1、 International Telecommunication Union ITU-T P.311TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2011) SERIES P: TERMINALS AND SUBJECTIVE AND OBJECTIVE ASSESSMENT METHODS Voice terminal characteristics Transmission characteristics for wideband digital handset and headset telephones Recommendati
2、on ITU-T P.311 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.30P.300Reference systems Series P.40 Objective mea
3、suring 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.800 Audiovisual quality in multimedia services Series P.900 Transmission perfor
4、mance 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.311 (03/2011) i Recommendation ITU-T P.311 Transmission characteristics for wideband digital handset and headset t
5、elephones Summary Recommendation ITU-T P.311 provides audio performance requirements for wideband (8000 Hz) handset and headset telephones. Requirements and test methods are specified for the major audio transmission parameters affecting wideband audio, including sending and receiving levels, freque
6、ncy response, noise, distortion, sidetone, stability, echo path and delay. Wideband audio represents a considerable departure from traditional narrow-band telephony, offering significantly improved quality. Major changes over the previous version of this Recommendation (2005) are as follows: The str
7、ucture of the Recommendation is modified, the objective measurement methods originally in Annex A have been transferred into the main body. In addition to sinusoidal and noise signals, speech-like stimulus signals as described in Recommendation ITU-T P.50 and Recommendation ITU-T P.501 are also reco
8、mmended for the measurements. HATS method is used for better simulation of real telephone communication. Specific headset requirements are incorporated. Some technical requirements and related test methods have been modified based on the latest research, e.g., frequency response, distortion, STMR, D
9、-factor, and delay. History Edition Recommendation Approval Study Group 1.0 ITU-T P.311 1995-04-18 12 2.0 ITU-T P.311 1998-02-27 12 3.0 ITU-T P.311 2005-06-06 12 4.0 ITU-T P.311 2011-03-01 12 ii Rec. ITU-T P.311 (03/2011) FOREWORD The International Telecommunication Union (ITU) is the United Nations
10、 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 issuing Recommendations on
11、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 topics. The approval of IT
12、U-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 “Administration“ is us
13、ed 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) and compliance with th
14、e 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 Recommendation is required of
15、 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 claimed Intellectual Pr
16、operty 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 Recommendation. However,
17、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 2012 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior w
18、ritten permission of ITU. Rec. ITU-T P.311 (03/2011) iii Table of Contents Page 1 Scope 1 2 Normative references 1 3 Definitions and abbreviations . 2 3.1 Definitions 2 3.2 Abbreviations . 3 4 Test arrangement 3 4.1 Test environment 3 4.2 Test set-up 3 4.3 Test signal . 5 4.4 Signal level . 6 4.5 Ac
19、curacy of measurements . 6 5 Handset technical requirements 7 5.1 Codec independent parameters . 7 5.2 Codec relevant parameters . 17 6 Headset technical requirements 19 6.1 General description . 19 6.2 Codec independent parameters . 19 Rec. ITU-T P.311 (03/2011) 1 Recommendation ITU-T P.311 Transmi
20、ssion characteristics for wideband digital handset and headset telephones 1 Scope This Recommendation provides audio performance requirements and test methods for digital handset and headset telephones capable of transmitting an audio bandwidth extending beyond the conventional telephony bandwidth o
21、f 300 Hz to 3400 Hz, to a bandwidth of approximately 100 Hz to 8000 Hz. Such telephones are known as wideband audio telephones, and will make use of digital encoding schemes such as in ITU-T G.722. IP terminals may support other coding algorithms. Wideband audio telephones are expected to be used in
22、 new services such as high quality audio conferencing, video conferencing and multimedia applications. The requirements listed in this Recommendation are primarily applicable to telephones using ITU-T G.722 encoding at 64 kbit/s, but should also be used as the basis of requirements for other wideban
23、d audio encoding schemes. This is still under study in ITU-T. Conventional telephone band (300 Hz-3400 Hz) digital handset telephones using encoding according to ITU-T G.711 and ITU-T G.726 are covered by ITU-T P.310. 2 Normative references The following ITU-T Recommendations and other references co
24、ntain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; users of this Recommendation are therefore encouraged to investigate
25、the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of
26、a Recommendation. ITU-T G.122 Recommendation ITU-T G.122 (1993), Influence of national systems on stability and talker echo in international connections. ITU-T G.711 Recommendation ITU-T G.711 (1988), Pulse code modulation (PCM) of voice frequencies. ITU-T G.722 Recommendation ITU-T G.722 (1988), 7
27、kHz audio-coding within 64 kbit/s. ITU-T G.726 Recommendation ITU-T G.726 (1990), 40, 32, 24, 16 kbit/s Adaptative Differential Pulse Code Modulation (ADPCM). ITU-T G.729.1 Recommendation ITU-T G.729.1 (2006), G.729-based embedded variable bit-rate coder: An 8-32 kbit/s scalable wideband coder bitst
28、ream interoperable with G.729. ITU-T G.1020 Recommendation ITU-T G.1020 (2006), Performance parameter definitions for quality of speech and other voiceband applications utilizing IP networks. ITU-T I.412 Recommendation ITU-T I.412 (1988), ISDN user-network interfaces Interface structures and access
29、capabilities. ITU-T P.10 Recommendation ITU-T P.10/G.100 (2006), Vocabulary 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. 2 Rec. ITU-T P.311 (03/2011) ITU-T P.57 Recommendation IT
30、U-T P.57 (2009), Artificial ears. ITU-T P.58 Recommendation ITU-T P.58 (1996), Head and torso simulator 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), Cal
31、culation of loudness ratings for telephone sets. ITU-T P.310 Recommendation ITU-T P.310 (2009), Transmission characteristics for narrow-band digital handset and headset telephones. ITU-T P.380 Recommendation ITU-T P. 380 (2003), Electro-acoustic measurements on headsets. ITU-T P.501 Recommendation I
32、TU-T P.501 (2009), Test signals for use in telephonometry. ITU-T P.581 Recommendation ITU-T P.581 (2009), Use of head and torso simulator (HATS) for hands-free and handset terminal testing. ITU-T P.1010 Recommendation ITU-T P.1010 (2004), Fundamental voice transmission objectives for VoIP terminals
33、and gateways. ETSI TS 126 171 ETSI TS 126 171 V9.0.0 (2010), Speech codec speech processing functions; Adaptive Multi-Rate Wideband (AMR-WB) speech codec; General description (3GPP TS 26.171 version 9.0.0 Release 9). IEC 61672-2 IEC 61672-2 (2003), Electroacoustics Sound level meters Part 2: Pattern
34、 evaluation tests. 3 Definitions and abbreviations 3.1 Definitions This Recommendation defines the following terms: 3.1.1 diffuse field equalization: Equalization of the HATS sound pick-up, equalization of the difference, in dB, between the spectrum level of the acoustic pressure at the ear-drum ref
35、erence point (DRP) and the spectrum level of the acoustic pressure at the HATS reference point (HRP) in a diffuse sound field with the HATS absent using the reverse nominal curve given in Table 3 of ITU-T P.58. 3.1.2 ear-drum reference point (DRP): Point located at the end of the ear canal, correspo
36、nding to the ear-drum position. 3.1.3 ear reference point (ERP): A virtual point for geometric reference located at the entrance to the listeners ear, traditionally used for calculating telephonometric loudness ratings. 3.1.4 HATS position: The HATS position is the correct handset position in handse
37、t measurement, it will give more realistic results compared with LRGP. See Annexes D, E and F of ITU-T P.64 for detailed information. 3.1.5 head and torso simulator (HATS): Manikin extending from the top of the head to the waist, designed to simulate the sound pick-up characteristics and the acousti
38、c diffraction produced by a median adult, and to reproduce the acoustic field generated by the human mouth. 3.1.6 wideband telephony: Transmission of speech with a nominal passband wider than 300 Hz-3400 Hz, usually understood to be 100 Hz-8000 Hz. Rec. ITU-T P.311 (03/2011) 3 3.2 Abbreviations This
39、 Recommendation also uses the following abbreviations (relevant abbreviations in ITU-T P.10 will also apply): CSS Composite Source Signal DRP Ear-Drum Reference Point ERP Ear Reference Point LRGP Loudness Rating Guard Ring Position LSTR Listener Sidetone Rating MRP Mouth Reference Point NR Noise Red
40、uction PN Pseudorandom Noise RLR Receiving Loudness Rating SLR Sending Loudness Rating STMR Sidetone Masking Rating TCL Terminal Coupling Loss TCLw Weighted Terminal Coupling Loss 4 Test arrangement 4.1 Test environment Unless stated otherwise, measurements shall be conducted under anechoic or quiet
41、 conditions: For some headsets or handset terminals with small dimension, an anechoic room will be required. An anechoic room used in wideband test shall be practically free-field down to a lowest frequency of 150 Hz, the handset or headset coupled with the HATS shall lie totally within this free-fi
42、eld volume. Satisfied free-field conditions are met if deviations from the ideal free-field conditions are less than 1 dB. Depending on the distance from terminal transducers to mouth and ear, a quiet office room may be sufficient, e.g., for handsets where the artificial mouth and artificial ear are
43、 located close to the acoustical transducers. In that case, a test room may be used which meets the following criteria: 1) The difference of sound pressure between the mouth opening and that at 5.0, 7.5 and 10 cm in front of the centre of the lip ring is within 0.5 dB of that which exists in a known
44、 acoustic free-field. 2) The difference of sound pressure between the mouth opening and the ear canal entrance point (EEP) at both the left and right ears of the HATS does not differ by more than 1 dB from that which exists in a known free-field. The ambient noise level shall be less than 64 dBPa(A)
45、 for all the tests, except for the condition when a simulated or real noise is used as part of the test environment. The test environment shall be free of mechanical disturbances. 4.2 Test set-up 4.2.1 General description To achieve the most realistic simulation of the “average“ subscriber, all meas
46、urements are performed by using HATS. Although HATS is thoroughly described in ITU-T P.58, the exact 4 Rec. ITU-T P.311 (03/2011) calibration and equalization of HATS can be found in ITU-T P.581. Note that the horizontal positioning of the HATS reference plane shall be guaranteed within 2. The appro
47、priate ear simulator is type 3.3 or 3.4 which are detailed in ITU-T P.57. The type of ear simulator and application force shall be indicated in the test report. The interface in Figure 1 must be capable of converting the digital output stream from the tested set (which may be in various formats, dep
48、ending on the specific type of telephone set, e.g., ISDN sets according to ITU-T I.412 or IP terminals), to a form compatible with the test equipment. Interfaces can be applied for the sending and receiving signals separately, taking into account telephone sets which are connected to various types o
49、f exchanges or gateways. The interface shall be capable of providing the signalling, supervision or routing function necessary for the terminal to be working in all test modes. In general, there are two approaches to evaluate the transmission performance of a wideband digital telephone: the direct approach and the reference codec approach. In the direct approach, the companded digital input or output bitstream of the telephone set is operated upon directly. In the reference codec approach, a co
