Blowing Your Horn

For divers on live-aboards in the deep blue sea, an air horn attached to the low pressure hose is often part of one’s safety equipment, supplementing a safety sausage. Supplementing, we say, because if you run out of air your air horn will not work.

Dive rmagazine tested four devices using a professional sound analysis machine to record sound levels. The human ear is most receptive to noises at a frequency of 2 kilohertz (2 kHz), so the volume was measured at that level. They also conducted subjective tests at a distance of 1,000 m.

The best device was the Buddy Blast, manufactured by AP valves. At 2 kHz its volume was 95.3 decibels (db) and could easily be heard at 1,000 m. “This was by far the loudest of everything tested.”

The Dive Alert, producing 83 db at 2 kHz could also be heard at 1,000 m. It was “a very loud unit ... but was not as good overall as the Buddy Blast.”

The Sub Alert (70.1 db Volume at 2kHz) “produced considerably less decibels than either the Dive Alert or the Buddy Blast. It made a very high-pitch squeal that could just be heard at 1,000 m.”

Trident’s Hammerhead (63.9 db Volume at 2kHz) “makes a very odd quacking’ noise, which was the least effective and could not be heard at 1,000 m.”