Effects of acoustic warning signal intensity in the control of visuospatial interference

The present study was designed to evaluate whether fixation point offsets have the same effects on the average latencies of prosaccades (responses towards target) and antisaccades (responses away from target). Gap and overlap conditions were run with and without an acoustic warning signal. The 'gap effect' was taken to be the difference in mean reaction time between gap and overlap trials. This effect was dramatically reduced by the presentation of the warning signal. Without this signal, fixation offsets can serve as warning signals themselves, which artifactually inflates the magnitude of the gap effect. The warning effect of fixation offsets was equivalent for pro and antisaccades. A significant gap effect is still evident with the acoustic warning signal; however, in this case it is associated primarily with prosaccades. These results replicate and extend our previous work demonstrating that, if their warning effects are controlled, the facilitatory effects of fixation point offsets are response dependent, and suggesting the existence of a component process (fixation release) which is closely linked with the processing architecture underlying target-directed saccades.

The considerations presented in Chapter 2, as well as the analysis results of the accidents that happened in machine operation (Dwiarek, 2004) have proved that the appropriate use

A psychoacoustic model is presented to facilitate the installation of acoustic warning devices in noisy settings, reflecting a major upgrade of a former tool, Detectsound. The model can be used to estimate the optimal level and spectrum of acoustic warning signals based on the noise field in the workplace, the hearing status of workers, and the attenuation provided by hearing protectors. The new version can be applied to a wider range of situations. Analyses can now be conducted to meet the functional requirements for a specific worker or to suit the needs for a group of co-workers sharing a work area. Computation of optimal warning signals can also be made from estimated hearing parameters based on the worker age, gender, and level and duration of noise exposure. The results of a laboratory validation study showed that the mean error in estimating detection thresholds for normal hearing individuals is typically within ±1 dB with a standard deviation of less than 2.5 dB in white noise or continuous noise fields. The model tends to yield slightly overestimated warning signal detection thresholds in fluctuating noises. Proper application of the tool also requires consideration of the variability in estimating noise levels, hearing status, and hearing protector attenuation under field conditions to ensure that acoustic warning signals are sufficiently loud and well adjusted in practice.

The aim of this study was to investigate spinal reflex (SR) modulation during the performance and learning of a precision locomotor task. Healthy subjects had to minimize foot clearance when repeatedly stepping on a treadmill over a randomly approaching obstacle. The subjects walked with reduced vision and were informed about the approaching obstacle and task performance by acoustic warning and feedback signals, respectively. SRs were randomly evoked by tibial nerve stimulation (with non-nociceptive and nociceptive stimulus intensity) during the mid-stance phase in both normal and pre-obstacle stepping. Foot clearance and electromyographic activity of the tibialis anterior and biceps femoris muscles of the right leg were analysed. Only if a delay was introduced between warning signal and nerve stimulation, was the SR amplitude in both muscles enhanced prior to obstacle steps compared with normal steps for both stimulus intensities. Thus, the reflex enhancement depended on the subject's awareness of the approaching obstacle. Improved performance was reflected in a decreased foot clearance, but did not correlate with the course of SR amplitude. It is concluded that obstacle stepping is associated with a facilitation of SR pathways, probably by supraspinal drive. This facilitation might provide assistance in safe obstacle stepping, e.g. to compensate quickly if resistance is encountered.

It is known that the increase of intensity on a warning signal (WS) usually decreases reaction times to targets and occasionally is accompanied by a startle reflex reaction that influences the speediness of response execution. In a simple detection task (Experiment 1), a detection task with catch trials (Experiment 2) and a Go-NoGo discrimination task (Experiment 3), we studied the relationship between response preparation and alerting mechanisms operating upon the presentation of warning signals. A WS was presented either synchronously with the target (simultaneous condition) or 1400 ms before it (delayed condition). In all three experiments, the intensity of the WS and the simultaneity between WS and target were orthogonally manipulated. Results confirmed shorter reaction times by increasing the WS intensity. In Experiment 1, all conditions presented a clear acoustic intensity effect. In Experiment 2 we observed shorter reaction times in higher intensity conditions but only when the WS and the target were presented simultaneously. In Experiment 3, the intensity effect was observed only when the WS preceded the target. In all experiments, trials where the WS triggered a startle reflex showed a systematic increase in reaction time, which was independent of response preparation and task demands. In general, our findings suggest that response preparation modulates the alerting mechanisms, as a function of task set, but not the startle reflex. The dissociation between intensity, response preparation and startle supports the interdependence between these mechanisms elicited by the presentation of warning signals.

To evaluate whether a reduction in radiation exposure can be achieved using a direct dosimeter with an acoustic warning signal (model EDD-30, Unfors Instruments, Billdal, Sweden). A total of 183 diagnostic and interventional angiographies of the pelvis and lower limbs using a direct dosimeter were analyzed. The vascular interventions were performed either by an experienced examiner (> 5000 interventions), an intermediate examiner (> 1000 interventions) or by a beginner (< 200 interventions). The measuring sensor of the direct dosimeter was attached to the back of the left hand, below the sterile glove, and was worn throughout the examination. If the limit values set on the dosimeter were exceeded, an acoustic signal sounded. At the end of the examination, the mean dose and the mean dose rate could be read off directly. Exposure is clearly dependent on the experience of the examiner. The highest mean dose rate was found for the beginner, followed by the intermediate examiner. The lowest dose rate was shown by the experienced examiner, even though he mostly performed complex interventions. Over the course of 3 months, an improvement in the average dose rate can be shown in the third month for the intermediate examiner. The use of a direct dosimeter with an acoustic warning signal is a practicable tool for sensitizing interventional radiologists to unavoidable radiation exposure, with the aim of reducing the dose. "Real-time" dosimetry represents a sensible extension of indirect protection of the radiation-exposed examiner in angiography.

Reaction time (RT) is shortened when a warning signal precedes the response signal, a finding attributed to response preparation during the foreperiod between the warning and response signals. In a previous experiment, we delivered transcranial magnetic stimulation (TMS) during the short constant foreperiod of a warned RT task and found simultaneous suppression of motor evoked potential (MEP) amplitude and reduction of short-interval intracortical inhibition (SICI) on warned trials (Sinclair and Hammond in Exp Brain Res 186:385-392, 2008). To investigate the extent to which these phenomena are associated with response preparation we measured MEP amplitude and SICI during the foreperiod of a warned RT task in which three different warning signals specified the probability (0, 0.5, or 0.83) of response signal presentation. MEP amplitude was suppressed (Experiment 1) and SICI reduced (Experiment 2) equally in all of the warned conditions relative to when TMS was delivered in the inter-trial interval (ITI) suggesting that the modulation of primary motor cortex excitability during the foreperiod does not depend on momentary response expectancy induced by the warning signal. The reduction of SICI and suppression of MEP amplitude can be explained by assuming that a warning signal induces automatic motor cortical activation which is balanced by a competing inhibition to prevent premature response. A composite measure which weighted both speed and accuracy of response was positively correlated with the MEP amplitude during both the foreperiod and the ITI, suggesting that high motor cortical excitability is associated with optimized preparatory strategies for fast and accurate response.

The use of acoustic warning signals to provide information about vehicle conditions to the driver and passengers is now possible through application of advanced electronics in recent automobile designs. These acoustic warning signals may be tones or synthesized voice. The signals can only be effective if they are audible and distinguishable by the vehicle occupants without being at an irritating level. This paper presents a method for measuring acoustic intensity in an automobile interior using the cross-spectral technique which may assist in determining audibility of signals. Effective methods for displaying these quantitative vector measurements using computer graphics are presented along with the results of testing. Finally, an important future need of correlating acoustic intensity measurements with published human perception levels is discussed.

Research and/or Engineering Questions/Objective This paper summarises the activities to be carried out within the project recently approved by the European Commission to develop effective warning systems to be implemented in electric vehicles particularly to protect vulnerable pedestrians such as visually impaired people and the elderly. The project, entitled eVADER from ‘Electric vehicle alert for detection and emergency response’, is currently sponsored by the EC with grant no. 285,095 and it combines the efforts of an international consortium made up of Universities, Research Institutes, Tier-one suppliers and OEM’s. One of the important objectives of the project is to recognise that recent studies suggest that vehicles, driven in electric mode, either hybrid or pure electric vehicles, are considerably quiet and, thus, that they constitute a safety hazard for pedestrians and bicyclists in traffic. It is claimed that such vehicles are not acoustically perceived due to the power unit being exchanged from a combustion engine to electric motors; something that essentially cuts away all power unit noise and leaves tyre/road noise, the latter of which is the same as for similar-sized vehicles with combustion engines. Actions have been taken by the US and Japanese governments as well as within international bodies such as UN/ECE and ISO, with the expected outcome that “minimum noise” of vehicles shall be measured with a standard method and legal limit values for such “minimum noise” shall be established. Methodology Recent findings reported in NHTSA Technical Report (September 2009) suggest that pedestrian and cyclist crashes involving both electric vehicle (EV) and Internal Combustion Engine (ICE) driven vehicles commonly occurred on roadways, in zones with low speed, with higher incidence rates for EV and Hybrid EV (HEV) or EV when compared with internal combustion driven vehicles (ICE). The study showed that for vehicles moving slowly or stopping, backing up or entering or leaving a parking place the HEV was about two times more likely to be involved in a pedestrian accident than ICE vehicles. Similar trend was also found for cyclists, particularly at intersections. Accordingly, special concern is given to noise at speeds below 20 km/h for which the problem is expected be the worst and where not enough data is available. Results eVADER will investigate the interior and exterior soundscape of electric vehicle for safe operation, considering driver’s feedback, feasible pedestrian reactions, driver and pedestrian warning systems and pedestrian safety. The project will also analyse innovative methods to improve the acoustic detectability of electric vehicles in urban scenarios. The project will define solutions to warn vulnerable users of a nearby moving vehicle while providing means for heightening the awareness of drivers in critical situations. Among other’s some of the most important areas covered by eVADER will be: (1) Optimum warning signals definition to induce correct driver reaction for safe operation. (2) Adaptation of the warning signals to the real in-service vibro-acoustic environment. (3) Optimum warning signals definition for pedestrians in close-to-accident situations. (4) Adaptation of the warning signals to real urban and exterior noise. (5) Integration of the generation of acoustic warning signals with in-vehicle intelligent systems data such as external microphones, vehicle speed (CAN) or Advance Driver Assistance (ADAS) systems. (6) Use of in-vehicle complementary information to improve directivity, timing, intensity, modulation and frequency characteristics of the warning signal, depending on real close-to accident scenario. (7) Optimum warning signals maintaining the quietness of residents. Limitations of this study The project is quiet ambitious because it must combine, psychoacoustic knowledge, electro-acoustic design of highly directive acoustic sources, state-of-the-art ADAS systems and other in-vehicle intelligent systems and integrate all of them to build up a clever warning system that will detect pedestrians and will act selectively when any of them are in a close-to-accident situation. This will guarantee that this warning system will no increase the noise pollution in cities. What does the paper offer that is new in the field including in comparison to other work by the authors? The concept of integrating ADAS and in-vehicle intelligent safety systems with a sophisticated and highly directional acoustic source is a novel concept not presented before. Conclusions The project analyses innovative methods to improve the acoustic detectability of electric vehicles in urban scenarios. The project also defines solutions to warn vulnerable users of a nearby moving electrical vehicles while providing means for heightening the awareness of drivers in critical situations.KeywordsElectricPedestrianDetectionWarning

Typical simple reaction-time (RT) paradigms usually include a warning signal followed by a variable foreperiod before the presentation of a reaction stimulus. Most current interpretations suggest that the warning stimulus alerts the organism and so results in faster processing of either the sensory or motor components of the task. In this study, electromyography (EMG) was used to detect both covert and overt motor errors in a simple warned RT task. Results show that warning signals may trigger automatic motor activations that are likely to cause false alarms. Distribution analysis reveals that 77% of all errors detected with EMG are erroneous responses to the warning signal. Accordingly, we propose that movement triggering needs to be temporarily inhibited before the stimulus to prevent premature responses during the foreperiod. This proactive inhibition would be responsible for a paradoxical increase in RT for conditions with short foreperiods compared with control conditions in which no warning signal is presented. These results call for a reassessment of the theoretical framework used to interpret the effects of warning signals.

Hearing is an important physiological function that humans rely on to sense the surrounding situations. It is well understood that acoustic cues are critical for pedestrians, bicycle and motorcycle riders to identify traffic, thus to avoid potential risks in a timely manner. Similarly, efficient and accurate perception of external acoustic warning signals (e.g., car horn and siren sounds) in the traffic environment are also important for driving safety. As modern vehicles are made more and more sound proofing, mainly for the sake of riding comfort, it is increasingly difficult for drivers to hear external sounds, which can impair the driver's hearing perception and detection of potential danger posed by nearby traffic through natural hearing. Currently, there is a lack of research in the literature regarding the relationship between the sound perception capability by drivers and driving safety. Therefore, this study focuses on investigating how well the acoustic warning signals in the surrounding traffic environment can be perceived by the driver under various conditions and its potential influences on driving safety. To correlate the effectiveness of drivers detecting the external traffic sound to the sound isolation level of the car body, the sound insulation performance of two selected passenger car models and the subjective sound localization accuracy through vehicle structures are measured. It is found that the existence of the car body, more specifically the car body sound insulation effect, noticeably degrades the sound localization accuracy of drivers. In addition, the perceived sound source direction is found to shift toward the side of the car body with lower sound insulation performance.

The goal of this study was to investigate changes of H-reflex amplitudes during a motor learning task. Subjects with reduced vision were instructed to step over an obstacle on a treadmill as low as possible, while the soleus H-reflex was elicited. Acoustic warning and feedback signals about performance were provided. Performance improvement was associated with a decrease of muscle activity, needed to step over the obstacle (rectus femoris, biceps femoris, tibialis anterior and gastrocnemius medialis muscles), and of foot clearance, while joint angle trajectories from knee and ankle became more stable. The experiment consisted of five runs, three with normal treadmill walking and two with randomly stepping over the obstacle (100 times). H-reflexes were elicited at early and late stance phase before stepping over the obstacle. H/M ratio, latency and duration were determined. The values of these measures were calculated for the onset and end of a run and their course over time was evaluated using a correlation coefficient. The largest adaptations with a significant increase of reflex amplitude occurred during the first obstacle run. This increase lasted only briefly and the reflex amplitudes decreased to their previous values. During the later obstacle run, no H-reflex modulation occurred. It is concluded that a motor learning task causes adaptational effects not only on performance, but also on H-reflex responses. The results indicate that most of the modulation of H-reflexes is probably due to supraspinal influences on reflex transmission. The observations made are probably less specific for this motor task (stepping over the obstacle), but rather associated with the increased attention required by the motor learning task during the first obstacle run.

We evaluated the acquisition and performance of a high-precision locomotor task in patients with Parkinson's disease (PD) and healthy subjects. All subjects walked on a treadmill and had to step repetitively as low as possible over an obstacle without touching it. During blocks 1 and 2, the subjects had full vision and received additional acoustic warning and feedback signals. During block 3, vision became restricted. Changes in foot clearance and the number of obstacle hits were evaluated. Initially, PD patients performed poorer and improved foot clearance slower. After task repetition, the groups performed similarly. Restricting vision deteriorated performance in both groups. The similar performance of PD patients after task repetition might indicate that adequate training could improve adaptive locomotor behavior in PD patients.

The influence of age on learning a locomotor task

The influence of age on learning a locomotor task