1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Supplement 20 (Series P) (03/93) TELEPHONE TRANSMISSION QUALITY OBJECTIVE ELECTRO-ACOUSTICAL MEASUREMENTS EXAMPLES OF MEASUREMENTS OF RESPONSES: DEPENDENCE ON EARCAP LEAKAGE LOSSES HANDSET RECEIVE-FREQUENCY S
2、upplement 20 to ITU-T Series P Recommendations (Previously “CC ITT Recommendations”) FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The ITU-T is responsible for studying technical, operating and tariff questions
3、and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendati
4、ons on these topics. Supplement 20 to ITU-T Series P Recommendations was prepared by the ITU-T Study Group XII (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased
5、to exist as of 28 February 1993. In its place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendati
6、on, no change has been made in the text to references containing the acronyms “CCITT, CCIR or IFRB” or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. 2 In this Recommen
7、dation, the expression “Administration” is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. O ITU 1994 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, incl
8、uding photocopying and microfilm, without permission in writing from the ITU. CONTENTS Page 1 Introduction 1 2 1 3 1 4 References 4 Examples of earcap leakage effects measured during telephone usage (real ears) . Examples of earcap leakage effects measured with artificial ears Supplement 20 - Series
9、 P (03/93) i Supplement 20 EXAMPLES OF MEASUREMENTS OF HANDSET RECEIVE-FREQUENCY RESPONSES: DEPENDENCE ON EARCAP LEAKAGE LOSSES (Helsinki, 1993) (referred to in Series P Recommendations) 1 Introduction The subject of handset earcap leakage losses has been studied on and off for a quite considerable
10、time by many organizations. The liberalization of the telecom market as well as “innovative” handset designs have now made the leakage problem more acute, i.e. in terms of customer complaints. The information given in this supplement is aimed to give some instructive examples as general information
11、on the subject. 2 Examples of earcap leakage effects measured during telephone usage (real ears) Figure 1 shows the Sound Pressure Level (CLBSPL) measured at 20 persons ears: a) under normal usage; b) when the subjects were asked to obtain a good seal by pressing the receiver hard to the ear. The ha
12、ndsets were of a conventional design, i.e. using high acoustic impedance earphones, that were driven electrically with a signal having constant spectrum. Note the large spread between individuals! These data originate from an investigation made by Swedish Telecom in 1967 and may be found in referenc
13、e SI. Further real ear data may be found in 21, 121, 191. 3 Examples of earcap leakage effects measured with artificial ears Figure 2 shows receive-frequency response for a modern German handset telephone, sealed on the knife edge of the CCITT Type 1P.57 (IEC 318) artificial ear (-), on this ear mod
14、ified to provide additional acoustic leak “Swedish” (-) or “German” (- - -), 13. Neither of the leaks are recommended by CCITT, however the “German” one is presently used by the German Administration for regulatory purposes. Figure 3 shows CCITT Round Robin (RR) telephone No. 4, a conventional desig
15、n having an IRS-shaped handset 14 measured on CCITT Recommendation P.57 Type MEC 3 18 artificial ear (- - -), Type 3.2 with “low leak” (-) and Type 3.2 with “high leak” (-) artificial ears respectively. For typical RLR differences refer to 14. Figure 4 is similar to 3 but shows results for RR teleph
16、one No. 2, using a low-acoustic impedance earphone design. It is noticeable that such a design is much less dependent on earcap leakage. Supplement 20 - Series P (03/93) 1 b) “Tight seal” V = 4.6 cm3 Ordinaty earcap FIGURE 1 SPL measured on 20 subjects; ordinary earcap 2 Supplement 20 - Series P (03
17、/93) Sealed “Swedish” leak “German” leak _ FIGURE 2 German telephone set FIGURE 2lP.64 . DO21 = 10 cm CCIT, Type 1 (IEC 318) P.57, Type 3.2 with “Low leak” P.57, Type 3.2 with “High leak” _ FIGURE 3 Sj,(f) RR handset phone Na 4 Supplement 20 - Series P (03/93) 3 4 il 250 500 lk 2k 4k 8k AL T1204180-
18、92/d4 CCIlT, Type 1 (IEC 318) P.57, Type 3.2 with ?Low leak? P.57, Type 3.2 with ?High leak? FIGURE 4 Sj,(O RR handset phone No. 2 (low Zg) References ZWISLOCKY (J.J.): An ear like coupler for earphone calibration, Rep. LSC-S-9. Lab. Sensory Commun., University de Syracuse, 1971. MODENA (G.) and REO
19、LON, (A.): ?A new artificial ear for telephone use?, J. Acoust. Soc. Am. 65 (3, pp. 1604-1610, 1978. Brel and Kjaer: ?On the measurement of the insertion gain of telephone systems using head and torso simulators (HATS): Separation into transmit and receive characteristics and comparison with classic
20、al coupler measurements?, CCITT, COM XII 224-E, Geneva, 1987. CCITT Handbook on Telephonometry, Chapter 1.4: ?On the telephonic responses?. In press, CCITT, Geneva. Telecom Electroacoustics Workshop proceedings, Naerum 1988. COM XII-15 (Special Rapporteur of Q. 12/XII): Round Robin experiment for ev
21、aluating the repeatability of measurements on pinna simulators. COM XII-38 (Germany): Leakage loss of telephone sets. COM XII-42 (Ellemtel): Suitable algorithm for LR calculation on earcap leaks. COM XII-43 (Ellemtel): Adaptor to IEC 318 for measuring earcap leaks. 4 Supplement 20 - Series P (03/93)
22、 COM XII-49 (Brel and Kjaer): The acoustic impedance of real and artificial ears - Implications for Sje and Le for CCITT Round Robin handset telephones. COM XII-50 (Brel and Kjaer): Frame of reference and artificial ears for 7 kHz wideband handset receiver measurements, sjd(Q and Gjd(Q. COM XII-66 (
23、Germany): Examination of the transfer function of various receiver capsules and handsets at the human hearing. COM XII-69 (Germany): Leakage loss of telephone sets: additional measurements with defined leaks. COM XII-73 (Special Rapporteur of Q. 12EII): Report on the Round Robin experiment for evalu
24、ating the repeatability of measurements on pinna simulators, October 1990. Delayed D.52 (Brel and Kjaer): Comments to contribution: Artificial head technique for determining the transfer functions of telecommunications equipment, October 1990. Delayed D.75 (Brel and Kjaer): Impedance measurements of
25、 leak adaptors for the IEC 318 Artificial ear, October 1990. Delayed D. 110 (Germany): Pinna simulator with a simplified mathematically describable geometry for determining the transfer functions of telephone equipment. Delayed D.98 (Germany): The behavior of telephone users in a noisy environment.
26、Delayed D.77 (Danish Technical Univ. and Brel and Kjaer): S, measurements on human subjects (extract), October 1990. TD 48 (Special Rapporteur of Q. 8EII): Necessary modifcation of W-weights following the change of Artificial ear, October 1990. COM XII-R 12, page 20: Question 12/XII - Artificial mouth and ears. TD 83 (Special Rapporteur of Q. 12EII): Draft Recommendation P.57 on the artificial ears, February 1992. TD 84 (Special Rapporteur of Q. 12EII): Draft Recommendation P.58 - Head and torso simulator for telephonometry, Februaryl992. Supplement 20 - Series P (03/93) 5
