Methods and systems for processing audio data, such as spatial audio data, in which one or more sound characteristics of a given component of a spatial audio signal are modified in dependence on a relationship between a direction characteristic of the given component and a defined range of direction characteristics; this enhances the listening experience of the listener. A spatial audio in a format using a spherical harmonic representation of sound components is decoded by performing a transform on the spherical harmonic representation, in which the transform is based on a predefined speaker layout and a predefined rule, the predefined rule indicating a speaker gain of each speaker arranged according to the predefined layout, when reproducing sound incident form a given direction; this provides an alternative to existing method of decoding spatial audio streams, which focus on soundfield reconstruction. A plurality of matrix transforms is combined into a combined transform, and the combined transform is performed on an audio signal; this saves processing resources of the audio system being used.