diff --git a/linux_voice_assistant/audio_volume.py b/linux_voice_assistant/audio_volume.py
new file mode 100644
index 0000000..a5f3a7e
--- /dev/null
+++ b/linux_voice_assistant/audio_volume.py
@@ -0,0 +1,149 @@
+"""System output volume helpers.
+
+LVA historically only adjusted mpv's per-player volume. On PipeWire/PulseAudio
+setups where the default sink volume starts low (e.g. 40%), HA shows LVA at
+100% while the actual OS sink remains capped.
+
+This module keeps the OS output volume aligned with LVA's persisted
+preferences.volume_level (0.0–1.0).
+
+We try backends in this order:
+  1) PipeWire: wpctl
+  2) PulseAudio (incl. pipewire-pulse): pactl
+  3) ALSA: amixer
+"""
+
+from __future__ import annotations
+
+import asyncio
+import logging
+import math
+import shutil
+import subprocess
+from typing import Optional
+
+_LOGGER = logging.getLogger(__name__)
+
+
+def _clamp01(v: float) -> float:
+    try:
+        v = float(v)
+    except Exception:
+        return 1.0
+    if math.isnan(v) or math.isinf(v):
+        return 1.0
+    return max(0.0, min(1.0, v))
+
+
+def _pactl_sink_from_output_device(output_device: Optional[str]) -> str:
+    """Best-effort mapping of mpv audio-device -> pactl sink name.
+
+LVA commonly uses:
+  - "pipewire/<pactl sink name>"
+  - "pulse/<pactl sink name>"
+  - "alsa_output...." (already a sink name)
+
+Fallback is @DEFAULT_SINK@.
+"""
+    if not output_device:
+        return "@DEFAULT_SINK@"
+
+    dev = output_device.strip()
+
+    for prefix in ("pipewire/", "pulse/"):
+        if dev.startswith(prefix) and len(dev) > len(prefix):
+            return dev[len(prefix) :]
+
+    if dev.startswith("alsa_output."):
+        return dev
+
+    # Some users pass the raw sink name without a prefix.
+    if "alsa_output." in dev:
+        return dev
+
+    return "@DEFAULT_SINK@"
+
+
+def _run_cmd(cmd: list[str], timeout_s: float = 2.0) -> tuple[bool, str]:
+    try:
+        proc = subprocess.run(
+            cmd,
+            check=False,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.STDOUT,
+            text=True,
+            timeout=timeout_s,
+        )
+        ok = proc.returncode == 0
+        out = (proc.stdout or "").strip()
+        return ok, out
+    except FileNotFoundError:
+        return False, f"command not found: {cmd[0]}"
+    except subprocess.TimeoutExpired:
+        return False, "timeout"
+    except Exception as e:
+        return False, repr(e)
+
+
+def set_output_volume(
+    volume_0_1: float,
+    output_device: Optional[str] = None,
+    logger: logging.Logger = _LOGGER,
+) -> bool:
+    """Set OS output volume to match LVA volume (0.0–1.0).
+
+Returns True if any backend succeeded.
+"""
+    vol = _clamp01(volume_0_1)
+
+    # --- 1) PipeWire: wpctl -------------------------------------------------
+    if shutil.which("wpctl"):
+        # wpctl accepts @DEFAULT_AUDIO_SINK@ and a linear factor (e.g. 0.40)
+        ok, out = _run_cmd(["wpctl", "set-volume", "@DEFAULT_AUDIO_SINK@", f"{vol:.3f}"])
+        if ok:
+            logger.debug("Set PipeWire sink volume via wpctl: %.3f", vol)
+            return True
+        logger.debug("wpctl set-volume failed: %s", out)
+
+    # --- 2) PulseAudio: pactl ----------------------------------------------
+    if shutil.which("pactl"):
+        sink = _pactl_sink_from_output_device(output_device)
+        pct = int(round(vol * 100.0))
+        ok, out = _run_cmd(["pactl", "set-sink-volume", sink, f"{pct}%"])
+        if ok:
+            logger.debug("Set Pulse sink volume via pactl: sink=%s pct=%d", sink, pct)
+            return True
+        logger.debug("pactl set-sink-volume failed: %s", out)
+
+    # --- 3) ALSA: amixer ----------------------------------------------------
+    if shutil.which("amixer"):
+        pct = int(round(vol * 100.0))
+        # Common mixer controls across SBC images.
+        for control in ("Master", "PCM", "Speaker", "Headphone"):
+            ok, out = _run_cmd(["amixer", "-q", "sset", control, f"{pct}%"])
+            if ok:
+                logger.debug("Set ALSA volume via amixer: control=%s pct=%d", control, pct)
+                return True
+            logger.debug("amixer sset %s failed: %s", control, out)
+
+    return False
+
+
+async def ensure_output_volume(
+    volume: float,
+    output_device: Optional[str] = None,
+    attempts: int = 10,
+    delay_seconds: float = 0.5,
+    logger: logging.Logger = _LOGGER,
+) -> bool:
+    """Retry output volume sync during startup.
+
+Useful at boot when PipeWire/Pulse/ALSA might not be fully ready yet.
+"""
+    for i in range(1, max(1, attempts) + 1):
+        ok = await asyncio.to_thread(set_output_volume, volume, output_device, logger)
+        if ok:
+            return True
+        if i < attempts:
+            await asyncio.sleep(delay_seconds)
+    return False