Enhancing perceptual performance of SBR and related HFR coding methods by adaptive noise-floor addition and noise substitution limiting

An apparatus for decoding an encoded signal to obtain an output audio signal that represents an original audio signal, wherein the apparatus comprises:

• a demultiplexor for receiving the encoded signal and obtaining therefrom a noise level parameter and spectral envelope parameters for high-frequency bands of the original audio signal and encoded audio data;
• an audio decoder for decoding the encoded audio data to obtain a decoded audio signal that represents low-frequency bands of the original audio signal, and for generating a reconstructed signal by replicating harmonics in the low-frequency bands of the decoded audio signal into the high-frequency bands and adding noise to replicated harmonics in the high-frequency bands, wherein the noise is adapted according to the noise level parameter and the reconstructed signal has levels adapted according to the spectral envelope parameters;
• and
• a synthesis filter bank for synthesizing the output audio signal from a combination of the decoded audio signal and the reconstructed signal.