Greg Dorr’s review published on Letterboxd:
This is a well-produced low-budget drama about a couple who attempt to infiltrate a cult, but it plays a fairly obvious game that isn't very satisfying. I think if it had gone on for another 10-30 minutes and explored the repercussions of its events on the main characters, it wouldn't have felt so much like the long setup to a quick punchline.
The acting is good, and the directing is strong, so I forgave several small, early gaps in credibility, but the gimmickry of the outcome is making me want to reconsider that. This seems like it will be one of those movies that I will like less and less the more I think about it.
This has been on my DVR for a few years, but I put off watching it because I was sure it could not live up to the standard set by Martha Marcy May Marlene. Maybe that's unfair, because Sound of My Voice never attempts to be a complex psychological drama. It's really just a cheap trick that takes itself very seriously.
I'm actually knocking off a star as I write this.