Earlier this month, the news reported the latest craze, cellphone Ringtones that only teens can hear. The National Public Radio (NPR) article Teens Turn ‘Repeller’ into Adult-Proof Ringtone describes how:

The war between teens and authority figures has a new — or old — front: ears. British shopkeepers tired of teenage loiterers have turned to the Mosquito teen repellent, which emits a high-pitch frequency that most teenagers can hear — but not most adults.

But now teens have struck back against the Mosquito: They are using the same sound to communicate without adults’ knowledge.

At issue is a text-message ringtone that emits the same pitch as the Mosquito. Using it, students can learn about a new message while they’re in class — where they’re not supposed to be using their cellphones. Most of their teachers can’t hear the alert.

No matter which side of the argument you’re on, the rest of the article is fascinating reading.

At the opposite end of the sound spectrum are amplified phones for baby boomers. This Week In Consumer Electronics (TWICE) reports that

According to the Hearing Loss Association of America, 28 million Americans (one in 10) suffer from some form of hearing loss. The percentage shifts dramatically for those age 65 or over to one out of three. According to the National Institutes of Health, the number of people aged 65 and over is expected to double in size within the next 25 years. By 2030, almost one out of every five Americans (72 million people) will be 65 years or older.

Manufacturers Panasonic, Uniden, VTech, Motorola, ClearSounds and Clarity are getting involved not merely in raising the amplification but in isolating the frequencies that the hearing-impaired usually miss.