Explorers of Ambisonics – Tom Todia


Ambisonic field recording equipment is hard to come by. Why?

Well, most of it is expensive. It’s rare. Few studios stock those kits. Before now, even fewer studios booked regular Ambisonic projects. As a result, being able to find and use Ambisonic gear was a rare pleasure.

That’s one reason why today’s featured guest has a special treat for us. Tom Todia has worked in game audio and Virtual Reality for over ten years. During that time, he has been involved with many projects field recording sound effects using Ambisonic kits. In today’s post, Tom details his extensive experience recording Ambisonic sound effects with a variety of specialized microphones and software. He relates how he integrates these recordings into his game audio projects, shares Ambisonic field recording tips with the community, and reveals two special experiences recording Ambisonic tracks beyond the studio.

Creative Field Recording: What inspired you to begin working in pro audio?

Tom Todia: Like most of us, I fell in love with music at a very young age. I found it amazing that something invisible could have such an emotional affect one me. My uncle Joe was a musician who owned an amazing stereo system. His equipment was like a space ship to me. Giant Cerwin-Vega speakers, mono block amplifiers, turntables, a vinyl collection to be in awe of and a fantastic 32 band graphic equalizer with red back lights.

Uncle Joe was not fond of allowing anyone to touch his equipment. I was given special access however, and would spend long amounts of time bringing all the 32 bands all the way down and building up the mix slowly. Thank you Uncle Joe!

After college I worked for a number of years in recording studio's in Miami. Engineering music was amazing, and reinforced that I needed to spend my life in among sound design and audio equipment.

CFR: How did you begin field recording? What was the first sound effect you captured?

TT: I bought my first portable recorder in the late 1990's, and I fell in love with it. It was the Sony PCM-M1 DAT with a small stereo mic that would connect on top. In those days, DAT was the high standard of quality. To a young audio nerd it felt like I had just bought a Cadillac.

I was living in Miami on South Beach at that time and I remember a red tail hawk that always flew above my apartment. I was reminded of old western movies each time I heard it. I recorded it one night and I was immediately hooked on capturing non-musical sound to try and add flavor to my sequenced music.

CFR: What was your first experience working with Ambisonic field recordings? What were your impressions of the format after having worked with “conventional” recording formats before?

TT: I have been working around sound for video games for the last 10 years under the name “Engine Audio.” My partner Chris Latham and I began teaching ourselves the technology behind game sound with free game mods, which led us to network with independent developers. I am a gamer at heart and have been since the days of the Commodore 64. If you enjoy the challenge of a complicated video game, you should try making one. Making a game is the hardest game you will ever play. One of the lingering issues in game audio mixing has always been panning and creating a natural-sounding sense of space and reflections. There have been some amazing strides over the years in game audio technology, but real time binaural mixing that doesn't break your CPU budget has always been on my mind.

Oculus Rift Development Kit 2

With the announcement of the Oculus came a rebirth of Virtual Reality, and suddenly there was an opening and a requirement for a real time binaural mix. I began reading up on Ambisonic recording and its history and fell into its trance. It really felt like the first new audio concept to enter my life in a long time. After studying the work of David Wood and Bruce Wiggins, I was scrambling to get my hands on a tetrahedral microphone.

My first Ambisonic recordings were of room tone. My partner Chris and I were working on a VR title where you are piloting a submersible device through a deep underwater cavern. My thought was that if I recorded aggressive room tone in an Ambisonic field, it would feel far more immersive than a stereo or even surround image through the game engine.

I was however wrong. After recording as many server rooms and metallic noisy environments as I could find, I discovered that the resulting audio image sounded almost mono. I became aware through experimenting that Ambisonic audio does not always offer great “space.” In order to capture a real sense of 360 presence you need the correct audio sources, reflections, and distance.

A few basic suggestions would be the following:

  1. Record sounds and locations that are somewhat specific in transient content. Soft tones and non distinct sources tend to blur together among the microphone capsules.
  2. Natural reverberation and diffusion can sound amazing when recorded correctly, but if you have too many aggressive reflections then the soundfield can ruin the spatial awareness.
  3. Experiment as much as possible with a variety of recordings, and carefully analyze them. Practice makes perfect.
  4. Be sure to find the correct method for converting, encoding, and decoding your recordings. It can be really easy to think your recordings are not translating well, when it might actually be an error in your tool set and pipeline.

CFR: What Ambisonic field recording equipment have you tried? Is there any gear that has made an impression on you in particular?

Zoom F8

TT: I have used a variety of recorders and microphone combinations to capture FOA (First Order Ambisonics). The Zoom F8 has become my “go to” Ambisonic recorder for several reasons. It has 8 microphone inputs, all of which can be trim locked. Each capsule on your Ambisonic microphone needs to have the same gain staging for the soundfield to be phase coherent. The F8 can also record a multi-channel .wav file and you need all channels of your Ambisonic field to remain time aligned, both while being recorded and processed. The cost and quality of the F8 verses other similarly capable recorders make it a really nice fit for Ambisonic recording as well. Double recording to channels 5-8 acts as a backup with a separate gain stage for any excessive and unexpected transient peaks. The unit also doubles as a USB multi-channel sound card.

I have been lucky enough to experiment and work with the CoreSound TetraMic and it is fantastic in size, frequency response, and build quality. Special thanks to my friend Fernando Delgado and Stickman Sound for keeping those in stock!

Soundfield SPS200

I also have worked with the SPS200 and the ST250 from Soundfield. The main functional difference between them (for my purposes) is that the SPS200 is software controlled when encoding from A Format to B Format, and the ST250 has a hardware box that handles encoding and decoding. The entire Soundfield line is incredible! Special thanks to loaning those to me goes to my friend good friend and composer Keith Lay, and my friend and audio tech guru Keith Andrews. I know several very cool Keith's!

Sennheiser Ambeo VR

Based on the cost and my experience with Sennheiser, I have been using the Ambeo microphone they produce lately. It has fantastic built in wind protection and shock absorption, and the frequency response and input impedance matches the Zoom F8 recorder like a glove.

CFR: What is your workflow for handling Ambisonic field recordings in the studio? You mentioned you’ve used a lot of tools in post. Can you share your experiences of them with readers?

TT: My partner Chris and I started working with Ambisonic recordings in the realm of VR. Our first project was implemented with Wwise (game audio middleware) and built in the Unreal game engine. I recorded some Ambisonic files with the SPS200 and used Auro-3D to handle the real time binaural mix in Wwise.

I found that room tone did not offer much more in an Ambisonic field than it does in surround or even stereo. It was apparent once implemented that without noticeable audio sources within a certain distance (around 6 feet at a minimum) that the imaging sounded like an omni mono recording. This caused me to look a little deeper into manipulating the Ambisonic soundfield with various workstation tool kits and enhancing it with mono layers.

I started with the “WigWare” encoders and decoders from Bruce Wiggins (thank you Bruce!). I also stumbled upon the very useful Ambisonic Tool Kit. Both of these encoder/decoder sets are not only free, but very powerful. Using these tools for the first time can be a bit overwhelming, so be sure to read and experiment. The amount of great information and tutorials on these kinds of tool kits is expansive. I have been using Reaper for the last few years and these kits work well with that DAW. In fact, Reaper is an excellent choice for Ambisonic encoding, processing, and decoding because of its very flexible routing.

One of the biggest issues with processing and mixing Ambisonic files is understanding the nature of the soundfield itself. Its important to understand that the channels operate essentially as a single entity, and the phase relationship needs to remain intact. Most of my favorite audio tools like iZotope RX and various other plug ins are not designed for multichannel processing (yet). So in some ways this can feel like a few steps forward, and several steps back.

CFR: Can you tell readers a bit about your favourite Ambisonic projects? What are some of your proudest accomplishments?

TT: There have been a number of satisfying moments and accomplishments for me personally. One milestone is still my first functional head tracking scenario. I remember I had recorded myself walking around in my front yard, and slating/recording my movement vocally as I walked in a circle. “This is me 10 feet in front of the mic, this is me walking clockwise to 90 degrees, this is me at 90 degrees with my mouth facing away from the array, etc.” Once I converted that file to B-Format and actually loaded it into a functional game map where my Vive head tracking allowed me to hear it in a real time binaural mix, I was in love. Closing my ears and hearing the 360 field respond correctly for the first time was addictive. It was unlike anything I had ever experienced in linear or non linear productions. If you have not yet had that moment yourself, I highly suggest it.

My favorite project to date is the one my partner Chris and I are currently working on. We have been recording interactions with several Orcas for a 360 video/audio experience. I can’t say much more about it at the moment, but I can talk about why its been so satisfying.

The amount of reflections that happen around water can create amazing amounts of echo that most directional microphones never quite capture. We have some First Order recordings of the Orcas breaching out of the water to create massive splashes. The intense white noise of the water movement mixed with the slap back off of the water create a scenario that is as close to the audio excitement of real life as I have ever experienced. Every time the Orcas jumped next to the microphone, I am sure it will be the end of the Ambeo’s short life. So far, it has managed to survive the abuse.

CFR: What do you feel about the state of Ambisonics, VR, and 360 sound for video? Do you feel it is still maturing? Where do you see things going in the future?

HTC Vive

TT: Without question the topic of 360 audio is still maturing, across all of its current uses. There is a fairly small number of people in the audio field who are working with it, but the community and knowledge base is growing by the day. One of the great leaps forward will happen in the end user experience. Right now we have the Vive, the Oculus, the Gear VR, the Daydream, etc. Each one of these platforms has their own unique price points, level of difficulty, and capabilities. When head tracking and personalized HRTF filters become affordable and cross platform, then we will see things really standardize and move forward. I feel like before too long, Ambisonics and realtime 360 binaural mixing will be ubiquitous. This is why so many of us are excited by the OSSIC headphones. Keep moving forward you guys!

OSSIC Headphones

CFR: What is your favourite Ambisonic field recording?

TT: Because of what a pivotal moment it was for me personally, that would be my very first nature recording I did. After some disappointing indoor recording attempts, I was able to hear a number of trees rustling in the wind along with a variety of insects and several birds in multiple locations. The spatial awareness in that recording sold me on Ambisonic sound and offered me an experience that was hypnotic.

Tom has generously provided a sample Ambisonic recording for readers to download and experiment with. Tom explains:

I thought this test might be useful for some people starting out. Its a very random and noisy recording of me walking around in my yard and slating my voice so I could hear the space offered by the microphone.

Download the B-Format file.

My thanks to Tom Todia for his thoughts on VR and Ambisonic field recording.

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