The Canadian-made Phonofonics II ($835) is said to be able to get a 55 dB sound level out of your iPod without using any external power.
Here’s how it works:
Through passive amplification alone, These unique pieces instantly transform any personal music player + earbuds into a sculptural audio console.
Without the use of external power or batteries, the Phonofone inventively exploits the virtues of horn acoustics to boost the audio output of standard earphones to up to 55 decibles* (or roughly the maximum volume of laptop speakers)
Upon connecting active earphones to the Phonofone their trebly buzzing is instantly and profoundly transformed into a warm, rich and resonant sound.
The Phonofonics II is a limited edition product at 200 units.