When you're actually running, the screen on your phone is not a great interface. It's in a pocket, strapped to an armband, or buried under a sleeve, and pulling it out to check pace mid-stride breaks form and breaks focus. Audio is the interface that actually works while your hands and eyes are busy doing something else. But that only holds if what comes through your headphones is worth interrupting your run for.

The failure mode: a tracker that will not shut up

The easy way to build audio cues is to announce everything: every heart rate blip, every few seconds of pace, every small fluctuation the sensors pick up. That fails fast. If a tracker talks constantly, you stop listening to it the same way you'd tune out a car alarm that goes off every time a truck drives past. The value of a voice cue is proportional to how rare and reliable it is: interrupt for something real, and stay quiet the rest of the time.

What's actually worth interrupting for

Zirv keeps the mid-run announcement list short and built around two events: a completed kilometer, and a real, sustained change in heart rate zone. Everything else, the normal second-to-second wobble in heart rate or pace that happens on every run, stays off the audio feed entirely. That's a deliberate filter, not a missing feature. The point is that when you do hear something, it's worth acting on.

How a zone change earns an announcement

Heart rate is noisy enough that a naive "announce every zone crossing" rule would talk constantly, flipping every time your heart rate hovered near a boundary between two heart rate zones. Zirv only announces a zone change after the new zone has held for 5 consecutive seconds, filtering out the momentary blips that do not represent a real shift in effort. On top of that there's a hard ceiling: no more than one zone announcement every 15 seconds, so even a genuinely unstable stretch of running does not turn into a stream of interruptions. Both numbers exist for the same reason, to keep the signal-to-noise ratio high enough that an announcement means something when it happens.

What the km split actually tells you

Every completed kilometer, Zirv announces your average pace for the run so far, in minutes and seconds per kilometer, along with your current heart rate if a sensor is connected. The important word there is average: it's the cumulative pace across the whole run up to that point, not the pace of the kilometer you just finished. That distinction matters for pacing a longer effort. The pace of your last split alone can swing with a hill, a red light, or just a rough patch, but the average pace so far is the number that actually tells you whether you're on track for the finish time you're aiming for. If the average keeps drifting slower each split, that's the signal to adjust, not a single fast or slow kilometer in isolation.

The quiet cues

Not every audio cue is about pace or zones. A short confirmation when the session starts tells you tracking is live before the phone goes back in your pocket. Auto-pause and auto-resume get their own announcements, so you know the tracker noticed you stopped at a light or paused for water without you having to check the screen. If a session sits paused for long enough, the app asks whether you're still working out, a quiet check-in rather than silently ending your session or letting it run indefinitely in the background. And when you finish, Zirv speaks a short summary covering duration, distance, average pace, and calories, so the run closes out with the numbers that matter without you needing to unlock your phone standing at the end of a route.

The zone, split, and auto-pause announcements are each optional: on by default, individually switchable off. If your preference is closer to silence, that's a setting, not a fight with the app.

iOS only, for now

Worth saying plainly: voice cues currently ship on iOS. If you're mixing lifting and running across hybrid training days, the audio feedback described here is part of the run side of that, available today only on iOS.

The takeaway

Good audio feedback mid-run is not about saying more, it's about saying less, and only when it's earned. A completed kilometer and a heart rate zone that's actually changed, held for 5 seconds and rate-limited to one announcement per 15 seconds, are worth interrupting a run for. Every other fluctuation is not. Get the average pace so far right, keep the quiet cues around pausing and finishing genuinely quiet, and the result is a tracker that talks rarely enough that you actually listen when it does.