Pop Tune Wrecks Data

Music has long been accused of disruptive mystical powers. Back in the pre-CD days, it was suggested that popular rock groups recorded secret messages backward, a technique known as backmasking.

But it seems that an eighties pop tune by Janet Jackson has the power to fry a perfectly good hard drive. The problem is resonant technology.

Destructive resonance

The properties of waveforms dictate the science of analog and digital technologies. For example, antennae on our shiny smartphones receive and transmit on specific frequencies, just as radio sets tune in broadcasts.

Sound waves at certain frequencies can have destructive effects, the most famous being breaking a wine glass by sound alone. “A glass has a natural resonance, a frequency at which the glass will vibrate easily,” says Wikipedia. “Therefore, the glass needs to be moved by the sound wave at that frequency. If the force from the sound wave making the glass vibrate is big enough, the size of the vibration will become so large that the glass fractures.”

Sounds dramatic. However: “To do it reliably for a science demonstration requires practice and careful choice of the glass and loudspeaker.” The stunt was used to hype a brand of recording tape in 1970s-era commercials — an opera singer hit a high note which caused a wine glass to shatter dramatically without being touched.

Constructive resonance

The best-known example of resonance used to reduce ambient noise (as opposed to creating glass shards) is a pair of noise-canceling headphones. To understand the principle, start with a refrigerator.

The fridge is an exemplar because of its intermittent motor, which produces a steady sine wave. When the internal temperature rises above a certain level, the motor turns on, creating a humming sound, and a microphone samples the sound. As the motor hum resembles a perfect sine wave, the microphone picks up the sound, which is then replicated out-of-phase by an internal device and played on a speaker close to the motor.

It's simple but also effective because the two out-of-phase sine waves cancel each other. Noise-cancelling technology is more complex: “To cancel the lower-frequency portions of the noise, noise-canceling headphones use active noise control or ANC,” says Wikipedia. “A microphone captures the targeted ambient sounds, and a small amplifier generates sound waves that are exactly out of phase with the undesired sounds. When the sound pressure of the noise wave is high, the canceling wave is low (and vice versa). The opposite sound waves collide and are eliminated or 'canceled’."

Canceling destructive pop music

So how did a pop tune cancel a spinning hard drive? A blog post by author, longtime Microsoft developer, and semi-official Windows historian Raymond Chen dishes the dirt.

“A major computer manufacturer discovered that playing the music video for Janet Jackson’s “Rhythm Nation” would crash certain models of laptops,” he writes. “One discovery during the investigation is that playing the music video also crashed some of their competitors’ laptops.”

Worse: “Playing the music video on one laptop caused a laptop sitting nearby to crash, even though that other laptop wasn’t playing the video!” “It turns out that the song contained one of the natural resonant frequencies for the model of 5400 rpm laptop hard drives that they and other manufacturers used,” writes Chen.

The fix? The manufacturer worked around the problem by adding a custom filter in the audio pipeline that detected and removed the offending frequencies during audio playback. Of course, if any other music or ambient noise produced similar frequencies, the hard drives might be subject to crashing anyway, but it's not Janet Jackson's fault.

Bridges, it turns out, are higher-profile victims of destructive resonance.

Bridge tolls

The most recent bridge to suffer the effects of resonance is London's Millennium Bridge, which opened on June 10, 2000. It promptly closed on June 12.

“Londoners nicknamed it the 'Wobbly Bridge' after pedestrians experienced an alarming swaying motion on its opening day,” says Wikipedia. “The bridge was closed later that day and, after two days of limited access, it was closed again for almost two years so that modifications and repairs could be made to keep the bridge stable and stop the swaying motion.” The reason? “Unexpected lateral vibration due to resonant structural response.”

But for a demonstration of destructive resonance, nothing tops the Tacoma Narrows Bridge Collapse of 1940. Film of the bridge oscillating like a candy ribbon before tearing itself apart has circulated for decades.

“The Tacoma Narrows Bridge opened to traffic on July 1, 1940, and collapsed into Puget Sound on November 7 of the same year,” writes William Tyrell on engineeringclicks.com. “At the time, it was the third longest suspension bridge in the world, just behind the Golden Gate Bridge and the George Washington Bridge.”

“Construction workers gave the bridge the nickname 'Galloping Gertie' as it began to have noticeable vertical oscillations in windy conditions,” writes Tyrell. “When the bridge experienced strong winds from a certain direction, the frequency oscillations built up to such an extent that collapse was inevitable,” says a report on history.com.

Pro tip for bridge architects: try to avoid nicknames like “Galloping Gertie” for your creations.

Critical resonance

How critical is this issue to CDOs in today’s on-prem/off-prem SSD-driven world? Not much, but it reminds us that external stress from unexpected sources can crater our precious data.

You can protect your hard drives against MTV's most destructive noise, but what about humidity? Dust? Heat buildup in specific areas?

Everyone who's worked with computer equipment for a long-enough period has some sort of destructive resonance story. Environments can and do take out swathes of data for arcane reasons...or no reasons whatsoever.

Backup, backup, backup.

Stefan Hammond is a contributing editor to CDOTrends. Best practices, the IoT, payment gateways, robotics and the ongoing battle against cyberpirates pique his interest. You can reach him at [email protected].

Image credit: iStockphoto/Alex_Bond