1、IEEE Std 1652-2008IEEE Standard for the Application ofFree Field Acoustic Reference toTelephony MeasurementsIEEE3 Park Avenue New York, NY 10016-5997, USA20 March 2009IEEE Communications SocietySponsored by theTransmission Access +1 978 750 8400. Permission to photocopy portions of any individual st
2、andard for educational classroom use can also be obtained through the Copyright Clearance Center. iv Copyright 2009 IEEE. All rights reserved. Introduction This introduction is not part of IEEE Std 1652-2008, IEEE Standard for the Application of Free Field Acoustic Reference to Telephony Measurement
3、s. The traditional acoustic reference point for telephony measurements in the receive direction is the ear reference point (ERP). Since the ERP has been used for decades, use of the ERP preserves compatibility with historical measurements and calculations. This is especially important with respect t
4、o receive loudness ratings, which are referenced to the ERP. Outside the field of telephony, the free field is the traditional acoustic reference point. Free field frequency response measurements of devices such as loudspeakers, multimedia terminals, and consumer audio equipment relate closely to wh
5、at is heard by the listener. For the same reason, the free field is also an appropriate reference point for telephony applications. In addition, free field measurements make it possible to compare the performance of handsets, headsets, and loudspeakers in both telephony and music listening applicati
6、ons. Notice to users Laws and regulations Users of these documents should consult all applicable laws and regulations. Compliance with the provisions of this standard does not imply compliance to any applicable regulatory requirements. Implementers of the standard are responsible for observing or re
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11、ough the issuance of amendments, corrigenda, or errata, visit the IEEE Standards Association web site at http:/ieeexplore.ieee.org/xpl/standards.jsp, or contact the IEEE at the address listed previously. For more information about the IEEE Standards Association or the IEEE standards development proc
12、ess, visit the IEEE-SA web site at http:/standards.ieee.org. v Copyright 2009 IEEE. All rights reserved. Errata Errata, if any, for this and all other standards can be accessed at the following URL: http:/standards.ieee.org/reading/ieee/updates/errata/index.html. Users are encouraged to check this U
13、RL for errata periodically. Interpretations Current interpretations can be accessed at the following URL: http:/standards.ieee.org/reading/ieee/interp/ index.html. Patents Attention is called to the possibility that implementation of this standard may require use of subject matter covered by patent
14、rights. By publication of this standard, no position is taken with respect to the existence or validity of any patent rights in connection therewith. The IEEE is not responsible for identifying Essential Patent Claims for which a license may be required, for conducting inquiries into the legal valid
15、ity or scope of Patents Claims or determining whether any licensing terms or conditions provided in connection with submission of a Letter of Assurance, if any, or in any licensing agreements are reasonable or non-discriminatory. Users of this standard are expressly advised that determination of the
16、 validity of any patent rights, and the risk of infringement of such rights, is entirely their own responsibility. Further information may be obtained from the IEEE Standards Association. Participants At the time this standard was completed, the Subcommittee on Telephone Instrument Testing Working G
17、roup had the following membership: John R. Bareham, Chair Glenn R. Hess, Vice Chair Al Baum Cliff Chamney Miguel Dearaujo Steve Graham Frederick Kruger Ron D. Magnuson Anthony Scott Christopher J. Struck Stephen R. Whitesell Allen Woo Bob Young The following members of the individual balloting commi
18、ttee voted on this standard. Balloters may have voted for approval, disapproval, or abstention. John R. Bareham Al Baum H. Stephen Berger Keith Chow Kevin Coggins Miguel De Araujo Carlo Donati Sunil Dsouza Daniel Foley Steve Graham Randall Groves Glenn R. Hess Werner Hoelzl Raj Jain Shinkyo Kaku Pio
19、tr Karocki Frederick Kruger Ronald Magnuson Michael S.Newman Gary Nissen Bartien Sayogo Jeffrey Schenck Anthony Scott Thomas Starai Christopher J. Struck Allen Woo vi Copyright 2009 IEEE. All rights reserved. When the IEEE-SA Standards Board approved this standard on 10 December 2008, it had the fol
20、lowing membership: Robert M. Grow, Chair Thomas Prevost, Vice Chair Steve M. Mills, Past Chair Judith Gorman, Secretary Victor Berman Richard DeBlasio Andy Drozd Mark Epstein Alexander Gelman William R. Goldbach Arnold M. Greenspan Kenneth S. Hanus Jim Hughes Richard Hulett Young Kyun Kim Joseph L.
21、Koepfinger* John Kulick David J. Law Glenn Parsons Ron Petersen Chuck Powers Narayanan Ramachandran Jon Walter Rosdahl Anne-Marie Sahazizian Malcolm Thaden Howard Wolfman Don Wright *Member Emeritus Also included are the following nonvoting IEEE-SA Standards Board liaisons: Satish K. Aggarwal, NRC R
22、epresentative Michael Janezic, NIST Representative Jennie Steinhagen IEEE Standards Program Manager, Document Development Matthew J. Ceglia IEEE Standards Program Manager, Technical Program Development vii Copyright 2009 IEEE. All rights reserved. Contents 1. Overview 1 1.1 Scope . 1 1.2 Purpose 1 1
23、.3 How to use this standard 1 2. Normative references 2 3. Definitions 2 4. The listening experience . 3 4.1 Acoustical reference points 3 4.2 Orthotelephonic Reference 3 4.3 Loudspeakers . 3 4.4 Telephone receivers . 5 5. Measurement procedure . 8 5.1 Receive frequency response 8 5.2 Other measurem
24、ents 10 5.3 Loudness rating 10 Annex A (normative) Translation from DRP to ERP . 11 Annex B (normative) Diffuse field correction 13 1 Copyright 2009 IEEE. All rights reserved. IEEE Standard for the Application of Free Field Acoustic Reference to Telephony Measurements IMPORTANT NOTICE: This standard
25、 is not intended to assure safety, security, health, or environmental protection in all circumstances. Implementers of the standard are responsible for determining appropriate safety, security, environmental, and health practices or regulatory requirements. This IEEE document is made available for u
26、se subject to important notices and legal disclaimers. These notices and disclaimers appear in all publications containing this document and may be found under the heading “Important Notice” or “Important Notices and Disclaimers Concerning IEEE Documents.” They can also be obtained on request from I
27、EEE or viewed at http:/standards.ieee.org/IPR/disclaimers.html. 1. Overview 1.1 Scope This standard provides the techniques and rationale for referencing acoustic telephony measurements to the free field. It applies to ear-related measurements such as receive, sidetone, and overall. 1.2 Purpose A co
28、mmon acoustic reference point is needed for comparing electroacoustic performance of handset, headset, handsfree, and other kinds of telephone terminals. It is also needed for comparing telephone terminals with other devices such as loudspeakers, mobile communication devices, multimedia terminals, a
29、nd consumer audio equipment. The free field is the appropriate reference point because the results relate closely to what is heard by the listener. Therefore, the free field is a more widely applicable reference point for telephony measurements than the traditional ERP (ear reference point). 1.3 How
30、 to use this standard Clause 4 provides information about loudspeaker and telephone listening, and how free field listening conditions relate to both. Start here to understand why it is desirable to use the free field reference. IEEE Std 1652-2008 IEEE Standard for the Application of Free Field Acou
31、stic Reference to Telephony Measurements 2 Copyright 2009 IEEE. All rights reserved. Clause 5 provides a practical method to translate measurements made on a head and torso simulator (HATS) to the free field. Start here to implement the standard. 2. Normative references The following referenced docu
32、ments are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments or corrigenda) applies. ITU-T Recommendation P.57 (2005), Artificial Ears.1ITU-T Recomme
33、ndation P.58 (1996), Head and Torso Simulator for Telephonometry. ITU-T Recommendation P.581 (2000), Use of head and torso simulator (HATS) for hands-free terminal testing. 3. Definitions For the purposes of this standard, the following terms and definitions apply. The Authoritative Dictionary of IE
34、EE Standards Terms should be referenced for terms not defined in this clause. 3.1 diffuse field: Sound field in which the time average of the mean-square sound pressure is everywhere the same and the flow of acoustic energy in all directions is equally probable. 3.2 drum reference point (DRP): A poi
35、nt located at the end of the ear canal, corresponding to the eardrum position. Syn: eardrum reference point. 3.3 eardrum reference point (DRP): See: drum reference point. 3.4 ear reference point (ERP): A virtual point for acoustic and geometric reference located outside the entrance to the ear canal
36、. The exact location is specified for each type of ear simulator. 3.5 free field: (simple definition) Sound field free of reflections. 3.6 free field: (complete definition) Sound field in a homogenous, isotropic medium free from boundaries. In practice, the effects of boundaries on a free field are
37、negligible over the region of interest. 3.7 head and torso simulator (HATS) for telephonometry: Manikin extending downward from the top of the head to the waist, designed to simulate the sound pick-up characteristics and the acoustic diffraction produced by a median human adult and to reproduce the
38、acoustic field generated by the human mouth. 3.8 orthotelephonic: The acoustical relationship between two people of equal height facing one another at a distance of 1 m in a quiet non-reverberant room. 1ITU-T publications are available from the International Telecommunications Union, Place des Natio
39、ns, CH-1211, Geneva 20, Switzerland/Suisse (http:/www.itu.int/). IEEE Std 1652-2008 IEEE Standard for the Application of Free Field Acoustic Reference to Telephony Measurements 3 Copyright 2009 IEEE. All rights reserved. 4. The listening experience 4.1 Acoustical reference points A measurement may b
40、e made at one point, but translated to another point. This may be necessary due to inaccessibility of the desired acoustical point. An acoustic reference point is somewhat like an electrical test point. The traditional reference point for telephony measurements is the ERP. Measurements of a telephon
41、e receiver may actually be collected at the ERP, or at the (simulated) eardrum (DRP), or possibly some other place. If the measurement is collected at some point other than the ERP, it is then translated to the ERP. In other words, the measurement is processed so that the result is the same as if it
42、 had been collected at the ERP in the first place. When using HATS, the measurement is collected at the DRP, where the microphone is located. The measurement is then translated to the ERP. But as the rest of this document demonstrates, the ERP is not the optimum acoustical reference point. 4.2 Ortho
43、telephonic Reference The orthotelephonic reference is a face-to-face conversation in a free field, at a distance of 1 m. The distance can be measured with respect to the mouth reference point (MRP) and the ERP, the center of the head, or some combination, but the basic idea is the same. (See Figure
44、1.) A telephone conversation using a handset is intended to approximate the acoustical experience of a face-to-face (free field) conversation, at least at one ear. The orthotelephonic reference is therefore fundamental in evaluating telephone performance. Even though a handset is placed on the ear,
45、and partly closes it, the acoustical performance should nonetheless be evaluated using the free field as the reference condition. 1 meterMRPERPFigure 1 Orthotelephonic reference 4.3 Loudspeakers Loudspeakers deliver sound to the listener without contacting the listeners head. IEEE Std 1652-2008 IEEE
46、 Standard for the Application of Free Field Acoustic Reference to Telephony Measurements 4 Copyright 2009 IEEE. All rights reserved. In general, loudspeaker-based audio systems that are considered to be high fidelity will exhibit a relatively flat frequency response in the free field. Thus a “flat”
47、frequency response is considered to be a major indicator of high-quality sound reproduction. (See Figure 2 and Figure 3.) Figure 2 Loudspeaker and free field measurement microphone Figure 3 Loudspeaker with flat frequency response, as measured in the free field Seen from the (DRP), the response incl
48、udes the effect of body, head, pinna, and ear canal. (See Figure 4 and Figure 5.) IEEE Std 1652-2008 IEEE Standard for the Application of Free Field Acoustic Reference to Telephony Measurements 5 Copyright 2009 IEEE. All rights reserved. Figure 4 Loudspeaker with human listener Figure 5 “Flat” louds
49、peaker measured at eardrum (DRP) 4.4 Telephone receivers Telephone receivers, and other earphones, deliver sound to the listener while in contact with the listeners head. If a telephone receiver is to have high-quality sound reproduction, similar to a loudspeaker, it should deliver the same response to the listeners ear. (See Figure 6 and Figure 7.) IEEE Std 1652-2008 IEEE Standard for the Application of Free Field Acoustic Reference to Telephony Measurements 6 Copyright 2009 IEEE. All rights reserved. Figure 6 Listener with telephone receiver Figure 7 “Fl
