The First CROS Hearing Aids?
Wayne Staab, PhD (and official Canadian Audiologist Audiology Historian) and Robert Traynor, PhD will alternate Stories from our Past which are about technical innovations and approaches that are now ubiquitous in our field or were important in the development of our field. In many cases, these stories will be written by the innovators themselves.
Posted on September 5, 2017 at hearinghealthmatters.org. Reprinted with permission.
In 1965, Harford and Barry were credited for the first accessible published description of across-head fitting1. It was called the CROS (Contralateral Routing of Offside Signals). Harford and Barry did acknowledge, however, that Wullstein and Wigand had published results on an almost identical across-head arrangement three years earlier2. The Wullstein and Wigand work has seldom been quoted in related literature in the US, perhaps because it was written in German3. But, were these the first CROS hearing aids?
Eyeglass Hearing Aids
Interestingly, even prior to Wullstein and Wigand’s publication in 1962, across-head hearing aid fittings were common. This concept was incorporated into the first eyeglass hearing aids. This was even prior to Fowler (1960) suggesting that for total monaural hearing loss, that a microphone could be placed on the bad ear side and use a bone-conduction vibrator at the good ear4. (Ken Berger reported that H.J. Salomon et al. in 1965 filed a patent that essentially followed Fowler’s bone vibrator coupled to an off-side microphone – patent #3,183,312).
At least since 1954, a number of hearing aid manufacturers produced eyeglass hearing aids in which both temples were needed to achieve across-head hearing. This was primarily due to the size of components, requiring that some components be placed in each temple, and the two sides hard wired to each other. Eyeglass hearing aids were common at the time as evidenced by the number of companies that made such units, and are listed in the following section. This information on companies and the designation of two-temple requirements for such aids was compiled from Berger’s book on hearing aids3.
Company and Year in Which Across-Head Eyeglass Hearing Aids Were Introduced
- Akumed MGH Glasses – 1954
- Acousticon Model A-235 – 1956
- Amplivox Model SA – 1956
- Ardente Acoustic Laboratories, LTD Model A – 1955
- Auditron (Globe) Model T12 – 1959
- Audivox Model “Spectacular” – 1956
- Aurex Model A400 – 1955
- Beltone Model Virtuoso – 1958
- Bommer Model FM – 1956
- Robert Bosch Elekrtronik Model Hörbrille – 1957
- Danavox International Glasses Model – 1956
- Deutsche Akustik-Gesellschaft Glasses Model – 1958
- Dicton Høreteknik Glasses Model – 1958
- The Dynaphone Co. DynaGlasses Model – 1956
- AG Für Elektro-Akustik Model Visaton – 1956
- Fortiphone LTD Model Spectette – 1956
- Gem Ear Phone Co. Glasses Model – 1957
- Linke-Hörgeräte Glasses Model – 1956
- Magnatone Corp. Model M1 – 1956
- Maico Electronics Model AF Transist-Ear – 1958
- V/O Medexport Model CO-2 – 1958
- Micro-Elektrik Ltd. Model B/05 – 1956
- Microtone Co. Model Vision-Ear Bone-Conduction glasses – 1954
- Otarion Electronics Inc. Model L.10 (Listener) – 1954
- Oticon Eyeglass Model – 1956
- Otoacustica Electronic Products Model Gamma (Telescope) – 1961
- Paravox Hearing Aid Co. Model I-G (I-Glas) – 1955
- N.V. Philips Gloeilampenfabrieken Model KL6100 – 1959
- Polyfon Hearing Aids Ltd. Model Optic Ear – 1958
- Radioear Corp. Model Stereo – 1958
- Rexton Model H-570 Glasses – 1960
- Siemens A.G. Glasses Model – 1957
- Skandiavox Model 60T – 1958
- Telex Corp. Model #44 – 1958
- Toepholm & Westermann A/S Model Sight-N-Sound Glasses – 1959
- Trans-Audio Co., Inc. Model Twin Temples – 1958
- Unex Laboratories, Inc. Model VE (Vision Ear) – 1955
- Wendton Model WT800 – 1955
An example of an across-head eyeglass hearing aid is provided in Figure 1. This is from the author’s collection and shows a Dicton unit from 1958. What follows is a report on this device to assist in explaining how the across-head eyeglass hearing aid was designed.
Author’s Note: What most hearing professionals do not realize is that during the mid 1950s into the early 1970s, eyeglass hearing aids were very much the fitting style. They were the “new” technology. In fact, according to Lybarger, they preceded behind-the-ear hearing aids in development history. (More on this in a later post).
Dicton Høreteknik Model C, Year = 1958
The Dicton eyeglass hearing aid was designed to take sound from one side of the head via a microphone pickup, and transferring sound to the contralateral ear using a wired arrangement through the eyeglass frame and temples to the ear. This was powered with a 625 cell and used an Oticon receiver housed in the off-side module. The hearing aid was manufactured in Copenhagen, Denmark by J. Laurberg Christianson with Skandiavox. It was distributed in the United States by Omega Electronics (Jose Manzini in New Orleans, LA) and in England by Leyton Instrument Company.
The remainder of this post is to show this across-head hearing aid in some detail because there seems to be little information available on such early across-head eyeglass hearing aids, even though they were quite popular.
Comparison to Later Eyeglass CROS Hearing Aids
A comparison of the Dicton to a later eyeglass CROS hearing aid (Maico Transist Ear, Year = about 1970) is shown in Figure 6.
First Non-Across-Head Eyeglass Hearing Aid
In fact, it was not until 1956 that the first eyeglass temple hearing aid was made that was not an across-head hearing aid. That unit was the Audivox (successor of Western Electric) “Spectacular.” It was a three transistor hearing aid and used a RM400 battery as its power supply (Figure 8 and 9).
- Harford, E., & Barry, J. (1965). A rehabilitative approach to the problem of unilateral hearing impairment: the contralateral routing of signals (CROS). Journal of Speech and Hearing Disorders, 30, 121-138.
- Wullstein, H.L. and Wigand, M.E. (1962). Über Hörhilfe zum Beidseitigen Hören für Einseitig Ertaubte und ihre Voraussetzungen (A hearing aid for single ear deafness and its requirements). Acta Otolaryngologica, 54, 1962, 136-142.
- Berger, K. (1970). The Hearing Aid and its Development. National Hearing Aid Society, Livonia, MI.
- Fowler, E. P. (1960). Bilateral hearing aids for monaural total deafness: a suggestion for better hearing. Archives of Otolaryngology, 72, 1960, 57-58.