Vehicle engine sound enhancement

Abstract

An engine harmonic enhancement system. The EHE system uses multiple parameters, such as engine load, gear, number of cylinders operating, and transmission ratio, to determine EHE gains to determine EHE gain. The EHE system determines a separate EHE gain for each harmonic.

What is claimed is: 
     
         1 . A method comprising:
 providing a fundamental frequency corresponding to the RPM of an engine of a vehicle;   determining a plurality of harmonics of the fundamental frequency;   determining a desired target of the plurality of harmonics, the target shape comprising, for each of the harmonics of the plurality of the harmonics, a gain value;   determining an engine harmonic enhancement gain curve comprising gain values as a function of engine load; and   combining the plurality of the harmonics, the target shape of the plurality of harmonics, and the engine harmonic enhancement gain curve to produce a set of harmonic enhancement signals;   wherein each harmonic of the plurality of harmonics is affected differently,   wherein determining of an engine harmonic enhancement gain curve for the at least one of the plurality of harmonics comprises:   determining the value of a parameter other than the engine load related to an operating condition of a vehicle; and   responsive to the value of the parameter and the engine load, determining the engine harmonic enhancement gain curve, and   wherein the parameter is the gear in which the vehicle is operating, the number of cylinders that are operating for an engine capable of operating on all cylinders or a subset of cylinders, or the transmission ratio of a continuously variable transmission.   
     
     
         2 . The method of  claim 1 , wherein the determining an engine harmonic enhancement gain curve comprises separately determining an engine harmonic gain curve for each harmonic. 
     
     
         3 . The method of  claim 1 , wherein the determining the engine harmonic enhancement gain curve further comprises determining separately an engine harmonic enhancement gain curve corresponding to each of the plurality of harmonics of the fundamental engine frequency, wherein the engine harmonic enhancement gain curve corresponding to at least one of the harmonics is different that the engine harmonic enhancement gain curves corresponding to the other harmonics. 
     
     
         4 . The method of  claim 3 , further comprising applying to the fundamental engine frequency and to each of the plurality of harmonics of the fundamental engine frequency a corresponding engine harmonic enhancement gain curve. 
     
     
         5 . The method of  claim 1 , wherein producing the set of harmonic enhancement signals comprises, for each harmonic of the plurality of harmonics, combining that harmonic, the gain value of the target shape for that harmonic, and the set of gain values of the gain curve for that harmonic separately from the other harmonics. 
     
     
         6 . The method of  claim 5 , further comprising:
 determining a rate of change of the RPM of the engine of the vehicle; and   ceasing to produce the set of harmonic enhancement signals, when the rate of change of the RPM is either small or decreasing.   
     
     
         7 . The method of  claim 5 , further comprising:
 determining a rate of change of the RPM of the engine of the vehicle; and   ceasing to product the set of harmonic enhancement signals, when the rate of change of the RPM is steady.   
     
     
         8 . An engine harmonic enhancement system, comprising:
 circuitry for providing a fundamental frequency corresponding to the RPM of the engine;   circuitry for determining a plurality of harmonics of the fundamental frequency;   circuitry for determining a desired target of the plurality of harmonics, the target shape comprising, for each of the harmonics of the plurality of the harmonics, a gain value;   circuitry for determining an engine harmonic enhancement gain curve comprising gain values as a function of engine load; and   circuitry for combining the plurality of the harmonics, the target shape of the plurality of harmonics, and the engine harmonic enhancement gain curve to produce a set of harmonic enhancement signals;   wherein the circuitry for affecting each harmonic of the plurality of harmonics affects each harmonic differently,   wherein the circuitry for determining of an engine harmonic enhancement gain curve for at least one of the plurality of harmonics comprises:   circuitry for determining the value of a parameter other than the engine load related to an operating condition of a vehicle; and   circuitry responsive to the value of the parameter and the engine load, determining the engine harmonic enhancement gain curve, and   wherein the parameter is the gear in which the vehicle is operating, the number of cylinders that are operating for an engine capable of operating on all cylinders or a subset of cylinders, or the transmission ratio of a continuously variable transmission.   
     
     
         9 . The apparatus of  claim 8 , wherein the circuitry for determining an engine harmonic enhancement gain curve comprises circuitry for separately determining an engine harmonic gain curve for each harmonic. 
     
     
         10 . The apparatus of  claim 8 , wherein the circuitry for determining the engine harmonic enhancement gain curve further comprises circuitry for determining separately an engine harmonic enhancement gain curve corresponding to each of the plurality of harmonics of the fundamental engine frequency, wherein the engine harmonic enhancement gain curve corresponding to at least one of the harmonics is different that the engine harmonic enhancement gain curves corresponding to the other harmonics; 
     
     
         11 . The apparatus of  claim 10 , further comprising:
 circuitry for applying to the fundamental engine frequency and to each of the plurality of harmonics of the fundamental engine frequency a corresponding engine harmonic enhancement gain curve.   
     
     
         12 . The apparatus of  claim 10 , further comprising:
 circuitry for determining a rate of change of the RPM of the engine of the vehicle; and   circuitry for ceasing to produce the set of harmonic enhancement signals, when the rate of change of the RPM is either small or decreasing.   
     
     
         13 . The apparatus of  claim 10 , further comprising:
 circuitry for determining a rate of change of the RPM of the engine of the vehicle; and   circuitry for ceasing to product the set of harmonic enhancement signals, when the rate of change of the RPM is steady.   
     
     
         14 . The apparatus of  claim 8 , wherein the circuitry for producing the set of harmonic enhancement signals combines the gain value of the target shape for each harmonic of the plurality of harmonics with the set of gain values of the gain curve for that harmonic separately from the other harmonics.