CN102148033A - Method for testing intelligibility of speech transmission index - Google Patents

Abstract

The invention relates to a method for testing the intelligibility of a speed transmission index. The method comprises the following steps: receiving a test signal transmitted by the tested speed transmission index at a position to be tested by adopting a microphone; transmitting the received test signal to a signal processing unit by the microphone; calculating a modulation transfer function (MTF) in an octave frequency band of 250-4000Hz by the signal processing unit; calculating a speech transmission index (STI) value according to the MTF; and judging the intelligibility of the speech transmission index according to the STI value. By adopting the method provided by the invention, five wider octave frequency bands (250-4000Hz) are contributed to the intelligibility of Chinese speech for weighting only, thus evaluation on the intelligibility of Chinese speech of a Chinese speech transmission index is ensured to be accurate, and the test speed is improved.

Description

A kind of speech transmission index method for testing definition

Technical field

The present invention relates to fields such as communication, voice alarm system, specifically be meant the method for testing of speech articulation in a kind of speech communication transmission system.

Background technology

For the speech transmission index lamprophonia whether, general language transmission index (STI) value that adopts IEC 60268-16 (2003) its transmission channel of canonical measure is defined as STI more than or equal to 0.65 as China's standard GB/T 16851-1997 to emergent sound system.The STI that measures Public Address system is very consuming time always.A complete measurement need obtain and analyze 98 groups of modulation transfer function (MTF)s.For Public Address system, in order to save Measuring Time, IEC 60268-16 (2003) adopts STIPA to carry out objective evaluation.But the measurement of STI-PA is very high to the requirement of ground unrest, can not contain pulse characteristics in the ground unrest, and its test macro can not be introduced stronger nonlinear distortion.And (all parts of identical sound pressure level and system all are activated) should be in case of emergency measured in the STI-PA of voice alarm system measurement.

Summary of the invention

In order to overcome the prior art above shortcomings, a kind of speech transmission index method for testing definition of the present invention, concrete technical scheme is as follows.

A kind of speech transmission index method for testing definition, it adopts microphone to receive the test signal of transmitting through tested speech transmission index in position to be measured, microphone is transferred to signal processing unit with the test signal that receives, signal processing unit is by calculating the modulation transfer function MTF of 250Hz to 4000Hz octave band, according to modulation transfer function MTF computational language transmission index STI value, judge the sharpness of speech transmission index according to language transmission index STI value.

In the above-mentioned method of testing, described test signal is an envelope modulated signal, and described signal processing unit carries out described calculating to the envelope modulated signal that receives after by octave band filtering, envelope detected, low-pass filtering again.

In the above-mentioned method of testing, described processing unit calculates the modulation transfer function of five octave bands of 250Hz to 4000Hz, again according to modulation transfer function MTF computational language transmission index STI value.

In the above-mentioned method of testing, the carrier wave of test signal for 250,500,1000,2000,4000Hz is the octave narrow band noise at center; Leave the isolation strip between each narrow band noise, the envelope modulated signal of test signal is the simple harmonic wave of extremely low frequency, and frequency is from 0.63Hz to 12.5Hz, and every 1/3oct gets 1; Its frequency is respectively 0.63Hz, 0.8Hz, 1.0Hz, 1.25Hz, 1.6Hz, 2.0Hz, 2.5Hz, 3.15Hz, 4.0Hz, 5.0Hz, 6.3Hz, 8.0Hz, 10.0Hz, 12.5Hz, totally 14 modulating frequencies

In the above-mentioned method of testing, signal processing unit carries out described calculating and comprises:

Obtain 5 MTF curves of octave separation in 250～4000Hz frequency range, every curve carries out spectrum analysis with 1/3 octave band in the 0.63-12.5Hz modulation frequency range; By the m that measures 5 * 14 data that obtain _{K, f}Matrix can be converted to 70 apparent signal to noise ratio snr respectively _{K, f}Numerical value, k are that octave band, f are modulating frequency,

${\mathrm{SNR}}_{k,f}=10\lg \frac{m_{k,f}}{1-m_{k,f}}\mathrm{dB}---\left(1\right)$

Then apparent signal to noise ratio snr _{K, f}Be limited in ± ask transmission index TI in the 15dB scope _{K, f}, and make 0≤TI _{K, f}≤ 1,

${\mathrm{TI}}_{k,f}=\frac{{\mathrm{SNR}}_{k,f}+15}{30}---\left(2\right)$

Transmission index TI by same octave band _{K, f}On average to obtain modulation transmissions index M TI _k:

${\mathrm{MTI}}_k=\frac{1}{14}\underset{f=1}{\overset{14}{\mathrm{\Σ}}}{\mathrm{TI}}_{k,f}---\left(3\right)$

Computational language transmission index STI:

$\mathrm{STI}=\underset{n=1}{\overset{5}{\mathrm{\Σ}}}{\mathrm{\ω}}_n{\mathrm{MTI}}_n---\left(4\right)$

ω _nAs shown in table 1.

In the above-mentioned method of testing, can also adopt MLS (maximal-length sequence) signal or swept-frequency signal to measure the impulse response of the described transmission channel of test, the m of 5 * 14 data of snr computation when application of formula (5) is according to impulse response and test then _{K, f}Matrix calculates the STI value according to formula (1)～(4),

$m\left(f\right)=\frac{\left|{\∫}_0^{\∞}{e}^{-j2\mathrm{\πft}}{p}^2\left(t\right)\mathrm{dt}\right|}{{\∫}_0^{\∞}{p}^2\left(t\right)\mathrm{dt}}\·{(1+{10}^{(-S/N)/10})}^{-1}---\left(5\right).$

In the above-mentioned method of testing, adopt acoustic software (as Dirac, Winmls etc.) to measure room impulse response, and application software calculate the MTI of 250～4000Hz octave band _kValue is calculated the STI value according to (4) formula then.

Compared with prior art, the present invention has following advantage and technique effect: the STI value that the present invention adopts the weighted value (GBT 15485-1995) of Chinese language articulation index to calculate the Chinese language transmission system is estimated its speech articulation, it is only to (250～4000Hz) carry out weighted to 5 bigger octave bands of Chinese language sharpness contribution, accuracy to guarantee the Chinese language sharpness of Chinese language transmission system is estimated has improved test speed.

Description of drawings

Fig. 1 is the test macro block diagram.

Fig. 2 is a STI measuring principle block diagram.

Fig. 3 is for measuring the MTF block diagram.

Fig. 4 is the test signal figure after envelope modulation.

Fig. 5 is the impulse response figure that measures.

Graph of a relation between the STI value that Fig. 6 obtains for kind of different weighted methods.

Fig. 7 a～Fig. 7 c is respectively STI value that 3 kinds of different weighted methods adopting IEC60268-16 (1988) standard, IEC60268-16 (2003) standard and the inventive method obtain and the match graph of a relation between the subjective Chinese articulation score.

Embodiment

Below in conjunction with accompanying drawing concrete enforcement of the present invention is described further, but enforcement of the present invention and protection domain are not limited thereto.

As Fig. 1, the audio-frequency test signal (modulation signal or random signal) relevant with measuring STI passes through speaker playback, the test signal that after tested speech transmission index transmission, adopts receiving element (microphone) to receive in position to be measured, calculate the modulation transfer function MTF of 250～4000Hz octave band then by signal processing unit (can adopt dsp chip to realize), calculate the STI value according to MTF.Realize block diagram as shown in Figure 2.

The method of testing detailed step is as follows:

1. measuring system should be configured by Fig. 2, and wherein the distance of measuring sound source and speaker-microphone is 0.5m.

The carrier wave of measuring-signal for 250,500,1000,2000,4000Hz is the octave narrow band noise at center, its intensity is with the language spectrum quite; Reserve the isolation strip between each narrow band noise, its envelope modulated signal is the simple harmonic wave of extremely low frequency, and its frequency is from 0.63Hz to 12.5Hz, and every 1/3oct chooses 1 modulating frequency, totally 14.

3. obtain 5 MTF curves of octave separation in 250～4000Hz frequency range.The block diagram of measurement MTF as shown in Figure 3.Every curve carries out spectrum analysis with 1/3 octave band in the 0.63-12.5Hz modulation frequency range.By the m that measures 5 * 14 data that obtain _{K, f}Matrix can be converted to 70 apparent signal to noise ratio snr respectively _{K, f}(k is that octave band, f are modulating frequency) numerical value.

${\mathrm{SNR}}_{k,f}=101g\frac{m_{k,f}}{1-m_{k,f}}\mathrm{dB}---\left(1\right)$

4. then apparent signal to noise ratio snr _{K, f}Be limited in ± ask transmission index TI in the 15dB scope _{K, f}, and make 0≤TI _{K, f}≤ 1.

${\mathrm{TI}}_{k,f}=\frac{{\mathrm{SNR}}_{k,f}+15}{30}---\left(2\right)$

5. by the transmission index TI of same octave band _{K, f}On average to obtain modulation transmissions index M TI _k:

${\mathrm{MTI}}_k=\frac{1}{14}\underset{f=1}{\overset{14}{\mathrm{\Σ}}}{\mathrm{TI}}_{k,f}---\left(3\right)$

6. computational language transmission index STI:

$\mathrm{STI}=\underset{n=1}{\overset{5}{\mathrm{\Σ}}}{\mathrm{\ω}}_n{\mathrm{MTI}}_n---\left(4\right)$

ω _nBe worth as shown in table 1.

The different STI computing method of table 1 weighted value ω _n

7. this test macro also can adopt MLS signal or swept-frequency signal to measure the impulse response of test transmission channel, the m of 5 * 14 data of snr computation when application of formula (5) is according to impulse response and test then _{K, f}Matrix calculates the STI value according to formula (1)～(4).This process can adopt existing commercial acoustic Survey Software such as Dirac, Winmls 2004 etc. to measure the MTI of 250～4000Hz octave band _kValue is calculated the STI value according to (4) formula then.

$m\left(f\right)=\frac{\left|{\∫}_0^{\∞}{e}^{-j2\mathrm{\πft}}{p}^2\left(t\right)\mathrm{dt}\right|}{{\∫}_0^{\∞}{p}^2\left(t\right)\mathrm{dt}}\·{(1+{10}^{(-S/N)/10})}^{-1}---\left(5\right)$

Practical measuring examples: measure the speech articulation of certain venue Public Address system at certain receiving position.

Method 1: the language spectrum signal is after envelope modulation (shown in Figure 4) in the time of will growing, play by Public Address system, adopt microphone to receive envelope modulated signal in position to be measured, signal processing unit carries out calculating after octave band filtering, envelope detected, the low-pass filtering m of 5 * 14 data to signal _{K, f}Matrix calculates the STI value according to formula (1)～(4).

Method 2: adopt acoustic measurement software Dirac to measure as shown in Figure 5 (as using index sweep measurement method) from Public Address system to the impulse response of accepting the position, and (250～4000Hz) signal and noise level go out 5 * 14 m by the Dirac computed in software to measure each octave band of receiving position _{K, f}(table 2) calculates the value of STI according to formula (1)～(4).

Table 2m _{K, f}, MTI, STI

The present invention is by in no reverberation with have under the reverberation condition, full range band Chinese language signal is carried out filtering, obtain having the speech articulation test signal of different frequency scope, estimate by subjective Chinese language sharpness, obtain having the speech articulation score of the Chinese language signal of different frequency scope, experimental result shows: in order to reach Chinese language sharpness preferably, the low-limit frequency scope of required Chinese language signal is 300-6000Hz.(250～4000Hz) carry out having very high correlativity (see figure 6), coefficient R=0.958 between the STI value that STI value that weighted obtains and employing I EC criterion calculation obtain to present embodiment by adopting 5 octave bands bigger to the contribution of Chinese language sharpness.Fig. 7 a～Fig. 7 c is STI value and the relation of the match between the subjective Chinese articulation score that 3 kinds of different weighted methods obtain, and table 1 is corresponding weighted value, coefficient R and standard deviation.This shows that the Chinese language sharpness can better be predicted and estimate to the STI value that the weighted method that the weighted that adopts among the IEC60268-16 (2003) and the application adopt obtains all.But, adopt IEC60268-16 (2003) thus standard need be measured the modulation transmissions index of 7 octave bands and obtains the STI value, and the present invention only need measure the modulation transmissions index of 5 octave bands and can obtain STI, can save Measuring Time like this.

Claims (7)

1. speech transmission index method for testing definition, it is characterized in that adopting microphone to receive the test signal of transmitting through tested speech transmission index in position to be measured, microphone is transferred to signal processing unit with the test signal that receives, signal processing unit is by calculating the modulation transfer function MTF of 250Hz to 4000Hz octave band, according to modulation transfer function MTF computational language transmission index STI value, estimate the sharpness of speech transmission index according to language transmission index STI value.

2. method of testing according to claim 1 is characterized in that described test signal is an envelope modulated signal, and described signal processing unit carries out described calculating to the envelope modulated signal that receives after by octave band filtering, envelope detected, low-pass filtering again.

3. method of testing according to claim 1 is characterized in that described processing unit calculates the modulation transfer function of five octave bands of 250Hz to 4000Hz, again according to modulation transfer function MTF computational language transmission index STI value.

4. method of testing according to claim 3, the carrier wave that it is characterized in that test signal for 250,500,1000,2000,4000Hz is the octave narrow band noise at center; Leave the isolation strip between each narrow band noise, the envelope modulated signal of test signal is the simple harmonic wave of extremely low frequency, its frequency is respectively 0.63Hz, 0.8Hz, 1.0Hz, 1.25Hz, 1.6Hz, 2.0Hz, 2.5Hz, 3.15Hz, 4.0Hz, 5.0Hz, 6.3Hz, 8.0Hz, 10.0Hz, 12.5Hz, totally 14 modulating frequencies.

5. method of testing according to claim 4 is characterized in that processing unit carries out described calculating and comprises:

Obtain 5 MTF curves of octave separation in 250～4000Hz frequency range, every curve carries out spectrum analysis with 1/3 octave band in the 0.63-12.5Hz modulation frequency range; By the m that measures 5 * 14 data that obtain _{K, f}Matrix can be converted to 70 apparent signal to noise ratio snr respectively _{K, f}Numerical value, k are that octave band, f are modulating frequency,

${\mathrm{SNR}}_{k,f}=101g\frac{m_{k,f}}{1-m_{k,f}}\mathrm{dB}---\left(1\right)$

Then apparent signal to noise ratio snr _{K, f}Be limited in ± ask transmission index TI in the 15dB scope _{K, f}, and make 0≤TI _{K, f}≤ 1,

${\mathrm{TI}}_{k,f}=\frac{{\mathrm{SNR}}_{k,f}+15}{30}---\left(2\right)$

Transmission index TI by same octave band _{K, f}On average to obtain modulation transmissions index M TI _k:

${\mathrm{MTI}}_k=\frac{1}{14}\underset{f=1}{\overset{14}{\mathrm{\Σ}}}{\mathrm{TI}}_{k,f}---\left(3\right)$

Computational language transmission index STI:

$\mathrm{STI}=\underset{n=1}{\overset{5}{\mathrm{\Σ}}}{\mathrm{\ω}}_n{\mathrm{MTI}}_n---\left(4\right)$

ω in the formula _nBe each octave band weighted value, corresponding to 250Hz～4000Hz octave band, ω _nBe respectively 0.072,0.144,0.218,0.327 and 0.234.

6. method of testing according to claim 5, it is characterized in that adopting maximal length sequence signal or swept-frequency signal to measure the impulse response of testing described transmission channel, the m of 5 * 14 data of snr computation when application of formula (5) is according to impulse response and test then _{K, f}Matrix calculates the STI value according to formula (1)～(4),

$m\left(f\right)=\frac{\left|{\∫}_0^{\∞}{e}^{-j2\mathrm{\πft}}{p}^2\left(t\right)\mathrm{dt}\right|}{{\∫}_0^{\∞}{p}^2\left(t\right)\mathrm{dt}}\·{(1+{10}^{(-S/N)/10})}^{-1}---\left(5\right).$

7. method of testing according to claim 6 it is characterized in that adopting acoustic software to measure room impulse response, and application software calculates the MTI of 250～4000Hz octave band _kValue is calculated the STI value according to (4) formula then.

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