Perceptions of implied hazard for visual and auditory alerting signals

Alan H.S. Chan *, Annie W.Y. NgDepartment of Manufacturing Engineering and Engineering Management, City University of Hong Kong, Kowloon Tong, Hong Kong

報告者：楊子群

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.

Aim and subjectiveAim and objective Reference Method Results Discussion Conclusion

Hunt et al. 1995 Studies have focused on the use of auditory enhancements for visual signals to minimize reaction time in human-machine systems.(not been fully investigated to urgency, danger, or lack of safe conditions.)Loeb & Fitch 2002

Belz et al. 2003

Woodson et al. 1992 The colours red, yellow and blue are frequently used in coding electrical( 電 ) and hydraulic(水壓 ) equipment and for marking safety hazards.

International guidelines

2002 Red=>stop and dangerYellow=>physical hazard and cautionBlue=>against starting or moving equipment under repair.

Chan et al. 2003 Cultural and geographical factor may have some common concepts like danger, emergency and safety.

Hong Kong Chinese and Thais =>red with potential hazard and radiation (輻

射 ) hazard.Korean =>orange with potential, yellow with radiation hazard.

MethodAim and objective Reference Method Results Discussion Conclusion

ISO/IEC 18025 2005 Total duration of light in a period is less than the total duration of darkness.

Thackray & Touchstone

1991 Flashing was found to be superior to colour alone in attracting attention to object in a display and in influencing the detectability of signal lights.Sanders &

McCormick1993

Howett et al. 1978 Most flash signals have been designed for operation at flash rates between 60 and 180 flashes per minute(fpm)

UNECE 2002 Level conditions requiring:Minimum=>1.0-1.6 Hz(about 60-96 fpm)Intermediate=>2.2-2.8 Hz(about 132-168 fpm)Highest=>3.3-4.0 Hz(about 198-240 fpm)

MethodAim and objective Reference Method Results Discussion Conclusion

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 )]

DesignAim and objective Reference Method Results Discussion Conclusion

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.

SubjectsAim and objective Reference Method Results Discussion Conclusion

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)

ApparatusAim and objective Reference Method Results Discussion Conclusion

【 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.

ProcedureAim and objective Reference Method Results Discussion Conclusion

Sort 1 9

Danger Dangerous Extremely dangerous

Urgency Urgent Extremely urgent

Unsafe Unsafe Extremely unsafe

1.Flash colour2.flash rate3.flash mode4.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]

Four hypothesesAim and objective Reference Method Results Discussion Conclusion

Tukey method:

Four hypothesesAim and objective Reference Method Results Discussion Conclusion

Flash colour

Level Mean

Red 6.371 A

Blue 4.626 B

Yellow 4.431 B

Tukey method:

Four hypothesesAim and objective Reference Method Results Discussion Conclusion

Flash rate

Level(fpm) Mean

240 5.501 A

180 5.324 A B

120 5.052 B

60 4.465 C

flashes per minute

Tukey method:

Four hypothesesAim and objective Reference Method Results Discussion Conclusion

Flash mode

Level Mean

Triple 5.381 A

Double 5.188 A

Single 4.687 B

Tukey method:

Four hypothesesAim and objective Reference Method Results Discussion Conclusion

Auditory alarm

Level Mean

Siren 5.708 A

Security(一般大眾 )

5.616 A B

Buzzer 5.411 B

No sound 3.607 C

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]• Flash colour, flash rate and flash mode [F(12, 431) = 2.39, p < .01]• Flash colour, flash mode and auditory alarm [F(12, 431) = 1.99, p < .05]• Flash rate, flash mode and auditory alarm [F(18, 431) = 2.26, p < .005]

Aim and objective Reference Method Results Discussion Conclusion

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 colours1) Chan and Courtney(2001) that red was the colour most frequently chosen to indicate the

concept of danger and hazard.2) Wogalter et al. (1998) also showed that the colour red connoted greater hazard than other

colours.

Flash rateHowett 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 modeTriple flash perhaps make the alerting signal beyond what is necessary.

Aim and objective Reference Method Results Discussion Conclusion

Aim and objective Reference Method Results Discussion 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.

Conclusion