1、 ETSI TS 103 224 V1.2.1 (2015-08) Speech and multimedia Transmission Quality (STQ); A sound field reproduction method for terminal testing including a background noise database TECHNICAL SPECIFICATION ETSI ETSI TS 103 224 V1.2.1 (2015-08)2 Reference RTS/STQ-247 Keywords noise, quality, speech, termi
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6、taff.aspx Copyright Notification No part may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm except as authorized by written permission of ETSI. The content of the PDF version shall not be modified without the written authorizatio
7、n of ETSI. The copyright and the foregoing restriction extend to reproduction in all media. European Telecommunications Standards Institute 2015. All rights reserved. DECTTM, PLUGTESTSTM, UMTSTMand the ETSI logo are Trade Marks of ETSI registered for the benefit of its Members. 3GPPTM and LTE are Tr
8、ade Marks of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners. GSM and the GSM logo are Trade Marks registered and owned by the GSM Association. ETSI ETSI TS 103 224 V1.2.1 (2015-08)3 Contents Intellectual Property Rights 4g3Foreword . 4g3Modal verbs terminology
9、 4g3Introduction 4g31 Scope 5g32 References 5g32.1 Normative references . 5g32.2 Informative references 5g33 Symbols and abbreviations . 6g33.1 Symbols 6g33.2 Abbreviations . 6g34 Methods for realistic sound reproduction . 7g35 Recording arrangement 7g35.0 General . 7g35.1 Microphone array setup 7g3
10、5.1.1 Principle limitations 7g35.1.2 Microphone calibration . 8g35.2 Microphone array setup for handset-type and headset terminals 8g35.3 Microphone array setup for hands-free terminals . 9g36 Loudspeaker setup for background noise simulation . 10g36.0 General setup 10g36.1 Test room requirements 11
11、g36.2 Equalization and calibration . 12g36.2.0 Overview of the equalization procedure . 12g36.2.1 Separate level adjustment for each loudspeaker . 12g36.2.2 System identification 12g36.2.3 Pre-processing of the impulse responses 13g36.2.4 Calculation of the inversion filters 14g36.2.4.0 Overview . 1
12、4g36.2.4.1 Inversion procedure . 15g36.2.4.2 Different microphones for different frequency bands . 16g36.2.4.3 Search for the optimum regularization factor 17g36.2.4.3.1 Basic methodology to find the optimum regularization factor 17g36.2.4.3.2 Extended methodology to find the optimum regularization
13、factor for frequencies above 2 kHz 18g36.2.5 First test of equalization and filter adjustment for inversion error compensation . 20g36.2.6 Accuracy of the equalization 20g36.3 Accuracy of the reproduction arrangement 21g36.3.0 Introduction. 21g36.3.1 Comparison between original sound field and simul
14、ated sound field . 21g36.3.2 Impact of handset positioner and phone on the simulated sound field . 23g36.3.3 Comparison of terminal performance in the original sound field and the simulated sound field . 23g36.3.3.1 Background noise transmission . 24g36.3.3.1.1 Handset 24g36.3.3.1.2 Handheld Hands-f
15、ree . 28g36.3.3.1.3 Desktop Hands-Free 29g36.3.3.2 S-/N-/G-MOS Analysis according to ETSI TS 103 106 . 29g36.3.3.2.1 Handset 29g36.3.3.2.2 Hands-free . 31g37 Background noise database 31g37.1 Reference noise recording 32g37.2 Background noise signals for terminal testing 33g3History 35g3ETSI ETSI TS
16、 103 224 V1.2.1 (2015-08)4 Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found in ETSI SR 000
17、314: “Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (http:/ipr.etsi.org). Pursuant to the ETSI IPR Policy, no investigati
18、on, including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the present document. Foreword This Technical Specificatio
19、n (TS) has been produced by ETSI Technical Committee Speech and multimedia Transmission Quality (STQ). The present document describes a sound field recording and reproduction technique which can be applied for all types of terminals but is especially suitable for modern multi-microphone terminals in
20、cluding array techniques. The present document provides an additional simulation technique which can be used instead of the part 1 of ETSI multi-part standard series ES/EG 202 396 “Speech quality performance in the presence of background noise“, as identified below: Part 1: “Background noise simulat
21、ion technique and background noise database“ i.7; Part 2: “Background noise transmission - Network simulation - Subjective test database and results“ i.8; Part 3: “Background noise transmission - Objective test methods“ i.9. The background noise simulation can be used in conjunction with the objecti
22、ve test methods as described in ETSI EG 202 396-3 i.9 and ETSI TS 103 106 i.10. Modal verbs terminology In the present document “shall“, “shall not“, “should“, “should not“, “may“, “need not“, “will“, “will not“, “can“ and “cannot“ are to be interpreted as described in clause 3.2 of the ETSI Draftin
23、g Rules (Verbal forms for the expression of provisions). “must“ and “must not“ are NOT allowed in ETSI deliverables except when used in direct citation. Introduction Background noise is present in most of the conversations today. Background noise may impact the speech communication performance of te
24、rminal and network equipment significantly. Therefore testing and optimization of such equipment is necessary using realistic background noises. Furthermore reproducible conditions for the tests are required which can be guaranteed only under lab type conditions. Since modern terminals incorporate m
25、ore advanced noise cancellation techniques, such as multi-microphone based noise cancellation, the use of microphone-array recording techniques and more realistic noise field simulations (compared to the method described in ETSI EG 202 396-1 i.7) are required. The present document addresses this top
26、ic by specifying a methodology for recording and playback of realistic background noise fields under conditions that are well-defined and able to be calibrated in a lab type environment. Furthermore a database with real background noises is included. ETSI ETSI TS 103 224 V1.2.1 (2015-08)5 1 Scope Th
27、e quality of background noise transmission is an important factor, which significantly contributes to the perceived overall quality of speech. Terminals, networks, and system configurations including wideband, superwideband, and fullband speech services can be greatly improved with a proper design o
28、f terminals and systems in the presence of background noise. The present document: describes a sound field simulation technique allowing to simulate the real environment using realistic background noise scenarios for laboratory use; contains a database including relevant background noise samples for
29、 subjective and objective evaluation. The present document describes the recording technique used for the sound field simulation, the loudspeaker setup, and the loudspeaker calibration and equalization procedures. Furthermore the present document specifies the test room requirements for laboratory c
30、onditions. The simulation environment specified can be used for the evaluation and optimization of terminals and of complex configurations including terminals, networks and others. The main application areas are: outdoor, office, home and car environment. The setup and database as described in the p
31、resent document are applicable for: Objective performance evaluation of terminals in different (simulated) background noise environments. Speech processing evaluation by using the pre-processed speech signals in the presence of background noise, recorded by a terminal. Subjective evaluation of termi
32、nals by performing conversational tests, specific double talk tests, or talking and listening tests in the presence of background noise. Subjective evaluation in third party listening tests by recording the speech samples of terminals in the presence of background noise. 2 References 2.1 Normative r
33、eferences References are either specific (identified by date of publication and/or edition number or version number) or non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the reference document (including any amendments) applies.
34、 Referenced documents which are not found to be publicly available in the expected location might be found at http:/docbox.etsi.org/Reference. NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee their long term validity. The following refer
35、enced documents are necessary for the application of the present document. Not applicable. 2.2 Informative references References are either specific (identified by date of publication and/or edition number or version number) or non-specific. For specific references, only the cited version applies. F
36、or non-specific references, the latest version of the reference document (including any amendments) applies. NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee their long term validity. ETSI ETSI TS 103 224 V1.2.1 (2015-08)6 The following
37、referenced documents are not necessary for the application of the present document but they assist the user with regard to a particular subject area. i.1 Berkhout, A. J., de Vries, D., Speech quality performance in the presence of background noise; Part 1: Background noise simulation technique and b
38、ackground noise database“. i.8 ETSI EG 202 396-2: “Speech Processing, Transmission and Quality Aspects (STQ); Speech quality performance in the presence of background noise; Part 2: Background noise transmission - Network simulation - Subjective test database and results“. i.9 ETSI EG 202 396-3: “Sp
39、eech and multimedia Transmission Quality (STQ); Speech Quality performance in the presence of background noise; Part 3: Background noise transmission - Objective test methods“. i.10 ETSI TS 103 106: “Speech and multimedia Transmission Quality (STQ); Speech quality performance in the presence of back
40、ground noise: Background noise transmission for mobile terminals-objective test methods“. i.11 ISO 3382-1: “Measurement of room acoustic parameters - Part 1: Performance spaces“. 3 Symbols and abbreviations 3.1 Symbols For the purposes of the present document, the following symbols apply: c Sound ve
41、locity 3.2 Abbreviations For the purposes of the present document, the following abbreviations apply: C Matrix of FFT coefficients of Compensation Filters DUT Device Under Test FFT Fast Fourier Transform H Matrix of FFT coefficients of Impulse Responses HATS Head And Torso Simulator IR Impulse Respo
42、nse MLS Maximum Length Sequence MOS Mean Opinion Score MRP Mouth Reference Point SNR Signal to Noise Ratio SPL Sound Pressure LevelETSI ETSI TS 103 224 V1.2.1 (2015-08)7 4 Methods for realistic sound reproduction For reproduction of real world sound fields there exists a variety of different methods
43、, two of them are wave field synthesis i.1 and Ambisonics i.2. Both methods, however, require a large number of microphones and loudspeakers to achieve a sound field reproduction which is sufficiently good for testing purposes. The Wave-Field synthesis setup is that complex and expensive that it can
44、 be neglected for laboratory purposes. Ambisonics, for example, has to be performed using 43 microphones and 43 loudspeakers to reach a good sound field reproduction up to 2 kHz in a sweet spot with radius 15 cm (using the rule of thumb in i.3). It furthermore cannot consider individual room charact
45、eristics or insufficiencies, but is only designed for rooms offering pure free field conditions. If, e.g. for testing purposes a HATS is positioned in the artificial noise field, the reproduction quality is reduced by an unknown amount. In summary, the Ambisonics approach is due to its design not fe
46、asible for the intended testing scenario. The present document introduces an alternative least mean squares method i.4, which requires eight recording channels and eight loudspeakers in order to achieve reasonably good reproduction results. The method is based on eight sweet spots at important testi
47、ng positions e.g. near the HATS, mainly at the microphone positions of modern phones. A reasonable reproduction of the recorded sound field at the corresponding eight points in the reproduction situation also yields good reproduction accuracy in between these points. This well-known property of soun
48、d fields is limited to an upper cut-off frequency which depends on the distances between the recording microphones (see clause 5.1.1). In clause 5, the recording technique required for this new method is described, while the setup allowing the reproduction in laboratories and the different steps of
49、the equalization procedure are introduced in clause 6. 5 Recording arrangement 5.0 General The sound field recording technique (Multi-point sound field recording technique) is based on optimization of the sound field reproduction at different points in space. The optimization criterion is based on minimization of the reproduction error at each microphone position. Based on this principle the microphone locations and as a consequence the points in space for which the sound field reproduction is mostly accurate can be chosen in a wide
