SAN JOSE, Calif. -- Google is in the midst of more than $120 million in construction projects at its Silicon Valley headquarters, including work on a series of new or previously secret hardware testing labs that hint at the Internet giant's expanding interest in crafting consumer devices like its rivals Apple and Microsoft.

Among the projects, revealed by a review of public records, are a lab to test a new consumer product under the brand name "home" that will wirelessly stream music or data to other household devices, apparently similar to a prototype home audio service Google demonstrated publicly last year. And, most intriguingly, Google is modifying a lab for a project enigmatically named "Project X," which appears to involve precision optical technology and could be part of the secret technology projects Google co-founder Sergey Brin is heading.

The highest-profile project will be a "Google Experience Center" under construction at the core of the Googleplex. The 120,000-square-foot center will be a kind of private museum for Google's most important clients and partners, where the company plans "to share visionary ideas, and explore new ways of working" with up to 900 VIPs and other important guests, according to documents Google filed with the city of Mountain View.

Google is joining a club that includes companies like Microsoft, Hewlett-Packard, Oracle, Boeing and IBM that have customer demonstration facilities to showcase products and technology to potential buyers, analysts and other partners.

"It really becomes the showcase for the company," veteran Silicon Valley technology analyst Rob Enderle said. "They are designed to impress. They are part of the sales process. The purpose is, you walk in and you have an 'oh, wow' moment."

Project X, which occupies a space with blacked-out windows at a central location of the Googleplex, includes the use of rare gases like argon, a plasma cleaner that can scrub materials of contaminants, and arcane optical-coating technology, city records show. While the purpose of Project X is unclear, Brin since last year has been focusing on a list of secret projects that include efforts to develop a driverless car.

Apple and Microsoft have extensive hardware testing facilities on their campuses, as they design and develop products like the iPhone or the Xbox gaming system, Enderle said. Like the Experience Center, those testing facilities can also be part of the sales process, allowing Google to demonstrate the reliability of new products.

"If you keep it close to the executive briefing center, you can bring in [manufacturing partners] or large customers, show them the testing as it's going on, make them more comfortable with that product," he said.