Project Tusk Phase 3 Notes: Audio Breakdown

This is a blog post in the Project Tusk series. To read about the project, see Project Tusk.

Basic Description

The Tusk helmet experience in Phases 1 and 2 relies on a secondary, one-unit low-profile stereo earphone and boom microphone headset that is slipped on before donning the helmet.

Here’s a video of the latest flight using the Phase 1 system:

For all Tusk videos, see the Project Tusk playlist on YouTube.

As you can see, it’s workable - but it’s uncomfortable. The helmet hardware puts significant pressure on the headset, which ultimately puts pressure on the wearer in the form of a headache. Flights over 30 minutes are not recommended with this headset/helmet combination, and it’s clear that Tusk must integrate the headset into the helmet to increase comfort for the wearer and increase immersion.

Phase 3 is meant to do exactly that; delivering audio - both output and input - through a system integrated into the helmet hardware itself.

It will be a challenging problem. Here’s why.

Unique Problems in Integrated Audio

Modern gaming audio is delivered at 44kHz, 16-bit stereo PCM sound. Headsets use either 3.5mm stereo jacks or USB connectors, and do not require external power to operate.

In a modern flight simulator, the headset delivers the simulator world audio (engines, wind noise, clicks of switches etc) as well as the avionics and radio audio (warning beeps and radio calls), all at a high-fidelity 44kHz.

Similarly, the modern headset microphone transmits more than just radio calls. In a modern gaming stream, there’s a great amount of the pilot chatting, whether talking to themselves, or the stream watchers, all at 44kHz. Voice recognition systems also require the high fidelity of the voice from the microphone if being used to control simulation elements.

This heavy audio workload presents a problem. Authentic, vintage communications headsets and microphones weren’t made for it. They were made for radio transmission at roughly 6kHz, low fidelity. In essence, telephone calls.

H-87B Earphone

For instance, the APH-6 helmet uses the H-87B earphone with a frequency response up to 7kHz. It can carry a radio transmission, but very little else.

Razer Ifrit

Compare to the Razer Ifrit, the low-profile headset worn under Tusk in Phase 1 and 2: it goes from 20Hz all the way up to 20kHz. It carries the entire gaming audio workload.

This article from Shure was useful in understanding some of the characteristics to look for in headsets.

Split Mixes and Stereo: The Scenarios

Modern simulators also give the option to separate out world sounds and radio sounds - either into different channels on the same audio device, or even into separate audio devices entirely.

Here are the scenarios I could foresee with Tusk:

Phase Diagram

Of the three, it’s most likely I’d use Scenario 1 - because I have discrete control of the mix of sounds coming in, I can boost radio vs. world sounds in software or vice-versa to get just the right mix and not require a secondary audio device. I have considered scenarios where I could project world sounds into the helmet, using its shell as a type of amplifier for all-around world sound, rather than the earcups, and reserve the earcups only for radio transmission, but that can always be done at a later time.

For maximum flexibility, the first audio device should be modern, embedded in the earcups, and can be demoted down to radio-only later - if I find some kind of secondary sound output into the helmet shell - through a software downmix to 7kHz.

The microphone is the same in all scenarios, a boom-type microphone ideally routed through a vintage wire boom as worn on the actual APH-6. There is also a microphone embedded in the oxygen mask, but this is reserved for Phase 4.

How To Move Forward - New Tech, Old Furniture

Whatever we decide to integrate into the helmet has to have modern audio performance in order to represent the game world and take speech input correctly - which means the old school H-87B earphones (and similar-era microphones) aren’t going to fly.

Instead, we’ll use modern audio equipment - 20kHz frequency range earphones and a modern microphone - but fuse it into the existing ear cups and a boom mic holder of the vintage APH-6.

Doing so - laying in the hardware so that it is flush with the furniture and is wired properly to connect to the Nimitz simulator rig, while not detracting from the authentic look and feel - will be a challenge.

Whether we buy new components or salvage the audio components from an existing headset, we’ll need get down to the basics - earphones and a microphone - then determine how to fit them up.

Stay tuned - that’s what comes next.

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