Dolby engineers discuss audio capture for football, MotoGP
The audio configuration of the average mass international sporting event, such as a football match in Serie A or the MotoGP tournament, is highly complex and always evolving. That was one of the messages that shone through when two Dolby European representatives – broadcast systems engineer Ignacio Díaz-Valdés Alonso and country manager Italy Philip Arlettio – discussed sports audio workflows during a press conference held in Milan recently.
They began by discussing the positioning of microphones in various strategic locations. Four omni-directional microphones are used to recreate a realistic environment. They are placed at the four corners of the field to capture the roar of the audience; other specific microphones capture the audio in the foreground and are highly directional, super-cardioid ‘shotguns’ located on the four sides of the perimeter of the field, capturing sounds even at 20-30 metres away with incredible precision – including the curses and insults of referees, players and coaches…!
These super directional microphones follow the action; the engineer opens some and closes others for this purpose.
Meanwhile, six directional microphones are situated for each longer side of the gridiron including two in the vertices in co-presence with minor sides. Four are always placed at regular intervals on the shorter sides of the field for a total of 16 microphones.
To complete the set-up a Soundfield microphone is placed on the stand used for the cameras along the main line to centre field, while another stereo microphone is in the same position.
The Soundfield microphone contains four capsules inside, placed in a special static support in order to record sounds coming from any direction and, along with a proper external processor, it is capable of producing a multi-channel audio omnidirectional 5.1 signal.
A completely different configuration is found in coverage of MotoGP, wherein the position of the microphones must perform dynamic capture even from ‘fixed’ locations.
The sound stage is complicated both from video and audio and perspectives. It is generally considered very problematic to create a good stereo image in such cases, and even more especially in terms of shooting to 5.1.
In the past each camera had two-channel audio with a microphone following the action placed right on the camera and a second positioned shooting in a fixed position about 20 metres from the passing bikes – so the sound in practice was not stereo.
For the 2013 edition, however, a decision has been taken to use a pair of stereo microphones fixed on each camera. Essentially, therefore, every interesting point of the circuit will be followed with a pair of microphones in stereo. When switching between the various cameras, the sound follows the picture and you obtain a significant ‘presence effect’.
For the surround, the sound team is creating an ambient ‘bed’ by placing microphones at strategic points. Moreover, since in each circuit some video walls showing the action to the public have been installed, the actual emotional reactions of the audience for each event in the track can be taken from that single location.
A 5.1 microphone is being placed along the finish line. Each camera takes up the bike that crosses the finish line and the effect of the enveloping surround sound expands everywhere, leading to some exciting results.
In practice, for the next season, it is expected that there will be as many as 34 microphones: 32 Audio-Technica devices (15 x 815B, 16 x 8035B, 1 x 825), a stereo mike by Shure, and Sennheiser’s MKH-418 stereo shotgun mic.
Audio capture for MotoGP and other sports continues to evolve rapidly, it is clear, but there are issues with home audio that still need to be addressed. TV flat panels with speakers inside remain scarce, whilst the detriment to the surround effect is only partially resolved by making use of so-called ‘soundbars’ – optional arrays of external loudspeakers which manage to combine a good wrap-around effect with high quality sound at a reasonable price.
To some degree, the circuit set-up is still a compromise between cost and performance; the use of all surround mics, for example, would deliver an even more comprehensive multichannel sound image, but might not be complementary to budgetary considerations.
Moreover, from an artistic point of view it is possible to switch between the many different cameras to achieve the ‘front audio’ of each shot, but to maintain a compelling ambience with only one fixed omnidirectional microphone.