Vehicle engine sound enhancement

A method comprising:

• in a vehicle engine harmonic enhancement system, providing a first engine harmonic signal, comprising
• providing harmonics of a fundamental harmonic frequency;
• providing a first set of harmonics of the fundamental harmonic frequency;
• separately equalizing each of the first set of harmonics of the fundamental harmonic frequency to provide equalized harmonics so that at least one of the equalized harmonics has a different equalization that at least one of the other equalized harmonics, wherein the providing the first engine harmonic enhancement audio signal comprises
• providing a stream of engine harmonic enhancement gains;
• smoothing the stream of engine harmonic enhancement gains to provide a stream of smoothed engine harmonic enhancement gains;
• and
• applying the stream of smoothing engine harmonic gains to the first engine harmonic enhancement audio signal.

In an vehicle audio system comprising a plurality of loudspeakers, an entertainment audio system, and an engine harmonic enhancement system, a method comprising:

• in the vehicle audio system, equalizing an entertainment audio signal to provide an equalized entertainment audio signal;
• providing an engine harmonic enhancement audio signal;
• equalizing the engine harmonic enhancement audio signal separately from the entertainment audio signal to provide an equalized engine harmonic enhancement audio signal so that the equalized harmonic enhancement signal has a different equalization than the equalized entertainment signal;
• and
• combining the equalized entertainment audio signal with the equalized engine harmonic enhancement audio signal.