Tunable exhaust system

1 . An exhaust system, comprising:

an exhaust conduit;

a piezoelectric patch secured to the exhaust conduit;

a sensor in operative communication with the exhaust conduit; and

a controller in operative communication with the piezoelectric patch and the sensor, wherein the controller is configured to provide an electrical signal to the piezoelectric patch and modify a sound emitted from the exhaust system.

2 . The exhaust system of claim 1 , wherein the sensor is configured to measure an acoustic property of the exhaust conduit, an acoustic property of an exhaust gas in the exhaust conduit, or a combination comprising one of the foregoing acoustic properties.

3 . The exhaust system of claim 1 , wherein the sensor comprises a microphone, an other piezoelectric patch, or a combination comprising at least one of the foregoing, located upstream of the piezoelectric patch.

4 . The exhaust system of claim 1 , wherein the sensor comprises a microphone, an other piezoelectric patch, or a combination comprising at least one of the foregoing, located downstream of the piezoelectric patch.

5 . The exhaust stream of claim 3 , wherein the sensor further comprises a microphone, other piezoelectric patch, or a combination comprising at least one of the foregoing, located upstream of the piezoelectric patch.

6 . The exhaust system of claim 1 , wherein the sensor is mounted on an outer surface of the exhaust conduit.

7 . The exhaust system of claim 1 , wherein the piezoelectric patch comprises lead zirconate titanate.

8 . The exhaust system of claim 1 , wherein the modulation occurs by wave interference.

9 . An exhaust system, comprising:

an exhaust conduit;

a piezoelectric patch secured to the exhaust conduit;

a sensor located upstream of the piezoelectric patch and in operative communication with the exhaust conduit, wherein the upstream sensor is configured to measure information comprising an acoustic property of the exhaust conduit, an acoustic property of an exhaust gas in the exhaust conduit, or a combination comprising one of the foregoing acoustic properties upstream of the piezoelectric patch; and

a controller in operative communication with the piezoelectric patch and the upstream sensor, wherein the controller is adapted to receive upstream measured information from the upstream sensor and is operable to extract an amplitude, frequency and/or phase of the upstream measured information and to selectively apply a predictive voltage to the piezoelectric patch to effect a transient mechanical deformation of the piezoelectric patch, wherein the transient mechanical deformation of the piezoelectric patch results in a transient localized distortion of a shape of the exhaust conduit, wherein the transient localized distortion of the shape of the exhaust conduit results in modulation of an emitted sound from the exhaust system.

10 . The exhaust system of claim 9 , wherein the upstream sensor is a microphone, an other piezoelectric patch, or a combination comprising at least one of the foregoing.

11 . The exhaust system of claim 9 , further comprising a sensor located downstream of the piezoelectric patch and in operative communication with the exhaust conduit, wherein the upstream sensor is configured to measure information comprising an acoustic property of the exhaust conduit, an acoustic property of an exhaust gas in the exhaust conduit, or a combination comprising one of the foregoing acoustic properties downstream of the piezoelectric patch.

12 . The exhaust system of claim 11 , wherein the downstream sensor is a microphone, an other piezoelectric patch, or a combination comprising at least one of the foregoing.

13 . The exhaust system of claim 11 , wherein the controller is further in operative communication with the downstream sensor, and is further adapted to receive downstream measured information from the downstream sensor, and is further operable to extract the amplitude, frequency and/or phase of the downstream measured information and to further selectively apply a corrective voltage to the piezoelectric patch to effect the transient mechanical deformation of the piezoelectric patch.

14 . The exhaust system of claim 9 , wherein the piezoelectric patch comprises lead zirconate titanate.

15 . The exhaust system of claim 9 , wherein the modulation occurs by wave interference.

16 . A method, comprising:

producing an exhaust gas in an exhaust conduit of an exhaust system;

measuring an acoustic property of the exhaust gas, an acoustic property of the exhaust conduit, or a combination comprising at least one of the foregoing acoustic properties;

applying an electrical signal to a piezoelectric patch, wherein the piezoelectric patch is secured to the exhaust conduit; and

deforming the piezoelectric patch mechanically to modulate a sound emitted from the exhaust system.

17 . The method of claim 16 , further comprising repeating, in sequence, the measuring, applying, and deforming in a continuous loop.

18 . The method of claim 17 , wherein the repeating results in vibration of the piezoelectric patch.

19 . The method of claim 16 , further comprising selecting a desired sound level and/or spectral character manually by a motor vehicle user.

20 . The method of claim 16 , further comprising setting a desired sound level and/or spectral character automatically based on a time and/or location of a motor vehicle.