diff --git a/src/sound/AudioClip.js b/src/sound/AudioClip.js
index 1c358eb..72c07db 100644
--- a/src/sound/AudioClip.js
+++ b/src/sound/AudioClip.js
@@ -7,10 +7,10 @@
  * @license Distributed under the terms of the MIT License
  */
 
-import {PsychObject} from '../util/PsychObject';
-import {PsychoJS} from '../core/PsychoJS';
-import {ExperimentHandler} from '../data/ExperimentHandler';
-import * as util from '../util/Util';
+import {PsychObject} from '../util/PsychObject.js';
+import {PsychoJS} from '../core/PsychoJS.js';
+import {ExperimentHandler} from '../data/ExperimentHandler.js';
+import * as util from '../util/Util.js';
 
 
 /**
diff --git a/src/sound/AudioClipPlayer.js b/src/sound/AudioClipPlayer.js
index eb53947..6e819be 100644
--- a/src/sound/AudioClipPlayer.js
+++ b/src/sound/AudioClipPlayer.js
@@ -7,8 +7,8 @@
  * @license Distributed under the terms of the MIT License
  */
 
-import {SoundPlayer} from './SoundPlayer';
-import {AudioClip} from "./AudioClip";
+import {SoundPlayer} from './SoundPlayer.js';
+import {AudioClip} from "./AudioClip.js";
 
 
 /**
diff --git a/src/sound/Microphone.js b/src/sound/Microphone.js
index e594153..a4dbc17 100644
--- a/src/sound/Microphone.js
+++ b/src/sound/Microphone.js
@@ -7,12 +7,12 @@
  * @license Distributed under the terms of the MIT License
  */
 
-import {Clock} from "../util/Clock";
-import {PsychObject} from "../util/PsychObject";
-import {PsychoJS} from "../core/PsychoJS";
-import * as util from '../util/Util';
-import {ExperimentHandler} from "../data/ExperimentHandler";
-import {AudioClip} from "./AudioClip";
+import {Clock} from "../util/Clock.js";
+import {PsychObject} from "../util/PsychObject.js";
+import {PsychoJS} from "../core/PsychoJS.js";
+import * as util from '../util/Util.js';
+import {ExperimentHandler} from "../data/ExperimentHandler.js";
+import {AudioClip} from "./AudioClip.js";
 
 /**
  * <p>This manager handles the recording of audio signal.</p>
diff --git a/src/sound/Sound.js b/src/sound/Sound.js
index 068cf6c..6d9e0c1 100644
--- a/src/sound/Sound.js
+++ b/src/sound/Sound.js
@@ -8,11 +8,11 @@
  * @license Distributed under the terms of the MIT License
  */
 
-import {PsychoJS} from '../core/PsychoJS';
-import {PsychObject} from '../util/PsychObject';
-import {TonePlayer} from './TonePlayer';
-import {TrackPlayer} from './TrackPlayer';
-import {AudioClipPlayer} from './AudioClipPlayer';
+import {PsychoJS} from '../core/PsychoJS.js';
+import {PsychObject} from '../util/PsychObject.js';
+import {TonePlayer} from './TonePlayer.js';
+import {TrackPlayer} from './TrackPlayer.js';
+import {AudioClipPlayer} from './AudioClipPlayer.js';
 
 
 /**
diff --git a/src/sound/SoundPlayer.js b/src/sound/SoundPlayer.js
index 8d088a5..9b55d0e 100644
--- a/src/sound/SoundPlayer.js
+++ b/src/sound/SoundPlayer.js
@@ -7,7 +7,7 @@
  * @license Distributed under the terms of the MIT License
  */
 
-import {PsychObject} from '../util/PsychObject';
+import {PsychObject} from '../util/PsychObject.js';
 
 
 /**
diff --git a/src/sound/TonePlayer.js b/src/sound/TonePlayer.js
index dfacd9a..a7a064e 100644
--- a/src/sound/TonePlayer.js
+++ b/src/sound/TonePlayer.js
@@ -9,7 +9,7 @@
 
 import * as Tone from 'tone';
 import { isNumeric } from "../util/Util.js";
-import {SoundPlayer} from './SoundPlayer';
+import {SoundPlayer} from './SoundPlayer.js';
 
 
 /**
diff --git a/src/sound/TrackPlayer.js b/src/sound/TrackPlayer.js
index 058d481..a481a66 100644
--- a/src/sound/TrackPlayer.js
+++ b/src/sound/TrackPlayer.js
@@ -7,7 +7,7 @@
  * @license Distributed under the terms of the MIT License
  */
 
-import {SoundPlayer} from './SoundPlayer';
+import {SoundPlayer} from './SoundPlayer.js';
 
 
 /**