Loudness interacts with semantics in auditory warnings to impact rear-end collisions Carryl L. Baldwin, Jennifer F. May Transportation Research Part F 14 (2011) 36– 42

Your site here Introduction  Acoustic parameters such as the loudness, pitch, speed, pulse rate and duration have been shown to affect the perceived urgency of auditory warnings.  Momtahan (1990) observed that sounds presented at 90 dB were rated as significantly more urgent than sounds presented at 75 dB.

Your site here  When CWS warning was presented at least 8 dB above ambient background noise, participants responded more quickly relative to the lower presentation level conditions.  At intermediate loudness levels, participants’ response time differed as a function of the semantic content.

Your site here Goal  Providing alarms at loudness levels at least 8– 10 dB above ambient background noise levels in the vehicle are essential to ensuring their audibility among older drivers (Baldwin, 2002)  The goal of the present investigation was to examine the relative impact and potential interaction of two key characteristics of verbal warnings, an acoustic characteristic (loudness) and a semantic characteristic (signal word).

Your site here Current investigation  two signal words (‘‘Danger” and ‘‘Notice”)  a low urgency level of 70 dBA or a high urgency level of 85 dBA  High urgency alarm (Danger at the high intensity) was expected to result in the fastest reaction time but more moderate urgency level alarms (Notice at 85 dB and Danger at 70 dB) were expected to result in the most appropriate response

Your site here Methods- CWS alarms  Participants- Thirty volunteers (57% females) between the ages of 18–26 years (mean age 21.1 years)  The signal words, ‘‘Notice” and ‘‘Danger” spoken by a female at a normal conversational level.  loudness levels approximating 70 and 85 dBA

Your site here  Alarms were presented via the driving simulator through speakers while the participant drove.  Each participant drove through five different scenarios, each containing one potential collision event or hazard paired with one of the four CWS alarms or the control.

Your site here Driving simulator and driving scenarios  The driving scenario of interest here consisted of an urban roadway with low traffic density.  Participants were asked to maintain a speed of 35 mph while interacting with vehicular traffic and pedestrians.

Your site here  Scenario A 十字路口忽然出現左方來車通過自車線 道.  Scenario B 十字路口忽然出現右方行人通過自車線 道.  Scenario C 後方出現超速的同向來車  Scenario D 對向來車在十字路口通過自車線道左 轉  Scenario E 前車在十字路口變慢欲左轉

Your site here Procedure  The nature of the experiment was explained to each participant and written informed consent was obtained.  Orientation drive to familiarize them with the handling characteristics of the simulated vehicle.  All simulated driving tasks (orientation and experimental) were approximately 3 min long.  The entire experimental paradigm lasted approximately 45 min

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Results- Hazard scenario  Of the 150 drives (30 participants 5 drives each), a total of 27 crashes (18%) were observed.  Of these 27 crashes, 12 (44.4%) occurred in Scenario C, referred to as the ‘‘speeder scenario.”

Your site here Results- CWS alarm type  發生碰撞中 The majority of those who crashed received either no warning (33%) or the most urgent signal word ‘‘Danger” at the highest – 85 dB intensity (33%).  Crash rates were low in the two moderate CWS alarm conditions (8.3% were in the Danger low intensity condition and 0% were in the Notice high intensity condition).

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Results-Subjective ratings  Ratings of perceived urgency and annoyance primarily contributed to this marginally significant multivariate effect.  A significant main effect for intensity was not found, nor was a significant interaction between signal word and intensity observed for the subjective ratings.

Your site here Results- Perceived urgency

Your site here Results- Annoyance

Your site here Discussion  Using a relatively low urgency level signal word at an acoustically salient loudness level may effectively alert without startling these drivers.  Drivers were presented with the CWS alarm – Notice at 85 dB – they apparently had time to assess the situation and react quickly enough to make the appropriate collision avoidance maneuver.