Apparatus for decomposing an audio signal into a background component signal and a foreground component signal, the apparatus comprising: a block generator for generating a time sequence of blocks of audio signal values; an audio signal analyzer for determining a block characteristic of a current block of the audio signal and for determining an average characteristic for a group of blocks, the group of blocks comprising at least two blocks, wherein the audio signal analyzer is configured for determining, as the block characteristic of the current block, a power measure or an energy measure for the current block and for determining, as the average characteristic for the group of blocks, an average power measure or an average energy measure for the group of blocks; and a separator for separating the current block into a background portion and a foreground portion in response to a ratio of the block characteristic of the current block and the average characteristic of the group of blocks, wherein the background component signal comprises the background portion of the current block and the foreground component signal comprises the foreground portion of the current block, wherein the background component signal is a noise-like signal, and wherein the foreground component signal is a transient signal, and wherein the separator is configured to calculate a separation gain from the ratio, to weight the audio signal values of the current block using the separation gain to obtain the foreground portion of the current block, and to determine the background portion, so that the background component signal constitutes a remaining signal, or to calculate a separation gain from the ratio, to weight the audio signal values of the current block using the separation gain to obtain the background portion of the current block, and to determine the foreground portion, so that the foreground component signal constitutes a remaining signal. a block generator for generating a time sequence of blocks of audio signal values; an audio signal analyzer for determining a block characteristic of a current block of the audio signal and for determining an average characteristic for a group of blocks, the group of blocks comprising at least two blocks, wherein the audio signal analyzer is configured for determining, as the block characteristic of the current block, a power measure or an energy measure for the current block and for determining, as the average characteristic for the group of blocks, an average power measure or an average energy measure for the group of blocks; and a separator for separating the current block into a background portion and a foreground portion in response to a ratio of the block characteristic of the current block and the average characteristic of the group of blocks, wherein the background component signal comprises the background portion of the current block and the foreground component signal comprises the foreground portion of the current block, wherein the background component signal is a noise-like signal, and wherein the foreground component signal is a transient signal, and wherein the separator is configured to calculate a separation gain from the ratio, to weight the audio signal values of the current block using the separation gain to obtain the foreground portion of the current block, and to determine the background portion, so that the background component signal constitutes a remaining signal, or to calculate a separation gain from the ratio, to weight the audio signal values of the current block using the separation gain to obtain the background portion of the current block, and to determine the foreground portion, so that the foreground component signal constitutes a remaining signal. to calculate a separation gain from the ratio, to weight the audio signal values of the current block using the separation gain to obtain the foreground portion of the current block, and to determine the background portion, so that the background component signal constitutes a remaining signal, or to calculate a separation gain from the ratio, to weight the audio signal values of the current block using the separation gain to obtain the background portion of the current block, and to determine the foreground portion, so that the foreground component signal constitutes a remaining signal.