Get alerted to incoming calls and text messages without a lot of impolite clamour with a subtle ultrasonic ringtone.
High-frequency ringtones caused a stir awhile back when it was discovered that kids were using them in schools, since older adults generally can't hear as high up the frequency scale as the young'ns.
While the novelty of hearing a ringtone your teacher can't hear is certainly thrilling for a high school student, using ultrasonic ringtones has a benefit outside of trying to dodge the boot of the man. For some time now I've used a 16.7kHz pulse as a notification sound on my phone. It's in just the right pitch to cut through other noise, I never confuse it with anything but what it is, and I've never found myself in line at the bank mistakenly whipping out my phone when somebody's Soulja Boy ringtone is blaring.
Where can you grab obscure ultrasonic ringtones without resorting to mixing them up yourself? At the link below you'll find 12 ringtones, ranging from 8kHz to 22.4kHz. You'll definitely want to test them out on your actual phone, your phone speaker is likely greatly inferior to the speakers you have hooked up to your computer and probably won't produce the same quality tone.