Merge f0272a6 into f87d063

albertms10 · Apr 22, 2023 · ef58cca · ef58cca
2 parents f87d063 + f0272a6
commit ef58cca
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diff --git a/lib/music_notes.dart b/lib/music_notes.dart
@@ -1,7 +1,7 @@
 library music_notes;
 
 import 'dart:collection' show SplayTreeSet;
-import 'dart:math' as math show min;
+import 'dart:math' as math show min, pow;
 
 import 'package:collection/collection.dart' show IterableExtension;
 import 'package:meta/meta.dart';

diff --git a/lib/src/music.dart b/lib/src/music.dart
@@ -3,6 +3,8 @@ part of '../music_notes.dart';
 /// Number of chromatic divisions in an octave.
 const int chromaticDivisions = 12;
 
+final double sqrt12_2 = math.pow(2, 1 / 12).toDouble();
+
 /// [Set] of [EnharmonicNote]s that form the chromatic scale.
 final Set<EnharmonicNote> chromaticScale = SplayTreeSet<EnharmonicNote>.of({
   for (var i = 1; i <= chromaticDivisions; i++) EnharmonicNote(i),

diff --git a/lib/src/note/note.dart b/lib/src/note/note.dart
@@ -207,6 +207,20 @@ class Note implements MusicItem {
     );
   }
 
+  /// Returns the frequency in Hertzs of this [Note] from the A4 reference.
+  ///
+  /// Example:
+  /// ```dart
+  /// Note.a.equalTemperamentFrequency() == 440
+  /// Note.gSharp.equalTemperamentFrequency() == 415.3
+  /// Note.c.equalTemperamentFrequency() == 261.63
+  /// Note.a.equalTemperamentFrequency(338) == 338
+  /// Note.bFlat.equalTemperamentFrequency(338) == 464.04
+  /// ```
+  double equalTemperamentFrequency([double a4Hertzs = 440]) {
+    return a4Hertzs * math.pow(sqrt12_2, Note.a.difference(this));
+  }
+
   /// Returns the string representation of this [Note] following the
   /// [scientific pitch notation](https://en.wikipedia.org/wiki/Scientific_pitch_notation).
   ///

diff --git a/test/src/note/note_test.dart b/test/src/note/note_test.dart
@@ -208,6 +208,78 @@ void main() {
       });
     });
 
+    group('.hertzsFromA()', () {
+      test('should return the hertzs of this Note from 440 Hz', () {
+        expect(Note.c.equalTemperamentFrequency(), closeTo(261.63, 0.01));
+        expect(Note.cSharp.equalTemperamentFrequency(), closeTo(277.18, 0.01));
+        expect(Note.dFlat.equalTemperamentFrequency(), closeTo(277.18, 0.01));
+        expect(Note.d.equalTemperamentFrequency(), closeTo(293.66, 0.01));
+        expect(Note.dSharp.equalTemperamentFrequency(), closeTo(311.13, 0.01));
+        expect(Note.eFlat.equalTemperamentFrequency(), closeTo(311.13, 0.01));
+        expect(Note.e.equalTemperamentFrequency(), closeTo(329.63, 0.01));
+        expect(Note.f.equalTemperamentFrequency(), closeTo(349.23, 0.01));
+        expect(Note.fSharp.equalTemperamentFrequency(), closeTo(369.99, 0.01));
+        expect(Note.gFlat.equalTemperamentFrequency(), closeTo(369.99, 0.01));
+        expect(Note.g.equalTemperamentFrequency(), closeTo(392, 0.01));
+        expect(Note.gSharp.equalTemperamentFrequency(), closeTo(415.3, 0.01));
+        expect(Note.aFlat.equalTemperamentFrequency(), closeTo(415.3, 0.01));
+        expect(Note.a.equalTemperamentFrequency(), 440);
+        expect(Note.aSharp.equalTemperamentFrequency(), closeTo(466.16, 0.01));
+        expect(Note.bFlat.equalTemperamentFrequency(), closeTo(466.16, 0.01));
+        expect(Note.b.equalTemperamentFrequency(), closeTo(493.88, 0.01));
+      });
+
+      test('should return the hertzs of this Note from 438 Hz', () {
+        expect(Note.c.equalTemperamentFrequency(438), closeTo(260.44, 0.01));
+        expect(
+          Note.cSharp.equalTemperamentFrequency(438),
+          closeTo(275.92, 0.01),
+        );
+        expect(
+          Note.dFlat.equalTemperamentFrequency(438),
+          closeTo(275.92, 0.01),
+        );
+        expect(Note.d.equalTemperamentFrequency(438), closeTo(292.33, 0.01));
+        expect(
+          Note.dSharp.equalTemperamentFrequency(438),
+          closeTo(309.71, 0.01),
+        );
+        expect(
+          Note.eFlat.equalTemperamentFrequency(438),
+          closeTo(309.71, 0.01),
+        );
+        expect(Note.e.equalTemperamentFrequency(438), closeTo(328.13, 0.01));
+        expect(Note.f.equalTemperamentFrequency(438), closeTo(347.64, 0.01));
+        expect(
+          Note.fSharp.equalTemperamentFrequency(438),
+          closeTo(368.31, 0.01),
+        );
+        expect(
+          Note.gFlat.equalTemperamentFrequency(438),
+          closeTo(368.31, 0.01),
+        );
+        expect(Note.g.equalTemperamentFrequency(438), closeTo(390.21, 0.01));
+        expect(
+          Note.gSharp.equalTemperamentFrequency(438),
+          closeTo(413.42, 0.01),
+        );
+        expect(
+          Note.aFlat.equalTemperamentFrequency(438),
+          closeTo(413.42, 0.01),
+        );
+        expect(Note.a.equalTemperamentFrequency(438), 438);
+        expect(
+          Note.aSharp.equalTemperamentFrequency(438),
+          closeTo(464.04, 0.01),
+        );
+        expect(
+          Note.bFlat.equalTemperamentFrequency(438),
+          closeTo(464.04, 0.01),
+        );
+        expect(Note.b.equalTemperamentFrequency(438), closeTo(491.64, 0.01));
+      });
+    });
+
     group('.scientificName', () {
       test(
         'should return the scientific pitch notation name for this Note',