import { VadOptions } from '../client';
/**
 * Adaptive energy threshold voice activity detection (VAD) implementation.
 * It can be used to enable hands-free operation of the SLU decoder.
 *
 * When enough frames with a signal stronger than SignalToNoiseDb have been detected, IsSignalDetected goes true. When enough silent frames have been detected, IsSignalDetected goes false after the sustain time.
 * Use its public fields to configure the static noise gate level, signal-to-noise level, activation/deactivation treshold (ratio of signal to silent frames) and the signal sustain time.
 * The background noise level gradually adapts when no signal is detected.
 *
 * IsSignalDetected can be used to drive SpeechlyClient's StartContext and StopContext automatically by setting ControlListening true.
 * @internal
 */
declare class EnergyTresholdVAD {
    isSignalDetected: boolean;
    signalDb: number;
    noiseLevelDb: number;
    vadOptions: VadOptions;
    readonly frameMillis: number;
    private energy;
    private baselineEnergy;
    private loudFrameBits;
    private vadSustainMillisLeft;
    constructor(frameMillis: number, vadOptions: VadOptions);
    adjustVadOptions(vadOptions: Partial<VadOptions>): void;
    resetVAD(): void;
    processFrame(floats: Float32Array, start?: number, length?: number, eos?: boolean): void;
    private determineNewSignalState;
    private adaptBackgroundNoise;
    private pushFrameHistory;
    private countLoudFrames;
}
export default EnergyTresholdVAD;