1、Copyright 1998 IEEE All Rights Reserved 1ANSI/IEEE Std 661-1979 (R2008)An American National StandardIEEE Standard Method for Determining Objective Loudness Ratings of Telephone ConnectionsSponsorTransmission Systems Committeeof theIEEE Communications SocietyReaffirmed September 25, 2008Approved June
2、 16, 1978IEEE Standards BoardApproved February 15, 1983American National Standards Institute Copyright 1979 byThe Institute of Electrical and Electronics Engineers, Inc 345 East 47th Street, New York, NY 10017, USANo part of this publication may be reproduced in any form, in an electronic retrieval
3、system or otherwise, without theprior written permission of the publisher.Authorized licensed use limited to: IHS Stephanie Dejesus. Downloaded on February 17, 2009 at 15:45 from IEEE Xplore. Restrictions apply.Joseph L. Koepfinger, Chairman William E. Andrus C. N. Berglund Edward J. Cohen Warren H.
4、 Cook David B. Dobson R. 0. Duncan Charles W. Flint Approved June 16,1978 IEEE Standards Board Ivan G. Easton, Secretary Jay Forster Ralph I. Hauser Loering M. Johnson Irving Kolodny William R. Kruesi Thomas J. Martin John E. May Irvin N. Howell, Jr, Vice Chairman Donald T. Michael Voss A. Moore Wil
5、liam S. Morgan Robert L. Pritchard Blair A. Rowley Ralph M. Showers B. W. Whittington I Authorized licensed use limited to: IHS Stephanie Dejesus. Downloaded on February 17, 2009 at 15:45 from IEEE Xplore. Restrictions apply.Foreword (This Foreword is not a part of IEEE Std 661-1979, Standard Method
6、 for Determining Objective Loudness Ratings of Telephone Connections.) . This IEEE Standard Method for Determining Objective Loudness Ratings of Telephone Connec- tions has been prepared in response to a need by the telecommunications industry for a standard method of testing transmission performanc
7、e of partial and overall telephone connections in a man- ner that reflects the attribute of subjective loudness. This document complements and is dependent on IEEE Std 269-1971, Standard Method for Measuring Transmission Performance of Telephone Sets. Individuals from private and government design,
8、manufacturing, and research organizations have given freely of their time in preparing, testing, and reviewing this standard. The IEEE will maintain this document current with the state of the technology. Comments, suggestions, and requests for interpretations should be addressed to: Secretary JEEE
9、Standards Board Institute of Electrical and Electronics Engineers 345 East 47th Street New York, New York 10017 This standard was prepared by the Subcommittee on Telephone Instrument Testing of the Transmission Systems Committee of the IEEE Communications Society. The members of the subcommittee are
10、: K. Simonson, Chairman E. S. Hineline, Jr, Secretary F. T. Andrews L. A. Berry C. F. Buster, Jr M. Chytil J. F. Dunlap J. B. Eppes R. P. Farrell R. F. Foster A. S. Howell J. J. Jetzt B. Katz M. J. Leach G. A. Ledbetter T. Lisbon N. G. Long R. P. McCabe A. Mankivsky D. J. Morgen L. Poradowski L. A.
11、Strommen J. L. Sullivan C. G. Svala . cp s Authorized licensed use limited to: IHS Stephanie Dejesus. Downloaded on February 17, 2009 at 15:45 from IEEE Xplore. Restrictions apply.SECTION Contents PAGE 1 . Introduction . 5 2 . ScopeandPurpose . 6 3 . Definitions . 6 3.2 Reference System . 6 3.1 Loud
12、nessRating 6 3.3 Objective Loudness Rating (OLR) . 7 3.4 Voltage and Pressure Levels 7 3.5 Overall Objective Loudness Rating (OOLR) . 7 3.7 Receiving Objective Loudness Rating (ROLR) . 7 3.10 Source/Load Impedance 7 3.11 LoudnessEquation 7 3.6 Transmitting Objective Loudness Rating (TOLR) . 7 3.8 Si
13、detone Objective Loudness Rating (SOLR) 7 3.9 Electrical Objective Loudness Rating (EOLR) 7 4 . References 8 5 . Instrumental Method 8 5.1 General . 8 5.2 Test Equipment . 8 5.3 Meamringsystem . 10 5.4 Calibration 13 5.5 Testprocedure . 13 6 . Computational Method 14 FIGURES Fig 1 H-Pad Circuit . 10
14、 Fig 2 Sending End of Measuring System . 11 Fig 3 Receiving End of Measuring System . 11 Fig 4 A-Measurement of Overall Objective Loudness Rating (OOLR); B-Measurement of Transmitting Objective Loudness Rating (TOLR); C-Measurement of Receiving Objective Loudness Rating (ROLR) ; D-Measurement of Sid
15、etone Objective Loudness Rating (SOLR); . E-Measurement of Electrical Objective Loudness Rating (EOLR); 12-13 Fig 6 Graphical Loudness Computation Form 15 TABLES Table 1 Table 2 Example of Computation of Transmitting Objective Loudness Rating . Example of Computation of Receiving Objective Loudness
16、Rating 16 16 APPENDIXES Appendix A Loudness Rating Method . 17 Appendix B Weighted Acoustic Source Signal 19 Appendix C Weighted Electrical Source Signal . 20 APPENDIX FIGURES Fig A1 Computation of Speech Loudness . 17 Fig B1 Sound Pressure Spectrum of Continuous Speech at Two Inches from the Lips o
17、f aTalker . 19 Authorized licensed use limited to: IHS Stephanie Dejesus. Downloaded on February 17, 2009 at 15:45 from IEEE Xplore. Restrictions apply.IEEE Standard Method for Determining Objective Loudness Ratings of Telephone Connections 1. Introduction The methods that are used to measure the tr
18、ansmission performance of telephone connec- tions may be divided into two classes: objective methods and subjective methods. This standard considers an objective method that can be used for measuring telephone connections in a man- ner that reflects the subjective attribute of loud- ness with an acc
19、uracy suitable for most tele- phone transmission engineering problems. The performance measure is expressed in terms of a defined reference and is referred to as an objec- tive loudness rating. The objective method utilizes a sound source to activate the telephone transmitter, and an acoustic couple
20、r and associated microphone (artificial ear) as an acoustic termination for the telephone receiver. The sound source con- sists of a source of electric energy, a special type of loudspeaker unit (artificial mouth), and such supplementary electric and acous- tic components as may be required so that
21、the ensemble provides a controlled sound field. The artificial mouth and artificial ear provide a simpler means of measuring characteristics of telephone connections than is possible with the human mouth and ear. The practical design of artificial mouths and artificial ears is such that they only ap
22、proximate their respective human counterparts. Thus telephone connection char- acteristics measured using these devices will only approximate and not duplicate those characteristics measured with human mouths and ears. However, experience has shown that characteristics determined using these devices
23、 are highly useful in telephone transmission Subjective methods for rating the transmis- sion performance of telephone connections involve human talkers and listeners. Commonly engineering. used subjective test methods include those based on loudness assessment, articulation, and judgment. 1-41 .l T
24、he particular method employed in any given situation depends on the transmission parameter( s) to be evaluated and on the performance measure criterion of interest, for example, articulation or loudness. Subjective methods have the particular ad- vantage that ratings obtained are direct meas- ures o
25、f performance. A major disadvantage of subjective methods is that they often require large groups of human subjects for long time periods in order that the results have signifi- cance. Objective methods, on the other hand, involve somewhat simpler and better controlled measurements, and a large numb
26、er of measure- ments can be made in a relatively short period of time. Moreover, measurements can be ob- tained that reflect subjective evaluation with suitable accuracy. This standard is concerned with a specific ob- jective method of determining the loudness ratings of telephone connections. The m
27、ethod is based on objective measurements and com- putations performed in such a manner that the numerical results obtained reflect the subjec- tive attribute of loudness. The method was derived, employing certain simplifying assumptions, to combine simplicity and reasonably close agreement between o
28、bjec- tively determined results and subjective re- sponses. (See Appendix A.) Results obtained with the method described in this standard and the relation of these results to subjective test results may vary with design, for example, size and shape of the telephone handset and the type of circuitry
29、used to control equalization Numbers in brackets refer to those of the references listed in Section 4 of this standard. 5 Authorized licensed use limited to: IHS Stephanie Dejesus. Downloaded on February 17, 2009 at 15:45 from IEEE Xplore. Restrictions apply.IEEE Std 661-1979 IEEE STANDARD METHOD FO
30、R DETERMINING OBJECTIVE or output level, or both. Thus, specific instances might occur where the results obtained accord- ing to the method described will not be suit- able for transmission engineering purposes, and supplementary subjective measurements may be required. It would, therefore, appear d
31、esir- able to establish correlation between subjective measurements and objective measurements separately for each telephone set design before the measurements obtained using the method of this standard are interpreted to reflect loud- ness performance under conditions of actual use. 2. Scope and Pu
32、rpose 2.1 The purpose of this standard is to describe a practical and reproducible method of deter- mining the loudness ratings of telephone con- nections. Loudness rating may be measured directly using appropriate test instruments and facilities, as specified in this standard, or may be computed us
33、ing the amplitude-frequency characteristic of the connection measured in accordance with IEEE Std 269-1971 51. 2.2 Loudness ratings determined using this standard may not exactly duplicate subjective loudness evaluations. Moreover, measured rat- ings and computed ratings determined using this standa
34、rd may not agree, particularly if the con- nection incorporates nonlinear elements. How- ever, differences are expected to be acceptably small for engineering purposes. For example, differences for connections utilizing linear microphones are expected to be small, result- ing only from instrument an
35、d measurement error, while for connections employing non- linear microphones, for example, carbon micro- phones, the differences may be larger. NOTE: For the purposes of this standard, a linear micro- phone is one that exhibits a one-to-one relation between input pressure and output voltage over its
36、 normal oper- ating range. 2.3 The procedures given in this standard may be used for determining the loudness rating of partial and complete telephone connections. For complete telephone connections, compris- ing overall and sidetone transmission paths, the procedures involve measurement of acoustic
37、 input and output pressures. For partial telephone connections comprising transmitting, receiving, or connection paths, the procedures involve measurement of acous- tic pressures and electric voltages. 2.4 Transmission planning of switched tele- phone networks is generally accomplished by working wi
38、th parts of connections, for example, customer loops (telephone sets, line facilities, and feeding bridges) or trunks, to ensure that when these parts are switched together, the re- sulting overall connections perform satisfactori- ly. When planning is based on loudness, the sum of the loudness loss
39、es determined for parts of a connection should closely approximate the loudness loss of the overall connection. For such purposes the recommended analysis band- width is 300-3300 Hz, which approximates the bandwidth of the more band-limiting compo- nents typically found in modern telephone net- work
40、s. There may be cases in which a wider bandwidth would be desirable (see Appendix A), and the methods of this standard will accom- modate such wider bandwidths. 2.5 The method of this standard is based on specification of (1) characteristics of a suitable artificial mouth, (2) a standard artificial
41、ear, and (3) appropriate auxiliary measuring instru- ments and facilities. The method is intnded for rating connections involving telephone sets equipped with handsets. The applicability of the method for the measurement of telephone sets incorporating special devices such as noise- exclusion transm
42、itters, distant-talking transmit- ters, ear insert receivers, or noise-exclusion re- ceivers (receivers equipped with circumaural earpads) has not been reviewed. However, the loudness theory on which this standard is based is sufficiently general that advances in the art may permit measurement of ma
43、ny such special devices using the methods specified in this standard. 3. Definitions NOTE: For terms not listed in this section, see Section 3 of IEEE Std 269-1971 5, ANSI Sl.1-1960 (R1976) 6, or ANSI/IEEE Std 100-1977 7. 3.1 Loudness Rating. The amount of frequency- independent gain that must be in
44、serted into a system under test so that speech sounds from the system under test and a reference system are equal in loudness. 3.2 Reference System. A system that provides 0 dB acoustic gain between a mouth reference 6 Authorized licensed use limited to: IHS Stephanie Dejesus. Downloaded on February
45、 17, 2009 at 15:45 from IEEE Xplore. Restrictions apply.LOUDNESS RATINGS OF TELEPHONE CONNECTIONS IEEE Std 661-1979 point at 25 mm in front of a talkers lips and an ear reference point at the entrance to the ear canal of a listener, when the listener is using an earphone. This system is assigned a l
46、oudness rating of 0 dB. The frequency characteristic of the system must be flat over the range 300-3300 Hz and show infinite attenuation outside of this range. NOTES : (1) If an actual reference system is constructed for subjective comparison purposes, the system response at 300 and 3300 Hz shall be
47、 down 3 f 1 dB relative to the midband response. The gain of the system shall be ad- justed to compensate for the finite slope of the filter skirts and deviation from flatness of the pass band. The amount of this adjustment CM be determined by first calculating the OLR (3.3) over a frequency range t
48、hat includes at least the 50 dB down points of the real response, and next calculating the OLR of the idea1 response, over the same frequency range. The difference between the OLRs is the required gain adjustment. (2) To the extent that the artificial mouth and arti- ficial ear replicate their avera
49、ge human counterparts, a virtual reference system is introduced by reason of the calibration of the test system described in Section 5. 3.3 Objective Loudness Rating (OLR). The rating of a connection or its components when measured according to this standard. 3.4 Voltage and Pressure Levels. Voltage and pressure levels ( VT , Vw , SE, and SM ) as used in definitions of this section are measured (as described in Section 5 of this standard) or com- puted (as described in Section 6 of this stand- ard). 3.5 Overall Objective Loudness Rating (OOLR) VT = output voltage of the transmi
