To better see and to hear you with … a better version of Google Glass is coming to more people.

The Internet giant, which recently put on its first public expo for the Internet-connected wearable devices that resemble eye glasses, is updating and expanding the Glass program.

As part of Glass’ expansion, Google is giving the early testers – known as “Explorers” – the option to exchange their current device for an improved version. The updated model includes an ear bud for better acoustics and will work on prescription frames.

“We want to say ‘thank you’ for all the amazing feedback we’ve been getting, so later this year, all Explorers will have a one-time option to swap out their existing Glass for a new one,” Google said in a blog.

“This hardware update will allow your Glass to work with future lines of shades and prescription frames, and we’ll also include a mono earbud.

The expanded sales will come as part of an invitation-only program announced Monday.

“[W]e’ve been experimenting with ways to expand the Explorer Program and it’s been going really well. So over the next few weeks, all Explorers will have the opportunity to invite three friends to join the program,” Google said.

“They’ll be able to buy Glass online and can have it shipped to their home, office, treehouse or igloo. We’re counting on you to get Glass to the people you think will make great Explorers. More Explorers means more feedback, and more feedback means better Glass.”

The roughly 10,000 Glass owners who began testing the device earlier this year will each be allowed to invite up to three people to buy the device. The early Glass users are primarily computer programmers and winners of an online contest conducted earlier this year.

The recipients of the invitations will have to pay $1,500 apiece for Glass, which works like a smartphone except that it’s worn on the head like a pair of spectacles. The device includes a speaker, a hand-free camera and a thumbnail-sized display screen attached to the frame above the right eye.

Google still plans to release a less-expensive model of Glass next year. The precise pricing and timing of the mass-market version still hasn’t been determined.

Relying on the early users of a test product to gradually widen the audience is a familiar strategy for Google. The Mountain View, Calif., company did something similar in 2004 after it released Gmail, its free email service.

Glass already has generated concerns among critics who worry that its hidden camera could invade the privacy of people who don’t realize that video or pictures are being taken of them. Others are concerned that Glass will thrust more technological distractions into society by making it even easier for people to be online at all times.

Google says it believes Glass will promote more meaningful interaction by giving people less reason to glance down at a smartphone screen every few minutes.