5aNSa4 – Preserving workers’ hearing health by improving earplug efficiency

Work carried out by researchers from ÉTS and the IRSST

Bastien Poissenot-Arrigoni – bastien.poissenot.1@ens.etsmtl.ca
Olivier Doutres –  olivier.doutres@etsmtl.ca
École de Technologie Supérieure
1100 Rue Notre-Dame Ouest,
Montréal, QC H3C 1K3

Franck Sgard – franck.sgard@irsst.qc.ca
Chun Hong Law – chunhonglaw@hotmail.com
505 Boulevard de Maisonneuve O.,
Montréal, QC H3A 3C2

Popular version of paper 5aNSa4 (Earcanal anthropometry analysis for the design of realistic artificial ears)
Presented Friday morning, December 11, 2020
179th ASA Meeting, Acoustics Virtually Everywhere

Noise exposure accounts for 22% of worldwide work-related health problems. Excessive noise not only causes hearing loss and tinnitus, but also increases the risk of cardiovascular diseases. To provide protection, workers normally wear earplugs. However, commonly available earplugs are often uncomfortable, since they don’t fit everyone’s ears equally well.

How could we improve the comfort and effectiveness of these earplugs? What aspects of the ear canal must be taken into account? To answer these questions, researchers from the École de technologie supérieure (ÉTS University) and the Institut de recherche en santé et sécurité du travail (IRSST) analyzed the varying structure of ear canals to find a correlation between their shapes and the effectiveness of three commonly-used models of earplugs.

Each one is unique
Just like fingerprints, ear canals are unique. So, to find the best compromise between comfort and efficiency, you need to understand the relationship between the shapes of ear canals and of earplugs.

Earplugs must not only fit properly inside the ear canal, but must also exert pressure against the walls of the canal in order to make a tight seal. However, if the plugs put too much pressure on the ear canal walls, they will cause the wearer pain.

The methodology
To study these aspects, 3D models of volunteer workers’ ear canals were created. These people wore three different types of earplugs.  To obtain the geometry of their ear canals, a moulding material was injected to create canal moulds. These moulds were then scanned by measurement software to establish the geometric characteristics of the ear canal, such as the width at various locations and the overall length.
F1_Earcanal_Modelisation.jpg
F2_Earplug_Attenuation_Measurement.jpg - earplug
The noise attenuation of the three models of earplugs was then measured for each volunteer. Two miniature microphones were installed in and around the plugs to measure the noise outside and inside the ear plug.A statistical analysis as well as algorithms based on artificial intelligence helped categorize the morphology of ear canals as a function of the degree of noise mitigation of each earplug.
 “F3_Ear_Anatomy.jpg”
Concrete applications
The results of the study show that the area of the ear canal called the “first bend” is closely linked to noise attenuation by earplugs. Groups of similar structures created using artificial intelligence will allow researchers to develop a multitude of tools for manufacturers, who will then be able to produce a range of more comfortable ear plugs. This will allow prevention professionals to suggest models suited to each worker’s ear canals.

3 March 2020: World Hearing Day

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4pNSa4 – Inciting our children to turn their music down: the “Age of Your Ear” concept

Jeremie Voix
Romain Dumoulin
École de technologie supérieure, Université du Québec, Montréal, Quebec, Canada

Popular version of paper 4pNSa4, “Inciting our children to turn their music down: the AYE concept.”
Presented Thu, Nov 08   1:45pm – 2:00pm in SALON C (VCC)
176th Meeting Acoustical Society of America and 2018 Acoustics Week in Canada (Canadian Acoustical Association) at the Victoria Conference Centre, Victoria, BC, Canada

Problem
According to the World Health Organization (WHO), more than 1.1 billion people are currently at risk of losing their hearing due to excessive exposure to noise. Of this, a significant proportion consists of children, youth and young adults who are exposing themselves to excessive levels of sound through various leisure activities (music players, concerts, movies at the theatre, dance clubs, etc.).

Existing solutions
To address this issue, many approaches have been developed, ranging from general awareness messages to volume limiters on personal music players. For instance, the recent “Make listening safe” [1] initiative from WHO aims at gathering all stakeholders, public health authorities, and manufacturers to define and develop a consolidated approach to limit these non-occupational sound exposures, based on dosimetry. Indeed, significant efforts have been put into the idea of assessing directly on a PMP (personal music player) the individual noise dose, i.e. the product of the sound pressure level  and the duration, induced during music listening.

Need to find a better way to sensitize the users
While many technical issues are still actively discussed in some related standards, a major concern arose with regards to the message communicated to the end-users. End-users need to be educated on the risk of noise induced hearing loss (NIHL) and its irreversibility, but at the same time they also need to be made aware that NIHL is 100% preventable pending safe listening practices are followed.

More importantly, end users have to be left with an appealing noise dose measurement. In that regard, expressing equivalent sound pressure level in decibels (dB) or the noise dose in percentage (%) is of little value given the complexity of one and the abstraction of the other. But communicating about the dangers of music playback is definitely something very new for most of the hearing conservation specialists and communicating with this particular group of youth is only adding to the difficulty.

Our approach
In the quest for a meaningful message to pass to these young end users, this article introduces a new metric, the “Age of Your Ears” (AYE), that is an indication of the predicted extra aging caused by the excessive noise dose each user is exposed to. To perform such prediction, a multi-regression statistical model was developed based on normative data found in ISO 1999 [2] standard. This way, an AYE value can be computed for each subject, using only his age, sex and sound exposure, to represent the possible acceleration of aging caused by excessive music listening, as illustrated in Fig. 1.

Age of Your Ear

Fig. 1: While hearing will normally worsen because of the natural aging process (dotted black line), this ageing can be dramatically accelerated because of over-exposure to noise (solid color lines).

Conclusions
In a world where personal musical players are ubiquitous, and have also been putting hearing at risk, it is interesting to see them as potential tool, not only to address the issues they created, but also for raising awareness on the dangers of Noise-Induced Hearing Loss at large.

The proposed AYE metric will be first implemented in a measurement manikin setup that is currently under development at the Centre for Interdisciplinary Research in Music Media and Technology, housed at the Schulich School of Music at McGill University (CIRMMT). This setup, further described in [3], is inspired by the “Jolene” manikin developed though the “Dangerous Decibels” program [4]. The resulting measurement kiosk will be complemented by a smartphone-based measurement app that will enable musicians to assess their entire noise exposure. It is hoped that the proposed AYE metric will be relevant and simple enough to have a beneficial impact on everyone’s safe hearing practices.

[1] WHO – Make Listening Safe- http://www.who.int/deafness/activities/mls/en/.

[2] ISO 1999:2013 – Acoustics – Estimation of noise-induced hearing loss, 2013.

[3] Jérémie Voix, Romain Dumoulin, Julia Levesque, and Guilhem Viallet. Inciting our children to turn their music down : the AYE proposal and implementation. In Proceedings of Meetings on Acoustics , volume Paper 3007868, Victoria, BC, Canada, 2018. Acoustical Society of America.

[4] Dangerous Decibels – JOLENE – http://dangerousdecibels.org/jolene