aging ear
n. Age-induced hearing loss, particularly of high-pitched sounds.
Some U.S. students are downloading a high-pitched ring tone to receive text messages in class, a tone that many teachers can't hear. As people age, many develop what's known as aging ear and can't hear high-frequency sounds.
—“Ring tone deaf,” Vancouver Sun, June 14, 2006
In that old battle of the wills between young people and their keepers, the young have found a new weapon that could change the balance of power on the cellphone front: a ring tone that many adults cannot hear. …

The principle behind it is a biological reality that hearing experts refer to as presbycusis, or aging ear. While Miss Musorofiti is not likely to have it, most adults over 40 or 50 seem to have some symptoms, scientists say.

While most human communication takes place in a frequency range between 200 and 8,000 hertz (a hertz being the scientific unit of frequency equal to one cycle per second), most adults' ability to hear frequencies higher than that begins to deteriorate in early middle age.
—Paul Vitello, “A Ring Tone Meant to Fall on Deaf Ears,” The New York Times, June 12, 2006
2003 (earliest)
While healthcare professionals who work with elderly patients can earn continuing education credits for participating in a more comprehensive CD version of the course, the public can take advantage of the program's animated illustrations and narrated presentations on hearing health topics, such as tinnitus and presbycusis (aging ear), for general information.
—“House Ear Institute and USC Partner to Offer Online Hearing Course,” Audiology Online, December 23, 2003