Move AudioBuffer definition to the Audio.d.ts and remove the previous import.

src/audio/Audio.d.ts

-import { Object3D } from './../core/Object3D';
-import { AudioListener } from './AudioListener';
-import { AudioContext } from './AudioContext';
-import { AudioBuffer } from "./PositionalAudio";
+import { Object3D } from "./../core/Object3D";
+import { AudioListener } from "./AudioListener";
+import { AudioContext } from "./AudioContext";
 
 // Extras / Audio /////////////////////////////////////////////////////////////////////
 
 export class Audio extends Object3D {
-  constructor(listener: AudioListener);
-  type: 'Audio';
+	constructor(listener: AudioListener);
+	type: "Audio";
 
-  context: AudioContext;
-  gain: GainNode;
-  autoplay: boolean;
-  buffer: null | Audio;
-  detune: number;
-  loop: boolean;
-  startTime: number;
-  offset: number;
-  playbackRate: number;
-  isPlaying: boolean;
-  hasPlaybackControl: boolean;
-  sourceType: string;
-  source: AudioBufferSourceNode;
-  filters: any[];
+	context: AudioContext;
+	gain: GainNode;
+	autoplay: boolean;
+	buffer: null | Audio;
+	detune: number;
+	loop: boolean;
+	startTime: number;
+	offset: number;
+	playbackRate: number;
+	isPlaying: boolean;
+	hasPlaybackControl: boolean;
+	sourceType: string;
+	source: AudioBufferSourceNode;
+	filters: any[];
 
-  getOutput(): GainNode;
-  setNodeSource(audioNode: AudioBufferSourceNode): this;
-  setMediaElementSource(mediaElement: MediaElementAudioSourceNode): this;
-  setBuffer(audioBuffer: AudioBuffer): this;
-  play(): this;
-  onEnded(): void;
-  pause(): this;
-  stop(): this;
-  connect(): this;
-  disconnect(): this;
-  setDetune(value: number): this;
-  getDetune(): number;
-  getFilters(): any[];
-  setFilter(value: any[]): this;
-  getFilter(): any;
-  setFilter(filter: any): this;
-  setPlaybackRate(value: number): this;
-  getPlaybackRate(): number;
-  getLoop(): boolean;
-  setLoop(value: boolean): void;
-  getVolume(): number;
-  setVolume(value: number): this;
-  /**
-   * @deprecated Use {@link AudioLoader} instead.
-   */
-  load(file: string): Audio;
+	getOutput(): GainNode;
+	setNodeSource(audioNode: AudioBufferSourceNode): this;
+	setMediaElementSource(mediaElement: MediaElementAudioSourceNode): this;
+	setBuffer(audioBuffer: AudioBuffer): this;
+	play(): this;
+	onEnded(): void;
+	pause(): this;
+	stop(): this;
+	connect(): this;
+	disconnect(): this;
+	setDetune(value: number): this;
+	getDetune(): number;
+	getFilters(): any[];
+	setFilter(value: any[]): this;
+	getFilter(): any;
+	setFilter(filter: any): this;
+	setPlaybackRate(value: number): this;
+	getPlaybackRate(): number;
+	getLoop(): boolean;
+	setLoop(value: boolean): void;
+	getVolume(): number;
+	setVolume(value: number): this;
+	/**
+	 * @deprecated Use {@link AudioLoader} instead.
+	 */
+	load(file: string): Audio;
+}
+
+export class AudioBuffer {
+	constructor(context: any);
+
+	context: any;
+	ready: boolean;
+	readyCallbacks: Function[];
+
+	load(file: string): AudioBuffer;
+	onReady(callback: Function): void;
 }

src/audio/PositionalAudio.d.ts

-import { AudioListener } from './AudioListener';
-import { Audio } from './Audio';
-
-export class AudioBuffer {
-  constructor(context: any);
-
-  context: any;
-  ready: boolean;
-  readyCallbacks: Function[];
-
-  load(file: string): AudioBuffer;
-  onReady(callback: Function): void;
-}
+import { AudioListener } from "./AudioListener";
+import { Audio } from "./Audio";
 
 export class PositionalAudio extends Audio {
-  constructor(listener: AudioListener);
+	constructor(listener: AudioListener);
 
-  panner: PannerNode;
+	panner: PannerNode;
 
-  setRefDistance(value: number): this;
-  getRefDistance(): number;
-  setRolloffFactor(value: number): this;
-  getRolloffFactor(): number;
-  setDistanceModel(value: string): this;
-  getDistanceModel(): string;
-  setMaxDistance(value: number): this;
-  getMaxDistance(): number;
-  setDirectionalCone(coneInnerAngle: number, coneOuterAngle: number, coneOuterGain: number): this;
+	setRefDistance(value: number): this;
+	getRefDistance(): number;
+	setRolloffFactor(value: number): this;
+	getRolloffFactor(): number;
+	setDistanceModel(value: string): this;
+	getDistanceModel(): string;
+	setMaxDistance(value: number): this;
+	getMaxDistance(): number;
+	setDirectionalCone(
+		coneInnerAngle: number,
+		coneOuterAngle: number,
+		coneOuterGain: number
+	): this;
 }