Abstract:
A continuously variable Helmholtz resonator for a vehicle air intake system having a vibratory input to the resonator wall to dynamically adjust the cancellation frequency for time-varying acoustical signals, and at least one of mean resonator volume control, mean resonator neck length control, and mean resonator neck diameter control whereby control of both the dynamic and the mean properties of the resonator provides a wide-tuning spectrum and facilitates canceling of time-varying acoustical signals.

Description:
FIELD OF THE INVENTION 
     The invention relates to a resonator and more particularly to a tunable Helmholtz resonator for a vehicle air intake system having a vibratory input to the resonator wall to dynamically adjust the cancellation frequency for time-varying acoustical signals, and at least one of mean resonator volume control, mean resonator neck length control, and mean resonator neck diameter control. 
     BACKGROUND OF THE INVENTION 
     In an internal combustion engine for a vehicle, it is desirable to design an air induction system in which sound energy generation is minimized. Sound energy is generated as fresh air is drawn into the engine. Sound energy is caused by the intake air in the air feed line which creates undesirable intake noise. Resonators of various types such as a Helmholtz type, for example, have been employed to reduce engine intake noise. Such resonators typically-include a single, fixed volume chamber, with a fixed neck length and fixed neck diameter, for dissipating the intake noise. 
     It would be desirable to produce a variable resonator system which militates against the emission of sound energy caused by the intake air and cancels acoustical signals. 
     SUMMARY OF THE INVENTION 
     Consistent and consonant with the present invention, a variable resonator system which militates against the emission of sound energy caused by the intake air and cancels acoustical signals, has been discovered. 
     The continuously variable resonator system comprises: 
     a housing having a chamber formed therein and a neck portion adapted to provide fluid communication between the chamber and a duct; 
     an engine speed sensor adapted to sense a speed of an associated engine; 
     means for controlling at least one of a volume of the chamber, a length of the neck portion, and a diameter of the neck portion, the means for controlling in communication with the engine speed sensor, and the means for controlling at least one of the volume of the chamber, the length of the neck portion, and the diameter of the neck portion responsive to the speed sensed by the engine speed sensor, wherein controlling at least one of the volume of the chamber, the length of the neck portion, and the diameter of the neck portion facilitates attenuation of a first desired frequency of sound entering the resonator; 
     a noise sensor disposed within the duct; 
     a vibratory displacement actuator disposed in the chamber of said housing, the vibratory, displacement actuator for creating a vibratory input responsive to noise levels sensed by the noise sensor, wherein the vibratory input cancels a second desired frequency of sound entering the resonator. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above, as well as other objects, features, and advantages of the present invention will be understood from the detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a schematic view of a first embodiment of a resonator, the resonator having means for continuously varying the mean resonator volume and means for creating a vibratory input to dynamically adjust the cancellation frequency for acoustical signals; 
     FIG. 2 is a schematic view of a second embodiment of a resonator, the resonator having means for continuously varying the mean resonator volume, means for continuously varying the mean resonator neck length, and means for creating a vibratory input to dynamically adjust the cancellation frequency for acoustical signals; 
     FIG. 3 is a schematic view of a third embodiment of a resonator, the resonator having means for continuously varying the mean resonator volume, means for continuously varying the mean resonator neck diameter, and means for creating a vibratory input to dynamically adjust the cancellation frequency for acoustical signals; 
     FIG. 4 is a schematic view of a fourth embodiment of a resonator, the resonator having means for continuously varying the mean resonator volume, means for continuously varying the mean resonator neck diameter, means for continuously varying the mean resonator neck length, and means for creating a vibratory input to dynamically adjust the cancellation frequency for acoustical signals; 
     FIG. 5 is a schematic view of a fifth embodiment of a resonator, the resonator having means for tuning including a plurality of necks of differing lengths with valves disposed therein and means for creating a vibratory input to dynamically adjust the cancellation frequency for acoustical signals; and 
     FIG. 6 is a schematic view of a sixth embodiment of a resonator, the resonator having means for tuning including a plurality of necks of differing lengths with valves disposed therein, means for continuously varying the mean resonator volume, and means for creating a vibratory input to dynamically adjust the cancellation frequency for acoustical signals. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, and particularly FIG. 1, there is shown generally at  10  an air resonator system incorporating the features of the invention. In the embodiment shown, a Helmholtz type resonator is used. It is understood that other resonator types could be used without departing from the scope and spirit of the invention. The air resonator system  10  includes a cylinder or housing  12 . A piston  14  is reciprocatively disposed in the housing  12 . A rod  16  is attached to the piston  14  and is operatively engaged with a positional controller  18  to vary a position of the piston  14  within the housing  12 . The housing  12  and the piston  14  cooperate to form a variable volume resonator chamber  20 . The chamber  20  communicates with a duct  22  through a resonator neck portion  24 . The duct  22  is in communication with an air intake system of a vehicle (not shown). 
     A first noise sensor  25  is connected to the duct  22 , upstream of the resonator system  10 . A second noise sensor  26  is connected to the duct  22 , downstream of the resonator system  10 . Any conventional noise sensor  25 ,  26  can be used such as a microphone, for example. The first noise sensor  25  and the second noise sensor  26  are in communication with a programmable control module of PCM  28 . An engine speed sensor  29  (engine not shown) is in communication with the PCM  28 . The PCM  28  is in communication with and controls the positional controller  18 . A vibratory displacement actuator  30  is disposed within the chamber  20  and is in communication with and controlled by the PCM  28 . An audio speaker or a ceramic actuator with a vibrating diaphragm may be used as the actuator  30 , for example. 
     In operation, the air resonator system  10  attenuates sound of varying frequencies. Air flows in the duct  22  to the engine, and sound energy or noise originates in the engine and flows from the engine to the atmosphere against the air flow. Alternatively, it is understood that the air resonator system  10  could be used in an exhaust system where the air flow and the noise flow are in the same direction, or from the engine. The noise enters the air resonator system  10  through the neck portion  24  and travels into the chamber  20 . The resonator system  10  may be tuned to attenuate different sound frequencies by varying one or more of the neck  24  diameter, the neck  24  length, and the chamber  20  volume. These are known as the mean resonator properties. In the embodiment shown in FIG. 1, the air resonator system  10  is tuned by varying the chamber  20  volume through varying the position of the piston  14  within the chamber  20 . 
     The first noise sensor  25  senses a sound level within the duct  22 . The sensed level is received by the PCM  28 . Based upon the noise level sensed, the PCM  28  causes the actuator  30  to create a vibratory input, or a dynamic resonator property, in the chamber  20  to prevent noise from propagating any further towards the air intake and to the atmosphere. The vibratory input of the actuator  30  is adjustable and therefore facilitates dynamic adjustment of the cancellation frequency. If the sensed noise frequency changes, the PCM  28  causes the actuator  30  to create a different vibratory input based upon the noise sensed. The second noise sensor  26  serves as an error sensor downstream of the actuator  30 . The second noise sensor  26  senses a noise level and sends a signal to the PCM  28 . The PCM  28  measures the difference between the output sound and a target level and facilitates further refining of the actuator  30  input. Care must be taken to avoid locating the second noise sensor  26  at a nodal point, which would result in a false reading that the noise has been attenuated. 
     Additionally, an engine speed is sensed by the engine speed sensor  29  and a signal is received by the PCM  28 . A desired position of the piston  14  is predetermined at engine speed increments and placed in a table in the PCM  28 . Thus, at a specific engine speed, the desired output is determined by table lookup in the PCM  28 . Based upon the engine speed sensed, the positional controller  18  causes the piston  14  to move to the desired position to attenuate the noise. If the engine speed changes, the PCM  28  will cause the piston  14  to move to a new desired position to attenuate the noise. 
     The combination of varying both the mean and dynamic properties of the resonator system  10  provides wide latitude in tuning the resonator system  10  for a desired noise frequency and canceling acoustic signals or noise in the air induction system for the vehicle. 
     Referring now to FIG. 2, there is shown generally at  10 ′ an air resonator system incorporating a second embodiment of the invention. In the embodiment shown, a Helmholtz type resonator is used. It is understood that other resonator types could be used without departing from the scope and spirit of the invention. The air resonator system  10 ′ includes a cylinder or housing  12 ′. A piston  14 ′ is reciprocatively disposed in the housing  12 ′. A rod  16 ′ is attached to the piston  14 ′ and is operatively engaged with a positional controller  18 ′ to vary a position of the piston  14 ′ within the housing  12 ′. The housing  12 ′ and the piston  14 ′ cooperate to form a variable volume resonator chamber  20 ′. The chamber  20 ′ communicates with a duct  22 ′ through a resonator neck portion  24 ′. The length of the neck  24 ′ is adjustable. In the embodiment shown, a flexible neck  24 ′ is shown. However, a neck  24 ′ which is telescoping, for example, may be used without departing from the scope and spirit of the invention. The duct  22 ′ is in communication with an air intake system of a vehicle (not shown). 
     A first noise sensor  25 ′ is connected to the duct  22 ′, upstream of the resonator system  10 ′. A second noise sensor  26 ′ is connected to the duct  22 ′, downstream of the resonator system  10 ′. Any conventional noise sensor  25 ′,  26 ′ can be used such as a microphone, for example. The first noise sensor  25 ′ and the second noise sensor  26 ′ are in communication with a programmable control module of PCM  28 ′. An engine speed sensor  29 ′ (engine not shown) is in communication with the PCM  28 ′. The PCM  28 ′ is in communication with and controls the positional controller  18 ′. A vibratory displacement actuator  30 ′ is disposed within the chamber  20 ′ and is in communication with and controlled by the PCM  28 ′. An audio speaker or a ceramic actuator with a vibrating diaphragm may be used as the actuator  30 ′, for example. A second positional controller  32 ′ is attached to the resonator system  10 ′ to vary the length of the neck  24 ′. The PCM  28 ′ is in communication with and controls the second positional controller  32 ′. 
     In operation, the air resonator system  10 ′ attenuates sound of varying frequencies. Air flows in the duct  22 ′ to the engine, and sound energy or noise originates in the engine and flows from the engine to the atmosphere against the air flow. Alternatively, it is understood that the air resonator system  10 ′ could be used in an exhaust system where the air flow and the noise flow are in the same direction, or from the engine. The noise enters the air resonator system  10 ′ through the neck portion  24 ′ and travels into the chamber  20 ′. In the embodiment shown in FIG. 2, the air resonator system  10 ′ is tuned by varying at least one of the chamber  20 ′ volume by varying the position of the piston  14 ′ within the chamber  20 ′ and by varying the neck  24 ′ length. 
     The first noise sensor  25 ′ senses a sound level within the duct  22 ′. The sensed level is received by the PCM  28 ′. Based upon the noise level sensed, the PCM  28 ′ causes the actuator  30 ′ to create a vibratory input, or a dynamic resonator property, in the chamber  20 ′ to prevent noise from propagating any further towards the air intake and to the atmosphere. The vibratory input of the actuator  30 ′ is adjustable and therefore facilitates dynamic adjustment of the cancellation frequency. If the sensed noise frequency changes, the PCM  28 ′ causes the actuator  30 ′ to create a different vibratory input based upon the noise sensed. The second noise sensor  26 ′ serves as an error sensor downstream of the actuator  30 ′. The second noise sensor  26 ′ senses a noise level and sends a signal to the PCM  28 ′. The PCM  28 ′ measures the difference between the output sound and a target level and facilitates further refining of the actuator  30 ′ input. Care must be taken to avoid locating the second noise sensor  26 ′ at a nodal point, which would result in a false reading that the noise has been attenuated. 
     Additionally, an engine speed is sensed by the engine speed sensor  29 ′ and a signal is received by the PCM  28 ′. A desired position of the piston  14 ′ and a desired length of the neck  24 ′ are predetermined at engine speed increments and placed in a table in the PCM  28 ′. Thus, at a specific engine speed, the desired output is determined by table lookup in the PCM  28 ′. Based upon the engine speed sensed, the positional controller  18 ′ causes the piston  14 ′ to move to the desired position to attenuate the noise. Alternatively, the second actuator  32 ′ is caused to change the length of the neck  24 ′ to attenuate the noise as desired. If it is desired, both the volume of the chamber  20 ′ and the length of the neck  24 ′ can be simultaneously varied to tune the resonator system  10 ′ to attenuate a desired noise frequency. If the engine speed changes, the PCM  28 ′ will cause the piston  14 ′ to move to a new desired position or cause the length of the neck  24 ′ to change to attenuate the noise. 
     The combination of varying both the mean and dynamic properties of the resonator system  10 ′ provides wide latitude in tuning the resonator system  10 ′ for a desired noise frequency and canceling acoustic signals or noise in the air induction system for the vehicle. 
     Referring now to FIG. 3, there is shown generally at  10 ″ an air resonator system incorporating a third embodiment of the invention. In the embodiment shown, a Helmholtz type resonator is used. It is understood that other resonator types could be used without departing from the scope and spirit of the invention. The air resonator system  10 ″ includes a cylinder or housing  12 ″. A piston  14 ″ is reciprocatively disposed in the housing  12 ″. A rod  16 ″ is attached to the piston  14 ″ and is operatively engaged with a positional controller  18 ″ to vary a position of the piston  14 ″ within the housing  12 ″. The housing  12 ″ and the piston  14 ″ cooperate to form a variable volume resonator chamber  20 ′. The chamber  20 ′ communicates with a duct  22 ″ through a resonator neck portion  24 ″. The diameter of the neck  24 ″ is adjustable. In the embodiment shown, a neck  24 ″ having only a portion of the diameter adjustable is shown. However, a neck  24 ″ where the diameter over the entire length, may be used without departing from the scope and spirit of the invention. To tune the resonator system  10 ″, changing the neck  24 ″ diameter only at one portion is sufficient. However, varying the neck  24 ″ diameter over the entire length will yield similar tuning characteristics. The duct  22 ″ is in communication with an air intake system of a vehicle (not shown). 
     A first noise sensor  25 ″ is connected to the duct  22 ″, upstream of the resonator system  10 ″. A second noise sensor  26 ″ is connected to the duct  22 ″, downstream of the resonator system  10 ″. Any conventional noise sensor  25 ″,  26 ″ can be used such as a microphone, for example. The first noise sensor  25 ″ and the second noise sensor  26 ″ are in communication with a programmable control module of PCM  28 ″. An engine speed sensor  29 ″ (engine not shown) is in communication with the PCM  28 ″. The PCM  28 ″ is in communication with and controls the positional controller  18 ″. A vibratory displacement actuator  30 ″ is disposed within the chamber  20 ″ and is in communication with and controlled by the PCM  28 ″. An audio speaker or a ceramic actuator with a vibrating diaphragm may be used as the actuator  30 ″, for example. A third positional controller  34 ″ is attached to the neck  24 ″ of the resonator system  10 ″ to vary the diameter of the neck  24 ″. The PCM  28 ″ is in communication with and controls the third positional controller  34 ″. 
     In operation, the air resonator system  10 ″ attenuates sound of varying frequencies. Air flows in the duct  22 ″ to the engine, and sound energy or noise originates in the engine and flows from the engine to the atmosphere against the air flow. Alternatively, it is understood that the air resonator system  10 ″ could be used in an exhaust system where the air flow and the noise flow are in the same direction, or from the engine. The noise enters the air resonator system  10 ″ through the neck portion  24 ″ and travels into the chamber  20 ″. In the embodiment shown in FIG. 3, the air resonator system  10 ″ is tuned by varying at least one of the volume of the chamber  20 ″ by varying the position of the piston  14 ″ within the chamber  20 ″ and by varying the diameter of the neck  24 ″. 
     The first noise sensor  25 ″ senses a sound level within the duct  22 ″. The sensed level is received by the PCM  28 ″. Based upon the noise level sensed, the PCM  28 ″ causes the actuator  30 ″ to create a vibratory input, or a dynamic resonator property, in the chamber  20 ″ to prevent noise from propagating any further towards the air intake and to the atmosphere. The vibratory input of the actuator  30 ″ is adjustable and therefore facilitates dynamic adjustment of the cancellation frequency. If the sensed noise frequency changes, the PCM  28 ″ causes the actuator  30 ″ to create a different vibratory input based upon the noise sensed. The second noise sensor  26 ″ serves as an error sensor downstream of the actuator  30 ″. The second noise sensor  26 ″ senses a noise level and sends a signal to the PCM  28 ″. The PCM  28 ″ measures the difference between the output sound and a target level and facilitates further refining of the actuator  30 ″ input. Care must be taken to avoid locating the second noise sensor  26 ″ at a nodal point, which would result in a false reading that the noise has been attenuated. 
     Additionally, an engine speed is sensed by the engine speed sensor  29 ″ and a signal is received by the PCM  28 ″. A desired position of the piston  14 ″ and a desired diameter of the neck  24 ″ are predetermined at engine speed increments and placed in a table in the PCM  28 ″. Thus, at a specific engine speed, the desired output is determined by table lookup in the PCM  28 ″. Based upon the engine speed sensed, the positional controller  18 ″ causes the piston  14 ″ to move to the desired position to attenuate the noise. Alternatively, the third positional controller  34 ″ causes the diameter of the neck  24 ″ to change to attenuate the noise as desired. If it is desired, both the volume of the chamber  20 ″ and the diameter of the neck  24 ″ can be simultaneously varied to tune the resonator system  10 ″ to attenuate a desired noise frequency. If the engine speed changes, the PCM  28 ″ will cause the piston  14 ″ to move to a new desired position or cause the diameter of the neck  24 ″ to change to attenuate the noise. 
     The combination of varying both the mean and dynamic properties of the resonator system  10 ″ provides wide latitude in tuning the resonator system  10 ″ for a desired noise frequency and canceling acoustic signals or noise in the air induction system for the vehicle. 
     Referring now to FIG. 4, there is shown generally at  10 ′″ an air resonator system incorporating a fourth embodiment of the invention. In the embodiment shown, a Helmholtz type resonator is used. It is understood that other resonator types could be used without departing from the scope and spirit of the invention. The air resonator system  10 ′″ includes a cylinder or housing  12 ′″. A piston  14 ′″ is reciprocatively disposed in the housing  12 ′″. A rod  16 ′″ is attached to the piston  14 ′″ and is operatively engaged with a positional controller  18 ′″ to vary a position of the piston  14 ′″ within the housing  12 ′″. The housing  12 ′″ and the piston  14 ′″ cooperate to form a variable volume resonator chamber  20 ′″. The chamber  20 ′″ communicates with a duct  22 ′″ through a resonator neck portion  24 ′″. The length and diameter of the neck  24 ′″ are adjustable. In the embodiment shown, a flexible neck  24 ′″ is shown. However, a neck  24 ′″ which is telescoping, for example, may be used without departing from the scope and spirit of the invention. Also, in the embodiment shown, a neck  24 ′″ having only a portion of the diameter adjustable is shown. However, a neck  24 ′″ where the diameter over the entire length, may be used without departing from the scope and spirit of the invention. To tune the resonator system  10 ′″, changing the neck  24 ′″ diameter only at one portion is sufficient. However, varying the neck  24 ′″ diameter over the entire length will yield similar tuning characteristics. The duct  22 ′″ is in communication with an air intake system of a vehicle (not shown). 
     A first noise sensor  25 ′″ is connected to the duct  22 ′″, upstream of the resonator system  10 ′″. A second noise sensor  26 ′″ is connected to the duct  22 ′″, downstream of the resonator system  10 ′″. Any conventional noise sensor  25 ′″,  26 ′″ can be used such as a microphone, for example. The first noise sensor  25 ′″ and the second noise sensor  26 ′″ are in communication with a programmable control module of PCM  28 ′″. An engine speed sensor  29 ′″ (engine not shown) is in communication with the PCM  28 ′″. The PCM  28 ′″ is in communication with and controls the positional controller  18 ′″. A vibratory displacement actuator  30 ′″ is disposed within the chamber  20 ′″ and is in communication with and controlled by the PCM  28 ′″. An audio speaker or a ceramic actuator with a vibrating diaphragm may be used as the actuator  30 ′″, for example. A second positional controller  32 ′″ is attached to the resonator system  10 ′″ to vary the length of the neck  24 ′″. The PCM  28 ′″ is in communication with and controls the second positional controller  32 ′″. A third positional controller  34 ′″ is attached to the neck  24 ′″ of the resonator system  10 ′″ to vary the diameter of the neck  24 ′″. The PCM  28 ′″ is in communication with and controls the third positional controller  34 ′″. 
     In operation, the air resonator system  10 ′″ attenuates sound of varying frequencies. Air flows in the duct  22 ′″ to the engine, and sound energy or noise originates in the engine and flows from the engine to the atmosphere against the air flow. Alternatively, it is understood that the air resonator system  10 ′″ could be used in an exhaust system where the air flow and the noise flow are in the same direction, or from the engine. The noise enters the air resonator system  10 ′″ through the neck portion  24 ′″ and travels into the chamber  20 ′″. In the embodiment shown in FIG. 4, the air resonator system  10 ′″ is tuned by varying at least one of the volume of the chamber  20 ′″ by varying the position of the piston  14 ′″ within the chamber  20 ′″; by varying the length of the neck  24 ′″, and by varying the diameter of the neck  24 ′″. 
     The first noise sensor  25 ′″ senses a sound level within the duct  22 ′″. The sensed level is received by the PCM  28 ′″. Based upon the noise level sensed, the PCM  28 ′″ causes the actuator  30 ′″ to create a vibratory input, or a dynamic resonator property, in the chamber  20 ′″ to prevent noise from propagating any further towards the air intake and to the atmosphere. The vibratory input of the actuator  30 ′″ is adjustable and therefore facilitates dynamic adjustment of the cancellation frequency. If the sensed noise frequency changes, the PCM  28 ′″ causes the actuator  30 ″ to create a different vibratory input based upon the noise sensed. The second noise sensor  26 ′″ serves as an error sensor downstream of the actuator  30 ′″. The second noise sensor  26 ′″ senses a noise level and sends a signal to the PCM  28 ′″. The PCM  28 ′″ measures the difference between the output sound and a target level and facilitates further refining of the actuator  30 ′″ input. Care must be taken to avoid locating the second noise sensor  26 ′″ at a nodal point, which would result in a false reading that the noise has been attenuated. 
     Additionally, an engine speed is sensed by the engine speed sensor  29 ′″ and a signal is received by the PCM  28 ′″. A desired position of the piston  14 ′″, a desired length of the neck  24 ′″, and a desired diameter of the neck  24 ′″ are predetermined at engine speed increments and placed in a table in the PCM  28 ′″. Thus, at a specific engine speed, the desired outputs are determined by table lookup in the PCM  28 ′″. Based upon the engine speed sensed, the positional controller  18 ′″ causes the piston  14 ′″ to move to the desired position to attenuate the noise. The second positional controller  32 ′″ can also cause the length of the neck  24 ′″ to change to attenuate the noise as desired. Alternatively, the third positional controller  34 ′″ causes the diameter of the neck  24 ′″ to change to attenuate the noise as desired. If it is desired, the volume of the chamber  20 ′″, the length of the neck  24 ′″, and the diameter of the neck  24 ′″, can all be simultaneously varied, or any combination thereof, to tune the resonator system  10 ′″ to attenuate a desired noise frequency. If the engine speed changes, the PCM  28 ′″ will cause the piston  14 ′″ to move to a new desired position, cause the length of the neck  24 ′″ to change, or cause the diameter of the neck  24 ′″ to change to attenuate the noise. 
     The combination of varying both the mean and dynamic properties of the resonator system  10 ′″ provides wide latitude in tuning the resonator system  10 ′″ for a desired noise frequency and canceling acoustic signals or noise in the air induction system for the vehicle. 
     Referring now to FIG. 5, there is shown generally at  40  an air resonator system incorporating a fifth embodiment of the invention. In the embodiment shown, a Helmholtz type resonator is used. It is understood that other resonator types could be used without departing from the scope and spirit of the invention. The air resonator system  40  includes a housing  42  which defines a resonator chamber  44 . The chamber  44  communicates with a duct  46  through a plurality of neck portion portions  48 . In the embodiment shown, four neck portions  48  are included in the resonator system  40 . It is understood that more or fewer neck portions  48  could be used as desired without departing from the scope and spirit of the invention. A solenoid valve  58  is disposed in each of the neck portions  48 . An actuator or a positional controller  60  is disposed on each of the solenoid valves  58 . It is understood that other valve types and other actuator types could be used without departing from the scope and spirit of the invention. The duct  46  is in communication with an air intake system of a vehicle (not shown). 
     A first noise sensor  53  is connected to the duct  46 , upstream of the air resonator system  40 . A second noise sensor  54  is connected to the duct  46 , downstream of the air resonator system  40 . Any conventional noise sensor  53 ,  54  can be used such as a microphone, for example. The first noise sensor  53  and the second noise sensor  54  are in communication with a programmable control module or PCM  56 . An engine speed sensor  57  (engine not shown) is in communication with the PCM  56 . The PCM  56  is in communication with and controls each of the positional controllers  60 . 
     A vibratory displacement actuator  62  is disposed within the chamber  44  and is in communication with and controlled by the PCM  56 . An audio speaker or a ceramic actuator with a vibrating diaphragm may be used as the actuator  62 , for example. 
     In operation, the air resonator system  40  attenuates sound of varying frequencies. Air flows in the duct  46  to the engine, and sound energy or noise originates in the engine and flows from the engine to the atmosphere against the air flow. Alternatively, it is understood that the air resonator system  40  could be used in an exhaust system where the air flow and the noise flow are in the same direction, or from the engine. The noise enters the air resonator system  40  through at least one of the neck portions  48  and travels into the chamber  44 . The resonator system  40  may be tuned to attenuate different sound frequencies by varying one or more of the neck diameter, the neck length, and the chamber  44  volume. These are known as the mean resonator properties. In the embodiment shown in FIG. 5, the resonator system  40  is tuned to attenuate different sound frequencies by selectively opening and closing the solenoid valves  58  to vary a length of the neck portion  48 . By using a proportional control type solenoid valve  58 , a diameter of the neck portion  48  can be controlled by controlling the degree which the solenoid valve  58  is open, thus changing two of the mean resonator properties. It is understood if it is desired to control only a neck length that on/off type solenoid valves can be used. It is also understood that by opening particular combinations of the solenoid valves  58  to change the diameter of the neck portion  48  and/or the length of the neck portion  48  the resonator system  40  can be tuned. 
     The first noise sensor  53  senses a sound level within the duct  46 . The sensed level is received by the PCM  56 . Based upon the noise level sensed, the PCM  56  causes the actuator  62  to create a vibratory input, or a dynamic resonator property, in the chamber  44  to prevent noise from propagating any further towards the air intake and to the atmosphere. The vibratory input of the actuator  62  is adjustable and therefore facilitates dynamic adjustment of the cancellation frequency. If the sensed noise frequency changes, the PCM  56  causes the actuator  62  to create a different vibratory input based upon the noise sensed. The second noise sensor  54  serves as an error sensor downstream of the actuator  62 . The second noise sensor  54  senses a noise level and sends a signal to the PCM  56 . The PCM  56  measures the difference between the output sound and a target level and facilitates further refining of the actuator  62  input. Care must be taken to avoid locating the second noise sensor  54  at a nodal point, which would result in a false reading that the noise has been attenuated. 
     Additionally, an engine speed is sensed by the engine speed sensor  57  and a signal is received by the PCM  56 . A desired position of the solenoid valves  58  are predetermined at engine speed increments and placed in a table in the PCM  56 . Thus, at a specific engine speed, the desired outputs are determined by table lookup in the PCM  56 . Based upon the engine speed sensed, the PCM  56  causes the positional controller  60  to open the appropriate combination of solenoid valves  58  disposed in the neck portion  48  to provide the desired tuning which will attenuate the noise. If the engine speed changes, the PCM  56  will cause a different combination of positional controllers  60  to open a different combination of solenoid valves  58  disposed in the neck portion  48  to provide the desired tuning which will attenuate the noise. By using the proportional control type solenoid valve  58 , the resonator system  40  provides both an incremental change in the neck portion  48  length and/or a continuous change in the neck portion  48  diameter. 
     The combination of varying both the mean and dynamic properties of the resonator system  10  provides wide latitude in tuning the resonator system  10  for a desired noise frequency and canceling acoustic signals or noise in the air induction system for the vehicle. 
     Referring now to FIG. 6, there is shown generally at  40 ′ an air resonator system incorporating a sixth embodiment of the invention. In the embodiment shown, a Helmholtz type resonator is used. It is understood that other resonator types could be used without departing from the scope and spirit of the invention. The air resonator system  40 ′ includes a housing  42 ′ which defines a resonator chamber  44 ′. A piston  64 ′ is reciprocatively disposed in the housing  42 ′. A rod  66 ′ is attached to the piston  64 ′ and is operatively engaged with an actuator or a positional controller  68 ′ to vary a position of the piston  64 ′ within the housing  42 ′. The housing  42 ′ and the piston  64 ′ cooperate to vary the volume of the chamber  44 ′. 
     The chamber  44 ′ communicates with a duct  46 ′ through a plurality of neck portions  48 ′. In the embodiment shown, four neck portions  48 ′ are included in the resonator system  40 ′. It is understood that more or fewer neck portions  48 ′ could be used as desired without departing from the scope and spirit of the invention. A solenoid valve  58 ′ is disposed in each of the neck portions  48 ′. An actuator or a positional controller  60 ′ is connected to each of the solenoid valves  58 ′. It is understood that other valve types and other actuator types could be used without departing from the scope and spirit of the invention. The duct  46 ′ is in communication with an air intake system of a vehicle (not shown). 
     A first noise sensor  53 ′ is connected to the duct  46 ′, upstream of the air resonator system  40 ′. A second noise sensor  54 ′ is connected to the duct  46 ′, downstream of the air resonator system  40 ′. Any conventional noise sensor  53 ′,  54 ′ can be used such as a microphone, for example. The first noise sensor  53 ′ and the second noise sensor  54 ′ are in communication with a programmable control module or PCM  56 ′. An engine speed sensor  57 ′ (engine not shown) is in communication with the PCM  56 ′. The PCM  56 ′ is in communication with and controls each of the positional controllers  60 ′. 
     A vibratory displacement actuator  62 ′ is disposed within the chamber  44 ′ and is in communication with and controlled by the PCM  56 ′. An audio speaker or a ceramic actuator with a vibrating diaphragm may be used as the actuator  62 ′, for example. 
     In operation, the air resonator system  40 ′ attenuates sound of varying frequencies. Air flows in the duct  46 ′ to the engine, and sound energy or noise originates in the engine and flows from the engine to the atmosphere against the air flow. Alternatively, it is understood that the air resonator system  40 ′ could be used in an exhaust system where the air flow and the noise flow are in the same direction, or from the engine. The noise enters the air resonator system  40 ′ through at least one of the neck portions  48 ′ and travels into the chamber  44 ′. The resonator system  40 ′ may be tuned to attenuate different sound frequencies by varying one or more of the neck diameter, the neck length, and the chamber  44 ′ volume. These are known as the mean resonator properties. In the embodiment shown in FIG. 6, the resonator system  40 ′ is tuned to attenuate different sound frequencies by selectively opening and closing the solenoid valves  58 ′ to vary a length of the neck portion  48 ′, or by opening particular combinations of solenoid valves  58 ′ to change the effective length and area of the neck portion  48 ′. By using a proportional control type solenoid valve  58 ′, a diameter of the neck portion  48 ′ can be controlled by controlling the degree which the solenoid valve  58 ′ is open, thus changing two of the mean resonator properties. It is understood if it is desired to control only a neck length that on/off type solenoid valves can be used. 
     The first noise sensor  53 ′ senses a sound level within the duct  46 ′. The′sensed level is received by the PCM  56 ′. Based upon the noise level sensed, the PCM  56 ′ causes the actuator  62 ′ to create a vibratory input, or a dynamic resonator property, in the chamber  44 ′ to prevent noise from propagating any further towards the air intake and to the atmosphere. The vibratory input of the actuator  62 ′ is adjustable and therefore facilitates dynamic adjustment of the cancellation frequency. If the sensed noise frequency changes, the PCM  56 ′ causes the actuator  62 ′ to create a different vibratory input based upon the noise sensed. The second noise sensor  54 ′ serves as an error sensor downstream of the actuator  62 ′. The second noise sensor  54 ′ senses a noise level and sends a signal to the PCM  56 ′. The PCM  56 ′ measures the difference between the output sound and a target level and facilitates further refining of the actuator  62 ′ input. Care must be taken to avoid locating the second noise sensor  54 ′ at a nodal point, which would result in a false reading that the noise has been attenuated. 
     Additionally, an engine speed is sensed by the engine speed sensor  57 ′ and a signal is received by the PCM  56 ′. A desired position of the solenoid valves  58  and a desired position of the piston  64 ′ are predetermined at engine speed increments and placed in a table in the PCM  56 ′. Thus, at a specific engine speed, the desired output is determined by table lookup in the PCM  56 ′. Based upon the engine speed sensed, the PCM  56 ′ causes the positional controller  60 ′ to open the appropriate combination of solenoid valves  58 ′ disposed in the neck portion  48 ′ having the desired length and/or total area which will attenuate the noise. If the engine speed changes, the PCM  56 ′ will cause a different positional controller  60 ′ to open the solenoid valve  58 ′ disposed in the neck portion  48 ′ having the desired length which will attenuate the noise. By using the proportional control type solenoid valve  58 ′, the resonator system  40 ′ provides both an incremental change in the neck portion  48 ′ length, and a continuous change in the neck portion  48 ′ diameter. The noise can also be attenuated by varying the chamber  44 ′ volume by varying the position of the piston  64 ′ within the chamber  44 ′. Based upon the engine speed, the PCM  56 ′ causes the positional controller  68 ′ to move the piston  64 ′ to a desired position to attenuate the noise. If the engine speed changes, the PCM  56 ′ will cause the piston  64 ′ to move to a new desired position to attenuate the noise. 
     If it is desired, the volume of the chamber  44 ′, the length of the neck portion  48 ′, and the diameter of the neck portion  48 ′, can all be simultaneously varied, or any combination thereof, to tune the resonator system  40 ′ to attenuate a desired noise frequency. If the engine speed changes, the PCM  56 ′ will cause the piston  64 ′ to move to a new desired position, cause the length of the neck portion  48 ′ to change, or cause the diameter of the neck portion  48 ′ to change to attenuate the noise. 
     The combination of varying both the mean and dynamic properties of the resonator system  40 ′ provides wide latitude in tuning the resonator system  40 ′ for a desired noise frequency and canceling acoustic signals or noise in the air induction system for the vehicle. 
     Two noise control structures have been discussed above and illustrated in the drawings. First is a system having a variable geometry resonator wherein at least one of a neck length, a neck diameter, and a resonator volume are changed to attenuate a desired noise. This type of system can be used for applications requiring the modification of a single noise frequency at each engine speed. As disclosed for the invention, the variable geometry system can incorporate continuously variable or discretely variable systems. The second system is an active noise system incorporating an actuator to create a vibratory input to cancel noise. A system of this type can be used for applications requiring the modification of multiple frequencies at each engine speed. However, using an active system alone can result in large, heavy, and expensive actuator systems. By combining the two systems, a wide range of complex noises can be attenuated and the size, weight, and cost of the actuator for the active noise system can be minimized. 
     From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.