System and method for optimized active controller design in an ANR system
View Patent ↗A tailored active noise control design method is presented that provides for improved noise attenuation performance for each individual user and improved hearing protection in a specified noise field as a function of a specified metric indicative of a noise reduction objection. Characteristics of individual users, behavior of the associated passive hearing protection, and the external noise environment are all concurrently accounted for in an automatic method for designing an active controller that limits the exposed noise level for a specific individual. The controller manufacturing process and implementation may be performed in-situ for each individual automatically. The design method may also account for actuator limitations and can be applied equally well to any passive/active noise control devices including headphones and earplugs.
1. A method for customizing a transfer function H for providing active noise reduction tailored to a user of a sound reduction device:
determining an ambient noise field “N” over a spectral segment;
selecting a design metric “M” indicative of a noise reduction objective for the sound reduction device;
determining a measure of the passive performance “P” of the sound reduction device;
determining a measure of the acoustic dynamic response “G” of a user of the sound reduction device to a control signal; and
customizing a transfer function “H” for the user based on “N”, “P” and “G” by minimizing a cost function of the form J=E[e T e], wherein
e
=
[
NMP
1
+
GH
]
n
represents the shaped signal whose average power J is equivalent to the chosen metric M for the user's plant G in the noise field N and passive control P, wherein “H” is tailored for the user of the controller processor;
receiving the customized transfer function “H” at the controller processor; and
implementing the customized transfer function “H” in a feedback control loop to achieve the noise reduction objective for the user.
2. The method for determining a transfer function H for providing active noise reduction tailored to a user of a sound reduction device of claim 1 , wherein selecting a design metric indicative of a noise reduction objective comprises selecting a design metric from the group consisting of a calculation of the amplitude-weighted sound pressure level, C-weighted sound pressure level, and loudness.
3. The method for determining a transfer function H for providing active noise reduction tailored to a user of a sound reduction device of claim 1 , wherein selecting a design metric indicative of a noise reduction objective comprises selecting a design metric indicative of hearing protection.
4. The method for determining a transfer function H for providing active noise reduction tailored to a user of a sound reduction device claim 1 , wherein selecting a design metric indicative of a noise reduction objective comprises selecting a design metric from a library of design metrics.
5. The method for determining a transfer function H for providing active noise reduction tailored to a user of a sound reduction device of claim 1 , wherein determining an ambient noise field “N” over a spectral segment comprises selecting an ambient noise field “N” from a library of noise fields.
6. The method for determining a transfer function H for providing active noise reduction tailored to a user of a sound reduction device of claim 1 , wherein the method further comprises optimizing the transfer function “H”.
7. A configurable controller for an active sound reduction device comprising a controller processor adapted to implement a transfer function “H” produced according to the method of claim 4 .
8. A configurable controller for an active sound reduction device comprising a controller processor adapted to implement transfer function “H” produced according to the method of claim 1 .
9. The method for determining a transfer function H for providing active noise reduction tailored to a user of a sound reduction device of claim 1 , further comprising:
means for determining whether a change has occurred in an ambient noise field “N” over a spectral segment used to determine the transfer function “H”;
means for determining whether a change has occurred in a measure of the passive performance “P” of a hearing protection device used to determine the transfer function “H”;
means for determining whether a change has occurred in a measure of the acoustic dynamic response “G” of a user of the hearing protection device to a control signal used to determine the transfer function “H”; and
applying means for producing a revised transfer function “H R ” if a change is detected in any one of N, P, and G.
10. The method for determining a transfer function H for providing active noise reduction tailored to a user of a sound reduction device of claim 9 further comprising:
means for selecting a design metric indicative of a noise reduction objective;
means for determining whether the selected design metric differs from the design metric used to determine the transfer function “H”; and
applying means for producing a revised transfer function “H R ” if the selected design metric differs from the from the design metric used to determine the transfer function “H”.