Toronto Rehabilitation Institute
A small (4 cm long), curved electronic device designed to fit behind the helix (outer rim) of the ear. It consists of two primary parts: A transparent, slightly flesh tinted curving canal called an ear hook, and an electronics enclosure. The ear hook is attached to the enclosure by a threaded connection.
This example includes a cable that attaches to a three-pin port at the bottom of the enclosure.
The plastic electronics enclosure is in colour, with a darker brown plastic used for the controls and the battery door.
Accession Number: 2025.rehab.25
Alternative Name:
Primary Materials: Plastic
Markings:
Height = 3.5, Width = .8; Length = 4; Length of cord = 32.
This is a supplemental microphone that is designed to be used with a hearing aid in cases when a user has no usable hearing on one side. The microphone connects to a hearing aid on the side of the better hearing ear. This arrangement, known as Contralateral Routing of Signal (CROS) is used to overcome the “head shadow effect” in which the better hearing ear is unable to properly perceive sounds from directions that are blocked by the head.
This microphone is linked to the hearing aid by a cable. Newer examples link the microphone to the hearing aid using a wireless Bluetooth signal.
This artifact is in good cosmetic condition. It is a component of a CROS hearing aid and is thus incomplete.
Associated Instruments:
Manufacturer: Widex A/S. Lynge, Denmark.
Date of Manufacture: c. 1990s
This artifact was among a number artifacts related to audiology and optometry collected from the Toronto Rehabilitation Institute at 130 Dunn Avenue on December 6, 2017.
Jaipreet Virdi (2024). Hearing Happiness : Deafness Cures in History. Chicago: The University of Chicago Press, 2020.
Jaipreet Virdi (2024). “Deaf Futurity: Designing and Innovating Hearing Aids.” Medical Humanities 50, no. 4 (2024): 678–84.
Neil Bauman (2023) “CROS hearing aids existed 10 years before they were even invented!” ENT & Audiology News 32, 5. (Webpage archived 18 January 2026).
Mara Mills (2011). “Hearing Aids and the History of Electronics Miniaturization.” IEEE Annals of the History of Computing 33, no. 2: 24–45.
Earl Harford and Joseph Barry (1965). “A rehabilitative approach to the problem of unilateral hearing impairment: The contralateral routing of signals (CROS).” Journal of Speech & Hearing Disorders, 30(2), 121–138.
H. L. Wullstein and M. E Wigand (1962). “Über Eine Hörhilfe Zum Beidseitigen Hören Für Einseitig Ertaubte Und Ihre Voraussetzungen.” Acta Oto-Laryngologica 54, nos. 1–6: 136–42.
The introduction of the CROS solution to unilateral hearing loss is typically credited to Professor of Audiology Earl Harford, PhD, and audiologist Joseph Barry. (See Harford Barry 1965). A similar system had earlier been introduced by Wullstein and Wigand in Würzburg, Germany. (See Wullstein and Wigand, 1962). Neil Bauman (2023) notes that similar across-head, eyeglass-mounted hearing aids had been available for a decade prior. It is clear that eyeglass-mounted hearing aid arrangements that had the potential to address unilateral hearing loss appeared quickly once the introduction of the transistor made that level of miniaturization possible.
The “behind the ear” (BTE) format of electronic hearing aid first emerged in the late 1950s. The small format was made possible by the development of transistors. integrated circuits, and button cell mercury batteries.