What Your Noise-Cancelling Headphones Can and Can’t Do

It shows a young boy playing an electric guitar on a bed while another child plays drums. A father is enjoying his quiet time, unaffected by the noise-canceling headphones. As a headphone expert, this scene drives me crazy because it’s not how noise-canceling headphones work.

Many people believe that noise-canceling headphones will block out all sound. Therefore, they are often purchased to reduce the noise of noisy office mates, barking dogs next door, or children at play. Unfortunately, active noise cancellation can only be effective for one of these things. (Spoiler alert: It’s the plane engine. It is due to the physics behind sound and how noise-canceling headphones work.

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Physics of active noise cancellation

According to physics what noise-cancelling headphones do or can’t do. Active noise reduction technology works primarily by using a principle called Phase cancellation. Sound travels in waves and moves the air molecules. These waves travel through the air to your ear canal, where they vibrate the eardrum. Therefore, the opposite amplitude and frequency of a sound wave can negate one another.

Imagine the air molecules as a string that is stretched between two points. A ripple would occur if someone pressed down on the string’s center. The string will barely move if someone presses down on it from the opposite direction. This visual isn’t a good representation of sound waves, but it can help you see how a wave reacts to its opposite phase.

The active noise-canceling headphones have tiny microphones placed on the inside and sometimes outside the earcups. They process the sound coming towards your ears and play the opposite sound through the headphone driver. As a result, you will notice a decrease in sound quality due to the opposing forces. This description is a simplified version of the core concept behind all ANC headphone designs.

This type of active noise canceling is best suited for lower frequencies, 50 Hz to 1 kHz. (If you are curious to hear the sound of 1 kHz, watch this video. Because lower frequencies produce longer waveforms, it is easier to align properly. Feedback is more common at higher frequencies. If the waveforms aren’t aligned correctly, it’s easier to detect. Most active noise-canceling headphones experience a noticeable decrease in their usefulness around 1 kHz. That is why ANC works better for reducing low-frequency, sustained sounds such as those from airplane engines and motors. It’s also why these headphones cannot filter out screaming children. We have spoken with researchers that ANC concepts are in development that can handle higher frequencies. However, that technology is still a ways off.

Which type of headphones should I buy?

What are types of headphones and why noise-cancelling headphones are commonly explained in detail? Active noise-canceling headphones can be a great choice for frequent flyers and people who don’t want their air conditioner to hum. What if you need to keep out barking dogs or human voices? Passive isolation is the solution. Passive isolation acts as a physical barrier between your ears and any sounds you don’t like to hear. Earcups and earpads are common features in noise-canceling headphones. They can block out as much high-frequency and mid-frequency noise as possible while still being comfortable. You get both active and passive noise reduction.

You have options if you want to hear only human voices or other high-frequency sounds. Passive headphones, which are typically less expensive, might be just as effective. Closed-back, over-ear headphones, especially those designed for recording, do a good job at muffled sounds like dogs barking, chattering coworkers, and kids playing.

Below is a chart. The Sony MDR7506 passive studio headphones are typically under $100. These headphones can block as much sound above 1 kHz as any active noise-canceling headphones. However, even the most expensive passive over-ear headphones won’t block all higher-frequency sounds. It is especially true if these sounds are loud. They can muffle most everyday sounds, but they won’t cause any damage to your ears. Focus.

This chart shows that a reduction of noise is achieved if it falls below 85 dB (the line with dots). The chart shows how much noise is reduced by reducing the line. The Sony MDR-7506 passive headphones are a far better choice than the active noise-cancelling ones. They reduce nearly as much sound above 1 Kilohertz than the active noise-cancelling headsets. Illustration by Wirecutter

We have found that earbuds designed to seal your ear canal completely and deeply are the best way to block higher-frequency sounds. Audiophiles often use Over-ear cables to enclose the ear canal. They can also block higher-frequency sounds. You can also add noise-isolating foam tips to your existing earbuds. These tips are often included with earbuds or can be purchased from third-party suppliers like Comply.

Apart from saving money, passive noise-isolating headphones or earbuds are more comfortable than ANC headphones. However, it can feel like your ears are popping, or it can be intense, similar to a headache. Some people do not feel it, and others can ignore it or adjust to it. However, for some, it is a major issue that prohibits them from wearing ANC headphones.

Other noise-blocking options

There are other options if you don’t succeed in ignoring distracting sounds after trying the above suggestions. For masking external noise, white noise and rain are great options. Tons of apps can do this. In addition, you can listen to your music at a reasonable volume to protect your ears. Experts recommend listening at 60 percent of the volume of your device for at least 60 minutes. After that, take a break for a few moments before you resume.

There are earplugs. You could wear earbuds with hearing protection earmuffs if you are highly distracted but still enjoy music. You won’t have the ability to control true wireless earbuds, and corded headphones will cause a wire crease on your cheek. Is it comfortable? It’s okay… as long as the earbuds aren’t too far out and the earmuffs have an adequate earcup, it is easy to get used to it. It is very effective, I will tell you. It may be the only thing that I have tried to block out the sound of a small rock band such as the one shown in the commercial.