Noise Cancellation and the Modern Soundscape
Inside Bose’s decades long project to make noise better.
The Sound of Innovation met with Bose Senior Engineer, Dan Gauger at Bose’s corporate HQ in Boston to talk about the physics and history behind Bose’s newest line of noise-canceling headphones.
In 1978 while on a Swissair flight, Dr. Amar Bose was preoccupied by a problem. The low, persistent drone of the plane’s engine was interfering with the sound coming from his headphones.
Is there a way, he wondered, to cancel out the noise while retaining the desired sound? He had an idea it might be possible.
It’s a simple one, really: in physics, any sound wave can be cancelled by an inverse wave. If a microphone within the headset were to detect the noise reaching someone’s ears, could the headphones issue an opposite sound wave that neutralizes, say, the drone of a jet engine? Dr. Bose immediately began conceptualizing how such a device might work while still in the air. By the time his plane touched down, he had outlined the fundamental mathematics of what it would take to solve this problem.
Those mathematics became the technology known as active noise cancellation — a term that’s been appropriated by imitators in the decades since that flight. The term refers to headphones that use a microphone to detect the noise you hear, then issue an inverse sound wave that cancels out the unwanted sound. If you’ve never tried them, activating a pair of Bose noise-canceling headphones feels like hitting the mute button on the world. It’s why the Bose name is on the side of the headphones you see on passengers’ heads all over the world.
Planes, of course, aren’t the only problem. The modern civilian soundscape is dense with ambient noise, especially in major cities. Plain and simple: noisy environments can be distracting, uncomfortable, and health-hazardous.
In fact, research conducted in 2015 revealed that the second-most frequent complaint made to 311 in New York City is noise — second only to complaints about lacking heat or hot water.
Bose noise cancellation technology works on lower-frequency sounds: idling cars, trucks, subways, loud parties, air conditioners, any noise you’ve probably accepted as an inescapable side effect of modern life.
Bose’s headphones have been actively reacting within fractions of a millisecond to any sound — from the roar of a jet engine to traffic noise to the ambience of a busy open office area — no matter how random — for more than 26 years. The result is industry-leading performance that’s been imitated elsewhere, but never duplicated.
More importantly, decades of in-house research at Bose are steadily pushing the boundary of what noise can be attacked actively. Today, faster chips, advanced software and integration of Bluetooth radios have led to the brand’s first wireless models — the QuietControl 30 and QuietComfort 35, which debuted this month.
The QC30 Bluetooth earbuds are incredibly liberating. They’re compact and light enough to make you want to use them in every environment. Having no wires to snag on exercise equipment or subway turnstiles means unencumbered movement.
In major metropolitan areas like Boston — near where Bose is based — or New York City or San Francisco, put on a pair of the wireless QC30s while walking, and it’s like you’re out for a walk in the woods. It feels comfortable and calm.
One of Gauger’s personal test routines is to see how his headphones fare when in a car as a passenger. “You know how you can open the window a little bit, you get this really deep sound. You can hear it, and even feel it buffeting you. I use conditions like that to push the headphones beyond their limit.” He even took the QC30s to the front row of concerts and all over urban Boston to make sure that they live up to the brand’s reputation.
The goal of modern Bose headphones, however, isn’t only to block out the world entirely. Click the in-line control to turn down the acoustic noise-canceling, and you’ll be able to hear someone calling your name or the saxophone being played by a street musician. You can dial in the amount of “awareness” and connection to your surroundings. Adjust the slider on the Bose app, or tap the second set of up-down buttons on the QC30’s in-line control, and you can turn the amount of noise-cancellation up or down, not just on and off, letting the sounds of the world come back as much or as little as you want. You can hear your train being called, or listen for traffic before you cross the street. That adjustability, Gauger says, “is something we knew ought to be in the product from the beginning — it’s a volume control for your ears.”
Using active noise cancellation in everyday situations, like walking or taking a bus, shows how Dr. Bose’s decades-old idea is so enduring. Other headphones will (incorrectly) claim noise cancellation through passive isolation. A pair of earbuds that you jam in to seal inside your canal and block out sound do not cancel sound. It’s the technological equivalent of sticking your fingers in your ears and can be just as uncomfortable. Worse, this approach means that vibrations originating in your body — like your own voice or footsteps — become weirdly amplified. Those vibrations, Gauger explains, are transmitted all the way up into your ear canal, where they become loud if your canal is blocked off. Bose active noise canceling headphones are designed to even neutralize those sounds, so the music fully compliments the environment and the your movement.
Gauger presents the scenario of wearing headphones at a cafe. “You want to be there, enjoy the coffee, and enjoy the energy of the people around you,” he says. “Turn on active noise cancellation and suddenly you have space for your thoughts. Rather than turn your music up, you can turn the world down.” The new adjustability function brings back the environment just to the degree that you choose when you want to feel present, or turn it down so you can concentrate. It’s the latest development on the original idea of noise cancellation.
Bose is focused on our ears and our hearing. If you unlock your phone and the screen is bright, you squint your eyes. But you can’t squint your ears. “Human hearing is an emotionally rich sense,” Gauger says. “Open the window and based on the sound, you can guess pretty accurately what season it is. But, while being so full of emotional resonance, it’s a sense we have little control over.” With features like controllable noise cancellation, Bose’s headphones are starting to give us this superpower-like control over our hearing.