Q:

What's with Interstellar's strange sound mixing?

I hope this question doesn't come across as too opinion-based, but when watching Interstellar I noticed, that the sound mixing was a bit "off". Dialogue was sometimes very hard to understand and simply overpowered by the sound effects or Hans Zimmer's (albeit amazing) score. Now normally I'd just brush that off based on the fact that I'm not a native speaker (though I've seen other better understandable movies in English), my theatre might not be perfect and not everything can be perfect in a movie. But I heard that others around the world uttered similar complaints, too and that Wikipedia says about the sound design:

Christopher Nolan said he sought to mix the film's sound to take maximum advantage of current sound equipment in theaters. Nolan paid close attention to designing the sound mix, for instance focusing on what buttons being pressed with astronaut-suit gloves would sound like. The studio's website said, "The sound on Interstellar has been specially mixed to maximize the power of the low end frequencies in the main channels as well as in the subwoofer channel."

Which, even though it comes from the probably biased studio website, suggests that there was special effort put into the sound editing. So I'd like to know, is there some unusual reason for the apparently strange sound mixing in this movie or was this just a naturally "not so good" part of the movie (or is it just me and my theatre)? Was this maybe due to the techinical reason that it was tailored to top-notch sound technology in theatres and therefore the sound in not too top-notch theatres had to suffer? Or was there even an actual intention behind this seemingly difficult understandability of the dialogue?

A:

As @DisgruntledGoat comments, this was all intentional. There's a fantastic Hollywood Reporter article, which includes an interview with Christopher Nolan, which discusses the reasons. To quote the most relevant parts from the article:

Since the movie’s opening on Nov. 5, some viewers have complained
  about the movie’s sound, claiming some key dialogue is difficult to
  hear and raising questions about whether it is the fault of the sound
  mix or the sound systems in some of the theaters where the film is
  playing. But Nolan said the movie’s sound is exactly as he intended
  and he praised theaters for presenting it correctly.

Nolan himself states:

“The theaters I have been at have been doing a terrific job in terms
  of presenting the film in the way I intended,” he continued. “Broadly
  speaking, there is no question when you mix a film in an
  unconventional way as this, you’re bound to catch some people off
  guard, but hopefully people can appreciate the experience for what
  it’s intended to be.”

He also stated:

“We made carefully considered creative decisions,” he said. “There are
  particular moments in this film where I decided to use dialogue as a
  sound effect, so sometimes it’s mixed slightly underneath the other
  sound effects or in the other sound effects to emphasize how loud the
  surrounding noise is. It’s not that nobody has ever done these things
  before, but it's a little unconventional for a Hollywood movie.”

Nolan also described the scene in the hospital, where Michael Caine's character died:

“The creative intent there is to be truthful to the situation — an
  elderly man dying and saying something somewhat unexpected. We are
  following the emotional state of Jessica’s character as she starts to
  understand what he’s been saying. Information is communicated in
  various different ways over the next few scenes. That’s the way I like
  to work; I don't like to hang everything on one particular line. I
  like to follow the experience of the character.”

So the sound decisions were clearly intentional and seem to be to give a more realistic tone to everything that was going on, involving the audience fully in the scene by allowing them to experience what the characters were experiencing - so, for example, in moments of great stress or shock, the actual dialogue becomes less important and instead we hear either the sound effects of their surroundings or the music Nolan chose.

A:

Yes, it was apparently intentional. I don't have the original source but here is a quote from critic Mark Kermode from the November 21st episode of the Kermode & Mayo podcast:

There's been an awful lot of fussing about the dialogue, right down to the point that Chris Nolan's had to be quoted in the press as saying: "You're not meant to be able to hear all of it. There are moments in which the dialogue is meant to be drowned out by the sound effects. That's how I mixed it."

This occurs at 41:15 in the episode.

A:

I'd like to agree with Andrew Martin's answer, and to offer my own interpretation of the quirky sound mix.
The voices are often accompanied by music, for example a flute synthesizer pad held on C5 kind of range, same as a female singing range... the music is often as loud or louder than the voice, to make it more emotive, and consequently it less intelligible, because the high frequencies of any voice clash with C5 chord, the ear can't isolate the voice as well. So you have to listen harder, more intensely.
The voices aren't mixed in a balanced way, as in with a flat sound spectrum. they have been heavily biased towards one frequency or other, which means that the voice's dynamic range is distorted, some dialogues are a bit tinny. You can hear spikes in the voice that emphasize the SSS, TSCH, and TSS sounds, a little bit, and mask some of the lower frequency vowels.
Some of the dialogue is in a fairly low voice, a casual half whisper, rather than a full throated voice, which doesn't help for clarity.
Most cinema's use particular care to isolate the vocal frequency spectrum from the other sounds, FX, Music, to keep it very clear. Interstellar is more reminiscent of unmixed and amateur sound mixing, and also masterfully mixed for a characterful tone and increased tension, like a suspense movie.

