/**
 * AudioEnvelope.ts
 *
 * ADSR envelope generator: attack/decay/sustain/release,
 * fade curves, ducking, and sidechain compression trigger.
 *
 * @module audio
 */
export interface ADSRConfig {
    attack: number;
    decay: number;
    sustain: number;
    release: number;
}
export type EnvelopeStage = 'idle' | 'attack' | 'decay' | 'sustain' | 'release';
export type CurveType = 'linear' | 'exponential' | 'logarithmic';
export declare class AudioEnvelope {
    private config;
    private stage;
    private level;
    private elapsed;
    private curve;
    constructor(config?: Partial<ADSRConfig>, curve?: CurveType);
    noteOn(): void;
    noteOff(): void;
    process(dt: number): number;
    private applyCurve;
    getLevel(): number;
    getStage(): EnvelopeStage;
    setConfig(config: Partial<ADSRConfig>): void;
    getConfig(): ADSRConfig;
    isActive(): boolean;
}
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