diff --git a/apps/HushApp/Shared/Features/Demo/HushDemoRootView.swift b/apps/HushApp/Shared/Features/Demo/HushDemoRootView.swift
index 3c4efa0..ee23eca 100644
--- a/apps/HushApp/Shared/Features/Demo/HushDemoRootView.swift
+++ b/apps/HushApp/Shared/Features/Demo/HushDemoRootView.swift
@@ -2,6 +2,7 @@ import SwiftUI
 
 struct HushDemoRootView: View {
     @StateObject private var store: HushDemoStore
+    @StateObject private var ambientAudio = HushAmbientAudioModel()
     @ObservedObject private var sleepSchedule =
         HushSleepScheduleController.shared
     @State private var isShowingSettings = false
@@ -55,6 +56,7 @@ struct HushDemoRootView: View {
                         HushRestTaskGeneratingView()
                     } else {
                         HushDoorView(
+                            ambientAudio: ambientAudio,
                             taskText: agentTaskText,
                             onOpenTask: openAgentTask,
                             onSettings: {
@@ -167,6 +169,23 @@ struct HushDemoRootView: View {
             openedSuggestionMessage = nil
             store.clearGeneratedRestSuggestion()
         }
+        .alert(
+            "声音暂不可用",
+            isPresented: Binding(
+                get: { ambientAudio.errorMessage != nil },
+                set: { isPresented in
+                    if !isPresented {
+                        ambientAudio.clearError()
+                    }
+                }
+            )
+        ) {
+            Button("好", role: .cancel) {
+                ambientAudio.clearError()
+            }
+        } message: {
+            Text(ambientAudio.errorMessage ?? "")
+        }
         .sheet(isPresented: $isShowingSettings) {
             HushSettingsView(
                 degraded: store.content.status.isFallback,
diff --git a/apps/HushApp/Shared/Features/HushDoor/HushDoorView.swift b/apps/HushApp/Shared/Features/HushDoor/HushDoorView.swift
index eae4a2f..a8c9ff1 100644
--- a/apps/HushApp/Shared/Features/HushDoor/HushDoorView.swift
+++ b/apps/HushApp/Shared/Features/HushDoor/HushDoorView.swift
@@ -1,6 +1,188 @@
+import AVFoundation
 import SwiftUI
 
+enum HushAmbientSound: String, CaseIterable, Identifiable {
+    case whiteNoise
+    case pinkNoise
+    case brownNoise
+    case oceanWaves
+    case rain
+
+    var id: String { rawValue }
+
+    var title: String {
+        switch self {
+        case .whiteNoise:
+            "白噪音"
+        case .pinkNoise:
+            "粉红噪音"
+        case .brownNoise:
+            "棕色噪音"
+        case .oceanWaves:
+            "海浪"
+        case .rain:
+            "轻雨"
+        }
+    }
+
+    fileprivate var resourceName: String {
+        switch self {
+        case .whiteNoise:
+            "white-noise"
+        case .pinkNoise:
+            "pink-noise"
+        case .brownNoise:
+            "brown-noise"
+        case .oceanWaves:
+            "ocean-waves"
+        case .rain:
+            "rain"
+        }
+    }
+}
+
+enum HushAmbientVolume: String, CaseIterable, Identifiable {
+    case quiet
+    case balanced
+    case clear
+
+    var id: String { rawValue }
+
+    var title: String {
+        switch self {
+        case .quiet:
+            "轻声"
+        case .balanced:
+            "平稳"
+        case .clear:
+            "清晰"
+        }
+    }
+
+    fileprivate var value: Float {
+        switch self {
+        case .quiet:
+            0.12
+        case .balanced:
+            0.2
+        case .clear:
+            0.32
+        }
+    }
+}
+
+@MainActor
+final class HushAmbientAudioModel: ObservableObject {
+    @Published var selectedSound: HushAmbientSound {
+        didSet {
+            defaults.set(selectedSound.rawValue, forKey: Self.soundKey)
+            guard isPlaying else { return }
+            startPlayback()
+        }
+    }
+
+    @Published var volume: HushAmbientVolume {
+        didSet {
+            defaults.set(volume.rawValue, forKey: Self.volumeKey)
+            player?.volume = volume.value
+        }
+    }
+
+    @Published private(set) var isPlaying = false
+    @Published private(set) var errorMessage: String?
+
+    private static let soundKey = "hush.ambient.sound"
+    private static let volumeKey = "hush.ambient.volume"
+
+    private let defaults = UserDefaults.standard
+    private var player: AVAudioPlayer?
+
+    init() {
+        selectedSound = HushAmbientSound(
+            rawValue: defaults.string(forKey: Self.soundKey) ?? ""
+        ) ?? .oceanWaves
+        volume = HushAmbientVolume(
+            rawValue: defaults.string(forKey: Self.volumeKey) ?? ""
+        ) ?? .balanced
+    }
+
+    func togglePlayback() {
+        isPlaying ? stopPlayback() : startPlayback()
+    }
+
+    func stopPlayback() {
+        player?.stop()
+        player = nil
+        isPlaying = false
+        deactivateAudioSessionIfNeeded()
+    }
+
+    func clearError() {
+        errorMessage = nil
+    }
+
+    private func startPlayback() {
+        player?.stop()
+        player = nil
+        isPlaying = false
+        errorMessage = nil
+
+        guard
+            let url = Bundle.main.url(
+                forResource: selectedSound.resourceName,
+                withExtension: "mp3"
+            )
+        else {
+            errorMessage = "声音资源还没有加入当前 App Target。"
+            return
+        }
+
+        do {
+            try activateAudioSessionIfNeeded()
+            let player = try AVAudioPlayer(contentsOf: url)
+            player.numberOfLoops = -1
+            player.volume = volume.value
+            player.prepareToPlay()
+            guard player.play() else {
+                throw HushAmbientAudioError.playbackFailed
+            }
+            self.player = player
+            isPlaying = true
+        } catch {
+            errorMessage = "暂时无法播放这个声音。"
+            deactivateAudioSessionIfNeeded()
+        }
+    }
+
+    private func activateAudioSessionIfNeeded() throws {
+        #if os(iOS)
+        let session = AVAudioSession.sharedInstance()
+        try session.setCategory(
+            .ambient,
+            mode: .default,
+            options: [.mixWithOthers]
+        )
+        try session.setActive(true)
+        #endif
+    }
+
+    private func deactivateAudioSessionIfNeeded() {
+        #if os(iOS)
+        try? AVAudioSession.sharedInstance().setActive(
+            false,
+            options: [.notifyOthersOnDeactivation]
+        )
+        #endif
+    }
+}
+
+private enum HushAmbientAudioError: Error {
+    case playbackFailed
+}
+
 struct HushDoorView: View {
+    @ObservedObject var ambientAudio: HushAmbientAudioModel
+
     let taskText: String
     let onOpenTask: () -> Void
     let onSettings: () -> Void
@@ -26,6 +208,65 @@ struct HushDoorView: View {
                 )
 
                 HStack(spacing: HushSpacing.xs) {
+                    Menu {
+                        Button(
+                            ambientAudio.isPlaying
+                                ? "停止播放"
+                                : "开始播放"
+                        ) {
+                            ambientAudio.togglePlayback()
+                        }
+
+                        Divider()
+
+                        Picker(
+                            "陪伴声音",
+                            selection: $ambientAudio.selectedSound
+                        ) {
+                            ForEach(HushAmbientSound.allCases) { sound in
+                                Text(sound.title).tag(sound)
+                            }
+                        }
+
+                        Picker(
+                            "音量",
+                            selection: $ambientAudio.volume
+                        ) {
+                            ForEach(HushAmbientVolume.allCases) { volume in
+                                Text(volume.title).tag(volume)
+                            }
+                        }
+                    } label: {
+                        Image(
+                            systemName: ambientAudio.isPlaying
+                                ? "speaker.wave.2.fill"
+                                : "speaker.slash"
+                        )
+                        .font(.system(size: 14, weight: .regular))
+                        .foregroundStyle(
+                            Color.white.opacity(
+                                ambientAudio.isPlaying ? 0.9 : 0.68
+                            )
+                        )
+                        .frame(width: 34, height: 34)
+                        .background(
+                            Circle().fill(Color.white.opacity(0.035))
+                        )
+                        .overlay(
+                            Circle().stroke(
+                                Color.white.opacity(
+                                    ambientAudio.isPlaying ? 0.2 : 0.1
+                                ),
+                                lineWidth: 0.8
+                            )
+                        )
+                    }
+                    .accessibilityLabel(
+                        ambientAudio.isPlaying
+                            ? "陪伴声音正在播放"
+                            : "选择陪伴声音"
+                    )
+
                     if let onOpenCompanion {
                         Button(action: onOpenCompanion) {
                             Image(systemName: "sun.max.fill")
diff --git a/content/ambient-sounds/README.md b/content/ambient-sounds/README.md
new file mode 100644
index 0000000..24628ef
--- /dev/null
+++ b/content/ambient-sounds/README.md
@@ -0,0 +1,30 @@
+# Hush Ambient Sound Assets
+
+These files are short, local loops for the Hush always-on companion. They are
+bundled for offline playback and must never be fetched from the network at
+runtime.
+
+All five source recordings are public-domain works hosted by Wikimedia
+Commons. The checked-in MP3 files are Wikimedia's generated MP3 transcodes of
+the original Ogg files.
+
+| Bundled file | Source | Source status |
+|---|---|---|
+| `white-noise.mp3` | [Whitenoisesound.ogg](https://commons.wikimedia.org/wiki/File:Whitenoisesound.ogg) | Public domain; ineligible for copyright |
+| `pink-noise.mp3` | [Pink.Noise.ogg](https://commons.wikimedia.org/wiki/File:Pink.Noise.ogg) | Released into the public domain by the author |
+| `brown-noise.mp3` | [Brownnoise.ogg](https://commons.wikimedia.org/wiki/File:Brownnoise.ogg) | Public domain; ineligible for copyright |
+| `ocean-waves.mp3` | [Beach sounds South Carolina.ogg](https://commons.wikimedia.org/wiki/File:Beach_sounds_South_Carolina.ogg) | Released into the public domain by the author |
+| `rain.mp3` | [Rain (1).ogg](https://commons.wikimedia.org/wiki/File:Rain_(1).ogg) | Released into the public domain by the author |
+
+Downloaded and verified on 2026-07-25. The app should start with sound off and
+must only begin playback after an explicit user action.
+
+## Integrity
+
+```text
+86744e9e365ce2d60f2b2c04a324082fba90bd4e5e20c0cba3ed994653e465d9  brown-noise.mp3
+d929ddcc476e7e25c5c0b3d59f37e50be7f557064c89fad4276122d9ba58ded2  ocean-waves.mp3
+0d617413a00d2b575055a6ec30ceb844a6d27f5937c595befe9a38f85d70827f  pink-noise.mp3
+a5c8ad766740caaa22cabdadca034d81a6b8122833188dddc2338b84d7fdb403  rain.mp3
+0c1cff70a1066c0f9e75c5b3d64c245fe9845130f54d3e699906eab0c45e2ac3  white-noise.mp3
+```
diff --git a/content/ambient-sounds/brown-noise.mp3 b/content/ambient-sounds/brown-noise.mp3
new file mode 100644
index 0000000..b9595c1
Binary files /dev/null and b/content/ambient-sounds/brown-noise.mp3 differ
diff --git a/content/ambient-sounds/ocean-waves.mp3 b/content/ambient-sounds/ocean-waves.mp3
new file mode 100644
index 0000000..e0301c5
Binary files /dev/null and b/content/ambient-sounds/ocean-waves.mp3 differ
diff --git a/content/ambient-sounds/pink-noise.mp3 b/content/ambient-sounds/pink-noise.mp3
new file mode 100644
index 0000000..63f9154
Binary files /dev/null and b/content/ambient-sounds/pink-noise.mp3 differ
diff --git a/content/ambient-sounds/rain.mp3 b/content/ambient-sounds/rain.mp3
new file mode 100644
index 0000000..676e84a
Binary files /dev/null and b/content/ambient-sounds/rain.mp3 differ
diff --git a/content/ambient-sounds/white-noise.mp3 b/content/ambient-sounds/white-noise.mp3
new file mode 100644
index 0000000..8e505e9
Binary files /dev/null and b/content/ambient-sounds/white-noise.mp3 differ
diff --git a/docs/demo-ambient-sounds-handoff.md b/docs/demo-ambient-sounds-handoff.md
new file mode 100644
index 0000000..99be02d
--- /dev/null
+++ b/docs/demo-ambient-sounds-handoff.md
@@ -0,0 +1,80 @@
+# Ambient Sounds Demo Handoff
+
+Owner: M2 / P4 -> M1 / P1
+
+## P4 delivery
+
+The Hush Door now exposes a small speaker menu with five local ambient loops:
+
+- white noise;
+- pink noise;
+- brown noise;
+- ocean waves;
+- light rain.
+
+Playback is off by default and begins only after a user action. The selected
+sound is stored locally. On iOS, playback uses the ambient audio-session
+category, mixes with existing audio, and does not request background-audio
+capability.
+
+Source and public-domain records are in:
+
+```text
+content/ambient-sounds/README.md
+```
+
+## P1 Xcode resource step
+
+M2 does not modify `project.pbxproj`. P1 should add these existing files to the
+Hush Xcode project:
+
+```text
+content/ambient-sounds/white-noise.mp3
+content/ambient-sounds/pink-noise.mp3
+content/ambient-sounds/brown-noise.mp3
+content/ambient-sounds/ocean-waves.mp3
+content/ambient-sounds/rain.mp3
+```
+
+Target membership:
+
+```text
+Hush
+HushMac
+```
+
+Do not add them to:
+
+```text
+HushDeviceActivityMonitor
+HushRestLiveActivity
+```
+
+Confirm all five files appear in **Build Phases -> Copy Bundle Resources** for
+both App targets. Keep the final bundled resource names unchanged:
+
+```text
+white-noise.mp3
+pink-noise.mp3
+brown-noise.mp3
+ocean-waves.mp3
+rain.mp3
+```
+
+No entitlement, Signing, Bundle ID, App Group, background mode, Swift Package,
+Contract, networking, or backend change is required.
+
+## Verification
+
+1. Build the `HushMac` scheme and run it on My Mac.
+2. Open the speaker menu on the Hush Door.
+3. Confirm every sound starts, changes while playing, loops, and stops.
+4. Confirm the app launches silently after a fresh start.
+5. Build the `Hush` scheme and repeat on an iPhone.
+6. Start other audio before Hush and confirm Hush mixes without taking over
+   device playback.
+7. Confirm leaving the Hush Door for another in-app route does not restart the
+   sound.
+
+If the App target does not contain the resource, Hush shows a local error
+instead of attempting a network download.