There is though a critically important 'Yes But'. And that is you'd better mean it, because if employees believe It's a sham and you're not genuine about giving people a voice (so-called 'pseudo voice') it will almost certainly backfire horribly.
Not only will employees keep their views or concerns to themselves, it appears to increase the likelihood of conflict at work. For details, Please check out this excellent blog from BPS Occupational Digest on Dutch research from a healthcare organisation.
So don't do a survey or put out a suggestion box unless you're genuinely prepared to act on what you find.