Disclosure of Invention
In order to overcome the above-mentioned drawbacks of the prior art, the present invention provides a method for estimating the noise reduction effect of an active noise control system.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a noise reduction effect estimation method of an active noise control system comprises the following steps,
s1, an error microphone picks up an error signal E of a secondary sound field in real time;
s2, estimating a primary noise signal D=E-Y of an error point, wherein an acoustic signal of a secondary sound source S reaching an error microphone E point through a secondary channel H is Y;
s3, calculating the sound pressure levels of the primary sound field and the secondary sound field of the error point;
s4, the sound pressure level difference of the primary sound field and the secondary sound field is the noise reduction amount, and the noise reduction amount can be used for evaluating the noise reduction effect.
Wherein:
the noise reduction amount calculation flow of the dual-channel active noise control system is as follows:
a. recording an error point real-time noise signal E, and outputting a signal S by a secondary sound source in real time;
b. the secondary sound source S reaches the acoustic signal Y at the point of the error microphone E via the secondary path H:
Y＝HT S
c. calculating the primary sound field, i.e. the desired signal D:
D＝E-Y
d. calculating noise level L of primary sound field and secondary sound field respectivelyd And Le ：
Where D (n) is the sound pressure signal at a certain moment of the desired signal D
Where E (n) is the sound pressure signal at a certain moment of the error signal E
e. Noise reduction amount LΔ Calculation of
LΔ ＝Ld -Le
Thereby completing the noise reduction estimation of the two-channel system;
the noise reduction amount calculation flow of the single-channel active noise control system is as follows:
a. error signal pickup:
the error point real-time noise signal e (n) is acquired in real time through an error microphone of the system;
b. calculating an error point secondary acoustic signal y (n) estimate:
y (n) =h (m) ×s (n) where h (m) is the path transfer function of the secondary source to the error microphone
c. Calculating an error point primary sound field signal estimated value d (n):
d(n)＝e(n)-y(n)
d. noise levels of the primary and secondary sound fields of the error point are calculated:
the calculation formula of the sound pressure level is:wherein p isref ＝2.0×10-5 P is the average sound pressure,
i.e.
From the above the error point primary sound field sound pressure level Ld The calculation formula is as follows:
error point secondary sound field sound pressure level Le The calculation formula is as follows:
noise reduction amount LΔ The calculation formula is as follows:
LΔ ＝Ld -Le
thereby completing the noise reduction amount estimation of the single channel system.
Further, in the step S3, if the sound level is required, the sound level is calculated after the filtering of the weight of the sound level.
Further, for the dual-channel active noise reduction system, the secondary sound source S is used for generating a secondary sound field, and is overlapped with the primary sound field, so that the purpose of reducing noise is achieved; the error microphone E is used for picking up an error signal of the secondary sound field; h represents a secondary path; d is denoted as the primary sound field before noise reduction; y is denoted as the secondary sound field where the secondary sound source S reaches the point of the error microphone E via the secondary path H.
The invention has the technical effects and advantages that:
1. the noise reduction effect, namely the noise reduction amount, is calculated and estimated in real time;
2. the control strategy can be changed according to the estimated noise reduction, so that the method has strong engineering application value;
3. the method for estimating the noise reduction amount of the active noise reduction system is provided explicitly, no additional hardware facilities are needed, and the implementation cost is low;
4. aiming at the double-channel active noise reduction system, the signal coupling between channels is considered, and the estimation accuracy is high, real-time and accurate;
5. the technology is suitable for people working at fixed points in a noisy environment for a long time, such as a noise reduction system arranged in a cab and a passenger cabin of an airplane, a locomotive, an automobile and the like, and is convenient for evaluating and feeding back the performance of the noise reduction system in real time.
Detailed Description
The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
The noise reduction effect estimation method of the active noise reduction system mainly comprises three parts of signal acquisition, filtering and estimation. A noise reduction effect estimation method of an active noise control system as shown in fig. 1, includes the steps of,
s1, an error microphone picks up an error signal E of a secondary sound field in real time;
s2, estimating a primary noise signal D=E-Y of an error point, wherein an acoustic signal of a secondary sound source S reaching an error microphone E point through a secondary channel H is Y;
s3, calculating the sound pressure levels of the primary sound field and the secondary sound field of the error point;
s4, the sound pressure level difference of the primary sound field and the secondary sound field is the noise reduction amount, and the noise reduction amount can be used for evaluating the noise reduction effect. The error signal E and the secondary path transfer function H required for the noise reduction effect estimation process are known in the noise reduction system.
Example two
The noise reduction amount calculation flow of the adaptive active noise control system is as follows:
a. recording an error point real-time noise signal E, and outputting a signal S by a secondary sound source in real time;
b. the secondary sound source S reaches the acoustic signal Y at the point of the error microphone E via the secondary path H:
Y＝HT S
c. calculating the primary sound field, i.e. the desired signal D:
D＝E-Y
d. calculating noise level L of primary sound field and secondary sound field respectivelyd And Le ：
Where D (n) is the sound pressure signal at a certain moment of the desired signal D
Where E (n) is the sound pressure signal at a certain moment of the error signal E
e. Noise reduction amount LΔ Calculation of
LΔ ＝Ld -Le
Thereby completing the noise reduction amount estimation of the system.
According to the calculation flow, the calculation conditions required by the method are met, and other hardware facilities are not required to be newly added.
Example III
The actual application of the noise reduction amount calculation method of the single-channel system comprises the following steps:
a. error signal pickup:
the error point real-time noise signal e (n) is collected in real time by an error microphone of the system.
b. Calculating an error point secondary acoustic signal y (n) estimate:
y (n) =h (m) ×s (n) where h (m) is the path transfer function of the secondary source to the error microphone
c. Calculating an error point primary sound field signal estimated value d (n):
d(n)＝e(n)-y(n)
d. noise levels of the primary and secondary sound fields of the error point are calculated:
the calculation formula of the sound pressure level is:wherein p isref ＝2.0×10-5 P is the average sound pressure,
i.e.
From the above the error point primary sound field sound pressure level Ld The calculation formula is as follows:
error point secondary sound field sound pressure level Le The calculation formula is as follows:
noise reduction amount LΔ The calculation formula is as follows:
LΔ ＝Ld -Le
thereby completing the noise reduction amount estimation of the system.
Example IV
FIG. 2 is a block diagram of a two-channel primary and secondary sound field algorithm, wherein for a two-channel active noise reduction system, a secondary sound source S is used for generating a secondary sound field, and is overlapped with the primary sound field to achieve the purpose of reducing noise; the error microphone E is used for picking up a secondary sound field signal; h represents a secondary path; d is denoted as the primary sound field before noise reduction; y is denoted as the secondary sound field where the secondary sound source S reaches the point of the error microphone E via the secondary path H.
Example five
For example, in a train cab based on active noise control dual channel system, it is necessary to display the noise level and noise reduction effect in the cab in real time.
The variable signals are expressed as follows:
a)s1 (n) and s2 (n) represents secondary sound signals respectively output from two secondary sound sources;
b)h11 (n) and h12 (n) represent the secondary path transfer functions of the secondary sound source No. 1 to the two error microphones, respectively;
c)h21 (n) and h22 (n) represent the secondary path transfer functions of the secondary sound source No. 2 to the two error microphones, respectively;
d)e1 (n) and e2 (n) represents real-time noise signals respectively received by two error microphones;
e)d1 (n) and d2 (n) represents the primary sound field, i.e. the desired signal, at the two error microphones;
f)y1 (n) and y2 (n) represents the acoustic signals generated at the two error microphones by the output of the secondary sound source;
the calculation flow is as follows:
a. input error point real-time noise signal e1 (n) and e2 (n)；
b. Calculating an error point secondary sound source signal estimated value:
c. calculating an error point primary sound field signal estimated value:
d. calculating the primary sound field sound pressure level L of the error pointd Value:
e. calculating the sound pressure level L of the secondary sound field of the error pointe Value:
noise reduction amount LΔ The calculation formula is as follows:
LΔ ＝Ld -Le
thereby completing the noise reduction amount estimation of the cab, LΔ L is the noise reduction of the systemd In-cabin noise level for non-noise reduction, Le The real-time noise in the cab is generated after noise reduction is started; in particular, when LΔ When the system is negative, the system is indicated to be faulty or unstable, and the system is also a judging basis for the robustness of the system.
The last points to be described are: first, in the description of the present application, it should be noted that, unless otherwise specified and defined, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be mechanical or electrical, or may be a direct connection between two elements, and "upper," "lower," "left," "right," etc. are merely used to indicate relative positional relationships, which may be changed when the absolute position of the object being described is changed;
the foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.