Monday, July 11, 2005

Dynamic Range, Batman, Underground and Ponniyin Selvan

Well, I wanted to write quite a bit about the new Batman film; but I suppose I should stick to one area that seems to be my preoccupation for now.

Most time these days I spend holed up in a sound edit suite in front of a DAW, looking to make tiny adjustments to (on last count) a ten track sound edit. I'm trying to bring it down to a manageable four tracks of effects with separate location audio and music. BTW, there was another place I loved spending time holed up in last week.

Getting back to some tech basics; even though the format our finished film will most circulate in would be DVD (we somehow never have the budget to make prints), the film will nevertheless be premiered in a proper cinema. Plus, the DVD format, or for that matter, the Digibeta video master, have surprisingly good audio reproduction abilities. I hope to keep the dynamic range of the audio content as large as possible on the film I'm working on.

The dynamic range of any piece of recording (and also of any medium) is of primary concern whilst mixing. In classical music, the softest and the loudest sounds are referred to as the pianissimo and fortissimo respectively. Middle-school physics teaches us that the range of hearing of the human ear is in between the threshold of hearing 0 db(SPL) and the threshold of pain, roughly about 140 db(SPL). In digital media, it is generally agreed that the bit rate of the audio data multiplied by 6 corresponds to the dynamic range of the data (the difference in volume between the highest possible and lowest possible sounds). So 8 bit data gives about 48db; 16 bit data gives about 96db and so on. In reality though, a floor level of noise usually takes up quite a bit of space at the lower end reducing the effective range by quite a bit.

Now, apart from the range and latitude (the levels of difference) present in the data, listening atmospheres and conditions also affect the dynamic range of an audio performance. A noisy atmosphere can affect the rendition of the pianissimo of uncompressed audio.

Getting back to audio content itself, the best way to enjoy the entire dynamic range of any piece of audio would be to listen to it straight: i.e. live! If you've listened to a cello played in front of you, you'd know what I'm talking about. When it comes to listening conditions apropos the medium, apart from real life, (included stage performances), it is the cinema hall that offers a comparatively large dynamic range. With noise reduction systems in operation from the 70s and digital sound since the 90s, the dynamic range offered is substantially high (almost close to 120 db).

Why this huge theoretical lecture when all I said was that I'd talk about a film? Any theatrical film that does not exploit the big dynamic range offered, is doing injustice to the medium. I saw Batman Begins, not just in a cinema, but in an Imax theatre. Unfortunately. the film's soundtrack was designed (though not necessarily mixed) for it to be seen on a DVD in a stereo television set in a medium size living room.

I do not know if the excuse is aesthetic preference of the filmmakers, but Hans Zimmer seems to have slapped mood-music almost throughout the film, over all the dialogue scenes. This for one, effectively raises the floor level of the audio by about 30db... That is a waste! Curiously, this 'made for a small screen' concept extended to the visuals as well, that seemed to hover fairly close-up to faces.

I do not blame filmmakers for creating films for the medium it is likely to make the most money, but when you intend to strike Imax prints, please take the effort to use the medium. I for one would love to exploit the 'size' (both aural and visual) offered by Imax.

Finally, what was the other place I liked to be holed up in?

Last week, I had the opportunity to do some sound recording on a documentary shot under the city of Bristol: That's right: Under the city of Bristol, in a cave system. Apparently, in the middle ages, a group of monks (and the name of their order slips my mind) built the one we filmed in: called Raven's Well Very Lord of the Ringsy!

I never thought I'd like spelunking, but the invitation to record 'silence' was too tempting. The moment we descended into the cave system, I knew what was coming. We're all familiar with the English expression that talks about hearing a pin drop. In Raven's Well, I could in-fact hear the (sometimes far away) water dripping sounds from many cracks through which an underwater spring spilled into the tunnels. After the core crew went away to shoot specific areas of the cave, I went into a branching tunnel, isolated myself in complete silence. I did do some recordings on the most convenient thing to take in there (a portable DAT recorder), but for most of the one hour I spent alone, I switched off the system, took off my headphones, switched off my head torch and sat there in complete darkness and complete silence.

For those of us who spend most of our time in aurally saturated places, the complete silence (accentuated by steady dripping sounds from various distances, and from variously shaped caverns on various surfaces) offered an aural experience I wish I could replicate for others. This was the exact aural opposite of where one would normally spend a weekend: a noisy nightclub. These caves gave me a symphony in pianissimo. The melody of the lowest sounds one can ever hear. The floor noise level was purely internal (I have tinnitus in my left ear).

In an hour of pure meditation, I could occasionally imagine Gollum sat next to me, but what I most thought about was how to replicate this experience in a cinema. I sure have a wonderful excuse in the exquisite dark tunnel scenes from Ponniyin Selvan.

When one designs the sound, one needs to be very aware of the technical details as well. The same selection of sounds, could be mixed differently for various media: broadcast radio and television, mono television in a noisy flat, stereo television, home theatre, stereo headphones, padded hedphones, computer sound system, small cinema, large hall, Imax etc. The dynamic range can be compressed correspondingly (raising the piannisimo level and reducing the fortissimo). Ravel's Bolero can certainly be mixed for radio broadcast and listened to in a kitchen, but the compression effectively takes away the beauty of the piece. But even while designing a soundtrack; ie. deciding on what sounds go in when and how, one can accomodate for the vagaries of the media. I feel that slapped on mood-music, effectively 'Muzak', is certainly a very television thing to do. Kubrick used Muzak as almost a parody of itself in (the very large) 2001 A Space Odyssey, but if one can design a soundtrack where one really respects the effect music can have on the audience, then I suppose it has to be used wisely, especially if one wants to exploit a large dynamic range. This hold true not only for music, but for any sound in a film. Walter Murch points out the meaning of clarity and density when it comes to film sound.

And when I start mentioning Murch, it is time to wind up!

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