Perceptions of implied haza rd for visual and auditory alerting signals

1. Perceptions of implied hazard for visual and auditory alerting signals Alan H.S. Chan *, Annie W.Y. Ng Department of Manufacturing Engineering and Engineering Management, City University of Hong Kong, Kowloon Tong, Hong Kong 報告者：楊子群

2. Aim and subjective • This study was to explore the use of visual and auditory alerting signals to effectively convey impressions of danger, urgency, and unsafe condition levels in warning system. • Objective was to study the effects of flash rate, flash mode, and auditory alarm type on perceived danger, urgency, unsafe condition level for the observers: • Hypothesis 1 => The perceived danger, urgency and unsafe condition levels for an alerting signal would increase with flash rate of visual signals . • Hypothesis 2 => The perceived danger, urgency and unsafe condition levels for an alerting signal would increase with number of flashes in a cycle . • Hypothesis 3=> The auditory icons would be perceived to have higher danger and unsafe condition levels than the abstract(抽象化)sounds. • Hypothesis4 => The combined visual–auditory signal would be more effective than visual signal alone in conveying the perception of urgency, unsafe condition level, and danger.

3. Method

4. Method

5. Design • Flash colour:red, yellow, blue. • Flash rate :60, 120, 180, 240 fpm. • Flash mode: single, double, triple. • Auditory alarm : no sound, siren, buzzer, security alarm(一般大眾知道的安全警報). • Altogether 144 different test conditions. • 432 trials were randomly presented for each subject and a 5-min rest was given after every 72 trials. • Asked to each condition once in relation to the three signal words: danger, urgency and unsafe.[Separately 9-point likert-type(李克特)]

6. Subjects • 23 Hong Kong Chinese(11 males and 12 females) • Ages ranged : 20 to 40 years(median = 28 years). • Did not report any hearing or sight problems during the experiment.

7. Apparatus • A laptop computer with 15.1”XGA display. • Visual FoxPro was used for the experiment. • Sennheiser HD 250 linear headphone • Digital sound level meter (UEI-DSM 100) • Luminance meter (Minolta model LS-110)

8. Procedure 【Step1】 Briefed about experiment. 【Step2】 Practice trials. 【Step3】 Clicked an on-screen start button when they were ready. §Random period of 2-3 s, simulated beacon was shown six seconds.(Display on the centre.) §Simultaneously an auditory alarm via the headphones. §Experiment time:1.5 h, altogether 144 trials, 5 min break after completion of 72 trials. 【Step4】 Asked to rate the perceived hazard level. §9-point likert-scale 【Step4】 Microsoft Excel files for further analyses.

9. Four hypotheses 1.Flash colour 2.flash rate 3.flash mode 4.auditory alarm Three ratings(danger, urgency, unsafe) was non significant. Hence, all used in general as the perceived hazard rating in further analyses and discussions. The ANOVA showed significant main effects for Flash colour [F(2, 431) =2355.12, p<.001] Flash rate [F(3, 431) =361.12, p<.001] Flash mode [F(2, 431) =301.51, p<.001] Auditory alarm [F(3, 431) =1735.80, p<.001]

10. Four hypotheses Tukey method:

11. Four hypotheses Tukey method: flashes per minute

12. Four hypotheses Tukey method:

13. Four hypotheses Tukey method:

14. The results of ANOVA also showed significant two- and three-way interaction effects . • Flash colour and flash rate [F(6, 431) =4.37, p < .001] • Flash colour and flash mode [F(4, 431) = 3.12,p < .05] • Flash colour and auditory alarm [F(6, 431) = 42.78,p < .001] • Flash rate and flash mode [F(6, 431) = 15.72, p < .001] • Flashcolour, flash rate and flash mode [F(12, 431) = 2.39, p < .01] • Flashcolour, flash mode and auditory alarm [F(12, 431) = 1.99, p < .05] • Flashrate, flash mode and auditory alarm [F(18, 431) = 2.26,p < .005]

15. Overall, the highest perceived hazard level(7.62) was noted for a red signal in double flash mode at 240 fpm when combined with a siren alarm. • Red colours • Chan and Courtney(2001) that red was the colour most frequently chosen to indicate the concept of danger and hazard. • Wogalter et al. (1998) also showed that the colour red connoted greater hazard than other colours. • Flash rate Howett et al.(1987) found that a high flash rate of 240 fpm improved warning beacon detection time while low flash rate of 60 fpm minimized discomfort glare. • Flash mode Triple flash perhaps make the alerting signal beyond what is necessary.

16. The perceived danger, urgency and unsafe condition levels for an alerting signal would increase with flash rate of visual signals (Hypothesis 1). Non significant difference between flash rates of 180 and 240 fpm, but significant difference between 120 and 240 fpm. • The perceived danger, urgency and unsafe condition levels for an alerting signal would increase with number of flashes in a cycle (Hypothesis 2). Non significant difference between double and triple modes, but double more greater single. • The auditory icons would be perceived to have higher danger and unsafe condition levels than the abstract sounds(Hypothesis 3). Security alarm(auditory icon) and siren, security alarm and siren is non significant difference. • The combined visual–auditory signal would be more effective than visual signal alone in conveying the perception of urgency, unsafe condition level, and danger (Hypothesis4). But Sorkin(1987) showed combined auditory warning is overburdened.

17. Conclusion • This experiment studied the perceptions of implied hazard for visual and auditory • alerting signals. • Significant interaction effects for flash colour and flash rate, flash colour and flash • mode, flash colour and auditory alarm, and flash rate and flash mode were • revealed. • Generally a red alerting signal in double flash mode at 240 fpm with siren alarm • resulted in the highest perception of intensity of hazard.