/// <reference types="node" />
import { Transform, TransformCallback } from "stream";
import { Hz } from "../global";
/**
 * A band pass filter using simple moving average low pass filters.
 * https://www.gaussianwaves.com/2010/11/moving-average-filter-ma-filter-2/
 * (To support old waveforms, not a very good audio filter.)
 * */
declare class MovingAverageBandPassFilter extends Transform {
    /** Lower frequency cut-off */
    private lo;
    /** Higher frequency cut-off */
    private hi;
    /** Length of first (high pass) moving average */
    private loAvLen;
    /** Length of second (low-pass) moving average */
    private hiAvLen;
    private sampleRate;
    private loSum;
    private hiSum;
    private loBuffer;
    private hiBuffer;
    constructor(lo: Hz, hi: Hz);
    /** Calculate moving average lengths based on sample rate of incoming PCM audio. */
    private setup;
    /** Apply filter to incoming audio chunk. */
    _transform(audio: AudioBuffer, encoding: string, callback: TransformCallback): void;
}
export { MovingAverageBandPassFilter };