How does noise reduction work?

There are two ways that noise cancelling headsets work, ergo, noise cancellation comes in two distinct forms. The first, known as ‘passive’ noise reduction is actually pretty obvious. For a good demonstration, hold your hand flat (as if you were attempting to ‘karate chop’ something) and then place it over your nearest ear (but don’t hit yourself, of course). Notice the muffling? That is passive noise reduction. By this measure, anything that covers your ears or blocks sound from entering them is a form of passive noise reduction. By this token, then, all headphones and headsets are passive noise reducers.


Tyler Lacoma, or, puts it this way: “Passive noise reduction seeks to eliminate outside interfering noise so you can listen more easily to music and other types of audio. With headphones that fit inside your ear, noise reduction is achieved by using gel tips to create a seal in your ear canal. With headphones that fit around the outside of your ear, advanced foams and padding block outside noise and create a quieter environment”.


Active noise reduction, then, involves drowning out incoming noise. How? Well, William Harris of How Stuff explains it thus: “(Active Noise Reducers) actually create their own sound waves that mimic the incoming noise in every respect except one: the headphone’s sound waves are 180 degrees out of phase with the intruding waves”.


Essentially, anything you put in your ear is a sound reducer, but this basic function can be designed for greater, or lesser, effect. Some shapes and designs have a better sound reduction effect than others, or, as the noise reduction feature from Learning About says:


“The shape of the headphone earcups and how it fits over the head determines to a large degree how much noise the headphones can block out”.


Of course, the active noise canceling headsets also have their drawbacks. According to Murat Demir of Street, active noise reducers suffer from the following problems:


“1. They consume power, usually supplied by a battery that must be replaced or recharged from time to time.

2. They may also not cancel all sound effectively. They may work well for sounds that are continuous, such as the hum of a refrigerator or the sound in an airplane cabin, but may prove ineffective against speech or other rapidly changing audio signals.

3. They may sometimes introduce additional noise, usually in the form of high-frequency hiss”.


However, Demir goes on to say that “You should always take the (noise cancellation) headphones in a long flight to enjoy a quieter environment and to keep you calm and relaxed”. Generally speaking, active noise reduction is the better choice, as you will experience greater comfort and clarity of sound. You may also find that active noise canceling headsets can be used to combat fatigue caused by the low frequencies experienced on trains and buses. This makes a noise canceling headset not only a choice product, but also one with more benefits than drawbacks.