diff --git a/CHANGELOG_UNRELEASED.md b/CHANGELOG_UNRELEASED.md
index e69de29..06b94b6 100644
--- a/CHANGELOG_UNRELEASED.md
+++ b/CHANGELOG_UNRELEASED.md
@@ -0,0 +1 @@
+- fix OnSpeakAloudTextResult params values documentation
diff --git a/lib/src/definitions.dart b/lib/src/definitions.dart
index 46bc432..7b76ddc 100644
--- a/lib/src/definitions.dart
+++ b/lib/src/definitions.dart
@@ -304,13 +304,16 @@ class OnSpeakAloudTextResult {
   /// A [String] that represents the language code, i.e. es-ES
   final String? lang;
 
-  /// A [Double] that represents the volume from 0.0 to 1.0
+  /// A [Double] that represents the volume from 0.0 to 1.0, default 1
+  /// https://developer.mozilla.org/en-US/docs/Web/API/SpeechSynthesisUtterance/volume
   final double? volume;
 
-  /// A [Double] that represents the speech pitch from 0.0 to 1.0
+  /// A [Double] that represents the speech pitch from 0.0 to 2.0, default 1
+  /// https://developer.mozilla.org/en-US/docs/Web/API/SpeechSynthesisUtterance/pitch
   final double? pitch;
 
-  /// A [Double] that represents the speech rate from 0.0 to 1.0
+  /// A [Double] that represents the speech rate from 0.0 to 10.0, default 1
+  /// https://developer.mozilla.org/en-US/docs/Web/API/SpeechSynthesisUtterance/rate
   final double? rate;
 
   const OnSpeakAloudTextResult(