diff --git a/README.md b/README.md
index 6b8a974..ccf5937 100644
--- a/README.md
+++ b/README.md
@@ -89,6 +89,38 @@ After that, connect your Android device to the same Wi-Fi network as your comput
 ./gradlew wrapper --gradle-version x.x.x --distribution-type all
 ```
 
+### Database Migration 🔀
+
+When adding a new database `@Entity` (or modifying an existing one), you need to prepare a database
+migration (SQL script) in
+[`app/src/main/java/ai/elimu/content_provider/room/db/RoomDb.java`](app/src/main/java/ai/elimu/content_provider/room/db/RoomDb.java).
+
+Follow these steps:
+
+1. Add the new/modified `@Entity` to [`app/src/main/java/ai/elimu/content_provider/room/entity/`](app/src/main/java/ai/elimu/content_provider/room/entity/)
+1. Add the entity's DAO interface to [`app/src/main/java/ai/elimu/content_provider/room/dao/`](app/src/main/java/ai/elimu/content_provider/room/dao/)
+1. Include the DAO interface in [`app/src/main/java/ai/elimu/content_provider/room/db/RoomDb.java`](app/src/main/java/ai/elimu/content_provider/room/db/RoomDb.java)
+1. Include the entity in the `entities` section of the `@Database` in [`app/src/main/java/ai/elimu/content_provider/room/db/RoomDb.java`](app/src/main/java/ai/elimu/content_provider/room/db/RoomDb.java)
+1. Bump the `@Database` version in [`app/src/main/java/ai/elimu/content_provider/room/db/RoomDb.java`](app/src/main/java/ai/elimu/content_provider/room/db/RoomDb.java)
+1. Build the code with `./gradlew clean build`
+1. Open the new database schema generated at `app/schemas/ai.elimu.content_provider.room.db.RoomDb/<version>.json`
+- Under `entities`, find the matching `tableName` and copy its SQL script from the `createSql` property.
+1. Open `RoomDb.java` and add a new method for the latest migration
+- Paste the SQL script from the above JSON schema, and replace `${TABLE_NAME}` with the name of the table you created/modified.
+- Include the migration in the `getDatabase` method in `RoomDb.java`.
+1. To run the database migration, launch the application on your device.
+
+**Tip #1:** To verify that your database migration ran successfully, look at the Logcat output and
+ensure that there are no RoomDb errors:
+```
+2023-11-27 11:46:50.662  6124-13233 ai.elimu.c....RoomDb$18 ai.elimu.content_provider.debug      I  migrate (23 --> 24)
+2023-11-27 11:46:50.663  6124-13233 ai.elimu.c....RoomDb$18 ai.elimu.content_provider.debug      I  sql: CREATE TABLE IF NOT EXISTS `LetterSound` (`revisionNumber` INTEGER NOT NULL, `usageCount` INTEGER, `id` INTEGER, PRIMARY KEY(`id`))
+```
+
+**Tip #2:** You can also use Android Studio's _Database Inspector_ to verify that the database
+migration succeeded:
+
+![](https://github.com/elimu-ai/content-provider/assets/1451036/4c462813-bac0-4d4c-9f62-8c4aa12252d9)
 
 ## Release 📦
 
diff --git a/app/schemas/ai.elimu.content_provider.room.db.RoomDb/24.json b/app/schemas/ai.elimu.content_provider.room.db.RoomDb/24.json
new file mode 100644
index 0000000..42b5964
--- /dev/null
+++ b/app/schemas/ai.elimu.content_provider.room.db.RoomDb/24.json
@@ -0,0 +1,629 @@
+{
+  "formatVersion": 1,
+  "database": {
+    "version": 24,
+    "identityHash": "272858d2cd99837310e007914ec3306b",
+    "entities": [
+      {
+        "tableName": "Letter",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`text` TEXT, `diacritic` INTEGER, `revisionNumber` INTEGER NOT NULL, `usageCount` INTEGER, `id` INTEGER, PRIMARY KEY(`id`))",
+        "fields": [
+          {
+            "fieldPath": "text",
+            "columnName": "text",
+            "affinity": "TEXT",
+            "notNull": false
+          },
+          {
+            "fieldPath": "diacritic",
+            "columnName": "diacritic",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "revisionNumber",
+            "columnName": "revisionNumber",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "usageCount",
+            "columnName": "usageCount",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "Sound",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`valueIpa` TEXT, `diacritic` INTEGER, `revisionNumber` INTEGER NOT NULL, `usageCount` INTEGER, `id` INTEGER, PRIMARY KEY(`id`))",
+        "fields": [
+          {
+            "fieldPath": "valueIpa",
+            "columnName": "valueIpa",
+            "affinity": "TEXT",
+            "notNull": false
+          },
+          {
+            "fieldPath": "diacritic",
+            "columnName": "diacritic",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "revisionNumber",
+            "columnName": "revisionNumber",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "usageCount",
+            "columnName": "usageCount",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "LetterSound",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`revisionNumber` INTEGER NOT NULL, `usageCount` INTEGER, `id` INTEGER, PRIMARY KEY(`id`))",
+        "fields": [
+          {
+            "fieldPath": "revisionNumber",
+            "columnName": "revisionNumber",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "usageCount",
+            "columnName": "usageCount",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "Word",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`text` TEXT NOT NULL, `wordType` TEXT, `revisionNumber` INTEGER NOT NULL, `usageCount` INTEGER, `id` INTEGER, PRIMARY KEY(`id`))",
+        "fields": [
+          {
+            "fieldPath": "text",
+            "columnName": "text",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "wordType",
+            "columnName": "wordType",
+            "affinity": "TEXT",
+            "notNull": false
+          },
+          {
+            "fieldPath": "revisionNumber",
+            "columnName": "revisionNumber",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "usageCount",
+            "columnName": "usageCount",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "Number",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`value` INTEGER NOT NULL, `symbol` TEXT, `revisionNumber` INTEGER NOT NULL, `usageCount` INTEGER, `id` INTEGER, PRIMARY KEY(`id`))",
+        "fields": [
+          {
+            "fieldPath": "value",
+            "columnName": "value",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "symbol",
+            "columnName": "symbol",
+            "affinity": "TEXT",
+            "notNull": false
+          },
+          {
+            "fieldPath": "revisionNumber",
+            "columnName": "revisionNumber",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "usageCount",
+            "columnName": "usageCount",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "Emoji",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`glyph` TEXT NOT NULL, `unicodeVersion` REAL NOT NULL, `unicodeEmojiVersion` REAL NOT NULL, `revisionNumber` INTEGER NOT NULL, `usageCount` INTEGER, `id` INTEGER, PRIMARY KEY(`id`))",
+        "fields": [
+          {
+            "fieldPath": "glyph",
+            "columnName": "glyph",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "unicodeVersion",
+            "columnName": "unicodeVersion",
+            "affinity": "REAL",
+            "notNull": true
+          },
+          {
+            "fieldPath": "unicodeEmojiVersion",
+            "columnName": "unicodeEmojiVersion",
+            "affinity": "REAL",
+            "notNull": true
+          },
+          {
+            "fieldPath": "revisionNumber",
+            "columnName": "revisionNumber",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "usageCount",
+            "columnName": "usageCount",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "Emoji_Word",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`Emoji_id` INTEGER NOT NULL, `words_id` INTEGER NOT NULL, PRIMARY KEY(`Emoji_id`, `words_id`))",
+        "fields": [
+          {
+            "fieldPath": "Emoji_id",
+            "columnName": "Emoji_id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "words_id",
+            "columnName": "words_id",
+            "affinity": "INTEGER",
+            "notNull": true
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "Emoji_id",
+            "words_id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "Image",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`title` TEXT NOT NULL, `imageFormat` TEXT NOT NULL, `revisionNumber` INTEGER NOT NULL, `usageCount` INTEGER, `id` INTEGER, PRIMARY KEY(`id`))",
+        "fields": [
+          {
+            "fieldPath": "title",
+            "columnName": "title",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "imageFormat",
+            "columnName": "imageFormat",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "revisionNumber",
+            "columnName": "revisionNumber",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "usageCount",
+            "columnName": "usageCount",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "Image_Word",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`Image_id` INTEGER NOT NULL, `words_id` INTEGER NOT NULL, PRIMARY KEY(`Image_id`, `words_id`))",
+        "fields": [
+          {
+            "fieldPath": "Image_id",
+            "columnName": "Image_id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "words_id",
+            "columnName": "words_id",
+            "affinity": "INTEGER",
+            "notNull": true
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "Image_id",
+            "words_id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "Audio",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`title` TEXT NOT NULL, `transcription` TEXT NOT NULL, `audioFormat` TEXT NOT NULL, `revisionNumber` INTEGER NOT NULL, `usageCount` INTEGER, `id` INTEGER, PRIMARY KEY(`id`))",
+        "fields": [
+          {
+            "fieldPath": "title",
+            "columnName": "title",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "transcription",
+            "columnName": "transcription",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "audioFormat",
+            "columnName": "audioFormat",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "revisionNumber",
+            "columnName": "revisionNumber",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "usageCount",
+            "columnName": "usageCount",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "StoryBook",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`title` TEXT NOT NULL, `description` TEXT, `coverImageId` INTEGER NOT NULL, `readingLevel` TEXT, `revisionNumber` INTEGER NOT NULL, `usageCount` INTEGER, `id` INTEGER, PRIMARY KEY(`id`))",
+        "fields": [
+          {
+            "fieldPath": "title",
+            "columnName": "title",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "description",
+            "columnName": "description",
+            "affinity": "TEXT",
+            "notNull": false
+          },
+          {
+            "fieldPath": "coverImageId",
+            "columnName": "coverImageId",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "readingLevel",
+            "columnName": "readingLevel",
+            "affinity": "TEXT",
+            "notNull": false
+          },
+          {
+            "fieldPath": "revisionNumber",
+            "columnName": "revisionNumber",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "usageCount",
+            "columnName": "usageCount",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "StoryBookChapter",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`storyBookId` INTEGER NOT NULL, `sortOrder` INTEGER NOT NULL, `imageId` INTEGER NOT NULL, `id` INTEGER, PRIMARY KEY(`id`))",
+        "fields": [
+          {
+            "fieldPath": "storyBookId",
+            "columnName": "storyBookId",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "sortOrder",
+            "columnName": "sortOrder",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "imageId",
+            "columnName": "imageId",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "StoryBookParagraph",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`storyBookChapterId` INTEGER NOT NULL, `sortOrder` INTEGER NOT NULL, `originalText` TEXT NOT NULL, `id` INTEGER, PRIMARY KEY(`id`))",
+        "fields": [
+          {
+            "fieldPath": "storyBookChapterId",
+            "columnName": "storyBookChapterId",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "sortOrder",
+            "columnName": "sortOrder",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "originalText",
+            "columnName": "originalText",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "StoryBookParagraph_Word",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`StoryBookParagraph_id` INTEGER NOT NULL, `words_id` INTEGER NOT NULL, `words_ORDER` INTEGER NOT NULL, PRIMARY KEY(`StoryBookParagraph_id`, `words_ORDER`))",
+        "fields": [
+          {
+            "fieldPath": "StoryBookParagraph_id",
+            "columnName": "StoryBookParagraph_id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "words_id",
+            "columnName": "words_id",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "words_ORDER",
+            "columnName": "words_ORDER",
+            "affinity": "INTEGER",
+            "notNull": true
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "StoryBookParagraph_id",
+            "words_ORDER"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      },
+      {
+        "tableName": "Video",
+        "createSql": "CREATE TABLE IF NOT EXISTS `${TABLE_NAME}` (`title` TEXT NOT NULL, `videoFormat` TEXT NOT NULL, `revisionNumber` INTEGER NOT NULL, `usageCount` INTEGER, `id` INTEGER, PRIMARY KEY(`id`))",
+        "fields": [
+          {
+            "fieldPath": "title",
+            "columnName": "title",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "videoFormat",
+            "columnName": "videoFormat",
+            "affinity": "TEXT",
+            "notNull": true
+          },
+          {
+            "fieldPath": "revisionNumber",
+            "columnName": "revisionNumber",
+            "affinity": "INTEGER",
+            "notNull": true
+          },
+          {
+            "fieldPath": "usageCount",
+            "columnName": "usageCount",
+            "affinity": "INTEGER",
+            "notNull": false
+          },
+          {
+            "fieldPath": "id",
+            "columnName": "id",
+            "affinity": "INTEGER",
+            "notNull": false
+          }
+        ],
+        "primaryKey": {
+          "columnNames": [
+            "id"
+          ],
+          "autoGenerate": false
+        },
+        "indices": [],
+        "foreignKeys": []
+      }
+    ],
+    "views": [],
+    "setupQueries": [
+      "CREATE TABLE IF NOT EXISTS room_master_table (id INTEGER PRIMARY KEY,identity_hash TEXT)",
+      "INSERT OR REPLACE INTO room_master_table (id,identity_hash) VALUES(42, '272858d2cd99837310e007914ec3306b')"
+    ]
+  }
+}
\ No newline at end of file
diff --git a/app/src/main/java/ai/elimu/content_provider/room/dao/LetterSoundDao.java b/app/src/main/java/ai/elimu/content_provider/room/dao/LetterSoundDao.java
new file mode 100644
index 0000000..aa4ef33
--- /dev/null
+++ b/app/src/main/java/ai/elimu/content_provider/room/dao/LetterSoundDao.java
@@ -0,0 +1,13 @@
+package ai.elimu.content_provider.room.dao;
+
+import androidx.room.Dao;
+import androidx.room.Insert;
+
+import ai.elimu.content_provider.room.entity.LetterSound;
+
+@Dao
+public interface LetterSoundDao {
+
+    @Insert
+    void insert(LetterSound letterSound);
+}
diff --git a/app/src/main/java/ai/elimu/content_provider/room/db/RoomDb.java b/app/src/main/java/ai/elimu/content_provider/room/db/RoomDb.java
index 1ae30bc..7562f12 100644
--- a/app/src/main/java/ai/elimu/content_provider/room/db/RoomDb.java
+++ b/app/src/main/java/ai/elimu/content_provider/room/db/RoomDb.java
@@ -13,6 +13,7 @@
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 
+import ai.elimu.content_provider.room.dao.LetterSoundDao;
 import ai.elimu.content_provider.room.dao.SoundDao;
 import ai.elimu.content_provider.room.dao.AudioDao;
 import ai.elimu.content_provider.room.dao.EmojiDao;
@@ -27,6 +28,7 @@
 import ai.elimu.content_provider.room.dao.StoryBookParagraph_WordDao;
 import ai.elimu.content_provider.room.dao.VideoDao;
 import ai.elimu.content_provider.room.dao.WordDao;
+import ai.elimu.content_provider.room.entity.LetterSound;
 import ai.elimu.content_provider.room.entity.Sound;
 import ai.elimu.content_provider.room.entity.Audio;
 import ai.elimu.content_provider.room.entity.Emoji;
@@ -42,7 +44,7 @@
 import ai.elimu.content_provider.room.entity.Video;
 import ai.elimu.content_provider.room.entity.Word;
 
-@Database(version = 23, entities = {Letter.class, Sound.class, Word.class, Number.class, Emoji.class, Emoji_Word.class, Image.class, Image_Word.class, Audio.class, StoryBook.class, StoryBookChapter.class, StoryBookParagraph.class, StoryBookParagraph_Word.class, Video.class})
+@Database(version = 24, entities = {Letter.class, Sound.class, LetterSound.class, Word.class, Number.class, Emoji.class, Emoji_Word.class, Image.class, Image_Word.class, Audio.class, StoryBook.class, StoryBookChapter.class, StoryBookParagraph.class, StoryBookParagraph_Word.class, Video.class})
 @TypeConverters({Converters.class})
 public abstract class RoomDb extends RoomDatabase {
 
@@ -50,6 +52,8 @@ public abstract class RoomDb extends RoomDatabase {
 
     public abstract SoundDao soundDao();
 
+    public abstract LetterSoundDao letterSoundDao();
+
     public abstract WordDao wordDao();
 
     public abstract NumberDao numberDao();
@@ -105,7 +109,8 @@ public static RoomDb getDatabase(final Context context) {
                                     MIGRATION_19_20,
                                     MIGRATION_20_21,
                                     MIGRATION_21_22,
-                                    MIGRATION_22_23
+                                    MIGRATION_22_23,
+                                    MIGRATION_23_24
                             )
                             .build();
                 }
@@ -314,4 +319,15 @@ public void migrate(SupportSQLiteDatabase database) {
             database.execSQL(sql);
         }
     };
+
+    private static final Migration MIGRATION_23_24 = new Migration(23, 24) {
+        @Override
+        public void migrate(SupportSQLiteDatabase database) {
+            Log.i(getClass().getName(), "migrate (23 --> 24)");
+
+            String sql = "CREATE TABLE IF NOT EXISTS `LetterSound` (`revisionNumber` INTEGER NOT NULL, `usageCount` INTEGER, `id` INTEGER, PRIMARY KEY(`id`))";
+            Log.i(getClass().getName(), "sql: " + sql);
+            database.execSQL(sql);
+        }
+    };
 }