A method and a device for determining a frequency mask disposed above or below a frequency spectrum of a detected signal determines every individual ordinate value of a first envelope curve disposed completely above or below the frequency spectrum as the maximum value or minimum value of a given number of respectively adjacent ordinate values of the frequency spectrum linked to a window function. Following this, each individual ordinate value of a second envelope curve disposed completely above or below the frequency spectrum and completely above or below the first envelope curve is determined as the maximum value or minimum value of a given number of respectively adjacent ordinate values of the frequency spectrum linked to a window function. Finally, a minimum number of ordinate values of the frequency mask from ordinate values of the first and/or second envelope curve disposed completely between the first and second envelope curve is determined, wherein in each case two successive ordinate values of the frequency mask with a maximum horizontal spacing distance within the first and second envelope curve can be reached in a linear manner relative to one another.