Pink noise through an 8 ms comb filter with high feedback, air moving through a pipe
Preview plays right here. The generator adds a sleep timer, full controls, and WAV export.
Hollow Tube is the sound of blowing gently across the end of a wide cardboard tube, or air moving through a long duct: a soft, woody, pitched breathiness with a fundamental near 125 Hz and a stack of harmonics above it. It is smoother and lower than Metal Wind.
The color is exactly 3, pink. A comb filter with an 8 millisecond delay, 80 percent feedback and a 50 percent mix creates evenly spaced resonances starting at about 125 Hz, which the ear reads as a hollow pipe. The envelope rises in 0.5 seconds, holds for 2 at full level and releases over 1, a short cycle of three and a half seconds. There is no pulse.
It is useful as a tonal bed for ambient music and for people who find the pipe-like character calming. Metal Wind is the brighter, harsher comb relative at 3 milliseconds, and Singing Pipes gets a similar pipe tone from resonant bandpass filters instead. Because the cycle is short, it feels more like a steady drone than a rhythm.