Hello! My name is Tobias Röddiger and I welcome you to the presentation of our paper "EarRumble:
Discreet Hands- and Eyes-Free Input by Voluntary Tensor Tympani Muscle Contraction". Smart
earables are becoming a ubiquitous platform with an ever-growing number of sensing capabilities
such as body motion, heart rate or even brain monitoring features. Traditionally, interaction
on such ear-worn devices occurs by performing input either directly on the ear or in the
immediate vicinity such as on the ear rim or the face of the user. In our paper we take
a completely different approach. We rely on tensor tympani muscle which is the second
smallest muscle found in the human body. It is located in the middle ear and some people
can contract it voluntarily to induce a dull rumbling sound - a phenomena also known as
"ear rumbling". So we asked ourselves: Can we us the rumbling ability for discreet interaction?
Hence, we explored the viability of tensor tympani contraction, developed a sensing device
that can be embedded into a standard earbud formfactor, implemented a recognition pipeline,
and conducted an application study using the EarRumble technique. We applied a lab-validated
online questionnaire and found out that 36-50% of the population possess the rumbling ability.
Out of those, over 80% could perform ear rumbling in isolation to any other movement and over
85% could perform rumbling in quick succession and also for prolonged times. So ear rumbling
proved to be a great opportunity for interaction. As the eardrum displaces inward during the
contraction of the tensor tympani, a pressure change can be observed in the sealed ear canal.
Therefore, we built an in-ear pressure sensing device that also has audio capabilities. We
initially propose three simple gestures. A rumble - which is a quick contraction of the
tensor tympani, a double rumble - by contracting the tensor tympani twice in quick succession,
and a hold rumble - by holding the tensor tympani contracted for about one second. We
also asked participants to perform multiple rumbles over the duration of five seconds
to initially explore the potential for complex interaction such as beat synchronization.
From related work we knew that changes in facial expression may also induce pressure
changes in the ear canal so we also collected a set of related activities. In total, we
recruited 16 participants. Using the collected data we built our recognition pipeline. We
use a threshold-based approach for activity detection and then extract 35 features from
each ear canal. We applied gradient-boosted decision trees for the final gesture prediction
and achieved 95% overall accuracy. We then applied the rumble technique in two applications
- a music player and for handling incoming phone calls and we compared our technique
to traditional input based on buttons. Six users preferred using rumbling for interaction
but they wished for more immediate feedback as the current response time of our recognition
pipeline is about 400 milliseconds. In our small sample we could not identify any significant
differences for the cognitive load. However, our results greatly highlighted the discreet
nature of the interaction technique. In this video you can see myself soldering an SMD
part, while skipping the song using ear rumble, which also underlines why users described the technique
as magical and almost telepathic. So, in conclusion EarRumble proved to be a viable, discreet,
and easy to use technique with earables that can be embedded into a standard earbud formfactor.
If you are interested in more details such as ease of use, comfort, details on the recognition
pipeline or also reaction times - please refer to our paper. Thank you.