Method for measuring reverberation time of master control room under high background noise condition

Abstract

The invention relates to the technical field of acoustic measurement, and particularly discloses a method for measuring reverberation time of a master control room under a high background noise condition. The method comprises the following operation steps: obtaining a sound pressure level decay signal; filtering the sound pressure level decay signal to obtain a sound pressure level decay signal and a decay curve pm (t) under each frequency; obtaining time tm corresponding to an intersection point of an oblique line segment and a horizontal line segment in the decay curve signal; obtaining a unit time noise energy mean value e; obtaining an attenuation period sound energy value Em (t) after the background noise energy is removed; and performing logarithmic operation on the Em (t) to obtain a sound pressure level decay curve Lpm (t), performing linear fitting to obtain a fitted slope k, and calculating reverberation time Tm through the slope. Through the technical means of eliminating background noise energy, the technical effect of reverberation time measurement under the condition of high background noise is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of acoustic measurement, and particularly relates to a method for measuring the reverberation time of a main control room under high background noise conditions. Background Art

[0002] The generally recognized definition of reverberation time is: the time required for the sound energy density to drop to 1 / 106 of the original value, which is equivalent to a sound pressure level decay of 60 dB. The reverberation time of a certain frequency band is the time required for the sound in the room to reach a steady state. After the sound source stops emitting sound, the residual sound in the room is repeatedly absorbed by the sound-absorbing material, and the average sound energy density decays from the original value to one millionth. It is represented by T60 or RT. If the reverberation time is too short, the sound is dry, dull, and not cordial and natural; if the reverberation time is too long, the sound will be mixed; when it is appropriate, the sound is mellow and pleasant. The reverberation time is an important evaluation index for quantitative estimation of sound energy in acoustic design.

[0003] For rooms such as main control rooms that have high requirements for mutual conversation and hearing, effective sound absorption treatment needs to be carried out during design to ensure a reasonable reverberation time. Various research literatures show that too long reverberation time has an adverse impact on background noise and speech intelligibility.

[0004] Common reverberation time measurement methods include the steady-state sound field cut-off method, impulse response integration method, etc. But they all need to meet certain background noise limit requirements and cannot be measured under high background noise conditions.

[0005] After some main control rooms have high background noise and poor speech intelligibility, they need to be retrofitted later. Before the retrofit, it is necessary to measure the current reverberation time. Since some equipment cannot be turned off during operation, there is strong background interference noise when measuring the reverberation time, and the signal-to-noise ratio during the test is low, so effective reverberation time test data cannot be obtained. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for measuring the reverberation time of a main control room under high background noise conditions to eliminate the influence of high background noise on the measurement of the reverberation time and measure its reverberation time in view of the above deficiencies in the prior art.

[0007] To solve the above problems, the technical solution of the present invention is as follows: A method for measuring the reverberation time of a main control room under high background noise conditions, the method comprising the following operating steps:

[0008] S1: Obtain a sound pressure level decay signal;

[0009] According to the standard method in GB / T 50076, obtain a sound pressure level decay signal by the truncated sound source method;

[0010] S2: Filter the sound pressure level decay signal to obtain the sound pressure level decay signal and decay curve p at each frequency m (t);

[0011] S3: Obtain the time t corresponding to the intersection point of the slant line segment and the horizontal line segment in the decay curve signal m ;

[0012] Using the time parameter of the test system as the step factor Δt, calculate the mean square deviation D from t e starting, t e -Δt, t e -2Δt, t e -nΔt n . Assume that when the mean square deviation D at t e -iΔt is greater than twice the value of the mean square deviation D at t i -(i - 1)Δt, then it is considered that t e = t i-1 -(i - 1)Δt; m = t e -(i - 1)Δt;

[0013] t m The mathematical calculation method of the value is objective, repeatable, and the data after calculation is also traceable;

[0014] Where:

[0015] t e —The termination time of the decay curve signal;

[0016] S4: Obtain the mean noise energy per unit time e;

[0017] Select the background noise signal within the range from t m to t m in p e (t) for energy integration to obtain the mean noise energy per unit time e;

[0018] The formula is as follows:

[0019] S5: Obtain the sound energy value E m (t) during the decay period after removing the background noise energy;

[0020] Select the signal within the range from t0 to t m in p m (t), integrate it using the pulse reverse integration method, subtract the background noise energy value corresponding to the integration period, and obtain the sound energy value E m (t);

[0021] The formula is as follows:

[0022] Wherein:

[0023] t0—the starting time of the decay curve signal;

[0024] S6: Take the logarithm of E m (t) to obtain the sound pressure level decay curve Lp m (t). After linear fitting, the slope k after fitting is obtained, and the reverberation time T is calculated through the slope m . The unit of the reverberation time T m is second;

[0025] The formula for taking the logarithm of the sound energy value in the decay period is: Lp m (t) = 10lg[E m (t)]

[0026] The operation formula for the reverberation time is:

[0027] The sound source signal for obtaining the sound pressure level decay signal in step S1 is pink noise.

[0028] Step S2 filters the collected signal through fast Fourier transform.

[0029] The remarkable effect of the present invention is that: the measurement method of the reverberation time of the main control room under high background noise conditions described in the present invention realizes the technical effect of measuring the reverberation time under high background noise through the technical means of eliminating the background noise energy. Description of the Drawings

[0030] Figure 1 is the flowchart of the measurement method of the reverberation time of the main control room under high background noise conditions described in the present invention; Detailed Embodiments

[0031] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without creative efforts belong to the scope of the present invention.

[0032] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "upper" is based on the orientation or positional relationship shown in the drawings, and is only for convenience and simplified description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0033] In the description of the present invention, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance.

[0034] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "connection", "setting", "installation", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0035] As Figure 1 shown, a method for measuring the reverberation time of a main control room under high background noise conditions, the method comprising the following operating steps:

[0036] S1: Obtain the sound pressure level decay signal;

[0037] According to the standard method in GB / T 50076, obtain the sound pressure level decay signal by the truncated sound source method, and the sound source signal is pink noise;

[0038] S2: Filter the sound pressure level decay signal to obtain the sound pressure level decay signal and decay curve p m (t) at each frequency;

[0039] Filter the collected signal by fast Fourier transform (FFT);

[0040] S3: Obtain the time t corresponding to the intersection point of the slant line segment and the horizontal line segment in the decay curve signal m ;

[0041] Taking the time parameter of the test system as the step factor Δt, calculate the mean square deviation D e starting from t e -Δt, t e -2Δt, t e -nΔt; n Assume that when the mean square deviation D e of t i -iΔt is greater than twice the value of the mean square deviation D e of t i-1 -(i - 1)Δt, then it is considered that t m = t e -(i - 1)Δt;

[0042] The mathematical calculation method of the value of t m is objective, repeatable, and the data after calculation is also traceable;

[0043] Wherein:

[0044] t e — Decay curve signal termination time;

[0045] S4: Obtain the average noise energy value e per unit time;

[0046] Select t from p m (t) to select the background noise signal within the range from t m to t e and perform energy integration to obtain the average noise energy value e per unit time;

[0047] The formula is as follows:

[0048] S5: Obtain the sound energy value E during the decay period after removing the background noise energy m (t);

[0049] Select the signal within the range from t0 to t in p m (t), perform integration on it using the pulse reverse integration method, subtract the background noise energy value corresponding to the integration period, and obtain the sound energy value E during the decay period m (t); m (t);

[0050] The formula is as follows:

[0051] Where:

[0052] t0 - Decay curve signal start time;

[0053] S6: Perform logarithmic operation on E m (t) to obtain the sound pressure level decay curve Lp m (t), through linear fitting, obtain the slope k after fitting, and calculate the reverberation time T through the slope m , and the unit of the reverberation time T m is seconds;

[0054] The formula for performing logarithmic operation on the sound energy value during the decay period is: Lp m (t) = 10lg[E m (t)]

[0055] The operation formula for the reverberation time is:

[0056] Enlightened by the ideal embodiments of the present invention as described above, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for measuring the reverberation time of a main control room under high background noise conditions, characterized in that: The method includes the following operating steps: S1: Obtain the sound pressure level decay signal; According to the standard method in GB / T 50076, obtain the sound pressure level decay signal by the truncated sound source method; S2: Filter the sound pressure level decay signal to obtain the sound pressure level decay signals and decay curves p m (t) at each frequency; S3: Obtain the time t corresponding to the intersection point of the slant line segment and the horizontal line segment in the decay curve signal m ; Taking the time parameter of the test system as the step factor Δt, calculate the time from t e Start, t e -Δt,t e -2Δt,t e -nΔt mean square error D n Assume that when t e -The mean square error D of iΔt i Greater than t e -(i-1)Δt mean square error D i-1 If the value is twice that of m =t e -(i-1)Δt; t m The mathematical calculation method for the value taken is objective, repeatable, and the data after calculation is also traceable; Wherein: t e — Decay curve signal termination time; S4: Obtain the average value e of the noise energy per unit time; Select t from p m (t), and perform energy integration on the background noise signal in the range from t m to t e to obtain the mean noise energy e per unit time; The formula is as follows: S5: Obtain the decay period sound energy value E m (t) after removing the background noise energy; Select the signal within the range from t0 to t in p m (t), and integrate it using the pulse reverse integration method, subtract the background noise energy value corresponding to the integration period, and obtain the acoustic energy value E m (t) during the decay period; m (t); The formula is as follows: Wherein: t0—the starting time of the decay curve signal; S6: Take the logarithm of E m (t) to obtain the sound pressure level decay curve Lp m (t). After linear fitting, obtain the slope k after fitting, and calculate the reverberation time T through the slope m , where the reverberation time T m is in seconds; The formula for taking the logarithm of the sound energy value in the decay period is as follows: The calculation formula for reverberation time is as follows:

2. The measurement method of the reverberation time in the main control room under high background noise conditions according to claim 1, characterized in that: The sound source signal for obtaining the sound pressure level decay signal in step S1 is pink noise.

3. The measurement method of the reverberation time in the main control room under the condition of high background noise according to claim 1, characterized in that: Step S2 filters the collected signal through fast Fourier transform.

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