Many airlines supply noise-canceling earphones within their business and first class cabins. Noise-cancelling is particularly helpful against plane engine noises. In such cases, the earphones tend to be about the same size as standard earphones. The actual electronics, located in the airline handrest, take the noise from the microphone behind the headphone, change it, and then add it back into the music signal.LimitationsNoise-canceling headsets have several limitations (which vary from vendor to vendor):They consume electrical power, commonly supplied by a Usb interface or a battery that has to sometimes be replaced or charged up again. Without electricity the headphones operate like a regular headphone or even will not function at all, on the other hand, several such as the Solitude X, originally created for armed forces intelligence operations, make use of a 'pass through' system permitting the headsets to continue to function normally, whether or not the power supply is used up.They work efficiently for sounds which are ongoing, for example the sound of a freezer or even the noise inside an airline cabin, but they are less efficient with speech and other fast changing sound signals.They might add additional noise, often in the form of high-frequency hiss.The noise-cancelling circuits needed for these headsets to operate naturally lessens sound quality.Earlier designs were usually thicker than conventional headphones. Nonetheless, new designs often incorporate the batteries inside pre-existing space. Although this typically minimizes the bulk, it won't decrease the extra weight of noise-cancelling headsets compared to traditional headphones.