export declare type Options = {
    /**
     * Center frequency of the band to use as a starting point (default `1000` Hz)
     */
    center?: number;
    /**
     * The audio spectrum for center frequencies (default `[15, 21000]`)
     */
    spectrum?: [number, number];
};
/**
 * Lower, center and higher frequencies bounds of a band
 */
export declare type Band = [number, number, number];
/**
 * Calculates and returns the frequency limits for octave bands.
 * @param fraction (default `1`) octave bands fraction
 * @param options (optional) bands limit options
 * @returns an array of bands, where each band is a tuple of `[lower, center, higher]` frequencies
 */
export declare const octaves: (fraction?: number, options?: Options) => Band[];
/**
 * Calculates the fractional bandwidth per given octave band:
 * `BW = (f_high - f_low) / f_center`
 * @param fraction (default `1`) octave band fraction
 */
export declare const bandwidth: (fraction?: number) => number;
/**
 * Calculates the frequency bounds for a given spectrum and number of bands
 * @param bands number of bands
 * @param spectrum the audio spectrum for bands' center frequencies (default `[15, 21000]`)
 * @returns an array of bands, where each band is a tuple of `[lower, center, higher]` frequencies
 */
export declare const equalizer: (bands: number, options?: Pick<Options, 'spectrum'>) => Band[];