Our aim was to provide Caleb with a set of tools and through practical investigation find out how they were best used for each different scene and the layers within it. Sound designer Caleb Knightley working with R&D's Chris Pike and Steven Marsh on the headphone mix E ach of these seems to have advantages in certain situations, as does good old stereo. Three different binaural techniques were used: anechoic binaural filters, binaural filters measured in a real room, and a parametric binaural room simulator. Using our production tools, each component could either be kept in stereo or binaurally positioned in 3D space.
We started from the original stereo multi-track session, including music, background sound, effects and dialogue layers. We have applied a range of processing techniques to the different layers of each scene.
In this production we have taken a different approach, rather than use virtual surround techniques, we have produced a dedicated headphone mix. We strongly believe that binaural techniques can create significantly better listening experiences for our audience. The perceived quality was found to vary significantly according to the source material used. Previous work has shown that even with the state-of-the-art virtual surround systems we don't currently get a big improvement in quality over a conventional stereo down-mix. On Saturday we released a player that does this in your web browser for a surround sound production of Under Milk Wood, you can read more about that here. In this approach existing surround sound content (such as a 5.1 mix) is rendered to a two-channel signal. One way in which binaural techniques are commonly used is to create virtual surround sound for headphones. We often call this 3D sound because it can give a plausible impression of sounds coming from outside of the listener's head at well defined positions in 3D space, as demonstrated in our recently published experiment. The primary application of binaural techniques is for headphone listening. This effect can be created in recordings with dummy head microphone techniques and also in post-production using digital signal processing, which is the approach we have taken here.
In brief, it aims to recreate the complex effect that the human body has on a sound reaching the auditory system to create a more realistic spatial impression for the listener. If you've not heard about binaural sound before, we've written about it a few times on this blog. As he mentions, we did not set out to be gimmicky, we wanted to use the tools that we have to enhance the original stereo mix with spatial effects whilst maintaining a high quality experience. You can read about Caleb's approach to mixing with our binaural system on the Radio 4 website.