diff --git a/js/moleculesandlight/view/MoleculeActionSoundGenerator.js b/js/moleculesandlight/view/MoleculeActionSoundGenerator.js
index 2371eec7..b4e527f7 100644
--- a/js/moleculesandlight/view/MoleculeActionSoundGenerator.js
+++ b/js/moleculesandlight/view/MoleculeActionSoundGenerator.js
@@ -26,7 +26,7 @@ const ABSORPTION_TO_ACTIVITY_SOUND_DELAY = 0.2; // in seconds
 class MoleculeActionSoundGenerator extends SoundGenerator {
 
   /**
-   * @param {ObservableArray<Molecule>}activeMolecules
+   * @param {ObservableArrayDef<Molecule>}activeMolecules
    * @param {BooleanProperty} simIsRunningProperty
    * @param {BooleanProperty} isSlowMotionProperty
    * @param {Object} [options]
diff --git a/js/moleculesandlight/view/PhotonEmissionSoundGenerator.js b/js/moleculesandlight/view/PhotonEmissionSoundGenerator.js
index 823cdafb..b6ed36d9 100644
--- a/js/moleculesandlight/view/PhotonEmissionSoundGenerator.js
+++ b/js/moleculesandlight/view/PhotonEmissionSoundGenerator.js
@@ -38,7 +38,7 @@ const PLAY_MOLECULE_EMISSION_X_POSITION = 0;
 class PhotonEmissionSoundGenerator extends SoundGenerator {
 
   /**
-   * @param {ObservableArray<Photon>} photons
+   * @param {ObservableArrayDef<Photon>} photons
    * @param {Object} [options]
    */
   constructor( photons, options ) {
diff --git a/js/photon-absorption/model/PhotonAbsorptionModel.js b/js/photon-absorption/model/PhotonAbsorptionModel.js
index df3ea898..6caa44dc 100644
--- a/js/photon-absorption/model/PhotonAbsorptionModel.js
+++ b/js/photon-absorption/model/PhotonAbsorptionModel.js
@@ -136,7 +136,7 @@ function PhotonAbsorptionModel( initialPhotonTarget, tandem ) {
   } ); // Elements are of type Molecule.
 
   // @public (read-only) {Emitter} - emitter for when a photon is emitted from the emission point - useful in addition
-  // to the photons ObservableArray because this is specifically for photon emission from the light source
+  // to the photons ObservableArrayDef because this is specifically for photon emission from the light source
   this.photonEmittedEmitter = new Emitter( { parameters: [ { valueType: Photon } ] } );
 
   // @public - Emits when the model has been reset