In 1964, officials at Marineland of the Pacific, in Southern California, were amazed to discover that a Shure Model 505 Microphone used to broadcast porpoise “speech” at the Sea Arena had become corroded and salt encrusted— but was still working. Years earlier, the microphone was permanently installed just above the surface of the water in a large tank, allowing the porpoises to deliver “speeches” as part of their daily performances for visitors. A plastic cover hermetically sealed the microphone from the air, but a pinhole break in the plastic allowed salt water to leak inside the cover. Over 12 to 15 months, the microphone became completely encrusted, but it was never noticed— because the public address system continued to perform flawlessly.
This Shure Model 505 Microphone is corroded but still operational after being used as a “public address system for porpoises” at Marineland of the Pacific, in California, in 1964.
According to James S. Long, superintendent of Marineland: “Gil Lewis, our staff electrician, was checking various audio components at the Sea Arena and, out of curiosity, decided to examine the plastic seal on the microphone. Only a 1⁄4-inch opening right in front of the diaphragm aperture had escaped the corrosion. But the microphone worked perfectly, and even the volume control was at exactly the same setting as when it was installed.”
The Model 505 was replaced in the Shure line by the Model 404, which was designed with a supertough, corrosion-proof case of Armo-Dur, offering better protection against oil, grease, fumes, and salt spray. The case also was able to sustain greater levels of mechanical shock and vibration.
The Model 404 was designed as a handheld microphone that “fit snugly in the palm of the hand.” Its rugged Armo-Dur case and high speech intelligibility “were ideally suited for outdoor use at sports arenas, athletic fields, and carnivals.”
