Yesterday I slept through my alarm clock going off—it is the standard high-pitched beep of a travel alarm, and I can’t hear it if my ear is on the pillow, even if I’m awake. I just checked with a microphone, amplifier, and the Bitscope oscilloscope, and the beep is at 2kHz, though most of the energy is in higher harmonics (about 25dB more in each of 4kHz and 6kHz than at 2kHz, and about 10dB more at 8kHz than at 2kHz).
My wife, who said that the sound filled the whole house, suggested that I get an alarm clock I can hear, so I googled “low frequency alarm clock” (her suggestion—I would have looked for “deaf alarm clock”, which also works, but gets a different set of retailers). The market seems pretty saturated, and I found a large selection at http://www.rehabmart.com/category/Hearing_Impaired_Clocks.htm.
Perhaps the most outrageous ad copy was for the “Sonic Boom Skull Alarm Clock”
This Sonic Boom Skull Alarm Clock (also known as “The Skull”) from Sonic Alert is designed for guys and girls who think outside the box. With red flashing eye sockets, a strip of orange flashing alert lights and the deadly bone crusher bed shaker, you might want to sleep with one eye open. Did we mention the skull snooze button? Go ahead and snooze. We dare you. If the Bone Crusher bed shaker included with the Sonic Boom Skull Alarm Clock doesn’t wake you, how about 113 decibels of alarm?
I have no intention of buying this gem, however, as I can get a cheap clock radio for $10, and I can still be woken up by speech frequencies (it is mainly the higher frequencies that I’ve lost—above 3kHz). If I really need a bed shaker, I can hook up the Puck loudspeakers that I bought some time ago for experimenting with vibration, though that would probably require breaking open the case of the clock radio and adding a power amplifier—bed shaking takes a lot more power than the tiny loudspeakers in a clock radio.