A large number of wireless audio transmitter products have emerged over the years. They promise to cut the cord to your audio equipment. We will examine the impact of new technologies on the performance of these products. Also, we'll examine if they keep their promise of eliminating the cable clutter.
The first form of wireless audio transmission was in the form of AM and FM radio stations. FM radio is still popular today. However, newer technologies have started to replace it. These include DAB broadcasts, satellite and HD radio. Today's wireless consumer devices such as wireless surround sound kits, baby monitors, Bluetooth audio transmitters and wireless microphones eliminate the cord.
Setting up speakers in another room and distributing music throughout the house are some of the applications of wireless audio. Many homes are not wired for audio. The technologies used today all have pros and cons as we will examine.
FM transmitters are using the most traditional technology in which audio is sent by changing the frequency of a radio-frequency carrier. This technology is called frequency modulation or FM. It is fairly simple to implement. Thus FM transmitters are very cost-effective. Also, FM transmission offers high range. As a result, most of today's 900 MHz wireless headphones use FM transmission. However, FM has some major drawbacks.
The first is the fact that the transmission will pick up noise and thus there will be some hiss or static. The amount of noise will actually vary depending on the location of the radio or receiver. This is due to the fact that the radio signal is bouncing off walls and will cancel itself out at different locations. This phenomenon is called multi-path fading. Using two antennae is one method some devices cope with this problem (diversity receivers). Another problem is that FM radios easily pick up interference from competing wireless transmitters.
Bluetooth has gained popularity recently for wireless audio transmission even though this protocol was primarily designed to connect computer peripherals. Bluetooth audio transmitters will convert the audio signal to digital information and then transmit via the Bluetooth protocol. Bluetooth is fairly robust in terms of interference in is well standardized. Bluetooth, however, has some problems in regard to wireless audio since it was not designed for wireless audio originally. The range of the transmission is only 30 ft or less. Also, Bluetooth does not have enough space to send an uncompressed CD-quality audio signal. Therefore the audio is compressed prior to the transmission. As a result of the audio compression, the audio quality will decrease. The final problem is the fact that Bluetooth will introduce a delay in the signal (also called latency) which is a problem when used together with video since the audio will be out of sync or if used in a surround sound setup where some of the speakers would be out of sync with the hard-wired speakers.
The technologies used for satellite radio and terrestrial digital radio offer high range. However, they also use extensive audio compression. Further, a delay of up to several seconds is introduced.
Another technology transmits the audio signal without compression digitally. This technology is used in wireless audio transmitters from Amphony. The audio signal will retain CD quality because no audio compression is used. The audio latency of this technology is less than 1 ms. Therefore it can be used for real-time applications such as wireless speaker kits in home theater setups.
By using error correction, this technology can cope with interference from competing wireless devices which is key in today's noisy environment. The Amphony transmitters operate at 5.8 GHz. This frequency space is less crowded than the 900 MHz or 2.4 GHz bands thus leading to a further improvement of reliability. In contrast to Bluetooth, any number of wireless receivers can operate from a single wireless audio transmitter which is a concern when distributing audio to several rooms within a home.
The first form of wireless audio transmission was in the form of AM and FM radio stations. FM radio is still popular today. However, newer technologies have started to replace it. These include DAB broadcasts, satellite and HD radio. Today's wireless consumer devices such as wireless surround sound kits, baby monitors, Bluetooth audio transmitters and wireless microphones eliminate the cord.
Setting up speakers in another room and distributing music throughout the house are some of the applications of wireless audio. Many homes are not wired for audio. The technologies used today all have pros and cons as we will examine.
FM transmitters are using the most traditional technology in which audio is sent by changing the frequency of a radio-frequency carrier. This technology is called frequency modulation or FM. It is fairly simple to implement. Thus FM transmitters are very cost-effective. Also, FM transmission offers high range. As a result, most of today's 900 MHz wireless headphones use FM transmission. However, FM has some major drawbacks.
The first is the fact that the transmission will pick up noise and thus there will be some hiss or static. The amount of noise will actually vary depending on the location of the radio or receiver. This is due to the fact that the radio signal is bouncing off walls and will cancel itself out at different locations. This phenomenon is called multi-path fading. Using two antennae is one method some devices cope with this problem (diversity receivers). Another problem is that FM radios easily pick up interference from competing wireless transmitters.
Bluetooth has gained popularity recently for wireless audio transmission even though this protocol was primarily designed to connect computer peripherals. Bluetooth audio transmitters will convert the audio signal to digital information and then transmit via the Bluetooth protocol. Bluetooth is fairly robust in terms of interference in is well standardized. Bluetooth, however, has some problems in regard to wireless audio since it was not designed for wireless audio originally. The range of the transmission is only 30 ft or less. Also, Bluetooth does not have enough space to send an uncompressed CD-quality audio signal. Therefore the audio is compressed prior to the transmission. As a result of the audio compression, the audio quality will decrease. The final problem is the fact that Bluetooth will introduce a delay in the signal (also called latency) which is a problem when used together with video since the audio will be out of sync or if used in a surround sound setup where some of the speakers would be out of sync with the hard-wired speakers.
The technologies used for satellite radio and terrestrial digital radio offer high range. However, they also use extensive audio compression. Further, a delay of up to several seconds is introduced.
Another technology transmits the audio signal without compression digitally. This technology is used in wireless audio transmitters from Amphony. The audio signal will retain CD quality because no audio compression is used. The audio latency of this technology is less than 1 ms. Therefore it can be used for real-time applications such as wireless speaker kits in home theater setups.
By using error correction, this technology can cope with interference from competing wireless devices which is key in today's noisy environment. The Amphony transmitters operate at 5.8 GHz. This frequency space is less crowded than the 900 MHz or 2.4 GHz bands thus leading to a further improvement of reliability. In contrast to Bluetooth, any number of wireless receivers can operate from a single wireless audio transmitter which is a concern when distributing audio to several rooms within a home.
About the Author:
Gunter Fellbaum has been developing audio and electronic products for over a decade. You can find further information regarding wireless surround sound transmitters as well as other wireless audio products from Amphony's website.
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