CN102148033B - 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 testing intelligibility of speech transmission index

Technical field

The present invention relates to the fields such as communication, voice alarm system, specifically refer to 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, be defined as STI as China's standard GB/T/T 16851-1997 to emergent sound system and be more than or equal to 0.65.The STI that measures Public Address system is always very consuming time.A complete measurement, need to obtain and analyze 98 groups of modulation transfer functions (MTF).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 ground unrest, 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 testing intelligibility of speech transmission index of the present invention, concrete technical scheme is as follows.

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

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

In above-mentioned method of testing, the carrier wave of test signal is the octave narrow band noise by 250,500,1000,2000, centered by 4000Hz; Between each narrow band noise, leave isolation strip, 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 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 in the 0.63-12.5Hz modulation frequency range with 1/3 octave band; By the m that measures 5 * 14 data that obtain _{K, f}Matrix can be converted to respectively 70 apparent signal to noise ratio snr _{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 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 then application of formula (5) is according to impulse response and test _{K, f}Matrix, calculate 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 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, then calculate the STI value according to (4) formula.

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 larger octave bands of Chinese language sharpness contribution, to guarantee the accuracy that the Chinese language sharpness of Chinese language transmission system is estimated, improved test speed.

The accompanying drawing explanation

Fig. 1 is the test macro block diagram.

Fig. 2 is 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 measured.

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 subjective Chinese articulation score.

Embodiment

Below in conjunction with accompanying drawing, specific embodiment of the invention is described further, but enforcement of the present invention and protection domain are not limited to this.

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 adopts receiving element (microphone) to receive in position to be measured after tested speech transmission index transmission, then by signal processing unit (can adopt dsp chip to realize), calculate the modulation transfer function MTF of 250～4000Hz octave band, calculate the STI value according to MTF.Realize that 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.

2. the carrier wave of measuring-signal is the octave narrow band noise by 250,500,1000,2000, centered by 4000Hz, and its intensity with the language spectrum quite; Between each narrow band noise, reserve isolation strip, 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.Measure the block diagram of MTF as shown in Figure 3.Every curve carries out spectrum analysis in the 0.63-12.5Hz modulation frequency range with 1/3 octave band.By the m that measures 5 * 14 data that obtain _{K, f}Matrix can be converted to respectively 70 apparent signal to noise ratio snr _{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 the impulse response that MLS signal or swept-frequency signal are measured the test transmission channel, the m of 5 * 14 data of snr computation when then application of formula (5) is according to impulse response and test _{K, f}Matrix, calculate 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, then calculate the STI value according to (4) formula.

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

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

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

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

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

The present invention is by without reverberation with have under the reverberation condition, Whole frequency band Chinese language signal is carried out to filtering, obtain having the Speech articulation test signal of different frequency scope, by subjective Chinese language sharpness, estimate, 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 (seeing Fig. 6), coefficient R=0.958 between STI value that STI value that weighted obtains and employing I EC criterion calculation obtain to present embodiment by adopting 5 octave bands larger to the contribution of Chinese language sharpness.Fig. 7 a～Fig. 7 c is the STI value that obtains of 3 kinds of different weighted methods and the match relation between subjective Chinese articulation score, and table 1 is corresponding weighted value, coefficient R and standard deviation.This shows, the Chinese language sharpness can better be predicted and estimate to the STI value that the weighted method that the weighted adopted in IEC60268-16 (2003) and the application adopt obtains all.But, adopt IEC60268-16 (2003) thus standard need to 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. testing intelligibility of speech transmission index, it is characterized in that adopting in position to be measured microphone to receive the test signal through tested speech transmission index transmission, the test signal that microphone will receive is transferred to signal processing unit, signal processing unit is by calculating the modulation transfer function of 250Hz to 4000Hz octave band, according to modulation transfer function computational language transmission index STI value, according to language transmission index STI value, estimate the sharpness of speech transmission index.

2. method of testing according to claim 1, is characterized in that described test signal is 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 signal processing unit calculates the modulation transfer function of five octave bands of 250Hz to 4000Hz, then according to modulation transfer function 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 is the octave narrow band noise by 250,500,1000,2000, centered by 4000Hz; Between each narrow band noise, leave isolation strip, 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 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 in the 0.63-12.5Hz modulation frequency range with 1/3 octave band; By the m that measures 5 * 14 data that obtain _k,fMatrix can be converted to respectively 70 apparent signal to noise ratio snr _k,fNumerical 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,fBe limited in ± ask transmission index TI in the 15dB scope _k,f, and make 0≤TI _k,f≤ 1,

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

Transmission index TI by same octave band _k,fOn 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 formula _nFor 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 the impulse response of adopting maximal length sequence signal or swept-frequency signal to measure the transmission channel of test language transmission system, the signal to noise ratio (S/N ratio) S/N when then application of formula (5) is according to impulse response p (t) and test calculates the m of 5 * 14 data _k,fMatrix m (f), calculate 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, then calculate the STI value according to (4) formula.

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