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of sound will focus more attention to the vital role it plays in
sound perception.
Temporal Variation in Alarms
More attention to the role that temporal variation plays in our
perception and auditory cognitive processes can open new
avenues for designing more distinguishable and ergonomic
alarms. Although different areas of alarm implementation
will necessitate careful analysis to ensure optimal usability,
embracing temporal variability holds great promise-particularly
with respect to the alarms used in medical devices [26].
The complexity that can be found even in single musical tones
holds important lessons that can be invaluable in generating
new ideas for auditory interface sounds [27].
One alarm problem that we think can benefit from temporal
variability is annoyance. Investigations have shown that
changing prototypical invariant alarms (Fig. 2, iii.) to temporally
variable alarms, whether by adding an exponentially
decaying or complex envelopes seen in musical sounds (Fig.
3), can decrease annoyance without harming learning or recognition
[22], [28].
Our team illustrated this in an experiment designed to assess
the benefits of introducing even slight temporal complexity
to otherwise standard alarm tones. We synthesized two sets of
alarm tones: one temporally variant in envelope and the other
invariant. The temporally invariant sounds had envelopes similar
to those seen in Fig. 2, while the temporally variable alarms
had exponentially decaying envelopes-similar to those produced
by musical instruments such as the marimba, piano, or
guitar. We found no difference in learning or recognition of the
alarm sounds; however, participants rated temporally variant
alarms as significantly less annoying in each of three independent
experiments. This illustrates that even slight changes
in the temporal profile of a sound can significantly decrease
annoyance relative to standard temporally invariant tones,
without negative affects to recognition of alarm sequences [22].
Although annoyance may seem a trivial concern, it is important
to remember that high alarm rates are documented in
many settings, from healthcare [9] to processing industries [5].
In healthcare, high alarm rates are a leading reason for hospital
staff switching off annoying alarms [29]. This has unfortunately
resulted in patient deaths due to alarms being turned
off or their volume turned down [2], [9]. It is unlikely that the
prevalence of alarms will decrease, as more technology is continually
introduced to monitor important developments. If
alarms are unavoidable, reducing their annoyance holds important
benefits. Embracing temporal variation offers one
clear path to create alarms that are less annoying without sacrificing
their communicative function.
Conclusion
We propose that future alarm sounds be designed with greater
attention to the abilities of the system processing them (i.e., human
perception) rather than the simplicity of the devices producing
them. Although there are many unique problems with specific
alarm implementations, embracing temporal variability
8
offers an under-explored path to improvement. In many domains,
the sheer number of alarms is unlikely to be reduced
due to increases in the number of problems and conditions that
should be monitored. Therefore, temporal variation promises
a relatively simple approach to reduce annoyance, without
having to change other alarm system parameters such as alarm
rate, safe thresholds, etc. Additionally as introducing temporal
variation to individual tones does not impair recognition
of tone sequences, these more complex alarm sounds can be
backwards compatible with invariant melodic alarms.
In the early days of sound synthesis, technical constraints
precluded complex temporal variation. Today, those engineering
constraints no longer apply. We can easily and
inexpensively generate a near-infinite range of sounds for use
in auditory interfaces. If birthday cards can feature musical
passages, why do so many highly advanced machines communicate
using sounds that appear stuck with limitations
from decades past? Ironically, when it comes to sounds such as
alerts on smartphones or in video games, designers routinely
use a wide array of temporally varying, complex sounds. Yet,
alarms critical to safety, which signal crucial information with
life-or-death consequences, routinely employ sounds no more
complex than a garbage truck backing-up!
Rather than mere " bells and whistles " [30], auditory interfaces
are integral to safe operations in many areas, often
providing a first warning sign to potential hazards. The human
auditory system can differentiate between numerous complex
sounds and does so on a regular basis when interacting with the
world. Careful attention to the types of sounds we are adept at
differentiating in general, and the ways musicians have chosen
to shape and create sound in particular, offers a rich source of inspiration
for designing more ergonomic and efficient auditory
interfaces [26], [27]. We believe greater collaboration between
auditory perception researchers, sound designers, musicians,
engineers, and industry-specific experts will lead to promising
new approaches to creating more effective alarms and auditory
interfaces-as well as safer and more pleasant environments.
References
[1] M. Jeon, " Auditory user interface design: practical evaluation
methods and design process case studies, " Int. J. Des. Soc., vol. 8,
no. 2, pp. 1-16, 2015.
[2] M. Cvach, " Monitor alarm fatigue: an integrative review, "
Biomedical Instrum. Technol., vol. 46, no. 4, pp. 268-277, 2012.
[3] J. Edworthy, E. Hellier, K. Titchener, A. Naweed, and R. Roels,
" Heterogeneity in auditory alarm sets makes them easier to
learn, " Int. J. Ind. Ergon., vol. 41, no. 2, pp. 136-146, Mar. 2011.
[4] J. P. Bliss, " Investigation of alarm-related accidents and incidents
in aviation, " Int. J. Aviat. Psychol., vol. 13, no. 3, pp. 249-268, 2003.
[5] J. C. Laberge, P. Bullemer, M. Tolsma, and D. V. C. Reising,
" Addressing alarm flood situations in the process industries
through alarm summary display design and alarm response
strategy, " Int. J. Ind. Ergon., vol. 44, no. 3, pp. 395-406, 2014.
[6] R. D. Patterson, " Auditory warning sounds in the work
environment, " Philos. Trans. R. Soc. London, vol. 327, no. 1241, pp.
485-492, 1990.
IEEE Instrumentation & Measurement Magazine
October 2021
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