In 1979 Johan H.M. Frijns (1961, The Hague) completed the Gymnasium-B and commenced to study Applied Physics at the Delft University of Technology. In 1982 he received the Bachelors degree (Hons.) and started to study simultaneously Medicine at the University of Leiden. In 1983 he completed the Propaedeuse in Medicine (Hons.) and obtained the Masters degree in Applied Physics (Hons.) in Delft with a thesis entitled Development of non-periodic stimuli for and investigation of the Binaural Edge Pitch. This work was performed in the Acoustical Perception Group (prof. dr. ir. F.A. Bilsen). In 1986 he obtained the Masters degree (Hons.) in Medicine at the Leiden University, where he passed the Artsexamen (Hons.) in 1988. In September 1988 he started with his research on cochlear implants in the ENT-department of what now is called the LUMC (Chairman: prof. dr. P.H. Schmidt). Between 1989 and 1994 he was educated to become an ENT-specialist and from then on he was affiliated to this clinic as a staff member (first chef de clinique, later head of the section General ENT). In 1995 he completed his PhD thesis (Hons.), entitled Cochlear Implants - A Modelling Approach (promotor Prof.Dr. J.J. Grote, Leiden and co-promotor Dr. J.H. ten Kate, Delft). This thesis was awarded the 1995 prize of the Dutch ENT society, and the second prize (1995-1996) of the Dutch Biophysical Society.
Clinically he sub-specialised in (neuro-)otology, while he became head of the Cochlear Implant Rehabilitation Centre Leiden (CIRCLE, 1999), which started a cochlear implant program, building on the growing body of translational research on the subject of his group. At present, CIRCLE has implanted more than 1000 patients (adults and children) with cochlear implants (CIs) and auditory brainstem implants (ABIs), with outcomes ranking amongst the world's best. Frijns is teacher in a number of post-academic courses and organized several international conferences.
In 2005 he became professor in Otology and Auditory Physics on behalf of the Heinsius-Houbolt Foundation. From 2005 to 2010 he was Chairman of the ENT-department of the LUMC. Since January 2006 he holds the ordinary Chair of Otorhinolaryngology, in 2016 renamed to Otology and Auditory Physics. The title of his inaugural lecture was Leids KNOOPpunt (Leiden nodal point). At present he is Chairman of the Centre for Audiology and Hearing Implants at the LUMC.