Sounds of success.

Byline: Olaf de Senerpont Domis

When the likes of Larry Sonsini, Sandy Robertson and Peter Gotcher take an active interest in a Silicon Valley technology legend, something's clearly afoot. For Dolby Laboratories Inc., that something is almost assuredly an initial public offering.

The storied San Francisco company, founded in 1965, is the top maker of audio signal processing systems for the motion picture, broadcasting, music and consumer electronics industries. Its widely recognized brand name is synonymous with noise reduction technology that enabled, among other things, multiple tracking, which helped define the psychedelic sounds of The Beatles and Jimi Hendrix on their groundbreaking albums of the late 1960s.

Dolby Labs, grown by founder and 100% owner Ray Dolby, 70, without a drop of outside investment, has yet to file an S-1 prospectus with the Securities and Exchange Commission. But the company's done everything short of that final step, making several key acquisitions to bulk up its product offerings and intellectual capital, hiring investment bank Morgan Stanley and …