SURROUND SOUND IN RADIO DRAMA EERO ARO Producer, Sound Designer Finnish Broadcasting Company, Radio Theatre Finland Radio drama can benefit from spatial sound as it releases the listener from the position of a spectator. General production tools for multichannel audio can be used in radio drama, but the setting between the performance and the listener has very little in common with multichannel music recordings. In a radio play the point of listening can change with time. Auditory objects can move and t he size and the character of the room may change, spaces may appear and disappear, and there can even be several layered rooms or spaces at the same time. All of this gets its final form in the mix. SURROUND SOUND IN RADIO DRAMA However, radio drama is not stage theatre. A radio The picture of a radio play is larger than any cinema drama listener is required to make an active screen. It has no frames or edges, as it builds up in the commitment, an “aural contract” with the play. [1] The imagination of the listener. goal of the radio play director is to make the listener stop listening and make him hear . In other words, to set The majority of radio dramas are made in two channel him free from the position of a spectator. This is where stereo. Stereo can express the directions of sound spatial sound reproduction can come to help, as it can sources and the depth and the width of the sound stage bring the listener inside the story by immersing him in front of the listener . with sound. Spatial sound gives more room for the placement of the sounds and for the reproduction of the However, many radio drama people feel that two spatial characteristics than two channel stereo. channel stereo is rather limited, as it is just mimicking the setting of a traditional stage theatre. In the classic Of course there is a paradox in here; if a radio play setting of the theatre the performers are placed on a takes place in the imagination of the listener, does the stage in front of the audience, who are sitting in their reproduction medium really matter at all? Wouldn’t seats opposite to the stage. This setting allows the mono or stereo do as well, or headphones or just a pair audience to follow the play without being taken into the of loudspeakers? play. It gives them a safe feeling, as they can choose whether they are taking part in the play or not. They There is at least one good reason to use spatial audio can be involved in the play if they wish to. for radio drama; multichannel listening causes less listening fatigue. This is because surround sound is In a well-made theatre play the spectator can identify closer to natural hearing than two channel stereo. With him- or herself with one of the characters, usually the stereo speakers, the sound image (with all of the protagonist. As long as this character is visible on the reverberation included) is located in front of the stage, there is a connection between the spectator and listener. With the headphones the sound image is what is happening on the stage. The spectator feels that localized inside the listeners head, not to mention the he or she is part of the play . This connection is very uncomfortable feeling of using headphones during a fragile and is easily broken. Any distracting sound, radio play with a long duration. light or off-stage movement can shatter this illusion. ILLUSIONS IN SOUND – AES 22 ND UK CONFERENCE 2007 X-1 EERO ARO Clarity actors work in contact with each other, and it is the If delivering information is the important thing, it is sound engineer who takes care of microphone practical to use mono sound. However, if several placement and the recording. people are talking in the studio at the same time, two channel stereo and surround sound help the listener to The actors need to pay extra attention when they move detect individual sound sources from the crowd, which on the left and the right side of the dummy-head. The in mono reproduction would be masked by louder sound image must not jump suddenly from the front to sounds. the back or vice versa, and that can happen very easily. Moreover, the speed of the movement must be different The illusion of space depending on the distance to the head. Surround sound reproduction creates an illusion of an auditory space. The cues are given both by the ambient Using non-dummy-head sound effects with the dummy sounds themselves and in the placement of the sounds, head dialog recordings would require additional but also in the spatial characteristics, such as the processing at the mix. reverberation and the reflections of the room. Matrixed surround systems Directing listener’s attention Matrixed systems were made for the cinema, in which The listener’s attention can be guided to a certain dialog must be localized to the picture. To achieve this, direction, in surround sound this can also be to the side the systems used bandwidth limiting of the (single) rear or behind the listener. channel, time delay to the rear speakers and adaptive control of the soundfield. Many of the adjustments EXPANDING FROM TWO CHANNEL STEREO were left for the home listener. Binaural techniques Binaural techniques were used for radio drama in the Matrixed systems were not very ideal for radio drama, 1970s. The BBC made a number of productions and because it wasn’t possible to place direct sounds at the dummy-heads were especially popular in Germany. rear. There was only one rear channel, so that sounds couldn’t be placed at any particular direction at the The good thing about binaural audio is that it delivers a back. Placing a voice in the rear channel sounded bad, three dimensional sound image with two channels only as the basic frequencies and the sibilances of human and the sound image can be very realistic. A downside speech were filtered out. Localization of a voice in the is that the listener must use headphones. Traditional rear channel was undefined because of the rear channel dummy-head techniques also have the problem that delay. It wasn’t possible to compensate for the rear most listeners don’t locate frontal sounds in front of channel delay either, because the home listener may them, but behind the head. There are solutions for these have adjusted the delay in his decoder by as much as 50 problems, but HRTF-processing or convolution milliseconds. panning are not yet everyday production techniques in radio drama, not to mention Ambiophonics or head- Advanced matrix systems, such as Dolby Pro Logic II, tracking in the listener’s home. Radio also still needs to solved most of the problems, but unfortunately PLII take care of the compatibility between mono, stereo and came to the market a little bit too late. Discrete digital spatial reproduction. With binaural techniques the multichannel systems were already there, and they are compatibility isn’t very good. Binaural stereo tends to much better suited for audio only applications. have a hole in the middle in loudspeaker listening. In the 1980s and 90s there was an alternative for If we look at binaural recording from the actor’s point transmitting surround sound via FM radio, and that was of view, there are certain problems. For an actor, a UHJ Ambisonics. UHJ didn’t suffer from the technical dummy-head represents a “one point microphone”. disadvantages of the original Dolby Surround, but Talking to a dummy-head needs extra training and unfortunately Ambisonic decoders were not commonly experience as compared to mono and stereo available. microphones that the actors are used to. The actors need to place themselves and make their movements in Discrete channel systems and 5.1 relationship to the dummy head. They constantly need Discrete 5.1 systems were quickly adopted by radio to keep in mind, where the “third listening person” is. drama in many countries as soon as they became The important contact between the actors is easily available. All five channels are full range and discrete. interfered with if they need to pay too much attention to If necessary, the LFE channel can be used for special the microphones. Best results are gained when the effects. x-2 ILLUSIONS IN SOUND – AES 22 ND UK CONFERENCE 2007 SURROUND SOUND IN RADIO DRAMA There are some problems with the ITU-R BS.775 Microperspective speaker layout, as the angles between the speakers Radio drama can sometimes use very strange and don’t support stable phantom images anywhere else unrealistic spaces and even microperspectives. If tiny than in front of the listener. The layout creates a nice microphones are put inside small machines, or example feeling of space, but not so good localization of virtual a mechanical alarm clock, the dimensions of the sound sources on the sides or at the back. original sound source are magnified when it is played back through loudspeakers. Unrealistic spaces can also THE AUDITORY PERSPECTIVE be created with convolution filters. Small spaces can be Realistic perspective (in the audience) modelled and used in the mix. Sometimes the point of The realistic sound perspective directly compares with listening can be inside a small space, such as a the real world. A realistic perspective usually has cupboard. following properties: - audience’s point of listening (POL) [2] RECORDING - stationary auditory objects Dialogue - clear picture of the space in which the performance Radio drama dialogue is usually recorded with mono or is taking place stereo microphones.