Sound processing for TV

When thinking about the production of a television program, an extremely important factor must be taken into account that brings great richness to audiovisual production: the post-production of sound. This is the stage between the recording of the program and the final product.

In the recording of a television production, different types of microphones are used, such as wireless, tie or lapel, table or pressure zone microphone (pzm) or others, which pass through a mixing console and are recorded directly on the audio recording tracks of the camcorders or on external audio recorders. That is why the audio for post-production is usually received in a DAT or can come directly in the pre-recorded video material for editing, in video formats such as Beta SP, Beta Digital, U-Matic or MiniDV, among others.

The first step to consider when starting post-production work is to dump that audio from the DAT or from the VTR to our workstation, which can be a workstation configured with a specialized application such as Pro Tools. Here all the processing will be done to, once finished, take it back to the master editing tape.

For a second instance it is convenient and necessary to have the edition finished and digitize the image to use it as a reference for the sound montage. This is so, even in the case of a TV program that has a production with little deployment, with dialogues and audience in floor or studio and some recorded notes, since this may require an intense post-production work, which then, include different sound effects or music tracks synchronized with the image.

To enter the image in a Pro Tools video track it is necessary to have a video digitizer board or card. It is important to note that this image is only a reference and will not be the one left in the final product, so it is not essential that the board is of very good quality or requires uncompressed processing.

At the beginning of the sound processing we have a video track with the visual reference, an audio track with the dialogues and another with the laughter of the audience, to continue with the same example. The basic processes applied to the soundtrack can be many. One of them is the noise reduction or noise reduction that consists of a tool that takes the main signal, which for this particular case could be a dialogue, and filters the noise or "dirt" of the sound sample. This process can be very useful in programs that include live phone calls, whose sound signal is quite dirty or with a high presence of interference or parasitic noises.

Once this "cleaning" of the shot is done, we normalize it. Normalization is a tool of the program that takes the entire audio sample and enlarges it, until the maximum peaks or the highest signal strength parts reach 0 dB. Some technicians usually normalize to –3 dB instead of 0 dB so as not to work so close to the limit; past the 0 decibel threshold the signal could begin to distort. And recently, when the dialogues are finished, you can "tie" them or synchronize them with the image. This operation is called lipsync technically. For this, the reference signal of the video track that we are viewing on an external monitor is used. On the Pro Tools screen appear all the tracks or tracks joined by a timeline, timeline, through which we match each dialogue with its corresponding image.

Many post-production islands have a small recording room that is usually used to record voiceovers, also called voiceovers. These voiceovers are not necessary in the recording of the program and are added directly in the sound post-production, under the same sound processing requirements as the other signals.

Another fundamental process within this chain is the musicalization of the recorded notes or even the entire program. For this it is necessary then, to create a new audio track where all the music tracks will be. Here the video reference is also used to synchronize the music with the beginning of a note, with the end of it, or with the two locations. Nowadays, the addition of effects is also widely used, such as library sounds synchronized with the image or sounds recorded precisely for this purpose. These sound elements are recorded on a different track than the music.

The equalization of the dialogues is another step of the utmost importance. The voices must be more or less within the same sound spectrum to achieve, in this way, an overall balance in the audio shot. It is also convenient to apply this process to voiceovers or voiceover registers recorded outside the program, which must have a "color" or an atmosphere similar to that of the dialogues, because otherwise they would sound too artificial. It is about preserving or reproducing the electroacoustic recording characteristics of the space in which they were originally recorded.

One of the last steps in sound processing is mixing work. In other words, it's the process of bringing all the elements of the soundtrack together. Mix the dialogues, laughs, voiceovers, musical tracks and sound effects, placing each sound in its corresponding plane. Once the mix has been dumped into a stereo audio track , it is convenient to equalize and normalize the shot. This is the final mix for the show.

Finally, we proceed to dump the audio in the editing master. For this you need to have a synchronizer – Digital Time Piece or USD Universal Slave Driver – that "enslaves" our Pro Tools digital station with the video player or VTR machine. This appliance takes the time code record from the VTR and sends it to the slave connector of the Pro Tools workstation to establish an accurate synchronization relationship. Once the equipment is synchronized, we dump the final mix into audio channels 1 and 2 of the VTR and with this our post-production work ends.

Good equipment for post-production work could be as follows:

1. AKG Solid Tube. Valve condenser microphone, polar cardioid diagram, with own source. Excellent for taking voices.
2. Neutrik Connectors
3. Yamaha 01V console. Digital, 16 channels. It has internal processors, moving faders and allows you to save the scenes.
4. Mac G3 workstation with Pro Tools 24 software 4.3, one 888 converter (analog/digital), 4 DSP cards. Plug in: Focusrite D3 compressor. The EQ, filters and normalizer of the program work very well.
5. External CD burner SCSI any brand.
6. Crown power of 100 W or greater.
7. Yamaha NS10 near field monitors.
8. Fostex DAT recorder, generator and time code reader.
9. Digidesign USD Synchronizer or MOTU Digital Time Piece

There are countless processes applicable in the post-production of the sound of a TV show. Many of them vary according to the problems we must solve or with the specific needs of the work and the client. The important thing is that these tools are extremely useful when it comes to improving the quality of an audiovisual production.