Apparatus for processing an audio signal

Apparatus for processing an audio signal comprising a number of samples, particularly so as to generate missing harmonics of low-frequency components in the audio signal, the apparatus comprising at least one audio processing device configured to:

• process an audio signal in a time-dependent representation of the audio signal particularly in a half-wave representation of the audio signal;
• determine an interval between a first zero-crossing and a further zero-crossing of the audio signal;
• determine a first set of sample points in the interval, the first set of sample points comprising a number of sample points at first positions in the interval;
• determine a second set of sample points in the interval, the second set of sample points comprising a number of sample points at second positions in the interval;
• modify the audio signal in the interval, on basis of an audio signal modification rule, by changing positions of the sample points of the first set of sample points in the interval such that each sample point of the first set of sample points is changed from its respective first position in the first set of sample points to its respective second position in the second set of sample points;
• apply the modified audio signal interval to the respective interval of the original audio signal so as to generate a modified audio signal;
• wherein
• the audio processing device is configured to modify the audio signal on basis of an audio signal modification rule specifying a defined change of positions of the sample points of the first set of sample points in the interval such that each sample point of the first set of sample points is changed from its respective first position in the first set of sample points to its respective second position in the second set of sample points;
• wherein
• the audio signal modification rule is or comprises a tilting function, configured to tilt a zero-crossing tangent of the audio signal in clockwise or counter-clockwise direction.