For about 100 of its 108 minutes, the Australian cop movie Noise rolls along smooth as silk, less a procedural and more a look into two minds affected in altogether different ways by a miserable crime, a perfectly efficient construct that hardly seems to go by at all, so effortless is it.

Then it has its last scene, which is so absolutely not any ending at all, by which I mean that it is exactly how the film would end if it were a supercool hipster drama that delighted in fucking with the audience. At no point have we been particularly anxious to see the resolution of the crime that forms the film's backbone, but the ending taunts us with its confusing "answers" that aren't, implying that it has revealed the killer, but leaving things so vague that I could only tell who the killer was because his character name in the credits was in scare quotes.

There are two possibilities: one is that the ending was all wrong for the movie, and the other is that the movie was fundamentally something other than what I thought it was. Since up until the ending, I mostly liked the movie that I thought I was watching, I'm content to assume it's the former, and just scrunch up my eyes and pretend that the ending didn't happen, and to hell with critical integrity.

So, one of my big pet peeves is that we have in cinema this marvelous toy called "sound," and such a vanishingly small number of filmmakers ever try to do interesting things with it. That said, there's one type of film that pretty much by default has to do so, and that is the story about sound (the granddaddy of the form is of course Coppola's masterpiece The Conversation). A film title Noise doesn't have to be about sound, of course, but in this particular case it is, and director Matthew Saville along with sound mixer/designer Emma Bortignon and sound editor Jed Palmer really do go all out.

To explain why will require the plot: in the film's bravura opening, teenage Lavinia (debuting Maia Thomas) hops on a subway train, iPod blazing, and is so intent on her music that she does not notice as seven passengers are shot and killed in her car until just in time to see the killer escape. Coming as it does hard on the heels of a seemingly random killing of a local woman on a roadside, this traumatises the community fiercely, and Office Graham McGahan (Brendan Cowell), who had hoped to get some medical leave to deal with his increasingly crippling tinnitus is assigned the night shift at a trailer in the dodgy part of town to listen to anybody who wants to come in as a witness, or just to talk about what has happened.

Hearing things you don't care to and not hearing things you need to are deeply ingrained to the story's evolution, and the filmmakers do marvelous work playing with that. Chiefly in the form of the nominal protagonist, Graham, whose hearing is interrupted constantly by a low ringing that occasionally and for no apparent reason picks up in intensity, sometimes to the point where he literally cannot make out any other sound. The soundscape is primarily subjective - that is, we hear what the characters hear, whether it be the constant buzz in Graham's scenes that eventually becomes such a natural part of the movie that it's startling when it cuts off, or Lavinia's heightened sensitivity to every little noise as a result of her post-traumatic stress. As I write this, I realize that it sounds like a cliché - ooh, she's scared of the big bangs! - but it's done in a way that seems much more imaginative than that.

Sometimes, anyway, the sound is more impressionistic, which is one of my favorite words that doesn't really mean anything. The use of diegetic music throughout cannot be traced to any one character's perspective, but it hangs over the movie anyway, filling up space and intensifying the moodiness of the neo-noir surroundings.

Mood and space are two very important things in film: they are often created through evocative lighting and mise en scène and editing, and mood in particular through dialogue and acting. And while all of these things are done awfully well (the writing by Saville, the cinematography by the well-named László Baranyai), it's really the sound that creates those things. All the details that would ordinarily be filled in with little visual touches are instead filled in with offscreen noise that immediately and effectively evokes a whole neighborhood. I can think of a few films that do something similar - The Haunting leaps to mind - but it's still exciting when it's done this well.

Hell, even That Ending uses some pretty aggressive sound design that cannot possibly be regarded as "natural" in any useful sense of that word.

But That Ending does call into question, for me at least, the degree to which this is an experiment in sound couched in a genre film versus a genre film with a really well-done soundtrack. Make no mistake, it's a fine genre film, more about psychology than policing and all the richer for it. But rich cop films aren't rare, and it's not a stand-out in that field, just good. I don't know. Sometimes you just really wish that narrative films didn't need narratives.