Headphone makers have been striving for years to protect your ears from the distractions of daily life, developing and refining noise-canceling technology that allows you to enjoy every note of your favorite without the intrusion of coffee-shop chatter or construction work in the street outside your home.

Our headphone ratings include more than two dozen noise-canceling models. (Find out how noise cancellation works, below.)

But headphone manufacturers acknowledge that not all noise from the outside world is evil. Instead of presenting us with a take-it-or-leave-it proposition, over the past year or so manufacturers have introduced models that let you adjust the amount of ambient noise that reaches your ears. That way you won't miss important information like, say, the final boarding call for your flight to Chicago.

Parrot (Zik 3 headphones), Bose, Sony, and Harman (JBL Everest Elite 700) make models with variable noise cancellation. 

I gave variable noise cancellation a try using the Bose QuietControl 30 in-ear headphones, $350, and the Sony MDR-1000X  studio-style headphones, $400. Both rate excellent for noise reduction and do a great job of playing audio. The Bose headphones provide excellent sound quality; the Sony, very good.

How Sony and Bose Let the Noise Back In

This image is of a pair of Sony noise-canceling headphones
The Sony MDR-1000X has buttons that let you select preset noise-canceling settings.
Photo: Terry Sullivan

The Sony MDR-1000X headphones have buttons on the side of one earcup that adjust the balance between the audio and ambient sounds based on three preset options.

The Ambient setting lets some outside sound reach your ears for situations where you might want to hear, say, a taxi horn or a child's cry more clearly. You can adjust the setting to more readily admit only voices.

Quick Attention lets you control the volume of the audio using a sensor embedded in the right earcup. If you want to listen in on a conversation, you cup the right earpiece with your hand and the music softens. Remove the hand, and the volume is restored.

While that all worked as promised, I found myself wanting to make finer adjustments to the noise-canceling effect. That's where the Bose QuietControl 30 came in. Instead of preset settings, this model allows you to move the noise-canceling level up or down using a control located on the cord. Using the Bose Connect smartphone app, you can also use the slider control on your touchscreen.

If you're out jogging, for example, you might set the control at the halfway mark so you're more aware of oncoming traffic. If you want to stop and say hello to a neighbor, you can turn it down even lower to engage in conversation. It's a powerful feature, and my guess is that more companies will soon follow Sony and Bose and include variable noise cancellation in their headphone lines.

This image is of a pair of Bose noise-canceling headphones
On the Bose QuietControl 30, you can more delicately adjust the noise canceling via a mobile app or the headphone controls.
Photo: Terry Sullivan

How Noise Cancellation Works

There are two types of noise cancellation: passive and active. (Variable noise-canceling headphones use the active type.) Headphones that encase your ears in a spongy cushion or plug them with a rubber earpiece employ passive noise cancellation. It's a relatively effective noise-cancellation technique, but it certainly limits your control.

Active noise cancellation relies on tiny microphones and circuitry that monitor the ambient noise around you and adjust the frequencies in the audio to muffle those sounds. It's pretty good at muting a constant noise like lunchroom babble, but less effective at singular outbursts (a doorbell or a baby's cry).

The resulting effect is that you can enjoy a song or an audio book with far less intrusion from the din of office chatter or car traffic. But for a long time, noise cancellation was a binary option: You could not reduce the outside commotion just a notch or two; your only option was to turn the tech on or off.

One thing to note: Active noise cancellation requires power. That means you have to regularly recharge the batteries in the headset. If they die, you might  still be able to listen to your music, but that tech wizardry that silences the lawn mower at your neighbor's house? It won't work.