APEX Insight: A lot of science goes into what we hear, see, touch, smell and taste in the airplane cabin. In this multipart feature, we take a look at recent developments targeted at each of the five senses.
There have been major advances in aviation over the past few decades, but aircraft cabins are still loud places. A result of spinning engine blades, aerodynamic drag and humming air-conditioning units, the constant midair rumbling noise you hear at 35,000 feet might not only be annoying, but could also have an impact on your health.
In a paper published in the Journal of Exposure Science and Environmental Epidemiology, a research team, including Joseph G. Allen of the Harvard T.H. Chan School of Public Health, measured the sound levels on 200 flights across six aircraft types and each flight phase. The research found that passengers and crew spent 72 percent of their flight time exposed to harmful sound levels higher than 80 decibels.
Research has also shown that short-term exposure to in-cabin noise can cause acute effects on learning, memory loss, stress hormones and sleep. It’s a challenge airplane makers are working on, but other companies are also finding novel ways to reduce the decibels inside the cabin.
One idea gaining traction is zonal systems, which consist of an array of small speakers embedded into the structure of a first-class seat or the headrest of a business-class seat. The technology works by using microphones that measure ambient noise levels. These sound signals are then processed by silicon chips in such a way that when reintroduced into the environment, the speakers will cancel out the noise levels that are being measured, through a principle known as destructive interference.
“It’s enough to improve your sleeping comfort when you’re in a noise field” – Mark Donaldson, SoundChip.
But how much ambient sound can they realistically cancel out? A pair of noise-canceling headphones can knock out up to 1,500 hertz of frequency, whereas a zonal type application might be able to cancel up to 500 hertz of frequency, according to Mark Donaldson, CEO of SoundChip.
Headphones tend to have much broader noise-canceling capability because of the close proximity between the microphone and the speaker. Zonal applications, in contrast, tend to have a much narrower bandwidth over which they can impart control because of the spatial separation of the speakers.
While a zonal system wouldn’t block the noise from chatty neighboring passengers, it could cancel out the rumble from an aircraft’s structural noise. “It’s enough to improve your sleeping comfort by removing some of that acoustic excitation that exists when you’re in a noise field, which has been proven to be extremely fatiguing,” Donaldson says.
But when will zonal systems become a common feature inside aircraft cabins? “It’s not something that’s coming into the industry in an explosive fashion like, say for example, moving from tape deck to video, but it’s something that will invariably end up being mainstream,” Donaldson says.
Keep your ears tuned for further announcements.
“The Sensory Experience” was originally published in the 8.4 August/September issue of APEX Experience magazine.