Defence researches audio warnings in the cockpit

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A CF-188 Hornet taxis onto the runway at Joint Base Pearl Harbor-Hickam, Hawaii during RIMPAC 2016 on July 29, 2016. Photo: MCpl Chris Ward, MARPAC Imaging Services ET2016-4626-09 ~ Un chasseur CF-188 Hornet circule sur la piste à la base interarmées Pearl Harbor-Hickam, à Hawaï, au cours de l’exercice RIMPAC 2016, le 29 juillet 2016. Photo : Cplc Chris Ward, Services d’imagerie des FMAR(P) ET2016-4626-09

With cockpit audio warnings, is the male or female voice more effective for getting the attention of pilots? This is something being investigated by Defence.

Auditory warnings are used in aircraft to alert the crew to hazards and their levels of danger. Failing to comply with a warning has led to aviation incidents and accidents.

Little is known about the effects of the acoustic parameters of verbal cockpit warnings on perceived urgency. Robert Arrabito, a Defence Scientist in the Human-Technology Interaction Group at Defence Research and Development Canada’s Toronto Research Centre, investigated the effects of the speaker’s gender and the voice style of verbal cockpit warnings on performance to help make warning messages distinct from speech on the flight deck.

In the past, it has been said that the female voice is easier to identify amid the flurry of radio chatter, but further research has proven otherwise. The increasing role of females in various aviation occupations in the CAF necessitated a re-examination of the gender of the speaker and intonation of warning messages to determine their applicability for male and female listeners. This information becomes important when you are talking about warnings that could avoid a catastrophic event.

Mr. Arrabito and his team had participants monitor the auditory channel and identify the verbal warning while performing a visual task. A male and female actor annunciated each warning word in three voice styles: monotone, urgent, and whisper. In the first of two experiments, the warning words were presented in a quiet background. In the second experiment, the warning words were presented in a background of speech babble which simulated cockpit radio communication.

The results of the first experiment showed that the monotone and urgent styles resulted in the fastest identification response time regardless of either the speaker or listener’s gender. The second experiment showed the male speaker annunciating warnings in either the monotone or the urgent styles resulted in the largest proportion of correct responses, and fastest identification response time regardless of the listener’s gender.

“If there are no competing background sounds, it doesn’t matter the sex of the talker annunciating the warnings,” said Mr. Arrabito. “But when you start to introduce speech babble, the sex of the talker annunciating the warnings becomes important. Various warnings by males and females showed listeners responded better to the male voice than the female. But that was in one particular study, so we can’t make a general assumption as to what voice type is better.”

The conclusion of this study was that the effective use of speech parameters and word semantics can increase the importance of verbal cockpit warnings.

Non-verbal warnings also studied

Mr. Arrabito also studied non-verbal warnings, where he investigated pilots’ judgement of urgency of the warnings in the CH-146 Griffon helicopter.

“We got to fly every day during the study and experience what the pilot and co-pilot would hear on the flight deck, and how they respond to certain warnings,” said Mr. Arrabito. “Some warnings weren’t loud enough to get your attention, but interestingly enough, those warnings were meant to be very important, where as another warning was quite loud and didn’t have as near as much importance.”

Are speech warnings better than non-speech warnings? Tested Griffon pilots told researchers that the warnings which sounded the most urgent to them were indeed the ones that had the least importance assigned to them.

The problem of conveying appropriate levels of urgency in non-speech warnings is also experienced in hospital operating rooms; anesthesiologists depend on auditory warnings to alert them to critical changes in the patient’s physiological condition.

“They have the same problem: the sounds that convey the most urgent warning may not necessarily be the loudest,” he said. “Non-verbal warnings are designed independently of each other. Lab studies have been carried out over many years, but in many instances non-verbal warnings are poorly designed because they do not connote the appropriate level of urgency.”

Mr. Arrabito continues to conduct research on auditory displays in support of the CAF. “It’s a lot of fun and I get to work with amazing individuals,” he said.

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