Skype, which is owned by eBay, says that it made the acquisition in order to add the companies' online voice engineering experts to its staff. They will help design and develop future versions of Skype's VoIP product.

Skype describes Sonorit and Camino as start-up companies building products for speech processing, coding and transmission over Internet-based networks.

Camino's speech products are geared towards mobile IP networks, according to a biography of Jonathan Christensen, Camino's president and CEO, on the Web site of an investment company for which he serves as an advisor.

Sonorit and Camino have been the subject of at least one lawsuit. In December, Global IP Sound AB (GIPS), a company that offers VoIP technologies, filed a lawsuit that charged them with violating trade secrets. GIPS said some Sonorit workers were former GIPS employees.

EBay bought VoIP provider Skype in 2005 for $2,5bn, aiming to help buyers and sellers using its online auction site to communicate with each other easily.