Vehicle engine sound enhancement

1. 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;

providing a second set of harmonics of the fundamental harmonic frequency; and

separately equalizing each of the second set of harmonics of the fundamental harmonic frequency,

wherein the equalizing the first engine harmonic enhancement audio signal comprises

equalizing the first engine harmonic enhancement audio signal to provide a first equalized engine harmonic enhancement signal and

transducing the first engine harmonic enhancement audio signal so that the apparent source of the transduced first sound enhancement audio signal is a first vehicle location; and

wherein the equalizing the second engine harmonic enhancement audio signal comprises equalizing the second engine harmonic enhancement audio signal to provide a second equalized engine harmonic enhancement signal so that the second equalized engine harmonic enhancement signal has a different equalization than the first equalized engine harmonic signal; and

transducing the second engine harmonic enhancement audio signal so that the second apparent source of the transduced second sound enhancement audio signal is a second vehicle location.

2. 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.

3. A method according to claim 2 , further comprising:

determining if the engine load is increasing or decreasing; and

if the engine load is decreasing, changing a smoothing parameter.

4. A method according to claim 2 , wherein the smoothing comprises low pass filtering.

5. 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.

6. A method according to claim 5 , wherein the providing the engine harmonic enhancement audio signal comprises

determining a fundamental harmonic frequency;

providing harmonics of the fundamental harmonic frequency;

separately equalizing each of the harmonics of the fundamental harmonic frequency.

7. A method according to claim 5 , wherein the equalizing the engine harmonic enhancement audio signal comprises

processing the engine enhancement audio signal to provide a plurality of engine enhancement audio signal each corresponding to one of the plurality of loudspeakers; and

separately equalizing each of the plurality of engine enhancement audio signals.