CN105301114A - Acoustic coating layer insertion loss measurement method based on multi-channel space-time inverse filtering technology - Google Patents

Abstract

Provided is an acoustic coating layer insertion loss measurement method based on a multi-channel space-time inverse filtering technology. The method comprises the following steps that 1, a multi-channel space-time inverse filtering emission signal is generated; 2, a direct signal is collected on the condition that a test sample does not exist; 3, a transmission signal is collected on the condition that the test sample exists; 4, an insertion loss measured value is calculated. According to the acoustic coating layer insertion loss measurement method based on the multi-channel space-time inverse filtering technology, a channel impulse response function containing information of a circuit channel and an underwater acoustic channel is obtained through constant interval emission of an emission array transducer and sequential receiving of a hydrophone, and the purpose of receiving a space acoustic energy focus and a time domain impulse waveform focus of the hydrophone is achieved through the simple and effective multi-channel space-time inverse filtering technology, so that the purposes of multi-path signal separation and reverberation suppression in acoustic coating layer insertion loss measurement are achieved, the space resolution of measurement parameters is improved, and the method is particularly suitable for acoustic performance tests of low-mid frequency materials. Meanwhile, it is verified that the method is effective in acoustic coating layer insertion loss measurement.

Description

A kind of acoustic stimulation insertion loss measuring method based on liftering technology during hyperchannel sky

Technical field

The present invention relates to a kind of measuring method of underwater sound overlayer full-page proof insertion loss.Underwater sound overlayer uses extensive and vital parts under water in Underwater Acoustics Engineering, and be the insertion loss performance of assessment acoustic stimulation sample, under laboratory condition, the insertion loss measurement of large part sample is main means.

Background technology

Acoustic stimulation refers to dedicated functionality acoustical material on the parts under water of being laid in and structure, is that parts realize an important means of Sound stealth under water.Along with the fast development of viscoelastic material and going deep into of Sound stealth technical research, acoustic stimulation product is comparatively complete, but can divide for by its different acoustic function watt to be shaken watt by sound eliminating tile, sound insulation, decoupling watt, array exhaust box etc.The energy of active probe sound wave can significantly absorb by acoustic stimulation on the one hand, and active sonar sound wave reflection is reduced, and reduces the acoustic target intensity of submerged structure, can suppress structure self radiated noise on the other hand.Thus, acoustic stimulation uniquely to reduce at present the effective technology that target strength can suppress again radiated noise, also just becomes our problem in the urgent need to address to its acoustical behavior research in underwater sound environment for use and parameters,acoustic measurement.

Insertion loss is one of important indicator weighing overlayer acoustical behavior.Existing acoustic stimulation insertion loss is measured must meet free-field condition.Large sample in free field is measured limited for the measurement capability of frequency acoustic performance parameter, along with the decline of frequency, because the acoustic absorbant of measurement environment surrounding cannot absorb sound wave completely, border all-bottom sound wave reflection can not be ignored, and measuring-signal is by reverberation serious interference.Meanwhile, because beam main lobe width can increase gradually with the reduction of frequency, namely main lobe resolving power can reduce gradually, and sample to be tested size is limited, when main lobe width is greater than sample to be tested size, can cause comparatively big error to test result.In addition, for the model of multilayer shell, the transmission performance usually need assessing every one deck sample respectively, to realize optimum comprehensive sound absorbing capabilities, thus has higher requirement to measurement.

Summary of the invention

In order to overcome existing acoustic stimulation insertion loss measuring technique in the test of medium and low frequency section, the deficiency that measuring result error is comparatively large, precision is lower, the invention provides one to be applicable to medium and low frequency section, effectively to reduce measuring error, to put forward high-precision acoustic stimulation full-page proof insertion loss measuring method, liftering technology when the method is empty by hyperchannel, the dimensional energy realizing transmitting at sample place focuses on and time domain impulse focuses on.

The present invention is as follows for solving the problems of the technologies described above adopted technical scheme.

An acoustic stimulation insertion loss measuring method for liftering technology time empty based on hyperchannel, described measuring method comprises the steps:

1) when generation hyperchannel is empty, liftering transmits: without in sample situation, each transducer of transducer array launches initialize signal successively, and nautical receiving set is Received signal strength successively, utilizes single channel liftering technology to obtain single channel liftering and transmits; According to the time delay spacing that transducer transmits, the liftering corresponding to each passage transmits and carries out time delay and even up, generate hyperchannel empty time liftering transmit;

2) without the collection of incoming signal in sample situation: liftering signal when transducer transmitting hyperchannel is empty, then according to liftering principle during sky, transmit and produce space-focusing and time domain is waveform of sharp pulses, the incoming signal p of hydrophone recordings sample at nautical receiving set place _i;

3) there is the collection of transmission signal in sample situation: the sample laying acoustic stimulation is put into test environment, repeat

2) step in, records transmission focusing signal p during test sample _t.

4) calculating of insertion loss measured value: utilize the computing formula of insertion loss to obtain

$I_L=-20\lg \left|\frac{p_t}{p_i}\right|$

Wherein I _lrepresent insertion loss value.

Technical conceive of the present invention is: launched by initial steering signal and nautical receiving set reception, obtain the Received signal strength comprising circuit channel and underwater acoustic channel information, by hyperchannel liftering technology, obtain transmitting of each array element of transducer array, penetrate through paroxysm, obtain receiving hydrophone place space-focusing and time domain is the signal of impulse form, thus realize space-focusing and the Time-Domain Pulse Compression of measuring-signal, and suppress reverberation.

Compared with existing insertion loss measuring method, advantage of the present invention is:

1) utilize liftering technology to carry out inversion calculation acquisition to the whole signal transmission channel comprising circuit channel and underwater acoustic channel to transmit, realize the Time-Domain Pulse Compression of incoming signal, be conducive to the separation of multipath signal.

2) synchronized transmissions of multi channel signals is utilized, improve incident wave main lobe resolution, reduce reverberation to the impact of measurement result, also can increase the spatial resolution of measurement parameter simultaneously, reduce the requirement to specimen size and the test space, be specially adapted to the test of medium and low frequency section Material acoustic performance.

3) test environment water body internal mechanism can because liftering technology during sky is set up equally under nonhomogeneous media environment, therefore, be eliminated on the impact of measuring-signal.

Accompanying drawing explanation

Fig. 1 is the measuring system overall schematic of the inventive method.

The space-focusing oscillogram of liftering technology when Fig. 2 is hyperchannel sky.

When Fig. 3 is hyperchannel sky, the time domain impulse of liftering technology focuses on oscillogram.

Fig. 4 is 5 millimeters thick steel plate sample insertion loss theories and measures comparison of test results figure.

Embodiment

Below in conjunction with accompanying drawing, the invention will be further described.

With reference to Fig. 1 ~ Fig. 4, a kind of acoustic stimulation insertion loss measuring method based on liftering technology during hyperchannel sky, for the measurement of finite space acoustic stimulation full-page proof insertion loss.The technical scheme of a whole set of measuring method is as follows:

1) when generation hyperchannel is empty, liftering transmits;

Without in sample situation, each transducer of transducer array launches initialize signal successively, and nautical receiving set is Received signal strength successively, if the frequency domain that transmits can be expressed as s (f), wherein f represents signal frequency, and Received signal strength is expressed as x _n(f), wherein n=1,2 ..., N represents that transducer is numbered, and N represents transducer number;

According to formula

$H_n\left(f\right)=\frac{x_n\left(f\right)}{s\left(f\right)}$

Estimate the channel response function H between each transmission channel and receiving hydrophone _n(f); For avoiding the singular problem occurred in inversion calculation, utilize formula

${\stackrel{\‾}{H}}_n^{-1}\left(f\right)=\frac{1}{H_n\left(f\right)+\mathrm{\ϵ}}$

Estimate the inverse function obtaining channel response wherein ε is a little value constant, unusual to avoid inverting; Inverse Fourier transform is done to this inverse function and obtains time domain Secondary Emission signal e _n(t), wherein t represents the time;

Utilize the signal transmission time interval of each transmitting transducer to liftering signal e _nt () is carried out time delay and is evened up, the e thus the liftering of acquisition hyperchannel transmits _n(t-τ _n), wherein τ _nfor the delay volume that each transmission channel is corresponding;

2) without the collection of direct signal during sample;

As shown in Figure 1, instrument is exported by computer system control hyperchannel individual control signal, through multichannel power amplifier, utilize transducer array synchronized transmissions by step 1) generate empty time liftering signal, meanwhile, the direct signal p when hydrophone recordings of computer system control focal position does not test sample _i.

3) collection of transmission signal during sample is had;

The sample laying acoustic stimulation is put into test environment, repeats 2) middle step, now record transmission focusing signal p during test sample _t.

4) calculating of insertion loss measured value;

The measurement data calculated needed for insertion loss can be obtained by above three steps.Utilize 2) and 3) the incoming signal p that gathers _iand transmission signal p _t, can be calculated insertion loss measured value is

$I_L=-20\lg \left|\frac{p_t}{p_i}\right|$

Example illustrates: be focusing effect during hyperchannel liftering technology empty in checking the present invention, carried out simulation analysis.Simulation pond measurement environment, if pond degree of depth 1.2m, length 15m, the water body velocity of sound is c _w=1480m/s, the density of water is ρ _w=1g/cm ³, be the thick sand bed of 20cm below water layer, its velocity of sound is respectively c _p=1700m/s, density is ρ _s=1.8g/cm ³, attenuation coefficient is α _s=0.5dB/ λ is the semi-infinite space of the hard end below sedimentary deposit.4 sound sources lay respectively at degree of depth 0.3m, 0.5m, 0.7m and 0.9m, receiving hydrophone range transmission battle array 10m, degree of depth 0.55m, and Received signal strength average signal-to-noise ratio is 15dB.In liftering algorithm, ε gets 0.05.When what Fig. 2 showed is hyperchannel sky, liftering is launched, the dimensional energy distribution figure of signal, Fig. 3 are the time domain waveform that receiving hydrophone receives, and wherein signal sampling rate is 50kHz.As seen from the figure, when hyperchannel is empty, liftering technology achieves space-focusing and the time domain impulse focusing of signal preferably.

For the validity of liftering technology in acoustic stimulation insertion loss is measured during checking hyperchannel sky, carry out basin test checking.Laboratory water tank is about 8m, wide 4m, depth of water 1.6m, and acoustic absorbant is posted at waveguide four sides, and bottom is covered with the fine sand of 0.25m.In experiment, ternary launches battle array with test sample at a distance of 7m.Test sample is steel plate, and its physical dimension is 1.1m × 1.0m × 5mm, and density is 7.84 × 10 ³kg/m ³, velocity of sound 5470m/s.The insertion loss data acquisition and processing (DAP) of 0.5kHz ~ 20kHz frequency has been carried out in this test.What Fig. 4 showed is steel plate sample insertion loss theory and test findings comparison diagram, as seen from the figure, even if under the pond guided-wave conditions that multipath phenomenon is very serious, measurement result of the present invention is basic consistent with calculated value, and each relative error measuring frequency corresponding is all less than 10%.

Claims (2)

1., based on an acoustic stimulation insertion loss measuring method for liftering technology during hyperchannel sky, described measuring method comprises the steps:

1) when generation hyperchannel is empty, liftering transmits;

2) without the collection of direct signal during sample: export instrument by computer system control hyperchannel individual control signal, through multichannel power amplifier, utilize transducer array synchronized transmissions by step 1) generate empty time liftering signal, meanwhile, the direct signal p when hydrophone recordings of computer system control focal position does not test sample _i;

3) have the collection of transmission signal during sample: the sample laying acoustic stimulation is put into test environment, repeat 2) middle step, now record transmission focusing signal p during test sample _t;

4) calculating of insertion loss measured value: utilize the incoming signal p gathered _iand transmission signal p _t, calculate insertion loss measured value $I_L=-20\lg \left|\frac{p_t}{p_i}\right|.$

2. as claimed in claim 1 a kind of empty based on hyperchannel time liftering technology acoustic stimulation insertion loss measuring method, it is characterized in that: described step 1) in, the process that when generation hyperchannel is empty, liftering transmits is: without in sample situation, each transducer of transducer array launches initialize signal successively, nautical receiving set is Received signal strength successively, if transmit, frequency domain can be expressed as s (f), and wherein f represents signal frequency, and Received signal strength is expressed as x _n(f), wherein n=1,2 ..., N represents that transducer is numbered, and N represents transducer number; According to formula estimate the channel response function H between each transmission channel and receiving hydrophone _n(f); For avoiding the singular problem occurred in inversion calculation, utilize formula estimate the inverse function obtaining channel response wherein ε is a little value constant, unusual to avoid inverting; Inverse Fourier transform is done to this inverse function and obtains time domain Secondary Emission signal e _n(t), wherein t represents the time; Utilize the signal transmission time interval of each transmitting transducer to liftering signal e _nt () is carried out time delay and is evened up, the e thus the liftering of acquisition hyperchannel transmits _n(t-τ _n), wherein τ _nfor the delay volume that each transmission channel is corresponding.