The radar is the whole problem

A Halo player glances at the radar constantly. It costs nothing, it is always there, and it shows everything moving within twenty-five metres. Take it away and you cannot know somebody is behind you until they shoot you.

So the motion tracker does more work here than it does there, and it is offered three ways, because it is asked for three different reasons.

Three channels, three jobs

A beacon carries height as pitch, which leaves panning free to carry direction and volume free to carry distance. Those are the three things each of those channels is actually good at, and using pitch for anything else would waste the only one that can express up and down at all.

Crouching hides you from it, as in Halo. That is the whole stealth game: a crouching player is invisible to the tracker and nearly silent on foot, and the counter is that they move at a third of your speed.

Four distances, not two

Every weapon has four recordings: the one you hear with it in your own hands, and three progressively more distant and reverberant ones. Which plays is decided by how far away the shooter is.

This is the single most valuable thing in the sound pack, and it is why the whole pack was rebuilt around the Halo 5 recordings rather than the much larger Halo Reach rip: those are the only ones recorded at close, far and very far as well as at the shooter's ear. Four tiers is what turns “a gun went off somewhere” into “a gun went off about forty metres away.”

Past the last tier a shot is not heard at all. That is deliberate. A map where everything is audible from everywhere is a map you cannot listen across.

Rooms have to sound like rooms

Without acoustics, a rifle fired in the open and the same rifle fired four floors down inside a Forerunner structure reach you as the same recording at the same volume, differing only in direction and loudness. In a game where hearing is the only sense there is, that throws away an enormous amount.

Three things, answering three questions:

The tail is the engine's and the reflections are ours

That split is not the obvious one and it is the reason both halves are there. The engine's freeverb node makes a convincing wash but cannot put the first bounce at a particular millisecond; we can, and that first bounce is the whole of what says how big a room is. Neither half manages it alone.

Doorways are the point

A wall occludes and a doorway does not, so walking along the outside of a building while a fight goes on inside it, the sound opens up as you pass the door and closes again after. That is how you find a door by ear rather than by walking into the wall until you stop hearing things.

Why one formula for every room was wrong

Every room's reverberation used to come from Sabine's formula on the bare wall material. That formula is a hundred years old, it captures the thing that matters — bigger and harder rings longer — and it failed badly at both ends of this game's range, for two reasons it cannot know about.

• A real room is full of things. Bare concrete absorbs six hundredths of what hits it, and a room made of nothing but bare concrete does not exist: an office has a carpet, a ceiling, desks and people, and comes to nearer a quarter. Fed the bare figure, a two-metre cupboard rang for a full second — longer than a school hall.
• The sky is not a surface. An open space is a box with no lid, and the energy that leaves through it does not come back. Sabine, given a valley, returned twenty-one seconds and was clamped to the ceiling — and so was every outdoor place on every map, which is why they all sounded the same and all sounded enormous.

So a place says what sort of place it is, and the kind carries a measured reverberation time for that sort of place.

How wet is a separate number from how long, and it is the one that matters outdoors. A field is not a room with a short tail; it is a place where almost nothing comes back at all, and a listener tells those apart instantly. That is why a hangar sends four decibels into its reverberation and open sand sends twenty-five: no amount of arithmetic on the absorption of sand was ever going to produce that gap.

A map does not have to say. The kind is guessed from the name of the place, then from what it is made of, then from how big it is, and the guess is right nearly every time — because a map author who writes “the armoury” or “Kikowani Street, west pavement” has already said what sort of place it is. Thirty-five existing maps got better acoustics without a line of map source changing.

Three tick boxes, and each does exactly one thing

The three questions above are three separate settings — the ring, the first bounce and the muffling — and every combination of them is a position somebody might genuinely want. There used to be a three-way switch above two of these, silently overriding both, so with the switch in its first position the boxes sat there ticked and doing nothing. A control that another control can override is a control nobody can read, and in a game whose whole subject is what you can hear, a settings screen that will not say what it has turned off is worse than one setting fewer.

Turning the muffling off is a real position rather than a compromise. Occlusion is the only part of this system that removes information rather than adding it: it makes a distant fight genuinely harder to hear, on purpose, because that is what a wall does. For somebody whose entire sense of the map is what reaches their ears, that trade may not be worth making, and it is not the game's call.

Zones, and why there are so many

A zone is what B reads out, and it is the only way anybody knows where they are. The rule the maps follow is:

If you could describe where you are to somebody over a radio, there should be a zone that says it.

Not one zone per room — one per part of a room. New Mombasa has a zone for every street, both pavements of every street, every kerb between a pavement and a road, every junction named for both streets that cross there, every doorway, and the front, middle and back of every room of every building. That is seven hundred and sixty-seven rectangles for one map, and it is what makes standing anywhere on it produce a sentence a person could repeat and be found from.

The kerbs matter more than they sound. Walking off a pavement into a road is a thing that happens to you rather than a thing you do.

Zones are said once per crossing and again if you leave and come back. A name repeated every time you shuffle about inside one room would be unusable.

The grenade beep

Halo never needed one. You could see a grenade at your feet. Without it, a grenade here would be an unavoidable death rather than a thing you have three seconds to walk away from. So a grenade is heard thrown, heard travelling, heard landing — on a recording chosen by what it landed on, because Reach recorded stone, metal and dirt separately — and then heard sitting there armed, beeping, until it goes off.