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Exploring Field Recording

This morning was jam-packed with exercises in sound recording, production meetings and a client shoot later that day that went until approx. 23.15 and left me with a lot new experiences not only in how to record sounds more professionally or in how production meetings in higher levels work and are organised, but also in regard to client work.

We had a guest lecturer come and talk to us about the fundamental principles of field recording and its very foundation, the signal chain. Although proper sound can have a tremendous impact on the quality of a film and is - to my mind - at least as important as the visuals, capturing it is per se not a difficult process. As our guest lecturer confirmed, it is rather a matter of practice to be able to collect clear and pristine foley and atmos than to understand the signal chain.

The Signal Chain for Capturing Sound:

1. Source

2. Microphone

3. Cable

4. Recording Device or Mixer

5. Monitor and Feedback (Headphones)

As with all chains, it is only as strong as its weakest link. If any disturbance occurs within these elements (a faulty XLR-cable or microphone, the recording device turned off, broken headphones), you can either hear it clearly in the recording or hear nothing at all.

Sound is, in its first instance, nothing else than compressed air, and thus, a physical phenomenon in itself. High frequencies consist of rather short and weak waves and are, as such, only able to travel short distances and unable to pass walls, whereas low frequencies have broad and long waves that are able to travel long ways and pass through walls (which is why we can often hear the bass sounds of a club or concert in the distance, but not the voice of the singer).

Sound waves will either enter the human ear or the microphone and get translated into electric signals. These signals are then either sent to the brain or a recording device and translated there into what we hear as sounds. Whereas this is a rather strongly simplified explanation, it was interesting to learn that, essentially physical, sound waves in both instances are translated into electrical signals before they are being transferred, inferred and expressed again.

But sound being physical also means that it is oftentimes manageable in regard to avoiding or filtering certain sounds on a recording. If wind blows, you can block it, either with a blanket, a wall, or even yourself, depending on the intensity.

There are, of course, also annoying sounds that are not that easy to eliminate. As with building works and seagulls crying (a real problem for sound recording here in Hartlepool!), you can either wait for a gap to record, ask for a break or scare away the culprits (preferably only the seagulls, not the construction workers). With computer fans and ticking clocks, you can either turn them off or take them out of the room, etc.

To make a long story short, sound is one of the elements of filmmaking that can be taken care of, even though it can sometimes be annoying to stop an otherwise perfect recording because your sound operator picked up a sound in the distance no one else can hear.

Moving on to the technical details of this sound recording session, we were introduced to the Xoom H6 that we used as a recording device during our exercise today.

Our lecturer introduced us to the basics of the menu and proper usage of a recording device. Here, the rule of thumb in field recording is basically that you take as much control as possible. While the device has a couple of interesting and useful functions, designed to make it comfortable to use, most of these functions and settings work in an automated way, that more often than not interferes and thus compromises the quality of the recording taken.

So what you basically want to ensure before taking your first recording is that you turn off any setting that results in an automated action of the Xoom. This means, e.g. turning off the 'Auto Gain Compressor' that compresses the recorded data into an .mp3-format of lesser quality instead of the industry standard format .wav (48.000 kHz, 24 bit).

You then also turn off features such as 'Auto Record' and 'Compressor', whereas you leave 'Pre-record', 'Limiter' and 'Backup Record' turned on. Compressors are designed to make quiet sounds louder and dial down louder sounds whereas the limiter will protect your recording against any clipping distortion (that nice, lovely screeching sound that follows whenever a source is exceeding the maximum sound levels on a recording).

While these sound like nice features to have, the compressor's function unfortunately has the disadvantage of not being sentient. Have you ever heard a recording where everything sounds fine until the speakers fall silent and you can suddenly hear a hissing noise in the silent breaks in between? That's the compressor for you, enhancing the silence!

And since it is easier to clear up, elevate, or dial down any sound you need in the mixer afterwards, we were given the recommendation of keeping the compressor turned off.

Going back to pre-record and backup-record, these two functions serve to give you better control over the sound levels and a failsafe for recording. Since pre-record requires the device to constantly listening, you can easily read the current stats of any sound in the room, pre-adjusting to the circumstances at hand.

Backup record, on the other hand, creates a second backup recording at 12 db less volume. While this recording is naturally quieter, it also means that the sound levels here don't peak as much (clipping distortion) or not at all. This is a useful tool if you had an unprecedented peak you could not dial out in time with one of the gain pods (as seen in the image down below).

Now we are coming to the beauties that are 'High Pass Filters' and 'Lo Cuts'. As our lecturer ensured us, both functions achieve essentially the same: Whereas a high pass filter lets high frequencies pass (and thus naturally cuts out low frequencies like the hum of traffic, for example), a lo cut also cuts the low frequencies out of recording.

Set your lo cut for the right track - in our example image above, track 3 - and choose your favourite frequency to cut (80 Hz for cutting out traffic noise). Here, I was surprised to learn that the choice of the exact lo cut frequency is rather a creative choice than a logical one. I already expected charts telling me what kind of frequency I should select for the relevant situation on hand. But then, like much within filmmaking, a lot of our learning depends on experimenting, learning by doing, and making creative choices out of that learning.

Having now set the Xoom H6 to the relevant settings, we proceeded to set the right levels for our test recording of a book reading. For the book reading, Katie was advised to set the gain (aka volume) to -16 db so that noises don't clip on recording. She set the 'Input Gain' (the mic's sensitivity of sound entering) and turned the phantom power on, since we were using a directional Røde mic with no individual power source of its own.

Finally, before recording, she was advised to set the gain level using the rotary dials as depicted above. With an average talking level, our lecturer said, we should tend to keep the levels in between -12db and -18db but not higher than -6db. In case the sound levels recorded should hit -6db, we were told to dial the gain down manually first when it hit the red.

After that, the rehearsal finally began. And I quickly understood on why rehearsals were needed: It is not only paramountly important to get a sense of how dynamic the actor speaks, you also need to learn the script by heart to anticipate any swings in volume or loud noises well in advance. And lastly, it needs a great deal of training to be able to dial down just the right amount without tinning out the actor speaking. Which happens quickly if you dial down too much and the actor is quickly reverting to a normal speaking level.

As of now, I've already previously worked on set with Xoom Hn4, but compared to what we learned today, my knowledge was really rather superficial. I'm looking forward to experimenting with the sound equipment in the future.

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©2019 by Svea Hartle

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