export declare function next_power_of_two(value: number): number;
export declare function fft_in_place(re: Float64Array, im: Float64Array): void;
export declare const WINDOW_TYPES: readonly ["hann", "gaussian", "none"];
export type WindowType = (typeof WINDOW_TYPES)[number];
interface WindowOptions {
    gaussian_alpha?: number;
}
interface PeriodogramOptions extends WindowOptions {
    window?: WindowType;
    zero_pad_factor?: number;
    component_weights?: ArrayLike<number>;
}
export interface PeriodogramResult {
    frequencies: Float64Array;
    power: Float64Array;
    n_fft: number;
    window: WindowType;
    window_energy: number;
    frequency_spacing: number;
    rayleigh_resolution: number;
    nyquist: number;
}
export declare const time_series_window: (n_samples: number, type: WindowType, options?: WindowOptions) => Float64Array;
export declare const correlation_window: (n_lags: number, type: WindowType, options?: WindowOptions) => Float64Array;
export declare function one_sided_periodogram(values: ArrayLike<number>, n_components: number, sample_interval: number, options?: PeriodogramOptions): PeriodogramResult;
export declare function cosine_spectrum_length(n_values: number, zero_pad_factor?: number): number;
export declare function even_cosine_spectrum(values: ArrayLike<number>, zero_pad_factor?: number): {
    spectrum: Float64Array;
    n_fft: number;
};
export {};