Voice itself doesn't have any facility to share an account between multiple people - though in theory there's nothing stopping you setting up a single account and sharing the password with multiple people.
e.g., you could have an address like 'email@example.com' that was a mailing list that forwarded email to everyone on your committee. You could then sign firstname.lastname@example.org as a Voice user, and share the password. Note though that you'd have to set up the email list on a different provider (e.g., some registrars have this facility if you register a domain from them, or you could use gmail), Voice won't do this for you.
In general I wouldn't really recommend this though - there'd be security implications to sharing the password to lots of users. And probems such as what happens if you want to remove someone from the committee? You'd have to change the password and only share it with the people still eligible to log in. Ultimately it'd probably be easier just to have everyone register themselves!
Note that you can Invite users to your site from the admin panel, which should make signing up easier.