Scalable audio coding

The invention relates to an audio encoder and decoder and methods for audio encoding and decoding. In a preferred encoder embodiment an audio signal is encoded by deterministic encoder means to form a first encoded signal part. A spectrum of the audio signal is determined and represented by an excitation pattern, i.e. spectral values corresponding to human auditory filters, as a second encoded signal part. A masking curve is also extracted based on the excitation pattern, thus improving encoding efficiency in terms of bit rate. In a preferred decoder the first encoded signal part is decoded by deterministic decoder means. A noise generator uses the decoded first signal part together with the second signal part, i.e. the excitation pattern for the original audio signal, to generate a noise signal. The noise signal is then added to the first decoded signal part to form an output audio signal. At the decoder side the masking curve is also extracted based on the second encoded signal part, i.e. the excitation pattern. The noise signal is generated so that the output audio signal exhibits an excitation pattern nearly identical to the original audio signal. Thus, a perceived high quality audio is obtained while the encoded signal is scalable since a possible deviation between encoding and decoding of the first signal part is compensated by the noise generator at the decoder side. In preferred embodiments the coding means comprises a sinusoidal coder.