1、Designation: E3150 18Standard Guide forForensic Audio Laboratory Setup and Maintenance1This standard is issued under the fixed designation E3150; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number i
2、n parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide sets forth recommendations for the creationof a forensic audio laboratory space as well as theconfiguration, verification, and maint
3、enance of the equipmentcontained within the lab.1.2 In designing and configuring an audio laboratory, it isimportant to consider the acoustical environment/room of thelaboratory, as well as climate control. Other than having aviable location for the laboratory, computer hardware andsoftware applicat
4、ions are the most important components of alaboratory.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine th
5、e applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issu
6、ed by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E1732 Terminology Relating to Forensic Science2.2 ISO/IEC Standard:3ISO/IEC 17025 General Requirements for the Competenceof Testing and Calibration Laboratories2.3 AES Standard:4A
7、ES Recommended Practice for Audio Preservation andRestoration Storage and Handling Storage ofPolyester-Base Magnetic Tape, AES Standard 22-1997,Reaffirmed 20082.4 SWGDE Standard:5SWGDE Recommendations for Validation Testing3. Terminology3.1 Definitions:3.1.1 For definitions of terms that may assist
8、in interpretingthis standard, refer to Terminology E1732.4. Significance and Use4.1 The design and configuration of an audio laboratory, aswell as the maintenance of equipment, are factors that must beconsidered to ensure an optimal environment to produce thebest results. This guide is intended to p
9、rovide general guidancefor laboratory setup and maintenance.4.2 This document is not meant to be an all-inclusive guideon how to set up a laboratory; nor does it contain informationpertaining to specific commercial products as it relates tocomputer hardware, forensic, and non-forensic software appli
10、-cations.4.3 When dealing with equipment and technology outsideyour area of expertise, consult with an appropriate specialist.5. Audio Laboratory Considerations5.1 EnvironmentThe physical environment, independentof equipment, in and around a forensic audio laboratory canhave a profound effect on the
11、 quality of work produced. Audiolaboratory design is a complex task and comprehensive refer-ences should be consulted, including Refs (1-4).65.1.1 AcousticsThe acoustic environment of a forensicaudio laboratory is the collection of ambient sounds andinfluences (for example, materials, resonances, ec
12、ho), which1This guide is under the jurisdiction of ASTM Committee E30 on ForensicSciences and is the direct responsibility of Subcommittee E30.12 on Digital andMultimedia Evidence.Current edition approved Oct. 1, 2018. Published October 2018. DOI: 10.1520/E3150-18.2For referenced ASTM standards, vis
13、it the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from International Organization for Standardization (ISO), ISOCentral Secretariat, BI
14、BC II, Chemin de Blandonnet 8, CP 401, 1214 Vernier,Geneva, Switzerland, http:/www.iso.org.4Available from Audio Engineering Society, Inc. (AES), InternationalHeadquarters, 551 Fifth Ave., Suite 1225, New York, NY 10176, http:/www.aes.org.5Available from the Scientific Working Group on Digital Evide
15、nce (SWGDE),https:/www.swgde.org.6The boldface numbers in parentheses refer to a list of references at the end ofthis standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with
16、 internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1can affect the quality of a forensic audio
17、 analysis. Eliminate orminimize sound distractions in the audio laboratory to preventconfusion as to what sounds are present on a recording (5).5.1.1.1 Acoustical impediments:(1) Background conversation, TV, radio, and music;(2) Computer and equipment cooling fans;(3) Air conditioning units and airf
18、low; and(4) Vibration.5.1.1.2 Steps can be taken to mitigate external noise in thelaboratory, such as(1) Using acoustic foam or other materials to absorbreverberation and echo,(2) Designing the laboratory with acoustic traps,(3) Rerouting unnecessary HVAC ducts,(4) Using acoustic baffling within the
19、 HVAC ducts that arepresent,(5) Using heavy wooden doors that seal tightly all aroundwhen closed, and(6) Using high-quality headphones during examinations toreduce extraneous sounds and maximize the audibility of thesignal being examined.5.1.2 Temperature and HumidityEnsure the temperatureand humidi
20、ty of the laboratory is within the manufacturersspecifications of the equipment. Equipment itself generatesheat and requires adequate ventilation to prevent heat buildupthat could affect the signal (AES Recommended Practice forAudio Preservation and Restoration, (6).5.1.3 Electromagnetic Interferenc
21、eInterference from a va-riety of electromagnetic sources can affect signal quality(7-10).5.1.3.1 Alternating current (AC) sources, such as powerlines, motors, lamp dimmers, fluorescent lights, and uninter-ruptible power supplies can create magnetic pickup loops thatcan induce noise into improperly r
22、outed signal cables. Separatetransformers and power lines from signal lines. If power andsignal lines must cross, have them cross at 90 to one another.5.1.3.2 Improper grounding can create ground loops. Manyfactors contribute to this phenomenon. Properly ground equip-ment and racks to minimize groun
23、d loops.5.1.3.3 Items that generate magnetic fields strong enough toaffect the integrity of any magnetic media nearby, such asloudspeakers, should be kept as far away as possible fromevidentiary recordings or removed from the laboratory.5.1.3.4 Cell phones, pagers, radios, and other radio fre-quency
24、 (RF) transmitting devices may interfere with cables orequipment and should be turned off or removed from thelaboratory.5.1.3.5 Cathode ray tube (CRT) video monitors can induceaudible noise in nearby or connected audio equipment. Do notplace playback/recording devices next to CRT monitors (11).5.2 S
25、ystem ConfigurationThe quality and arrangement ofequipment, cables, connectors, interfaces, and software directlyaffects the audio signal (2, 5, 7, 12).5.2.1 Computer and Network SystemsProcess evidence ona system isolated from people not authorized to access theevidence. It is also important to ens
26、ure that computers andnetwork systems are secure. It is recommended to have aseparate computer for searching the Internet for unique codecs,proprietary players, etc.5.2.2 Audio EquipmentChoose playback, processing, andrecording equipment suitable for the task at hand, usingprofessional and broadcast
27、 grade equipment where possible.5.2.3 Signal PathThe signal path is the complete route ofthe audio data from the source through all of the connectors,interfaces, cables, and software to the destination. Designsignal paths with the least amount of degradation. Use cablesand connectors of sufficient q
28、uality and minimal length tominimize signal loss and reduce the opportunity for interfer-ence. For analog audio runs, maximize the use of balancedlines over unbalanced lines (10, 13).Avoid stacking adapters tointerconnect equipment. It is preferable to use a cable designedfor the particular interfac
29、es involved. Be aware of the imped-ance and level of analog interfaces (7). Loudspeakers are notrecommended for conducting forensic audio analyses, but ifotherwise used during an examination, ensure that they arecapable of reproducing the full frequency spectrum of theaudio signal.5.2.4 Transmission
30、 FormatChoose the signal format thattransmits the audio data with the least amount of degradation,loss, or attenuation. This decision depends upon what formatsare available on the equipment being used. Minimize thenumber of digital to analog and analog to digital conversions(14, 15).5.3 System Verif
31、icationOnce the equipment and intercon-nections are configured, updated, or changed, run test signalsthrough the various components to verify that everything isoperating as expected.5.3.1 CalibrationCalibration is the process of establishingthe relationship between measurements and known standardval
32、ues (see Terminology E1732). If a piece of equipment is thebasis for measurements in which the numerical results them-selves have decisive relevance to examinations, then it iscritical that it be calibrated. Equipment producing thesemeasurements, such as signal generators and spectrumanalyzers, shou
33、ld be calibrated to a traceable standard (seeISO/IEC 17025). Calibration should occur according to themanufacturers specifications, after any significant mainte-nance or repair, or if it fails a control test.5.3.2 New or Temporary EquipmentCertain audio exhibitswill require equipment that is not a r
34、egular part of thelaboratory. This new or temporary equipment can include:(1) Submitted devices,(2) Equipment or codecs acquired to support the format ofsubmitted media,(3) Older or archived equipment, and(4) Newly acquired equipment.5.3.2.1 Optimizing the playback of audio exhibits mayrequire inter
35、facing this equipment to the system. Refer to anyavailable user manuals to ensure proper use of unfamiliarequipment. Take reasonable precautions when installing un-known or untested software onto the system, such as backupand virus scanning. Due to the possible instability within, orincompatibility
36、between third-party codecs or utilities, it isrecommended that the use of these programs be limited to astand-alone computer or virtual machine. Test any new orE3150 182unfamiliar software or equipment on known data before use onexamination materials. Refer to SWGDE Recommendationsfor Validation Tes
37、ting.5.4 MaintenanceEquipment with moving parts or partssubject to wear should undergo routine inspection and main-tenance. Records should be kept to ensure that this task isperformed regularly and according to the manufacturers speci-fications. Maintenance can include, but is not limited to:(1) Cle
38、aning and demagnetizing electromagnetic heads intape decks,(2) Cleaning and checking the capstans and rollers in tapedecks, and(3) Azimuth alignment.5.4.1 Maintenance of digital equipment and computers caninclude:(1) Defragmenting hard drives;(2) Updating anti-virus software and performing a virusch
39、eck on computers;(3) Updating computer operating systems as necessary; and(4) Updating software, firmware, drivers, and codecs.5.5 Document how equipment is interconnected duringexam, signal formats used, new or temporary equipment, andverification tests done on new equipment.6. Keywords6.1 audio; e
40、quipment maintenance; forensic audio; labora-tory setupREFERENCES(1) Forensic Science Laboratories Facilities Working Group, “ForensicScience Laboratories: Handbook for Forensic Planning, Design,Construction, and Relocation,” NIST Interagency/Internal Report 7941, June 2013.(2) Jorgensen, F., The Co
41、mplete Handbook of Magnetic Recording, 4thed., McGraw-Hill/TAB Electronics, New York, NY, 1996.(3) Everest, F., and Pohlmann, K., Master Handbook of Acoustics, 5th ed.,McGraw-Hill/TAB Electronics, New York, NY, 2009.(4) Everest, F., and Pohlmann, K., Handbook of Sound Studio Construc-tion: Rooms for
42、 Recording and Listening, McGraw-Hill/TABElectronics, New York, NY, 2012.(5) Koenig, B., Lacey, D., and Herold, N., “Equipping the ModernAudio-Video Forensic Laboratory,” Forensic ScienceCommunications, Vol 5, No. 2, April 2003.(6) Van Bogart, J., Magnetic Tape Storage and Handling: A Guide forLibra
43、ries and Archives, The Commission on Preservation and Access,Washington, DC, 1995.(7) Ballou, G., Handbook for Sound Engineers, 4th ed., Focal Press,Burlington, MA, 2008.(8) Muncy, N., “Noise Susceptibility in Analog and Digital SignalProcessing Systems,” Journal of the Audio Engineering Society,Vol
44、43, No. 6, June 1995, pp. 435453.(9) Whitlock, B., “Balanced Lines in Audio Systems: Fact, Fiction, andTransformers,” Journal of the Audio Engineering Society, Vol 43, No.6, June 1995, pp. 454464.(10) Fause, K., “Fundamentals of Grounding, Shielding, andInterconnection,” Journal of the Audio Enginee
45、ring Society, Vol 43,No. 6, June 1995, pp. 498516.(11) Brown, J., “New Understandings of the Use of Ferrites in thePrevention and Suppression of RF Interference to Audio Systems,”in Audio Engineering Society 119th Convention Fall Preprints, NewYork, NY, October 2005, pp. 10741085.(12) Koenig, B., “E
46、nhancement of Forensic Audio Recordings,” Journalof the Audio Engineering Society, Vol 36, 1988, pp. 884894.(13) Macatee, S., “Considerations in Grounding and Shielding AudioDevices,” Journal of the Audio Engineering Society, Vol 43, No. 6,June 1995, pp. 472483.(14) Pohlmann, K., Advanced Digital Au
47、dio, Sams Publishing,Indianapolis, IN, 1991.(15) Pohlmann, K., Principles of Digital Audio, 3rd ed., McGraw-Hill,Inc., New York, NY, 1995.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this st
48、andard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years a
49、ndif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO
