles has encouraged mass production of alternative energy vehicles, such as hybrid and electric cars. Many of these vehicles are capable of very quiet operation. While reducing noise pollution is desirable, quieter vehicles could negatively affect pedestrian safety because of reduced sound cues compared to louder internal combustion engines. Three studies were performed to investigate people's concern about this issue. In Study 1, a questionnaire completed by 378 people showed substantial positive interest in quiet hybrid and electric cars. However, they also indicated concern about the reduced auditory cues of quiet vehicles. In Study 2, 316 participants rated 14 sounds that could be potentially added to quiet alternative-energy vehicles. The data showed that participants did not want annoying sounds, but preferred adding “engine” and “hum” sounds relative to other types of sounds. In Study 3, 24 persons heard and rated 18 actual sounds within 6 categories that were added to a video of a hybrid vehicle driving by. The sounds most preferred were “engine” followed by “white noise” and “hum”. Implications for adding sounds to facilitate pedestrians' detection of moving vehicles and for aiding drivers' awareness of speed are discussed.     

The semantic associations of acoustic parameters commonly used in the design of auditory information and warning signals

Two experiments are described in which the effects of acoustic parameters, and changes in those acoustic parameters, on the salience of 42 pre-selected adjectives are explored. In experiment 1 four sets of seven stimuli each varying only along one of the four acoustic parameters pitch, speed, inharmonicity and rhythm were scaled along the 42 adjectives. Parameter-adjective associations showing significant effects both in terms of consistency (Kendall's W') and in linear mapping (regression) numbered 7 for pitch, 3 for speed, 2 for inharmonicity and 1 for rhythm. Three of the four parameters produced significant levels of both consistency and linear mapping for the adjective ‘urgent’. In the second experiment, the overall meaning of complete within-parameter stimulus sets were explored and many differences both within and between parameters and adjectives were found. The results were used to design five trend monitoring sounds for helicopter flight, three of which are described in detail in this paper.     

A cross-cultural comparison of perceived hazard in response to warning components and configurations: US vs. China

There is increasing momentum towards international harmonization of warning standards. Therefore, it is critical to determine the applicability of existing standards across different cultures. Perceived hazard in response to isolated warning components (colors, signal words and symbols) and warning configurations was examined as a function of culture of the product-user (US vs. China) to determine the extent to which ANSI (American National Standards Institute)-recommended components/configurations communicate the expected level of hazard across cultures. 40 college students in the US and 43 in China rated colors, signal words, symbols, and complex configurations on a scale from 1 (not at all hazardous) to 9 (extremely hazardous). US participants consistently provided higher ratings of perceived hazard than Chinese participants. Cross-cultural differences were also observed in the relative levels of perceived hazard assigned to different levels of a label component, particularly in response to colors. However, relative levels of perceived hazard among more complex configurations were similar across culture, even though Chinese participants continued to provide lower absolute ratings of perceived hazard. These results have important implications - if it is assumed that perceived hazard-level must attain some threshold value in order to trigger compliance, then differences in perception could result in a failure of product-users to take appropriate precautions.     

Warning signals for potential accounting frauds in blue chip companies - An application of adaptive resonance theory

With the constantly changing and deceptive strategies that can be concealed in complex of financial statements, traditional means of financial analysis is unable to detect these accounting frauds in advance. In order to detect new accounting frauds and find out the true meaning of off-balance sheet arrangements, we propose an easy and feasible method using an unsupervised learning system. In unsupervised learning, the training of the network is entirely data-driven and no target results are provided. The features that do not help in clustering can be removed. With unsupervised learning it is possible to learn larger and more complex relations than with supervised learning. In the demonstration, we extract four non-traditional warning signals using adaptive resonance theory, with Enron and WorldCom as prototypes to identify the possibility of potential fraud of a company that investors or analysts may be concerned with.     

Spatial smoothing based methods for direction-of-arrival estimation of coherent signals in nonuniform noise

Spatial smoothing techniques have been widely used to estimate the directions-of-arrival (DOAs) of coherent signals. However, in general these techniques are derived under the condition of uniform white noise and, therefore, their performance may be significantly deteriorated when nonuniform noise occurs. This motivates us to develop new methods for DOA estimation of coherent signals in nonuniform noise in this paper. In our methods, the noise covariance matrix is first directly or iteratively calculated from the array covariance matrix. Then, the noise component in the array covariance matrix is eliminated to achieve a noise-free array covariance matrix. By mitigating the effect of noise nonuniformity, conventional spatial smoothing techniques developed for uniform white noise can thus be employed to reconstruct a full-rank signal covariance matrix, which enables us to apply the subspace-based DOA estimation methods effectively. Simulation results demonstrate the effectiveness of the proposed methods.     

Discriminant analysis of multivariate time series: Application to diagnosis based on ECG signals

In analysing ECG data, the main aim is to differentiate between the signal patterns of healthy subjects and those of individuals with specific heart conditions. We propose an approach for classifying multivariate ECG signals based on discriminant and wavelet analyses. For this purpose we use multiple-scale wavelet variances and wavelet correlations to distinguish between the patterns of multivariate ECG signals based on the variability of the individual components of each ECG signal and on the relationships between every pair of these components. Using the results of other ECG classification studies in the literature as references, we demonstrate that our approach applied to 12-lead ECG signals from a particular database compares favourably. We also demonstrate with real and synthetic ECG data that our approach to classifying multivariate time series out-performs other well-known approaches for classifying multivariate time series.     

脉冲噪声环境下宽带循环平稳信号DOA估计算法（2010年10月投稿，现发去电子稿）

针对传统二阶循环相关算法在脉冲噪声环境中的显著退化问题,本文以 稳定分布为噪声模型,提出基于分数低阶循环相关的波达方向（DOA）估计算法。利用分数低阶循环相关的相移特性,将宽带循环平稳信号的DOA估计问题转化为“中心频率”为 的窄带问题,解决了宽带情况下DOA估计困难的问题。计算机仿真结果进一步验证了此算法的有效性,且性能优于传统SC-SSF算法。     

Perceived risks and customer needs of geographical accessibility in electronic commerce

Customer needs of geographical accessibility still plays an important role in electronic commerce, though the extent to which it does so varies according to the characteristics of products, services and the market strategies of firms. In this study, factors affecting customer needs of geographical accessibility and their structural relationships were investigated through a customer survey and statistical analysis using the methods of confirmatory factor analysis and structural equation modeling. The result shows that the three independent factors, unease of delivery, complexity of services, and trust and reliability affect significantly customer needs of geographical accessibility, with perceived risks of distant orders being a mediating factor in the relationship.     

The effects of prior warning and lifting-induced fatigue on trunk muscle and postural responses to sudden loading during manual handling

This study investigated the effects of warning and lifting-induced fatigue on trunk muscle activity and postural responses to sudden loading. Thirty-one male subjects were subjected to sudden loading of a hand-held box with and without prior warning, before and after either lifting-induced fatigue or light callisthenic exercises. Results showed that warning did not alter the level of trunk muscle activity prior to sudden loading. Following warning, there was a reduction in all muscle and joint onset latencies and the magnitude of hip and knee flexion. Although fatigue did not influence muscle and joint initiation, it did negate the effects that warning had on reducing joint displacement. These findings indicate that warning prior to sudden loading may enhance postural responses, reduce ranges of joint motion and increase stability. However, the benefits of prior warning for reducing ranges of joint motion may not be present when a person is fatigued. Sudden unexpected loading and fatigue arising from manual handling practices in the workplace have been identified as contributing factors to the risk of low back injury. Findings from this study provide information that is important for the design of interventions intended to reduce the incidence of manual handling-related back injuries.     

Reduction of quantization noise via periodic code for oversampled input signals and the corresponding optimal code design

This paper proposes to reduce the quantization noise using a periodic code, derives a condition for achieving an improvement on the signal to noise ratio (SNR) performance, and proposes an optimal design for the periodic code. To reduce the quantization noise, oversampled input signals are first multiplied by the periodic code and then quantized via a quantizer. The signals are reconstructed via multiplying the quantized signals by the same periodic code and then passing through an ideal lowpass filter. To derive the condition for achieving an improvement on the SNR performance, first the quantization operator is modeled by a deterministic polynomial function. The coefficients in the polynomial function are defined in such a way that the total energy difference between the quantization function and the polynomial function is minimized subject to a specification on the upper bound of the absolute difference. This problem is actually a semi-infinite programming problem and our recently proposed dual parameterization method is employed for finding the globally optimal solution. Second, the condition for improving the SNR performance is derived via a frequency domain formulation. To optimally design the periodic code such that the SNR performance is maximized, a modified gradient descent method that can avoid the obtained solution to be trapped in a locally optimal point and guarantee its convergence is proposed. Computer numerical simulation results show that the proposed system could achieve a significant improvement compared to existing systems such as the conventional system without multiplying to the periodic code, the system with an additive dithering and a first order sigma delta modulator.     

Optimal digital filtering of continuous signals in time lag systems

The problem of the optimal estimation of continuous processes by discrete measurements in the presence of time lag (delay) is considered. On the basis of the theory of parametric transfer functions, an optimal, periodically nonstationary filter is developed, which affords a minimum of the estimation error variance at any instant of time. The comparison is performed of the obtained solution with the optimal stationary filter, which ensures a minimum of the mean (by continuous time) error variance. It is shown that in the problem of estimation of the Markov process of the first order, a simpler stationary filter with the fixer of order zero is insignificantly inferior to the optimal filter.     

Perceived risks, counter-beliefs, and intentions to use anti-/counter-terrorism websites: An exploratory study of government–citizens online interactions in a turbulent environment

This study examines the relationships between various risks, beliefs, and behavioral intentions that are related to citizens' use of anti-/counter-terrorism e-Government websites. The data was collected through two surveys within a one-year interval — before and after the Iraqi regime was expelled by the US coalition army. The results suggest that perceived privacy risk from an anti/counter-terrorism authority is the major obstacle in citizen-to-government anti/counter-terrorism information flow, while citizens' belief in the authority's domain competence greatly influences citizens' dependence on anti/counter-terrorism website information. Other findings and implications are discussed, and directions for future research are suggested.     

Parameter identification of periodical signals: Application to measurement and analysis of ocean wave forces

This article presents an approach based on state observers to identify the parameters of an unknown periodic force exerted on a mechanical system. This approach comprises two stages and can be executed in real time by using only displacement measurements. The first stage goal is the estimation of the coefficients of a Fourier series that approximates the periodic force. From the estimated coefficients, the phase and the amplitude of the signal can be simultaneously computed; and from the estimated force, in a second stage, the frequencies of the signal can be estimated. To perform the tasks at each stage, two state observers were designed. To show the applicability of the proposed approach, the reconstruction of a wave force affecting a marine structure as well as the computation of the amplitude and phase of its spectral components was taken as case of study. The performance of the state observer was examined by means of simulations and off-line tests carried out with experimental data. Such data were obtained by executing laboratory tests and measuring waves in the Caribbean sea.     

Quantifying and predicting the effects of basic text display variables on the perceived urgency of warning labels: tradeoffs involving font size,border weight and colour

Design variables surrounding the presentation of signal words in warnings have been previously shown to affect performance, or variables likely to be related to performance. The present study emphasized the signal word WARNING by presenting it in red, surrounded by a red border. It was at the head of an otherwise black pesticide label that used 8-point type. A study using 24 undergraduates investigated the effect of signal-word font size (8 to 32 points), white space around the signal word (2 to 32 points), and border width (1 to 8 points) on the rated urgency of the label. A measure of the aesthetic merit of each label was also obtained from nine design students and professionals. Seven levels of each variable were used, covering the practically-useful range of each variable in the circumstances. Results showed a linear relationship between each variable and perceived urgency, with text size having the greatest effect, followed by border width. It was shown that, within the variable ranges used, the perceived urgency of the emphasized signal word resulted from the sum of the urgencies associated with the separate dimensions used in the emphasis. Tradeoffs are discussed—for example an increase of 4 points in text size produced the same increase in urgency rating as produced by an increase in border width of 2-3 points. A second study, using a further 24 students, compared the red labels with labels in black only. It was found that the signal word had to be approximately twice as big in black as in red to give the same perceived urgency. Design implications of the finding that the most urgent labels are not necessarily the most aesthetically pleasing are discussed.     

Perceived argument quality's effect on threat and coping appraisals in fear appeals: An experiment and exploration of realism check heuristics

Persuasion is key to encourage compliance with information security policies through fear appeals, though research has not examined how the perceived quality of their arguments affects threat and coping appraisals. Because we know that perceived argument quality can influence attitudes and behavior, it may improve fear appeal effectiveness. The results of a scenario-based field experiment suggest that perceived argument quality increases response efficacy perceptions and compliance intentions. We also examine emerging heuristics about how to use realism checks in scenario-based research and find that current realism check heuristics in behavioral information security research may be misguided, contributing to biased interpretation.