The Java plug-in for web browsers used by the VoxForge applet relies on the NPAPI (Netscape Plug-in API) cross platform plugin architecture.

Starting with Windows Chrome Version 42, Google has added an additional step to configuring NPAPI based plugins like Java to run: 

1. In your URL bar, enter:
   chrome://flags/#enable-npapi
   
2. Click the Enable link for the Enable NPAPI configuration option.
3. Click the Relaunch button that now appears at the bottom of the configuration page.

(Note: Chrome NPAPI support was removed from the Linux platform starting with Chrome version 35)

You can still use:  Firefox, Internet Explorer or Safari.

Update - Sept 15, 2015, from Google website:

Plugin-based content doesn't work on Chrome

To make browsing with Chrome safer, faster, and more stable, we stopped allowing NPAPI plugins on September 1, 2015.

Plugins that use NPAPI, including Silverlight, Java, and Unity, won’t work.