An apparatus for generating bandwidth extension output data for an audio signal, the audio signal comprising components in a first frequency band and components in a second frequency band, wherein the bandwidth extension output data are adapted to control a synthesis of the components in the second frequency band, the apparatus comprising: a noise floor measurer for measuring a noise floor to generate noise floor data of the second frequency band for a time portion of the audio signal; a signal energy characterizer for deriving a sibilance parameter or a spectral tilt parameter as energy distribution data, wherein the signal energy characterizer therefore is adapted to receive the first frequency band and the second frequency band, the energy distribution data characterizing an energy distribution in a spectrum of the time portion of the audio signal, the sibilance parameter or the spectral tilt parameter identifying an increasing or decreasing level of the audio signal with frequency; and a processor for combining the noise floor data and the energy distribution data to obtain the bandwidth extension output data, wherein the processor is configured to change the noise floor data in accordance to the energy distribution data to obtain modified noise floor data, the modified noise floor data indicating a modified noise floor being increased or decreased, depending on the energy distribution data, over the noise floor indicated by the noise floor data, wherein the change of the noise floor data is such that the modified noise floor is increased for an audio signal comprising a first degree of sibilance compared to an audio signal comprising a second degree of sibilance, the second degree being lower than the first degree, wherein the apparatus for generating bandwidth extension output data is configured to perform an external decision to determine whether the time portion of the audio signal either is a speech signal or is a non-speech signal, wherein the noise floor data measured by the noise floor measurer is used as the bandwidth extension output data, when the time portion of the audio signal is a non-speech signal, and wherein the signal energy characterizer is configured to perform, when the time portion of the audio signal is a speech signal, an additional speech analysis to determine a degree of sibilance of the speech signal, and wherein the processor is configured to add the modified noise floor data to a bitstream as the bandwidth extension output data, when the time portion of the audio signal is a speech signal. a noise floor measurer for measuring a noise floor to generate noise floor data of the second frequency band for a time portion of the audio signal; a signal energy characterizer for deriving a sibilance parameter or a spectral tilt parameter as energy distribution data, wherein the signal energy characterizer therefore is adapted to receive the first frequency band and the second frequency band, the energy distribution data characterizing an energy distribution in a spectrum of the time portion of the audio signal, the sibilance parameter or the spectral tilt parameter identifying an increasing or decreasing level of the audio signal with frequency; and a processor for combining the noise floor data and the energy distribution data to obtain the bandwidth extension output data, wherein the processor is configured to change the noise floor data in accordance to the energy distribution data to obtain modified noise floor data, the modified noise floor data indicating a modified noise floor being increased or decreased, depending on the energy distribution data, over the noise floor indicated by the noise floor data, wherein the change of the noise floor data is such that the modified noise floor is increased for an audio signal comprising a first degree of sibilance compared to an audio signal comprising a second degree of sibilance, the second degree being lower than the first degree, wherein the apparatus for generating bandwidth extension output data is configured to perform an external decision to determine whether the time portion of the audio signal either is a speech signal or is a non-speech signal, wherein the noise floor data measured by the noise floor measurer is used as the bandwidth extension output data, when the time portion of the audio signal is a non-speech signal, and wherein the signal energy characterizer is configured to perform, when the time portion of the audio signal is a speech signal, an additional speech analysis to determine a degree of sibilance of the speech signal, and wherein the processor is configured to add the modified noise floor data to a bitstream as the bandwidth extension output data, when the time portion of the audio signal is a speech signal.