Noise-canceling headphones block out ambient sound. This is useful in noisy environments like trains. They work by monitoring sound outside of the headphone through a microphone and then canceling that sound out. Technically, they do this by copying the sound wave outside, and then they make that sound wave go out of phase. It's a bit like swimming upstream. If a river's downstream current equals your upstream strength, you stay still. In this case you create quiet.
Instructions
1. Decide what design you want and the trade-off you want to make among size, portability and cost. Designs fall in two camps: over-the-head and earbud. Over-the-head headphones tend to be larger and less compact. Earbud headphones can be transported in your pocket.
2. Consider digital noise-canceling over-the-ear headphones, which reduce ambient noise by 99 percent. They have settings for different environments like an airplane, train and office. Some have built-in equalizers so you can balance bass, mid- and high- range frequencies. As of July 2009, some cost hundreds of dollars. Noise-canceling earbuds can reduce noise by about 75 percent and are smaller and cheaper.
3. Decide whether you will be using the headphones for long periods. If so, consider a lithium-ion rechargeable battery. Also, traveling around a lot can cause the cord to get tangled. Look for headphones with a travel case. And check if the headphones have a monitor function. The monitor function allows you to temporarily hear surrounding sound, for example, a train conductor announcement.
4. If possible, listen to the headphones before buying them.
Tags: environments like, monitor function, sound wave, that sound
