Explorers of Ambisonics – Anna Bertmark


Today’s guest, Anna Bertmark, is a Swedish sound designer now based in the UK. I had originally met Anna through Twitter. I had known she was a talented sound supervisor and designer, and I was quite delighted when her Ambisonic field recording sessions showed up when researching this series. I wrote to her and asked if she would like to share her experiences with us. She kindly agreed.

In today’s post Anna describes how she travels worldwide capturing Ambisonic field recordings for her films. She also shares her Ambisonic workflow, and her thoughts about the future of the format.

Creative Field Recording: Why did you begin working in sound?

Anna Bertmark: It was though coincidence I found my first job in sound after graduating (I moved to London from Sweden to study Music Technology in the early 2000’s), as assistant to sound designer Paul Davies (Hunger, The Queen, We Need To Talk About Kevin). I knew very little about film sound as a profession, but it felt like a natural succession of my previous skills in some part, although a completely new world in terms of how to think about sound.

CFR: What compelled you to begin field recording? What was your first field recording?

AB: I think it was while working on feature films where we needed to record additional specific sound effects that weren’t already in the sound library. Later, as a freelancer, I worked on creating sound effect libraries for library music companies in the UK and Sweden. That was the best training, finding out how to get the best recordings through doing a lot of research and trial and error. I got to decide on which sounds to include, so was thrilled to take the chance to go and record things like helicopters, weapons and race cars too, which I would rarely get the chance to do. Also, learning how to organise access to these kind of environments is a big part of the job as a field sound recordist. After gaining more recording experience through projects like that, I started recording libraries for myself when supervising feature films, which really helps in making every film sound unique and authentic.

I’ve used surround microphones in the past on commissioned libraries, and found most were quite clunky and noisy. One one film I actually used the Zoom H6 M/S with a couple of DPA 4060’s pinned to my shoulders, which I know sounds crazy to some, but turned out to sound really good in the cinema. The re-recording mixer was a bit surprised when I told them which setup I’d used, which goes to show it’s the ear rather than the gear that’s important. I don’t use the H6 when recording quiet room tones, to avoid any noise floor issues. I usually find myself recording in situations where I hardly have any microphone set-up time, so apart from high quality; portability and discretion are my priorities for field recording kits.

CFR: Can you share with readers how you first discovered the Ambisonic technique?

I had been reading about it for some time and when a potential VR job got in touch. I wanted to do some testing with the format. My friend and colleague, production mixer Emanuele Costantini, told me about the Ambisonic mics that he had tried in the past and recommend the Soundfield, which was also easiest for me to get hold of.

Soundfield ST450

At the same time, I was looking for a compact and easy way to record in surround, which the Soundfield would be great for too.

CFR: You mentioned to me that you have used Ambisonic field recordings for 5.1 tracks for your feature films. Can you share with readers a bit more about that project, and why you decided to use Ambisonics for it?

AB: After my test recordings with the Soundfield ST450 and getting familiar with the B-format set-up, I decided it would be good for capturing surround ambiences by converting the B-format to 5.0 or 5.1. I was prepping to go to Kolkata, India, to record a sound library for a feature film I was supervising that was shooting out there, and although it’s not the most discrete-looking mic, I decided it would be my best option out there. It worked out really well and the resulting 5.1 recordings have great dynamic, clarity and width. Listening back to then while editing took me right back to being in the 2nd loudest city on earth!

CFR: What kit did you use to record Ambisonic tracks? What did you think of it?

AB: I had the Soundfield ST450, Rycote blimp and windjammer, recorded onto a Zoom F8. I also took a Sennheiser MKH 416 for anything I wanted to zoom in on in mono. It was a great kit, portable and with no technical hiccups.

By the way, I had been briefed beforehand that the Soundfield ST450 needs a few minutes to acclimatise when going between environments that differ in temperature and humidity (from air conditioned rooms/cars into into the hot & humid Kolkata sunshine, for example!).

CFR: What is your workflow for getting the raw B-format recordings into your workstation, and then onto the screen?

AB: Soundfield offers their B-format decoder SurroundZone2 as a free download on their website, which is easy to use and gives a nice overview of the B-format conversion possibilities. You can easily derive a multitrack file from 5.0 to 7.1, stereo and mono. For this project I never intended to use the recordings as B-format, but to convert them into a conventional multitrack file for linear track laying.

I import my 4-track B-format recording on to a quad track in Pro Tools 11, and have SurroundZone2 as an insert on the track, then with the 5.1 output setting in the plug-in, off-line bounce out as a 5.1 file.

CFR: Do you have any future plans for using Ambisonic field recordings in your work?

Samsung Gear 360

AB: Over the coming months, I’m going to work on a VR showcase, using my Ambisonic recordings and also recordings to go with some 360 videos I’ve made using the Samsung Gear 360. I also have access to the HTC Vive which, with the help of some programer friends, I’ll be experimenting to find out what works with this new technology. There are many sound ideas and psychoacoustic devices that I use in film, that I’m sure can be made even more effective in the VR medium.

HTC Vive

CFR: Ambisonics have been experiencing a lot of attention in recent years. Can you share your opinion on its uses? Do you think it is a good one-size-fits all format, or is it best for particular uses?

AB: Although the Ambisonic recording format has been around for decades; now with VR and AR taking off a bit and starting to become more accessible to audiences and developers, microphone manufactures are coming out with new exciting Ambisonic microphones.

However, I believe that detailed Ambisonic recordings will be somewhat limited in its use for anything other than accompanying videos or live feeds (potential use of VR in news and immersive video calls, which could be the future of Skype), as users would expect to be able to see any obvious objects present in the sound recording. I think Ambisonics will be standard in all 360 cameras, documentary and VR broadcasting, if VR headsets will become commonplace in the future so there’ll be a demand.

SubPac M2

For other VR film/games/experiences; just taking surround recordings of sparse ambiences with added layers, converted into B-format and combined with spatially placed sound objects and sounds linked to actions and other interactive objects, then rendered into stereo, as VR games do now, is a more practical way of working I think. But I could be wrong. That’s the beauty of discovering the possibilities of new technology. I also really like the idea of transferring low frequencies into physical vibrations using things like SubPac’s M2 vests, which I got to try in Marshmallow Laser Feast’s VR experience In the Eyes of the Animal. Although mostly being an invisible art, I think sound is the most versatile actually physical medium currently available in storytelling and for creating experiences, so I’m very excited about exploring this emerging area more.

My thanks to Anna Bertmark for sharing her experiences with us!

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