Headphones are a way to provide stereo sound without outfitting a room with a surround-sound speaker system. Additionally, headphones allow users to make their listening experience mobile by hooking up to portable music-playing devices such as MP3 and compact disc players. Though many headphones provide a seemingly personal listening experience to the user, they also bleed music and sound loud enough for surrounding people to hear. This kind of sound leaking is limited or even totally eliminated with certain types of headphones.
Over the Ear Headphones
Preferred by many studio producers, over the ear headphones feature padded cups that fit over the user's ear, sealing the sound-generating element of the headphone and trapping most noise. Additionally, the speaker components of all over the ear headphones project sound directly into the ear canal, unlike other models that project sound at an angle. However, some over the ear headphones, particularly those favoured by studio musicians and producers, are so powerful they project deep bass or high tenor notes away from the user, causing some sound bleed.
Intra-conch Ear Buds
Intra-conch ear buds, commonly referred to as "ear buds" fit inside the outer ear, resting just above the ear's inner canal. As with over the ear headphones, they project noise directly into the ear canal. Because of their closer proximity, however, ear buds can be used effectively at a lower volume. Because they lack the padding and insulation of over the ear headphones, ear buds can emanate a lot of ambient noise away from the user if they are played at high volumes. In most cases, however, volumes that could emanate ambient noise would result in an uncomfortable or even potentially harmful listening experience for the user.
Intra-canal Ear Buds
Representing an advancement in ear bud technology, intra-canal ear buds fit inside the inner ear canal, typically using a rubberised padding to simultaneously hold the bud in place, while also providing insulation against outside noise for the user, and insulation for people around the user form the noise he or she is hearing. Because of their extremely close proximity to the ear, intra-canal ear buds can be played at extremely low levels while still providing an enjoyable listening experience. Additionally, because they project sound directly into the ear canal and are insulated from the outside, intra-canal ear buds leak virtually no sound.
Active Noise-Reduction Headphones
Active noise-reduction headphones come in a variety of constructions, from over the ear headphones to intra-canal ear buds. They literally use noise to fight noise. Through a combination of white noises, they eliminate sounds that might otherwise interfere with the user's ability to hear music being played through the headphones. The only sound that active noise-reduction headphones bleed is indistinguishable white noise.