How can binaural and spatial audio enhance the emotional experience of podcasts and radio plays? The following article by VDT sound engineer Felix Stäblein dives deep into the hybrid mix of binaural recordings and sound design, processed with dearVR PRO for the Podcast play "Dark Audio Moments", produced by Axel Springer Audio GmbH.
About the podcast and entering production
The spark of an idea for Dark Audio Moments lit up our imagination in March 2020 during some talks with Christoph Falke, Managing Director of Axel Springer Audio. The goal was to develop a revolutionary “Blairwitch” horror story in which the listener is placed in the middle of the action instead of being an objective listener.
When looking at the statistics, we found that podcasts are predominantly consumed in Stereo by users on mobile devices whilst using headphones. The technical hurdle of switching to an immersive format like binaural audio was therefore virtually a nonissue in regards to headphone usage. Moreover, the binaural format offers much higher immersion than most of the other audio formats, and this could help us get closer to the Blairwitch intensity.
This advantage pushed us towards a 3D audio production with a binaural approach and moved us away from regular Stereo and Ambisonics solutions. For the production, we finally decided on a hybrid approach consisting of binaural recordings mixed with the sound design, which we later processed with the spatializer plugin dearVR PRO.
Our final setup for the binaural on-location recordings was initialized in May 2020 and during the production process, it was further optimized based on our handling and mobility requirements. Our final treatment was then set up for the best possible reproduction of sound sources localization information with the lowest possible inherent noise.
The recordings for the first season of DARK AUDIO MOMENTS started in August 2020. The team consisted of a producer group around Simone Terbrack, the authors Christoph Dittert, Björn Berenz (Die Drei ???) and Perry Rhodan, as well as many well-known german voice actors like Joachim Kerzel (German voice of Anthony Hopkins) or Charles Rettinghaus (German voice of Jamie Foxx).
The ongoing pandemic situation required a somewhat different recording concept for the voice recordings. Again, our choice of the hybrid solution proved to be the right one, as it allowed for the voice actors to act together simultaneously without endangering each other’s health.
In contrast to conventional sound recording, the binaural recording process is more demanding. You can't just record a sound and then push it to the ‘right’ place. In binaural, factors such as distance, spatial information, and timing, have to be considered beforehand and constantly checked during the recording process. Alongside the binaural takes that were recorded with a dummy head, we also captured the voice actors in a convention manner to then at a later stage combine the binaural recordings and the post-produced spatial audio with dearVR PRO.
HYBRID POST PRODUCTION
We aimed to achieve the most accurate results and a perfect merging of the binaurally recorded atmospheric sound and the conventionally recorded actors, which we subsequently positioned in the three-dimensional space using dearVR PRO. To facilitate this technique we created a speech reference beforehand for each atmospheric recording, which enabled us to merge the two worlds by automating the real-time auralization of dearVR PRO. This step was probably the most time-consuming. Nevertheless, the work was worth it because with dearVR PRO's highly advanced room presets, we managed to weave the two formats together seamlessly.
The sound design followed the same hybrid approach relying on a combination of binaurally recorded audio and sounds subsequently positioned with dearVR PRO in the three-dimensional space. We were able to mitigate the risk of the unwanted background noise of the direct recording. Again, dearVR PRO's real-time auralization worked perfectly and enabled us seamless integration of both audio sources.
Overall, the dearVR PRO spatializer plugin was a reliable companion for realizing the project, and it integrated beautifully into our existing production workflow. Due to the easy to use approach of dearVR PRO and the tight integration of placement and real-time auralization in one plugin, (which is unique) the integration of the rendered material with the captured sounds taken from real environments worked flawlessly.
MASTERING AND OUTLOOK
Looking back at the project, it can be stated that a good immersion mainly results from the sound impression of the environment and the captured sounds rather than an exact positioning of individual speakers or sounds.
During the mastering, we only used an EQ and a brickwall limiter to absorb distortions caused by unwanted peaks in levels. The renunciation of large mastering chains is not decisive and today, even in the field of television, using a "large mastering" is often renounced.
As long as the processing of the individual tracks is correct, it is likely to create a compact sounding mix that meets the loudness and frequency response standards of conventional productions just by automating the faders.
The feedback for our podcast has been overwhelmingly positive. We received many enthusiastic messages from audio experts, podcast producers, and listeners. Furthermore, we can also track the positive impact by looking at the download statistics.
Since podcasts are often listened to through headphones, the "limitation" of the 3D effect is well suited, and the scattering losses were manageable. At the moment, we're in the starting phase of producing a second season, and we're looking forward to using dearVR plugins again to see how we can push the art of podcasts to the next level.