diff --git a/app.vue b/app.vue
index 19a71a9..bd42654 100644
--- a/app.vue
+++ b/app.vue
@@ -30,6 +30,8 @@ useHead({
   ],
 });
 
+defaultAlertAudioSource().value = `${useRuntimeConfig().app.baseURL}alert.mp3`;
+
 onMounted(async () => {
   try {
     // スリープを無効化
diff --git a/components/settings.vue b/components/settings.vue
index bc3b8eb..fd7543a 100644
--- a/components/settings.vue
+++ b/components/settings.vue
@@ -85,7 +85,7 @@ const removeAudio = (fileName: string, sourceState: globalThis.Ref<string>, stor
 
   // メモリ上の音源/名前を元に戻す
   fileNameState.value = 'デフォルトの音声';
-  sourceState.value = "/alert.mp3";
+  sourceState.value = defaultAlertAudioSource().value;
 }
 
 const onAlertAudioChange = async (e: Event) => {
diff --git a/composables/states.ts b/composables/states.ts
index 03bd0a4..6e60efe 100644
--- a/composables/states.ts
+++ b/composables/states.ts
@@ -11,12 +11,16 @@ export const time = () => useState<Date>('time', () => dayjs().toDate());
 
 // 現在のセンサー情報のソース
 export const sensorSource = () => useState<string>('sensorSource', () => "rpi");
+
+// alert.mp3のソース
+export const defaultAlertAudioSource = () => useState<string>('defaultAlertAudioSource', () => '/alert.mp3');
+
 // タイマーの音声のソース
-export const timerAlertSource = () => useState<string>('timerSource', () => "/alert.mp3");
+export const timerAlertSource = () => useState<string>('timerSource', () => defaultAlertAudioSource().value);
 // チャイムの音声ソース
-export const chimeSource = () => useState<string>('chimeSource', () => "/alert.mp3");
+export const chimeSource = () => useState<string>('chimeSource', () => defaultAlertAudioSource().value);
 // 予鈴の音声ソース
-export const preChimeSource = () => useState<string>('preChimeSource', () => "/alert.mp3");
+export const preChimeSource = () => useState<string>('preChimeSource', () => defaultAlertAudioSource().value);
 
 // タイマーのインターバル
 export const interval = () => useState<Pausable | null>('interval', () => null);