Hybrid mode-scattering/sound-absorbing segmented liner system and method

A hybrid mode-scattering/sound-absorbing segmented liner system for attenuating a sound field in a duct comprising:

• a mode-scattering segment capable of mode scattering an initial sound field in the duct;
• an active-control component within the mode-scattering segment comprising a controller, a reference signal determined from the initial sound field, and a sound-generating device, whereby the controller, in response to the reference signal, is capable of causing the sound-generating device to generate sound that mode scatters the initial sound field into an altered sound field;
• and
• a sound-absorbing segment positioned acoustically downstream of the mode-scattering segment and that is capable of attenuating the altered sound field, resulting in an attenuated sound field;
• wherein the sound-generating device is a piezoelectric transducer and wherein the sound-absorbing segment further comprises an active-control component to attenuate the altered sound field.

A hybrid mode-scattering/sound-absorbing segmented liner system for attenuating a sound field in a duct comprising:

• a mode-scattering segment capable of mode scattering an initial sound field in the duct;
• an active-control component within the mode-scattering segment comprising a controller, a reference signal determined from the initial sound field, and a sound-generating device, whereby the controller, in response to the reference signal, is capable of causing the sound-generating device to generate sound that mode scatters the initial sound field into an altered sound field;
• and
• a sound-absorbing segment positioned acoustically downstream of the mode-scattering segment and that is capable of attenuating the altered sound field, resulting in an attenuated sound field;
• wherein the reference signal is determined by a microphone positioned acoustically upstream of the mode-scattering segment.

A hybrid mode-scattering/sound-absorbing segmented liner system for attenuating a sound field in a duct comprising:

• a mode-scattering segment capable of mode scattering an initial sound field in the duct;
• an active-control component within the mode-scattering segment comprising a controller, a reference signal determined from the initial sound field, and a sound-generating device, whereby the controller, in response to the reference signal, is capable of causing the sound-generating device to generate sound that mode scatters the initial sound field into an altered sound field;
• and
• a sound-absorbing segment positioned acoustically downstream of the mode-scattering segment and that is capable of attenuating the altered sound field, resulting in an attenuated sound field;
• wherein the initial sound field is generated by a fan positioned within the duct, and wherein the reference signal is determined from a fan tachometer that measures the rotational speed of the fan.

A hybrid mode-scattering/sound-absorbing segmented liner system for attenuating a sound field in a duct comprising:

• a mode-scattering segment capable of mode scattering an initial sound field in the duct;
• an active-control component within the mode-scattering segment comprising a controller, a reference signal determined from the initial sound field, and a sound-generating device, whereby the controller, in response to the reference signal, is capable of causing the sound-generating device to generate sound that mode scatters the initial sound field into an altered sound field;
• a sound-absorbing segment positioned acoustically downstream of the mode-scattering segment and that is capable of attenuating the altered sound field, resulting in an attenuated sound field;
• and
• an altered sound-measuring component positioned acoustically downstream of the mode-scattering segment and acoustically upstream of the sound-absorbing segment and that is capable of continuously measuring the altered sound field, wherein the controller, in response to the altered sound field as measured by the altered sound-measuring device, is capable of continuously altering the sound-generating device to maximize the mode scattering of the active-control component.

A hybrid mode-scattering/sound-absorbing segmented liner system for attenuating a sound field in a duct comprising:

• a mode-scattering segment capable of mode scattering an initial sound field in the duct;
• an active-control component within the mode-scattering segment comprising a controller, a reference signal determined from the initial sound field, and a sound-generating device, whereby the controller, in response to the reference signal, is capable of causing the sound-generating device to generate sound that mode scatters the initial sound field into an altered sound field;
• a sound-absorbing segment positioned acoustically downstream of the mode-scattering segment and that is capable of attenuating the altered sound field, resulting in an attenuated sound field;
• and
• an error sound-measuring component positioned acoustically downstream of the sound-absorbing segment and that is capable of continuously measuring the attenuated sound field, wherein the controller, in response to the attenuated sound field as measured by the error sound-measuring device, is capable of continuously altering the sound-generating device to minimize the attenuated sound field.

A method for attenuating a sound field in a duct having an initial propagation angle in a duct comprising the steps of:

• determining the initial sound field in the duct;
• calculating an appropriate added sound field in response to the determined initial sound field such that the added sound field would mode scatter the initial sound field;
• generating an added sound field in the duct that mode scatters the initial sound field into an altered sound field;
• and
• attenuating the altered sound to produce an attenuated sound field;
• wherein the sound field is generated by a fan within the duct, and wherein the step of determining the initial sound field further comprises the step of measuring the rotational speed of the fan.

A method for attenuating a sound field in a duct having an initial propagation angle in a duct comprising the steps of:

• determining the initial sound field in the duct;
• calculating an appropriate added sound field in response to the determined initial sound field such that the added sound field would mode scatter the initial sound field;
• generating an added sound field in the duct that mode scatters the initial sound field into an altered sound field;
• and
• attenuating the altered sound to produce an attenuated sound field;
• wherein:
• the step of calculating the added sound field further comprises the step of continuously determining the attenuated sound field;
• and
• the step of generating the added sound field further comprises continuously altering the added sound field in response to the attenuated sound field to minimize the attenuated sound field.