Carson Leong designed computer speakers that bellow out as the volume increases:
To turn the volume down, simple squeeze the skin to the desired volume. This creates a more tactile and visual experience for the user, where functions do not have to be operated by simply pressing buttons.
Link via DVICE | Designer's Website
the correct word is billow
billow: bil·low (bl)
n.
1. A large wave or swell of water.
2. A great swell, surge, or undulating mass, as of smoke or sound.
v. bil·lowed, bil·low·ing, bil·lows
v.intr.
1. To surge or roll in billows.
2. To swell out or bulge: sheets billowing in the breeze.
bellow: bel·low (bl)
v. bel·lowed, bel·low·ing, bel·lows
v.intr.
1. To make the deep roaring sound characteristic of a bull.
2. To shout in a deep voice.