Water was passed slowly through a 6mm inner diameter tube hanging 1750mm from the surface of the water. The water depth was 150mm in a standard bucket of height 200mm, diameter 260mm.

Sounds

Taken from a single recording, with only intermediate silences removed. They are quiet, so turn up your volume.

• A01
• A02
• A03
• A04
• A05
• A06
• A07
• A08
• A09

The sounds are remarkably similar. Note the strong background noise from the recording computer. The dominant frequencies of this noise are roughly:

Dominant frequencies of contaminating noise

Relative Magnitude	Frequency (Hz)
0.3174	516
0.3169	344
0.2407	172
0.1250	689

Notes

• Droplet impact consistently forms large surface bubbles and the standard "bloop" noise
• The surface cavity seems to form the large surface bubble, which survives for an instant and then pops. Size is approx. 40-50mm in diameter.
• The collapse of the main cavity sometimes forms small (<10mm) bubbles which can survive for a long time.
• Phsyically disrupting cavity/bubble formation eliminates the droplet noise
• Rising pitch seems to correspond in time with the closing of the bubble cavity. (need photos...)
• Weak "spitting" noise as bubbles break
• Adjusting height so main cavity does not form almost totally eliminates the droplet noise.

Spectrogram

All the spectrograms look the same, modulo some noise.

• Note the contaminating noise frequencies at the bottom.
• The strong vertical bars correspond to small "tss" noises which I believe are bubble breaks and very small splashes.
• The rising frequency feature in the middle of the sound (0.4s-0.5s)is the characteristic "bloop" noise associated with water droplets. It is very distinct and occurs in all the recordings.