1、 International Telecommunication Union ITU-T P.57TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (12/2011) SERIES P: TERMINALS AND SUBJECTIVE AND OBJECTIVE ASSESSMENT METHODS Objective measuring apparatus Artificial ears Recommendation ITU-T P.57 ITU-T P-SERIES RECOMMENDATIONS TERMINALS AND SUBJECTI
2、VE 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 Objective measuring apparatus Series P.50P.500Objective electro-acoustical meas
3、urements 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 performance and QoS aspects of IP end-points Series P.1000 Communications
4、involving vehicles Series P.1100 For further details, please refer to the list of ITU-T Recommendations. Rec. ITU-T P.57 (12/2011) i Recommendation ITU-T P.57 Artificial ears Summary Recommendation ITU-T P.57 specifies the electro-acoustical characteristics of artificial ears to be used for telephon
5、ometric measurements. Three devices are specified: a telephone band type for measurements on traditional telephone sets, an insert earphone type and a type faithfully reproducing the characteristics of the human ear. The latter type (type 3) is specified in four configurations. The requirements of t
6、he third one (type 3.3 Pinna simulator) have been slightly modified in this revision of Recommendation ITU-T P.57 by specifying its construction by a softer elastomer. Besides this, the description of the applicability of all couplers has been changed, now allowing for an overlap in their usability
7、according to the receiver type under test. History Edition Recommendation Approval Study Group 1.0 ITU-T P.57 1993-03-12 XII 2.0 ITU-T P.57 1996-08-30 12 3.0 ITU-T P.57 2002-07-14 12 3.1 ITU-T P.57 (2002) Cor. 1 2005-01-27 12 4.0 ITU-T P.57 2005-11-29 12 5.0 ITU-T P.57 2009-04-29 12 6.0 ITU-T P.57 2
8、011-12-14 12 ii Rec. ITU-T P.57 (12/2011) FOREWORD The International Telecommunication Union (ITU) 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 o
9、rgan of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing 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 th
10、e topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics. 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 ar
11、e prepared on a collaborative basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendat
12、ion may contain certain mandatory provisions (to ensure, e.g., interoperability or applicability) 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 use
13、d to express requirements. The use of such words does not suggest that compliance with the Recommendation 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 Intellec
14、tual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed 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 received noti
15、ce of intellectual property, protected by patents, which may be required to implement this Recommendation. 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 2
16、012 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without the prior written permission of ITU. Rec. ITU-T P.57 (12/2011) iii Table of Contents Page 1 Scope and object . 1 1.1 Scope 1 1.2 Object . 1 2 References. 1 3 Definitions 1 3.1 Terms defined elsew
17、here 1 3.2 Terms defined in this Recommendation . 2 4 Abbreviations and acronyms 4 5 Artificial ear types 4 5.1 Type 1 artificial ear 5 5.2 Type 2 artificial ear 6 5.3 Type 3 . 8 5.4 Calibration of the artificial ears type 1 and type 3.2 19 5.5 Performance verification of the artificial ears types 2
18、, 3.1, 3.3 and 3.4 . 22 5.6 Atmospheric reference conditions 22 5.7 General requirements 22 5.8 Ear-drum reference point to ear reference point correction . 22 Annex A A practical procedure for determination of the acoustic input impedance of artificial ears . 23 A.1 Introduction 23 A.2 Calibration
19、of the impedance probe . 24 A.3 Artificial ear calibration . 25 Appendix I Comparative acoustical input impedance measurements on the artificial ears Types 3.3 and 3.4 and on human ears . 26 I.1 Introduction 26 I.2 Data overview . 26 I.3 Artificial ear measurements 27 I.4 Human ear measurements . 28
20、 I.5 Comparison between human and artificial ear measurements . 36 Appendix II Illustration of the mobile phone-shaped impedance probe used in Appendix I 44 Bibliography. 46 Rec. ITU-T P.57 (12/2011) 1 Recommendation ITU-T P.57 Artificial ears 1 Scope and object 1.1 Scope This Recommendation specifi
21、es the artificial ears for telephonometric use. Three types are recommended, covering the different transducers, types, sizes and technologies. The methods of use of the artificial ears are outside the scope of this Recommendation; however, some general rules are provided about the application force
22、 and the positioning of transducers. 1.2 Object Three types of artificial ears are defined: 1) a telephone-band type for measurements on traditional telephone sets; 2) a type for measuring insert earphones; 3) a type which faithfully reproduces the characteristics of the median human ear. 2 Referenc
23、es 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 indicated were valid. All Recommendations and other references are subject to revision; users o
24、f 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 Recommendations is regularly published. The reference to a document within this Recommendati
25、on does not give it, as a stand-alone document, the status of a Recommendation. 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-acoustic measurements on headsets. IEC 60318-1 IEC 60318-1 (2009), E
26、lectroacoustics Simulators of human head and ear Part 1: Ear simulator for the measurement of supra-aural and circumaural earphones. IEC 60318-4 IEC 60318-4 (2010), Electroacoustics Simulators of human head and ear Part 4: Occluded-ear simulator for the measurement of earphones coupled to the ear by
27、 means of ear inserts. IEC 61260 IEC 61260 (1995), Electroacoustics Octave-band and fractional-octave-band filters. 3 Definitions 3.1 Terms defined elsewhere None. 2 Rec. ITU-T P.57 (12/2011) 3.2 Terms defined in this Recommendation This Recommendation defines the following terms: 3.2.1 acoustically
28、 closed earphones (nominally sealed): Earphones which are intended to prevent any acoustic coupling between the external environment and the ear canal. 3.2.2 acoustically open earphones (nominally unsealed): Earphones which intentionally provide an acoustic path between the external environment and
29、the ear canal. 3.2.3 artificial ear: A device for the calibration of earphones incorporating an acoustic coupler and a calibration microphone for the measurement of sound pressure, and having an overall acoustic impedance similar to that of the average human ear over a given frequency band. 3.2.4 ci
30、rcum-aural earphones: Earphones which enclose the pinna and seat on the surrounding surface of the head. Contact to the head is normally maintained by compliant cushions. Circum-aural earphones may touch but not significantly compress the pinna (see Figure 1). P.57(09)_F01CaudalBackFrontRostralRight
31、 earhorizontalsectiona) Circum-aural (open) b) Circum-aural (closed)Figure 1 Circum-aural earphones 3.2.5 ear canal entrance point (EEP): A point located at the centre of the ear canal opening. 3.2.6 ear canal extension: Cylindrical cavity extending the simulation of the ear canal provided by the oc
32、cluded-ear simulator out of the concha cavity. 3.2.7 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. 3.2.8 ear simulator: Device for measuring the output sound pressu
33、re of an earphone under well-defined loading conditions in a specified frequency range. It consists essentially of a principal cavity, acoustic load networks and a calibrated microphone. The location of the microphone is chosen so that the sound pressure at the microphone corresponds approximately t
34、o the sound pressure existing at the human ear-drum. 3.2.9 ear-drum reference point (DRP): A point located at the end of the ear canal, corresponding to the ear-drum position. 3.2.10 insert earphones: Earphones which are intended to partially or completely enter the ear canal (see Figure 2). Rec. IT
35、U-T P.57 (12/2011) 3 P.57(09)_F05a) Insert (open) b) Insert (closed)Figure 2 Insert earphones 3.2.11 intra-concha earphones: Earphones which are intended to rest within the concha cavity of the ear. They have an external diameter (or maximum dimension) of less than 25 mm but are not made to enter th
36、e ear canal (see Figure 3). P.57(09)_F04a) Intra-concha (open) b) Intra-concha (closed)Figure 3 Intra-concha earphones 3.2.12 occluded-ear simulator: Ear simulator which simulates the inner part of the ear canal, from the tip of an ear insert to the ear-drum. 3.2.13 pinna simulator: A device which h
37、as the approximate shape of dimensions of a median adult human pinna. 3.2.14 supra-aural earphones: Earphones which rest upon the pinna and have an external diameter (or maximum dimension) of at least 45 mm (see Figure 4). 4 Rec. ITU-T P.57 (12/2011) P.57(09)_F02Earreferencepoint (ERP)a) Supra-aural
38、 (open) b) Supra-aural (closed)Entranceto earcanalFigure 4 Supra-aural earphones 3.2.15 supra-concha earphones: Earphones which are intended to rest upon the ridges of the concha cavity and have an external diameter (or maximum dimension) greater than 25 mm and less than 45 mm (see Figure 5). P.57(0
39、9)_F03Figure 5 Supra-concha (open) earphones 4 Abbreviations and acronyms This Recommendation uses the following abbreviations and acronyms: ANOVA ANalysis Of VAriance DRP ear-Drum Reference Point EEP Ear canal Entrance Point ERP Ear Reference Point HATS Head And Torso Simulator LRGP Loudness Rating
40、 Guard-ring Position 5 Artificial ear types The fundamental purpose of an artificial ear is to test a receiver under conditions that most closely approximate actual use by real persons. The recommendations that follow are based upon the manner in which the receivers are intended to be used. Modifica
41、tions to an artificial ear or test procedure shall not be made. To avoid alteration of the specified concha volume and/or leak, flexible sealing material, such as putty, shall not be used. Of the artificial ears defined below, those with a flexible pinna are intended to most closely resemble the man
42、ner in which the receivers are intended to be used. Rec. ITU-T P.57 (12/2011) 5 In the narrow-band (100 Hz to 4 kHz), the type 3.3 artificial ear resembles the human ear most closely and is the preferred choice, irrespective of the device to be tested. Use of artificial ears type 1 and 3.2 is limite
43、d to their scope of usability, described below. Comparative acoustic impedance measurements of the artificial ear types and human ears were conducted on a large scale and are shown in Appendix I. For wider-band applications, further study is still needed. 5.1 Type 1 artificial ear The type 1 artific
44、ial ear is specified in IEC 60318-1. It is recommended that the type 1 artificial ear should only be used as a legacy ear simulator for measurements on large, supra-aural or supra-concha, hard-cap, conically symmetrical receivers, which naturally seal to the simulator rim, intended for narrow-band t
45、elephony applications (100 Hz to 4 kHz). The type 1 artificial ear should not be used for receivers that do not meet these specifications. The acoustic input impedance and the frequency sensitivity response of the type 1 artificial ear are determined with reference to the ERP as specified in clause
46、5.4. The nominal modulus of the impedance curve and the corresponding tolerance limits are given in Table 1. Table 1 Acoustical impedance for type 1 artificial ear (IEC 60318) Frequency (Hz) Acoustical imp. (dB re 1 Pa s/m3) Tolerance ( dB) Frequency(Hz) Acoustical imp. (dB re 1 Pa s/m3) Tolerance (
47、 dB) 100 145.6 1 950 134.5 1 106 145.3 1 1000 134.0 1 112 145.0 1 1060 133.4 1 118 144.6 1 1120 132.8 1 125 144.3 1 1180 132.2 1 132 144.0 1 1250 131.7 1 140 143.7 1 1320 131.1 1 150 143.4 1 1400 130.6 1 160 143.2 1 1500 130.1 1 170 143.0 1 1600 129.6 1 180 143.0 1 1700 129.4 1 190 142.9 1 1800 129.
48、2 1 200 142.8 1 1900 129.2 1 212 142.9 1 2000 129.3 1 224 142.9 1 2120 129.5 1 236 143.1 1 2240 129.7 1 250 143.2 1 2360 129.8 1 265 143.4 1 2500 129.8 1 280 143.5 1 2650 129.6 1 300 143.7 1 2800 129.2 1 315 143.6 1 3000 128.6 1 335 143.7 1 3150 127.9 1 6 Rec. ITU-T P.57 (12/2011) Table 1 Acoustical
49、 impedance for type 1 artificial ear (IEC 60318) Frequency (Hz) Acoustical imp. (dB re 1 Pa s/m3) Tolerance ( dB) Frequency(Hz) Acoustical imp. (dB re 1 Pa s/m3) Tolerance ( dB) 355 143.6 1 3350 127.0 1 375 143.3 1 3550 125.9 1 400 143.0 1 3750 124.8 1 425 142.7 1 4000 123.2 1 450 142.2 1 4250 121.5 1 475 141.7 1 4500 119.5 1 500 141.3 1 4750 117.1 1 530 140.7 1 5000 114.2 1 560 140.1 1 5300 109.6 1 600 139.4 1 5600 104.7 1 630 138.9 1 6000 109.6 1 670 138.3 1 6300 113.6 1 710 137.6 1 6700 117.0 1 750 137.1 1 7100 119.5 1 800 1
