1、 International Telecommunication Union ITU-T P.310TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (06/2009) SERIES P: TERMINALS AND SUBJECTIVE AND OBJECTIVE ASSESSMENT METHODS Voice terminal characteristics Transmission characteristics for narrow-band digital handset and headset telephones Recommend
2、ation ITU-T P.310 ITU-T P-SERIES RECOMMENDATIONS TERMINALS AND SUBJECTIVE AND OBJECTIVE ASSESSMENT METHODS Vocabulary and effects of transmission parameters on customer opinion of transmission quality Series P.10 Voice terminal characteristics Series P.30 P.300 Reference systems Series P.40 Objectiv
3、e measuring apparatus Series P.50 P.500 Objective electro-acoustical measurements Series P.60 Measurements related to speech loudness Series P.70 Methods for objective and subjective assessment of speech quality Series P.80 P.800Audiovisual quality in multimedia services Series P.900 Transmission pe
4、rformance and QoS aspects of IP end-points Series P.1000 Communications involving vehicles Series P.1100 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T P.310 (06/2009) i Recommendation ITU-T P.310 Transmission characteristics for narrow-band digital handset and he
5、adset telephones Summary Recommendation ITU-T P.310 provides audio performance requirements and associated testing methods for narrow-band (300-3400 Hz) digital handset and headset telephones. Requirements and test methods are specified for the major audio transmission parameters including sending a
6、nd receiving frequency response, loudness rating, noise, distortion, out-of-band signals, linearity, sidetone, echo and delay. This Recommendation is only applicable to digital telephones using encoding conforming to Recommendations ITU-T G.711 (64 kbit/s, PCM) and ITU-T G.726 (32 kbit/s, ADPCM). IP
7、 terminals and wireless headsets are not covered in this recommendation. Source Recommendation ITU-T P.310 was approved on 22 June 2009 by ITU-T Study Group 12 (2009-2012) under Recommendation ITU-T A.8 procedures. ii Rec. ITU-T P.310 (06/2009) FOREWORD The International Telecommunication Union (ITU
8、) is the United Nations specialized agency in the field of telecommunications, information and communication technologies (ICTs). The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issu
9、ing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these top
10、ics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression
11、 “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g., interoperability or applicability)
12、and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not suggest that compliance with the Recomme
13、ndation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of c
14、laimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may be required to implement this Rec
15、ommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2010 All rights reserved. No part of this publication may be reproduced, by any means whatsoeve
16、r, without the prior written permission of ITU. Rec. ITU-T P.310 (06/2009) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions and abbreviations. 2 3.1 Definitions 2 3.2 Abbreviations . 3 4 Test configuration. 4 4.1 Measurement approaches for testing digital telephones. 4 4.2 Test equipment .
17、5 4.3 Measurement set-up 6 4.4 Test environment 7 4.5 Test signal and level . 7 4.6 Accuracy of test equipment 7 5 Handset technical requirements 8 5.1 Sending characteristics . 8 5.2 Receiving characteristics 14 5.3 Sidetone characteristics 20 5.4 Echo path loss characteristics. 22 5.5 Delay. 25 6
18、Headset technical requirements 25 6.1 Sending characteristics . 25 6.2 Receiving characteristics 26 6.3 Echo path loss characteristics. 26 Annex A Distortion allowances 28 Bibliography. 29 Rec. ITU-T P.310 (06/2009) 1 Recommendation ITU-T P.310 Transmission characteristics for narrow-band digital ha
19、ndset and headset telephones 1 Scope This Recommendation deals with sending and receiving frequency response, loudness rating, noise, distortion, out-of-band signals, linearity, sidetone, echo and delay of narrow-band (300-3400 Hz) digital handset and headset telephones using “Waveform“ encoding acc
20、ording to ITU-T G.711 (PCM at both 64 and 56 kbit/s) and ITU-T G.726 (ADPCM, 32 kbit/s). IP terminals and wireless headsets are not covered in this Recommendation. The use of digital telephones using ITU-T G.728 (LD-CELP, 16 kbit/s) and mobile/cordless telephones are under study. Requirements applic
21、able to low acoustic impedance transducers and digital telephone sets using non-linear techniques are under study. The requirements listed in this Recommendation should also be used as the basis of requirements for other “waveform“ encoding schemes. The values given in this Recommendation should be
22、used for developing specifications which will include assigning tolerances, etc. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indi
23、cated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T R
24、ecommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T G.122 Recommendation ITU-T G.122 (1993), Influence of national systems on stability and talker echo in international connec
25、tions. ITU-T G.131 Recommendation ITU-T G.131 (2003), Talker echo and its control. ITU-T G.711 Recommendation ITU-T G.711 (1988), Pulse code modulation (PCM) of voice frequencies. ITU-T G.712 Recommendation ITU-T G.712 (2001), Transmission performance characteristics of pulse code modulation channel
26、s. ITU-T G.726 Recommendation ITU-T G.726 (1990), 40, 32, 24, 16 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM). ITU-T G.728 Recommendation ITU-T G.728 (1992), Coding of speech at 16 kbit/s using low-delay code excited linear prediction. ITU-T I.412 Recommendation ITU-T I.412 (1988), ISD
27、N user-network interfaces Interface structures and access capabilities. ITU-T I.430 Recommendation ITU-T I.430 (1995), Basic user-network interface Layer 1 specification. 2 Rec. ITU-T P.310 (06/2009) ITU-T O.41 Recommendation ITU-T O.41 (1994), Psophometer for use on telephone-type circuits. ITU-T O
28、.131 Recommendation ITU-T O.131 (1988), Quantizing distortion measuring equipment using a pseudo-random noise test signal. ITU-T O.133 Recommendation ITU-T O.133 (1993), Equipment for measuring the performance of PCM encoders and decoders. ITU-T P.10 Recommendation ITU-T P.10/G.100 (2006), Vocabular
29、y for performance and quality of service. ITU-T P.50 Recommendation ITU-T P.50 (1999), Artificial voices. ITU-T P.51 Recommendation ITU-T P.51 (1996), Artificial mouth. ITU-T P.57 Recommendation ITU-T P.57 (2009), Artificial ears. ITU-T P.58 Recommendation ITU-T P.58 (1996), Head and torso simulator
30、 for telephonometry. ITU-T P.64 Recommendation ITU-T P.64 (2007), Determination of sensitivity/frequency characteristics of local telephone systems. ITU-T P.79 Recommendation ITU-T P.79 (2007), Calculation of loudness ratings for telephone sets. ITU-T P.380 Recommendation ITU-T P.380 (2003), Electro
31、-acoustic measurements on headsets. ITU-T P.501 Recommendation ITU-T P.501 (2007), Test signals for use in telephonometry. ITU-T P.502 Recommendation ITU-T P.502 (2000), Objective test methods for speech communication systems using complex test signals. ITU-T P.581 Recommendation ITU-T P.581 (2000),
32、 Use of head and torso simulator (HATS) for hands-free terminal testing ISO 3 ISO 3:1973, Preferred numbers Series of preferred numbers. ISO 1996-1 ISO 1996-1:2003, Acoustics Description, measurement and assessment of environmental noise Part 1: Basic quantities and assessment procedures. 3 Definiti
33、ons and abbreviations 3.1 Definitions This Recommendation defines the following terms: 3.1.1 0 dB reference point: To preserve compatibility with existing codecs already in use in local digital switches, which are defined as a 0 dBr point, the codec (A- or -law) should be defined as follows: D/A con
34、verter A digital test sequence (DTS) representing the PCM equivalent of an analogue sinusoidal signal whose r.m.s. value is 3.14 dB (A-law) or 3.17 dB (-law) below the maximum full-loaded capacity of the codec will generate 0 dBm across a 600-ohm load. Here DTS is defined as a periodic sequence of c
35、haracter signals as given in ITU-T G.711. A/D converter A 0 dBm signal generated from a 600-ohm source will give the digital test sequence representing the PCM equivalent of an analogue sinusoidal signal whose r.m.s. value is 3.14 dB (A-law) or 3.17 dB (-law) below the maximum full load capacity of
36、the codec. Rec. ITU-T P.310 (06/2009) 3 3.1.2 acoustic reference level (ARL): Defined as the acoustic level at MRP which results in a 10 dBm0 output at the digital interface. 3.1.3 digital telephone set (DT): A digital telephone set is one in which the A/D and D/A converters are built in and the con
37、nection to the network is via a digital bitstream. 3.1.4 HATS position: The HATS (head and torso simulator) position (see Annexes D and E of ITU-T P.64) is the correct handset position for measuring sensitivity and frequency response characteristics. The HATS position has been shown to be essentiall
38、y identical to the LRGP (loudness rating guard-ring position), except for the mouth simulator direction, which has been corrected with a 19 downwards rotation to more closely match real talkers. For handsets with omnidirectional microphones, measurements on the two heads may differ slightly, typical
39、ly less than 1 dB. For handsets with directional or noise-cancelling microphones, the differences will be larger, and the HATS position will give the more realistic results. 3.2 Abbreviations Relevant abbreviations in ITU-T P.10 will apply. This Recommendation uses the following abbreviations: A/D A
40、nalogue-to-Digital ARL Acoustic Reference Level D/A Digital-to-Analogue DRP earDrum Reference Point DTS Digital Test Sequence ERP Ear Reference Point ERUP Estimated Real Use Position HATS Head And Torso Simulator ISDN Integrated Services Digital Network LRGP Loudness Rating Guard-ring Position LSTR
41、Listener SideTone Rating MRP Mouth Reference Point PABX Private Automatic Branch Exchange PCM Pulse Code Modulation RLR Receiving Loudness Rating RTP Recommended Test Position RWP Recommended Wearing Position Sje Receiving Sensitivity (Artificial Ear) SJE Receiving Sensitivity (Real Ear) SLR Sending
42、 Loudness Rating Smj Sending Sensitivity (Artificial Mouth) SMJ Sending Sensitivity (Real Mouth) Ssi(diff) Sending Sensitivities for diffuse sound Ssi(direct) Sending Sensitivities for direct sound 4 Rec. ITU-T P.310 (06/2009) STMR SideTone Masking Rating TCL Terminal Coupling Loss TCLw Weighted Ter
43、minal Coupling Loss Sm Difference between the sending sensitivities for diffuse and direct sound 4 Test configuration 4.1 Measurement approaches for testing digital telephones In general, there are two approaches for evaluating the transmission performance of a digital telephone, the direct approach
44、 and the codec approach. The direct approach is, in principle, the most accurate although the use of the codec approach may sometimes be advantageous. ITU-T recommends both methods to evaluate the voice transmission performance of a digital handset or headset telephone using “Waveform“ encoding conf
45、orming to ITU-T G.711 (PCM at 64 kbit/s and 56 kbit/s) and ITU-T G.726 (ADPCM, 32 kbit/s). 4.1.1 Direct digital processing approach In this approach, shown in Figure 4-1, the companded digital input/output bitstream of the telephone set is operated upon directly. The advantage is that most of the te
46、st signals, if sampled at 8 kHz, can be generated and analysed without the need for resampling and A/D or D/A conversion. Multi-plexerDigital setControlPCMDirectdigitalprocessingunitInterfaceSMA/DD/ASEFigure 4-1 Digital telephone test arrangement (direct digital processing approach) 4.1.2 Codec appr
47、oach In this approach, shown in Figure 4-2, a codec is used to convert the companded digital input/output bitstream of the telephone set to the equivalent analogue values, so that existing test procedures and equipment can be used. This codec should be a high-quality codec whose characteristics are
48、as close as possible to ideal (see clause 4.2.2). Multi-plexerinterfaceControl“Reference codec“test bedAnalogueinstrumentsDigital setSMSEA/DD/AD/AA/D600 600 Figure 4-2 Digital telephone test arrangement (codec approach) Rec. ITU-T P.310 (06/2009) 5 NOTE The digital telephone test equipment will, in
49、general, be connected to the telephone under test through an interface. Such an interface should be able to provide all the signalling and supervisory sequences necessary for the telephone set to be working in all test modes. The interface must be capable of converting the digital output stream from the tested set (which may be in various formats, depending on the specific type of telephone set, e.g., conforming to ITU-T I.412 for ISDN sets), to a form compatible with the test equipment. In
