use carrier sound for balloon velocity, see #483

phetsims · Feb 16, 2021 · 2bb3dbd · 2bb3dbd
1 parent 7c5f913
commit 2bb3dbd
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Showing 8 changed files with 130 additions and 19 deletions.
diff --git a/js/balloons-and-static-electricity/view/BalloonVelocitySoundGenerator.js b/js/balloons-and-static-electricity/view/BalloonVelocitySoundGenerator.js
@@ -9,16 +9,17 @@
 
 import LinearFunction from '../../../../dot/js/LinearFunction.js';
 import merge from '../../../../phet-core/js/merge.js';
-import NoiseGenerator from '../../../../tambo/js/sound-generators/NoiseGenerator.js';
+import SoundClip from '../../../../tambo/js/sound-generators/SoundClip.js';
+import driftVelocityLoop from '../../../sounds/carrier-000_wav.js';
+// import driftVelocityLoop from '../../../sounds/carrier-001_wav.js';
+// import driftVelocityLoop from '../../../sounds/carrier-002_wav.js';
 import balloonsAndStaticElectricity from '../../balloonsAndStaticElectricity.js';
 
-// constants
-const INITIAL_CENTER_FREQUENCY = 500;
+// function for mapping the speed of the balloon to the playback rate of the carrier sound, empirically determined
+const mapSpeedToPlaybackRate = new LinearFunction( 0, 3, 0.5, 2, true );
+const mapSpeedToOutputLevel = new LinearFunction( 0, 3, 0.2, 1, false );
 
-// function for mapping the speed of the balloon to the center frequency of the filter
-const mapSpeedToFrequency = new LinearFunction( 0, 3, INITIAL_CENTER_FREQUENCY, INITIAL_CENTER_FREQUENCY * 2, true );
-
-class BalloonVelocitySoundGenerator extends NoiseGenerator {
+class BalloonVelocitySoundGenerator extends SoundClip {
 
   /**
    * {Property.<number>} balloonVelocityProperty - velocity of the balloon when drifting (i.e. when it is not being
@@ -27,31 +28,54 @@ class BalloonVelocitySoundGenerator extends NoiseGenerator {
    */
   constructor( balloonVelocityProperty, options ) {
 
-    options = merge( {
-        noiseType: 'pink',
-        centerFrequency: INITIAL_CENTER_FREQUENCY,
-        qFactor: 400,
+    options = merge(
+      {
+        loop: true,
 
-        // The output level has to be far higher than normal, since so much of the noise energy ends up getting filtered
-        // out.
-        initialOutputLevel: 15.0
+        // {number) The output level is set as a function of the speed at which the balloon is moving.  This value
+        // specifies the maximum value.  It will generally be between 0 and 1.
+        maxOutputLevel: 0.5
       },
       options
     );
 
-    super( options );
+    // options checking
+    assert && assert(
+      !options.initialOutputLevel,
+      'initialOutputLevel should not be specified for this sound generator'
+    );
+
+    // Start the initial output level at zero so that the sound will fade in smoothly the first time it is played.
+    options.initialOutputLevel = 0;
 
-    // monitor the molecule oscillation amplitude and update local state
+    super( driftVelocityLoop, options );
+
+    // Monitor the balloon velocity and modify the output sound as changes occur.
     balloonVelocityProperty.lazyLink( velocity => {
       const speed = velocity.magnitude;
       if ( speed > 0 ) {
-        if ( !this.isPlaying ){
-          this.start();
+        if ( !this.isPlaying ) {
+
+          // Before starting playback, set the playback rate immediately, otherwise there can be a bit of the "chirp"
+          // sound.
+          this.setPlaybackRate( mapSpeedToPlaybackRate( speed, 0 ) );
+
+          // Start the sound playing.
+          this.play();
+        }
+        else{
+
+          // Set the playback rate.  This will use the nominal time constant, which should lead to a reasonably smooth
+          // transition of the rate as the velocity changes.
+          this.setPlaybackRate( mapSpeedToPlaybackRate( speed ) );
         }
-        this.setBandpassFilterCenterFrequency( mapSpeedToFrequency( speed ) );
+
+        // Set the output level based on the velocity.
+        this.setOutputLevel( mapSpeedToOutputLevel( speed, 0.1 ) * options.maxOutputLevel );
       }
       else if ( speed === 0 && this.isPlaying ) {
         this.stop();
+        this.setOutputLevel( 0 );
       }
     } );
   }

diff --git a/sounds/carrier-000.wav b/sounds/carrier-000.wav
diff --git a/sounds/carrier-000_wav.js b/sounds/carrier-000_wav.js
diff --git a/sounds/carrier-001.wav b/sounds/carrier-001.wav
diff --git a/sounds/carrier-001_wav.js b/sounds/carrier-001_wav.js
diff --git a/sounds/carrier-002.wav b/sounds/carrier-002.wav
diff --git a/sounds/carrier-002_wav.js b/sounds/carrier-002_wav.js
diff --git a/sounds/license.json b/sounds/license.json
@@ -31,6 +31,30 @@
     "license": "contact [email protected]",
     "notes": "created by Ashton Morris (PhET Interactive Simulations)"
   },
+  "carrier-000.wav": {
+    "text": [
+      "Copyright 2002-2020 University of Colorado Boulder"
+    ],
+    "projectURL": "http://phet.colorado.edu",
+    "license": "contact [email protected]",
+    "notes": "created by Ashton Morris (PhET Interactive Simulations)"
+  },
+  "carrier-001.wav": {
+    "text": [
+      "Copyright 2002-2020 University of Colorado Boulder"
+    ],
+    "projectURL": "http://phet.colorado.edu",
+    "license": "contact [email protected]",
+    "notes": "created by Ashton Morris (PhET Interactive Simulations)"
+  },
+  "carrier-002.wav": {
+    "text": [
+      "Copyright 2002-2020 University of Colorado Boulder"
+    ],
+    "projectURL": "http://phet.colorado.edu",
+    "license": "contact [email protected]",
+    "notes": "created by Ashton Morris (PhET Interactive Simulations)"
+  },
   "grab-magnet.mp3": {
     "text": [
       "Copyright 2002-2020 University of Colorado Boulder"