Auditory Warning Research Articles

Auditory Warnings Invoking Startle Response Cause Faster and More Intense Neck Muscle Contractions Prior to Head Impacts

High-pressure level and sudden sound, especially during an elevated state of alertness can elicit a startle response. Startle response can induce sudden, intense muscle activations. Some studies have shown that increasing neck muscle activation during impact situations can reduce the risk of concussion and neck injury. This research aimed to study muscle coactivation patterns, contraction latency and the level of muscle activation in startle response compared to the voluntary response. To achieve this goal, a testbed capable of applying impacts to the head in four directions was created. Auditory (115 dB) startle stimulus was delivered and muscle activation measured using sEMG on neck muscles during startle and voluntary responses. We investigated a 1000 ms time period starting at the time that the sound is played to the time at impact. Results indicate that the first muscle activation in startle response is 2.1 times higher, 5.9 times faster and involved more muscles than in a voluntary response.

Toward a Better Understanding of In-Vehicle Auditory Warnings and Background Noise.

The effectiveness of three types of in-vehicle warnings was assessed in a driving simulator across different noise conditions. Although there has been much research comparing different types of warnings in auditory displays and interfaces, many of these investigations have been conducted in quiet laboratory environments with little to no consideration of background noise. Furthermore, the suitability of some auditory warning types, such as spearcons, as car warnings has not been investigated. Two experiments were conducted to assess the effectiveness of three auditory warnings (spearcons, text-to-speech, auditory icons) with different types of background noise while participants performed a simulated driving task. Our results showed that both the nature of the background noise and the type of auditory warning influenced warning recognition accuracy and reaction time. Spearcons outperformed text-to-speech warnings in relatively quiet environments, such as in the baseline noise condition where no music or talk-radio was played. However, spearcons were not better than text-to-speech warnings with other background noises. Similarly, the effectiveness of auditory icons as warnings fluctuated across background noise, but, overall, auditory icons were the least efficient of the three warning types. Our results supported that background noise can have an idiosyncratic effect on a warning's effectiveness and illuminated the need for future research into ameliorating the effects of background noise. This research can be applied to better present warnings based on the anticipated auditory environment in which they will be communicated.

The comparison of auditory, tactile, and multimodal warnings for the effective communication of unexpected events during an automated driving scenario

In an automated car, users can fully engage in a distractor task, making it a primary task. Compared to manual driving, drivers can engage in tasks that are difficult to interrupt and of higher demand, the consequences can be a reduced perception of, and an impaired reaction to, warnings. In this study we compared three in-vehicle warnings (auditory, tactile, and auditory-tactile) which were presented during three highly attention capturing tasks (visual, auditory, and tactile) while the user was engaged in a self-driving car scenario, culminating in an emergency brake event where the warning was presented. The novel addition for this paper was that three set paced, attention capturing tasks, as well the three warnings were all designed in a pilot study to have comparable workload and noticeability. This enabled a direct comparison of human performance to be made between each of the attention capturing tasks, which are designed to occupy only one specific modality (auditory, visual or haptic), but remain similar in overall task demand. Results from the study showed reaction times to the tactile warning (for the emergency braking event) were significantly slower compared to the auditory and auditory-tactile (aka multimodal or multisensory) warning. Despite the similar reaction times between the in-vehicle auditory warning and the multimodal warning, the multimodal warning led to a reduced number of missed warnings and fewer false responses. However, the auditory and auditory-tactile warnings were rated significantly more startling than the tactile alone. Our results extend the literature regarding the performance benefits of multimodal warnings by comparing them with in-vehicle auditory warnings in an autonomous driving context. The set-pace attention capturing tasks in this study would be of interest to other researchers to evaluate the interaction in an automated driving context, particularly with hard to interrupt and attention capturing tasks.

The effectiveness of auditory forward collision warning alerts

The objective of this study is to evaluate the effects of auditory warning characteristics from a forward collision alert system on drivers’ avoidance behavior. A driving simulator study was designed and conducted with a pre-collision scenario that included a lead vehicle decelerating. This scenario is used to examine whether any casual relationship exists between the auditory alert characteristics and collision avoidance. The study included 192 participants across the U.S. The auditory characteristics, including fundamental frequency and duty cycle, were examined at three urgency levels. The data from the study was analyzed using Partial Least Squares (PLS) path modeling. The collision avoidance behavior was measured using two reaction times (throttle release, brake) and three response intensities (maximum brake pedal force, maximum lane deviation and response type). All tested warning alerts resulted in reduced collision rates, shorter reaction times, larger maximum brake pedal force, and larger maximum lane deviation when compared to the baseline condition without a warning. Participants were also more likely to simultaneously brake and steer when given an alert. The models illustrate that the auditory warning information has both a direct and indirect effect on occurrence of collisions, with the indirect effect playing a more important role on collision avoidance than the direct effect. The findings also showed that the low urgency level of duty cycle and high urgency level of fundamental frequency are not recommended for collision warning alerts.

Effect of Response Method on Driver Responses to Auditory Warnings in Simulated Semi-autonomous Driving

We examined how drivers’ response to automation warnings could improve driver performance by testing the traditional direct-response method against a new indirect-response method. A direct response, for which drivers manually take over control of the car after hearing the warning and seeing the scenario, was compared to an indirect response, for which drivers press a “yes” or “no” button to assist the automation in making a correct choice. Results showed no reaction time (RT) difference between the response methods, but accuracy was better for the direct response. Subtracting the action-execution time from RT showed that the indirect response took longer to mentally process, explaining why the indirect method was not faster and pointing to a potential source of increased errors. Buttons presses in the indirect method could eventually be faster, but better ways to convey the warning to the user and improve the human-machine interface are needed in future research.

Utility of Visual and Auditory Warning Alerting for Traffic Avoidance during UAS Operations

Minimum Operational Performance Standards (MOPS) are being developed to support the integration of Unmanned Aircraft Systems (UAS) in the National Airspace System (NAS). Input from subject matter experts and multiple research studies have informed display requirements for Detect-and-Avoid (DAA) systems aimed at supporting timely and appropriate pilot responses to collision hazards. DAA alerting is designed to inform pilots of potential threats to “DAA well clear”; the two highest alert levels – caution and warning – indicate how soon pilot action is required and whether there is adequate time to coordinate with the air traffic controller (ATC). Additional empirical support is needed to clarify the extent to which warning-level alerting impacts DAA task performance. The present study explores the differential effects of the auditory and visual cues provided by the DAA Warning alert, and performance implications compared to caution-only alerting are discussed.

Analysing Balance Loss in VR Interaction with HMDs

Immersive virtual reality (VR) has been used in different fields such as training, educational programs, entertainment, psychological treatments, and rehabilitation. Despite its broad utilization, some issues limit its application such as the loss of balance. Balance is disturbed because visual stimuli received from the virtual scenario are not in harmony with perceived stimuli by the proprioception and vestibular systems that remain in contact with the real environment. With the increasing popularity and accessibility of high-quality VR systems, concerns have been raised about the propensity of VR to induce balance loss. Balance is essential for safe use of VR experience and its loss can result in severe injury. In this work, we present a methodology and the necessary tools to quantify the influence of VR on the user’s balance and assess risk of falls during VR interaction. By means of an experiment making use of an Oculus Rift and a MS Kinect Sensor, we observe, quantify and compare the effect of VR scenes with different levels of danger on the balance of users, as well as the effect of visual and auditory warnings of balance loss. Results suggest that auditory signs were not effective in warning users about risk of fall, and that the order which the scenes are presented to users affects their behavior. Users who were first presented to a more challenging scene proceeded more carefully and most of the time carried this behavior to the other less challenging scenes.

The Evolution of Soundscape Appraisal Through Enactive Cognition.

We propose a framework based on evolutionary principles and the theory of enactive cognition (“being by doing”), that addresses the foundation of key results and central questions of soundscape research. We hypothesize that the two main descriptors (measures of how people perceive the acoustic environment) of soundscape appraisal (‘pleasantness’ and ‘eventfulness’), reflect evolutionarily old motivational and affective systems that promote survival through preferences for certain environments and avoidance of others. Survival is aimed at ending or avoiding existential threats and protecting viability in a deficient environment. On the other hand, flourishing occurs whenever survival is not an immediate concern and aims to improve the agent’s viability and by co-creating ever better conditions for existence. As such, survival is experienced as unpleasant, and deals with immediate problems to be ended or avoided, while flourishing is enjoyable, and therefore to be aimed for and maintained. Therefore, the simplest, safety-relevant meaning attributable to soundscapes (audible safety) should be key to understanding soundscape appraisal. To strengthen this, we show that the auditory nervous system is intimately connected to the parts of our brains associated with arousal and emotions. Furthermore, our theory demonstrates that ‘complexity’ and ‘affordance content’ of the perceived environment are important underlying soundscape indicators (measures used to predict the value of a soundscape descriptor). Consideration of these indicators allows the same soundscape to be viewed from a second perspective; one driven more by meaning attribution characteristics than merely emotional appraisal. The synthesis of both perspectives of the same person–environment interaction thus consolidates the affective, informational, and even the activity related perspectives on soundscape appraisal. Furthermore, we hypothesize that our current habitats are not well matched to our, evolutionarily old, auditory warning systems, and that we consequently have difficulty establishing audible safety. This leads to more negative and aroused moods and emotions, with stress-related symptoms as a result.

Adaptive warning signals adjusted to driver passenger conversation: Impact of system awareness on behavioral adaptations

The study investigated behavioral adaptation caused by warning signals that adaptively support drivers engaged in a passenger conversation. Novel advanced driver assistance systems (ADAS) could monitor the driver state to provide warnings adjusted to the driver’s current need for support. While first research indicates positive effects of dynamically adjusting ADAS, the overall safety potential of such adaptive systems remains unclear as little is known about adverse behavioral effects. Occasional inappropriate support due to an incorrect prediction of the current driver state might lead to critical situations when drivers are aware of the adaptive nature of the system and thus rely on the expected system behavior. To better understand behavioral adaptation to dynamically adjusting warnings, 46 participants driving on a test track reacted to two types of warnings (auditory, vibrotactile-auditory) while engaging in driver-passenger conversation or not. In a compensating warning strategy, vibrotactile-auditory warnings were displayed during conversations and auditory warnings in situations without conversation. This strategy was compared to a non-compensating warning strategy in which these assignments were reversed. The impact of behavioral adaptation was measured by considering reactions to simulated failures of these strategies. The role of system awareness for behavioral adaptation was investigated by manipulating awareness of these warning strategies across groups. We found that vibrotactile-auditory warnings reduced the detrimental effects of conversation on reaction times. Crucially, adverse behavioral adaptation was observed whenever an expected vibrotactile-auditory warning was replaced by an auditory warning but this effect was restricted to drivers in the awareness group. The results show that adaptive warning signals optimize the effectiveness of warnings during driver-passenger conversation but adverse behavioral adaptation develops when drivers are aware of the underlying warning strategy. This implies that future adaptive systems are less likely to be associated with behavioral adaptation if the adaptive nature of the system remains unnoticeable to the driver. Our findings could be used for developing and optimizing user-centered ADAS.

Auditory Task Irrelevance: A Basis for Inattentional Deafness.

ObjectiveThis study investigates the neural basis of inattentional deafness, which could result from task irrelevance in the auditory modality.BackgroundHumans can fail to respond to auditory alarms under high workload situations. This failure, termed inattentional deafness, is often attributed to high workload in the visual modality, which reduces one’s capacity for information processing. Besides this, our capacity for processing auditory information could also be selectively diminished if there is no obvious task relevance in the auditory channel. This could be another contributing factor given the rarity of auditory warnings.MethodForty-eight participants performed a visuomotor tracking task while auditory stimuli were presented: a frequent pure tone, an infrequent pure tone, and infrequent environmental sounds. Participants were required either to respond to the presentation of the infrequent pure tone (auditory task-relevant) or not (auditory task-irrelevant). We recorded and compared the event-related potentials (ERPs) that were generated by environmental sounds, which were always task-irrelevant for both groups. These ERPs served as an index for our participants’ awareness of the task-irrelevant auditory scene.ResultsManipulation of auditory task relevance influenced the brain’s response to task-irrelevant environmental sounds. Specifically, the late novelty-P3 to irrelevant environmental sounds, which underlies working memory updating, was found to be selectively enhanced by auditory task relevance independent of visuomotor workload.ConclusionTask irrelevance in the auditory modality selectively reduces our brain’s responses to unexpected and irrelevant sounds regardless of visuomotor workload.ApplicationPresenting relevant auditory information more often could mitigate the risk of inattentional deafness.

Active noise control system in a fire helmet – a proposal of the solution

An auditory warning signal emitted by a moving emergency vehicle is intended to inform other road users about an approaching emergency vehicle and the need to give way to it. Emission of a warning signal with the highest possible sound pressure level is the main method of ensuring the audibility and recognition of the warning signal by traffic participants at unknown and varying traffic noise, acoustic insulation of vehicles and noise in the interior of the vehicle. The A-weighted sound pressure level of the auditory warning signal reaching the interior of an emergency vehicle may exceed 90 dB, which can be harmful to the hearing, can adversely affect psychophysical fitness of the crew members and can significantly hinder verbal communication in the vehicle. This article presents the concept and results of numerical simulations of an active noise control system in fire helmets, which will reduce the exposure of the crew to the warning signal and improve the quality of verbal communication in an emergency vehicle. This system is integrated with the signal generation system. The Notch algorithm and the NLMS adaptation algorithm were used in the system's control algorithm. The construction of the controller was based on a microcontroller from the STM32F4 family.

Investigation of auditory potentials and cognitive impairment in premenstrual syndrome.

Premenstrual syndrome is a term which is used for describing of somatic, cognitive, emotional, and behavioral symptoms that occur during the luteal phase of menstrual cycle in women of reproductive age; symptoms rapidly improve at the onset of menstruation. In this study, we aimed to reveal if cognitive functions are affected or not in PMS and if the subjects are affected, we try to explain this situation by an objective diagnostic test. Ethical committee approval was taken for this project on 09.03.2012 and numbered 050.99-60. In this study, in order to determine premenstrual syndrome, "Premenstrual Syndrome Scale" that is developed by Gençdoğan (2006) with 44 items, Likert type, and 9 subgroups was used. Sample size was calculated using simple random sampling with a confidence level of 95% and confidence interval of 0.05. A total of 60 participants were included in the study (calculated sample size was 30 for each group). Each group was recorded in the ENMG-UP laboratory using the OIP auditory warning and the "oddball two-tone discrimination task" method. Latency measurements were taken from the highest point of the peak, and amplitude measurements were taken from peak to peak with a cursor. Comparisons of P300 wave latencies obtained via sparse auditory stimulus in PMS and non-PMS groups were made and findings were summarized in one of the tables. Recordings are taken from three scalp regions: parietal and central, respectively. PMS women have longer P300 wave latencies in all regions compared to non-PMS group, whereas there is no significant difference between P300 amplitude.

Metacognitive judgements of perceptual-motor steering performance

Control of skilled actions requires rapid information sampling and processing, which may largely be carried out subconsciously. However, individuals often need to make conscious strategic decisions that ideally would be based upon accurate knowledge of performance. Here, we determined the extent to which individuals have explicit awareness of their steering performance (conceptualised as "metacognition"). Participants steered in a virtual environment along a bending road while attempting to keep within a central demarcated target zone. Task demands were altered by manipulating locomotor speed (fast/slow) and the target zone (narrow/wide). All participants received continuous visual feedback about position in zone, and one sub-group was given additional auditory warnings when exiting/entering the zone. At the end of each trial, participants made a metacognitive evaluation: the proportion of the trial they believed was spent in the zone. Overall, although evaluations broadly shifted in line with task demands, participants showed limited calibration to performance. Regression analysis showed that evaluations were influenced by two components: (a) direct monitoring of performance and (b) indirect task heuristics estimating performance based on salient cues (e.g., speed). Evaluations often weighted indirect task heuristics inappropriately, but the additional auditory feedback improved evaluations seemingly by reducing this weighting. These results have important implications for all motor tasks where conscious cognitive control can be used to influence action selection.

The Benefits and the Costs of Using Auditory Warning Messages in Dynamic Decision-Making Settings

The failure to notice critical changes in both visual and auditory scenes may have important consequences for performance in complex dynamic environments, especially those related to security, such as aviation, surveillance during major events, and command and control of emergency response. Previous work has shown that a significant number of situation changes remain undetected by operators in such environments. In the current study, we examined the impact of using auditory warning messages to support the detection of critical situation changes and to a broader extent the decision making required by the environment. Twenty-two participants performed a radar operator task involving multiple subtasks while detecting critical task-related events that were cued by a specific type of audio message. Results showed that about 22% of the critical changes remained undetected by participants, a percentage similar to that found in previous work using visual cues to support change detection. However, we found that audio messages tended to bias threat evaluation toward perceiving objects as more threatening than they were in reality. Such findings revealed both benefits and costs associated with using audio messages to support change detection in complex dynamic environments.

Left or Right: Auditory Collision Warnings for Driving Assistance Systems

Assistance driving systems aim to facilitate human behavior and increase safety on the road. These systems comprise common systems such as forward collision warning systems, lane deviation warning systems, and even park assistance systems. Warning systems can communicate with the driver through various modalities, but auditory warnings have the advantage of not further tasking visual resources that are primarily used for driving. Auditory warnings can also be presented from a certain location within the cab environment to be used by the driver as a cue. Beattie, Baillie, Halvey, and McCall (2014) assessed presenting warnings in stereo configuration, coming from one source, and bilateral configuration, panned fully from left or right, and found that drivers felt more in control with lateral warnings than stereo warnings when the car was in self-driving mode. Straughn, Gray, and Tan (2009) examined laterally presented auditory warnings to signal potential collisions. They found that the ideal presentation of warnings in either the avoidance direction, in which the driver should direct the car to avoid a collision, or the collision direction, in which the potential collision is located, was dependent on time to collision. Wang, Proctor, and Pick (2003) applied the stimulus-response compatibility principle to auditory warning design by using a steering wheel in a non-driving scenario and found that a tone presented monaurally in the avoidance-direction led to the fastest steering response. However, the reverse finding occurred when similar experiments utilized a driving simulator in a driving scenario (Straughn et al., 2009; Wang, Pick, Proctor, & Ye, 2007). The present study further investigated how to design spatially presented auditory collision warnings to facilitate drivers’ response to potential collisions. Specifically, tones indicating a pedestrian walking across the road were presented either in the avoidance direction or in the collision direction. The experimental task consisted of monitoring the road for potential collisions and turning the wheel in the appropriate direction to respond. Additionally, time to collision was manipulated to investigate the impact of the timing of the warning and increasing time pressure on the steering response. Time to collision was manipulated by half second intervals from two to four seconds resulting in five different time-to-collision scenarios. Lastly, the effect of individual differences in decision-making styles were also considered by using two decision-making style questionnaires. Results from the experiment showed that the presentation of a collision warning in the collision direction led to faster responses when compared to the warning in the avoidance direction. This result may be due to the collision warning directing the attention of the participant to the location of the threat so that they can more quickly make a response decision. Further, the advantage of avoidance-direction warnings over collision-direction warnings was greater with greater time to collision. Results showed that participant responses to varying time to collision influenced their reaction time. The participants appeared to have not relied solely on the auditory tones, but rather they utilized the warning tones in conjunction with visual information in the environment. These results from this study have implications for improving collision avoidance systems: Presentation of a collision warning in the direction of the collision may be more intuitive to drivers, regardless of time to collision.

Designing feedback to mitigate teen distracted driving: A social norms approach

ObjectiveThe purpose of this research is to investigate teens’ perceived social norms and whether providing normative information can reduce distracted driving behaviors among them. BackgroundParents are among the most important social referents for teens; they have significant influences on teens’ driving behaviors, including distracted driving which significantly contributes to teens’ crash risks. Social norms interventions have been successfully applied in various domains including driving; however, this approach is yet to be explored for mitigating driver distraction among teens. MethodForty teens completed a driving simulator experiment while performing a self-paced visual-manual secondary task in four between-subject conditions: a) social norms feedback that provided a report at the end of each drive on teens’ distracted driving behavior, comparing their distraction engagement to their parent’s, b) post-drive feedback that provided just the report on teens’ distracted driving behavior without information on their parents, c) real-time feedback in the form of auditory warnings based on eyes of road-time, and d) no feedback as control. Questionnaires were administered to collect data on these teens’ and their parents’ self-reported engagement in driver distractions and the associated social norms. ResultsSocial norms and real-time feedback conditions resulted in significantly smaller average off-road glance duration, rate of long (>2s) off-road glances, and standard deviation of lane position compared to no feedback. Further, social norms feedback decreased brake response time and percentage of time not looking at the road compared to no feedback. No major effect was observed for post-drive feedback. Questionnaire results suggest that teens appeared to overestimate parental norms, but no effect of feedback was found on their perceptions. ConclusionFeedback systems that leverage social norms can help mitigate driver distraction among teens. Overall, both social norms and real-time feedback induced positive driving behaviors, with social norms feedback outperforming real-time feedback.

Can an aircraft be piloted via sonification with an acceptable attentional cost? A comparison of blind and sighted pilots

In the aeronautics field, some authors have suggested that an aircraft's attitude sonification could be used by pilots to cope with spatial disorientation situations. Such a system is currently used by blind pilots to control the attitude of their aircraft. However, given the suspected higher auditory attentional capacities of blind people, the possibility for sighted individuals to use this system remains an open question. For example, its introduction may overload the auditory channel, which may in turn alter the responsiveness of pilots to infrequent but critical auditory warnings. In this study, two groups of pilots (blind versus sighted) performed a simulated flight experiment consisting of successive aircraft maneuvers, on the sole basis of an aircraft sonification. Maneuver difficulty was varied while we assessed flight performance along with subjective and electroencephalographic (EEG) measures of workload. The results showed that both groups of participants reached target-attitudes with a good accuracy. However, more complex maneuvers increased subjective workload and impaired brain responsiveness toward unexpected auditory stimuli as demonstrated by lower N1 and P3 amplitudes. Despite that the EEG signal showed a clear reorganization of the brain in the blind participants (higher alpha power), the brain responsiveness to unexpected auditory stimuli was not significantly different between the two groups. The results suggest that an auditory display might provide useful additional information to spatially disoriented pilots with normal vision. However, its use should be restricted to critical situations and simple recovery or guidance maneuvers.

Evaluation of the effects of in‐vehicle traffic lights on driving performances for unsignalised intersections

Ground traffic lights are essential for maintaining traffic efficiency and safety at intersections. However, unsignallised intersections are still frequent in actual traffic environments. With the development of new forms of vehicular communication, in-vehicle traffic lights can assist drivers at unsignallised intersections. The authors proposed two types of in-vehicle traffic lights to assist drivers; these corresponded to two-way and all-way stop-controlled intersections. They adopted gap acceptance theory and a first-come-first-served strategy to determine passing priority for the two types of intersections, respectively. They then conducted a driving simulator experiment involving 23 participants, to investigate driver behaviours elicited by the proposed system. They prepared four experimental conditions with combinations of in-vehicle traffic lights and auditory warnings. The authors’ experimental results indicated that in-vehicle traffic lights were associated with significantly longer post-encroachment times and a significantly shorter maximum brake stroke. In terms of eye-gaze behaviours, the percentage of gaze concentration to the road centre area and mean glance durations were deemed acceptable for the avoidance of visual distraction, when in-vehicle traffic lights were presented via a head-up display. Therefore, their analysis of driver behaviours indicates that in-vehicle traffic lights can effectively provide driver assistance at unsignallised intersections.

Augmented reality warnings in vehicles: Effects of modality and specificity on effectiveness

In the future, vehicles will be able to warn drivers of hidden dangers before they are visible. Specific warning information about these hazards could improve drivers’ reactions and the warning effectiveness, but could also impair them, for example, by additional cognitive-processing costs.In a driving simulator study with 88 participants, we investigated the effects of modality (auditory vs. visual) and specificity (low vs. high) on warning effectiveness. For the specific warnings, we used augmented reality as an advanced technology to display the additional auditory or visual warning information. Part one of the study concentrates on the effectiveness of necessary warnings and part two on the drivers’ compliance despite false alarms.For the first warning scenario, we found several positive main effects of specificity. However, subsequent effects of specificity were moderated by the modality of the warnings. The specific visual warnings were observed to have advantages over the three other warning designs concerning gaze and braking reaction times, passing speeds and collision rates. Besides the true alarms, braking reaction times as well as subjective evaluation after these warnings were still improved despite false alarms. The specific auditory warnings were revealed to have only a few advantages, but also several disadvantages.The results further indicate that the exact coding of additional information, beyond its mere amount and modality, plays an important role. Moreover, the observed advantages of the specific visual warnings highlight the potential benefit of augmented reality coding to improve future collision warnings.

Effects of auditory and tactile warning on response to visual hazards under a noisy environment

A warning signal presented via a visual or an auditory cue might interfere with auditory or visual information inside and outside a vehicle. On the other hand, such interference would be certainly reduced if a tactile cue is used. Therefore, it is expected that tactile cues would be promising as warning signals, especially in a noisy environment. In order to determine the most suitable modality of cue (warning) to a visual hazard in noisy environments, auditory and tactile cues were examined in this study. The condition of stimulus onset asynchrony (SOA) was set to 0ms, 500ms, and 1000ms. Two types of noises were used: white noise and noise outside a vehicle recorded in a real-world driving environment. The noise level LAeq (equivalent continuous A-weighted sound pressure level) inside the experimental chamber of each type of noise was adjusted to approximately 60 dB (A), 70 dB (A), and 80 dB (A). As a result, it was verified that tactile warning was more effective than auditory warning. When the noise outside a vehicle from a real-driving environment was used as the noise inside the experimental chamber, the reaction time to the auditory warning was not affected by the noise level.