RF Wireless Headphones

RF Wireless Headphones
Radio Frequency (RF) wireless tv headphones typically operate in the 800-900 MHz band although they may soon follow cordless phone technology and move on to higher frequencies like 2.4 GHz and 5.8 GHz. RF technology has the ability to penetrate through walls and obstacles which gives the added benefit of actually being able to receive wireless audio in several rooms of a house from a single source in one room. With RF wireless headphone transmission the two strereo channels (lefty and right) are modulated into a single frequency for transmission and then demodulated at the receiving side back into left and right channels.
Keep in mind that wireless technology is always susceptible to intereference and/or signal loss. Intereference is caused by other RF wireless devices transmitting within a certain rage of your receiver. In certain circumstances a signal from another device (cordless phone, wireless network, or wireless video tranmsitter) can create static (or noise) in the reception of your headphones. This is especially true when the other device is operating at the same or similar frequency.
Signal loss on the other hand is caused by a weak or lost transmission. This too results in static, poor audio quality, or loss of sound alltogether. Signal loss is due to one of two factors. Either the distance from the transmitter to the receiver is too far for a clear strong signal to be receievd by the headphones, or the signal is being "blocked" in some manner by obstacles. Some of the most troublesome obtacles for RF wireless headphones are metal and water. Metal objects could be a firewall built within a wall, furniture, shelving, fencing (when using outdoors) or extensive plumbing/duct work. RF signal cannot penetrate metal well resulting in a weakening of the signal. Water is not commonly found in your living room so its not usually a problem factor but since the human body contains mostly water it can be an obstacle. For this reason it is helpful to keep the transmitter above head level if at all possible especially in circumstances where there may be obstacles (human or other) between the headphone wearer and the transmitter.

Infrared Headphones
Infrared wireless tv headphones operate by sending their signal in the form of a beam of light typically in the 2-4 MHz band. Due to this fact they are primarily a line of sight device. Meaning you must be able to visually see from the transmitter to the receiver to successfully receive your signal. Most infrared systems are limited to about a 30 foot range with clear open line of sight. With Infrared wireless headphones you get true stereo (left and right channel) separation. This results in excellent stereo sound quality. Infrared transmission is less prone to interference in that it is a line of sight technology. Meaning you can have a similar transmission device in the room right next door without having any negative impact on your reception as long as the signal does not make its way into your room

from - http://www.wireless-headphones.net/