Worldwide shipments of Bluetooth chipsets and, by extension, devices that use those chipsets, is set to double for the second straight year, according to a market study released Tuesday by In-Stat/MDR.

Specifically, the study said that the number of Bluetooth chipsets will grow to 146 million units in 2004, which is roughly double the number from 2003. Similarly, the number of Bluetooth chipsets shipped in 2003 was double that of 2002, the study noted.

The study also pointed to wireless stereo headsets using Bluetooth as a product category it expects to grow quickly. Currently, mono headsets used for hands-free operation of cell phones are popular and, if vendors can keep costs down, stereo headsets for listening to music should also become popular, according to the study.

The study also found that demand for Bluetooth-enabled mono headsets outstrips supply in Europe, but that the opposite is true in the U.S. In a statement, In-Stat/MDR blamed a lack of promotion of by U.S. wireless operators for the disparity.