import type { IProc } from "./api.js";
import { Delay } from "./delay.js";
/**
 * Extension of {@link feedbackDelay} with an additional filter/proc applied to
 * the feedback itself (e.g. a low pass filter).
 *
 * @param n - delay length
 * @param filter - IProc applied to feedback
 * @param feedback - feedback factor (default: 0.5)
 */
export declare const filterFeedbackDelay: (n: number, filter: IProc<number, number>, feedback?: number) => FilterFeedbackDelay;
export declare class FilterFeedbackDelay extends Delay<number> {
    filter: IProc<number, number>;
    protected _feedback: number;
    constructor(n: number, filter: IProc<number, number>, _feedback?: number);
    next(x: number): number;
    feedback(): number;
    setFeedback(feedback: number): void;
}
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