The Conch Shell Horn - A Geek’s Eye View

After a couple of months in the Bahamas listening to other cruisers serenading the sunset with their conch shell horns, I decided that it was time to make my own horn. The little girl selling them in the Nassau straw market explained the simple procedure: hit the tip with a hammer to make a mouth piece, then use a dab of Bondo to fill in the hole made to clean out the animal. Then she held the shell up to her mouth and blew. Out came the mournful melodious note that echos over so many anchorages at sunset. Child’s play.

The first thing I needed was an appropriate shell. Strombus gigas had nothing to fear from my vegetarian self. Rather than killing one, I wandered the beach looking for a shell that had been pre-liberated from its gastropod owner by some molluscivore. Bondo was not something to be found in my on board inventory, so I needed a shell with a narrow hole that could be filled in with caulking. Eventually, I found one that fit my criteria, although no one would argue that it was the prettiest shell they had ever seen.

Back on board, I got out my hammer and braced the shell against the cockpit combing. I gave the tip a sharp rap. The shock instantly freed every grain of sand trapped in the shell. It began to pour all over the deck like a broken hourglass with a bad case of the runs. I grabbed the shell and raced for the rail leaving behind a thick and spreading trail of sand. I held the shell over the side while the sand poured and poured, and then poured some more.

After the biblical flood had ceased, and several minutes had been spent sweeping, I had the shell braced in place again. Another sharp rap. The hammer bounced off without even making a chip. I raised the hammer again and swung it down harder. Boing! Harder, harder, even harder! The shell was completely unfazed. I began wailing on it as hard as I could. Ha! Is that the best you can do! I lifted the hammer up over my head and brought it down like Thor, the mighty thunder god, himself. Crash! Finally, the shell gave in, leaving a horribly jagged opening that looked nothing like a mouthpiece.

A bit of chiselling and sanding resulted in something that wouldn’t cut too deeply into my lips. Caulk was applied over the cleaning hole and left to cure. Not wanted to subject the other cruisers to my learning pains, I waited until the next day when I was underway to try blowing it.

The whole thing was basic highschool physics. The shell was merely an open air column like any brass instrument. Standing waves of sound could be set up inside the shell such that my lips formed a loop at one end, a node formed in the centre, and a second loop formed at the opening. So long as the wavelength of the sound was twice the length of the coiled up air column in the shell, a resonance could be set up, fantastically amplifying the buzzing of my lips. Shorter waves could also be made to resonate, so long as the length of the shell was a multiple of half the wavelength. Overtones would be created this way giving the horn its unique sound. It would also create some room for error for a guy who couldn’t figure out the exact frequency at which to vibrate his lips.

The frequency required for my lips was of course related to the wavelength of the sound by the wave equation: v = λf, where v = the speed of sound, λ = the wavelength, and f = the frequency. The speed of sound was given by v = 0.6T + 332 m/s, where T = temperature in ^oC. My lips were nothing but a set of vibrating strings governed by a touch of basic string theory. Sound waves would vibrate in a string similarly to an open air column except that the nodes would be found at the ends of the string and a loop formed in the middle. The frequency was again given by the wave equation. The frequency could be altered by varying the length, tension, diameter, and density of the string according to: f₁/f₂ = L₂/L₁× T₁/ T₂ × d₂/d₁ × ρ₂/ ρ_1, where: f = frequency, L = length, T = tension, d = diameter, and ρ = density.

The effective length of my lips could be adjusted by squeezing them together at various distances from the centre of my mouth. The tension could be controlled by flexing the muscles of my lips. Diameter and density could only by manipulated by Julia Roberts’ plastic surgeon.

The theory was elementary, now all I had to do was make it happen in practice. The problem was that I am a science nerd, not a musician, and had never successfully played an instrument. I puckered my lips, brought the shell up to them and blew. BLAAAATT!!! The unmistakably phlegmatic sound of a sea elephant in heat. More tension. GROOAAANNN!!! The call of a dying harp seal. Wet my lips, squeeze them farther apart. BRAAHHHH!!!! A male walrus proclaiming himself beach master. My cat ran for cover. Less tension. THLIIIITTT!! Cow flatulence. You could practically smell the methane. At least the other sounds were sea creatures! Pucker more. FRIIIPPPP!!!. The patented note of a whoopie cushion.

I stumbled around my cockpit lightheaded from my exertions. My cat eyed me cautiously from under a cushion, her paws over her ears. When the world stopped spinning, I took a huge breath, lifted the shell once more, and blew. A deep vibration began to feedback into my lips. The shell shook in my hands. My lips went numb with the mad oscillations. Resonance filled my chest as my ribs quivered in and out. The call echoed off of my sails and spread out over the banks. I saw visions of torches being juggled over Mallory Square, sailboats bobbing in an Abaco anchorage, and in front of white Exuma beaches, all dyed with the reds and oranges of the sunset. Could that have been the elusive green flash?

The next day I was on a beach enjoying sundowners with my fellow cruisers. As the sun dipped below the horizon, I was silhouetted against a glowing crimson Jumentos sky. I stood proudly, chest out, legs shoulder width apart, master of the conch. Long blonde hair cascaded over my shoulders, while a tanned muscular arm brought the shell to my lips. FRIIIPPPP!!! Whoopie cushion. BRAAHHHH!!!! Walrus. GROOAAANNN!!! Harp seal. BLAAAATT!!! Sea elephant...