To Repeat or Not to Repeat? Using EEG to redesign Auditory Alarms
Our brain has built-in mechanisms to stop our minds from wandering. There is no doubt that this is highly useful for work, or driving a car, but our brain is also easily capable of deceiving us. This phenomenon isn’t just limited to vision: our auditory system can, believe it or not, be affected to the point of becoming completely deaf.
Inattentional deafness to critical alarms has increasingly been observed in cockpits and operation rooms, where pilots and hospital staff are not able to detect unexpected changes in their auditory environment, leading to a major safety issue.
When an auditory alarm repeats, our brains may habituate to it and begin to perceive it less and less. This is known as the repetition-suppression (RS) effect. Researchers from the University of Taiwan aimed to combat this by proposing and inserting pitch and intensity modulated alarms in identical repeating patterns, which aims to reduce the effects of RS without using new alarms which can cause extra efforts to memorize.
Background and Context: EEG is an electrophysiological monitoring method using non-invasive electrodes placed on the scalp to record the electrical activity of the brain. It has often been utilized in the fields of ergonomics (study of people’s efficiency in their working environment) and brain computer interaction (BCI). Previous research in this realm has experimented with different auditory warning signals which were designed to influence perceptions, reaction times, arousal, alert and attentiveness by analyzing EEG frequencies alongside their behaviors. This study aimed to find an effective method of maintaining a users auditory attention and perception to repeated auditory alarms by reducing RS, and using EEG. In order to do so researchers had to ask themselves two important questions: 1. What are the effects on RS of repeating auditory alarms against realistic background noise? 2. Can this modulation method reduce RS?
Procedure: To conduct this experiment, 14 participants (six females and eight males, 21–26 years old), were chosen. These participants had no signs of hearing problems, brain disease, or brain injury. The researchers played a subtitled silent movie on a laptop placed in front of each participant, and used speakers to present the audio stimuli. Each participant sat on a chair in a noise-filtered chamber, and was told to focus on the silent movie while listening to the stimuli. A non-invasive 32-channel EEG cap was used to measure the participants’ brain activity. To simulate a noisy real-world environment, the standard stimuli was of ambient sound recorded in a coffee shop. All deviants consisted of five alarms, and followed one of three alarm patterns.
Results: This study was greatly successful in confirming two things: repeating identical auditory alarms do induce an RS effect; and the use of modulated alarms could reduce it. Furthermore, pitch and intensity modulated alarms had different influences on RS: with the former acting more quickly, but the latter, more strongly.
Ultimately through this study, it was proven that repeating identical tones can induce RS and reduce the participants’ awareness of the alarms in question. But by inserting pitch and intensity-modulated alarms between identical repeating sounds, participants were able to become more aware of their surroundings, therefore meaning that this study succeeded in reducing the RS effect without resorting to multiple different tones. Furthermore, EEG was found to be useful for examining the effects of modulated alarms on RS in a more realistic scenario.
Future Work and Limitations: Researchers reached many milestones through this study, but admit that they have a lot more work to do, as the experiment did not come without its fair share of limitations. One of the biggest of these limitations being that, the experiment only used sine waves as auditory alarms, while there are a wide array of auditory alarms that people experience in their daily lives. It was proposed that future studies on this topic include a distinctive amount of real-world auditory alarms, to increase the validity of the results. Furthermore, multiple sessions should have been done in the experiment, to control for any interactive effects of the multiple deviants. Lastly, pitch and intensity are not the only categories of modulation that can be applied to alarms, so it was proposed that future studies look into harmonic intensity and timbre.
Ultimately through these findings, researchers were able to create design implications that would help create more effective, efficient, and safe repeating auditory alarms. There is a long way to go as far as the future of auditory alarms and the safety involved of those around them goes, but a step in the right direction has been made to moderate the RS effect and increase spatial awareness of those affected.
Reference:
Yi-Chen Lee, Fu-Yin Cherng, Jung-Tai King, and Wen-Chieh Lin. 2019. To Repeat or Not to Repeat? Redesigning Repeating Auditory Alarms Based on EEG Analysis. In Proceedings of the 2019 CHI Conference on Human Factors in Computing Systems. ACM, 513.
