ASTM_F_2504_-_05_2014.pdf

Designation:F250405(Reapproved 2014)Standard Practice forDescribing System Output of Implantable Middle EarHearing Devices1This standard is issued under the fixed designation F2504;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This practice defines means for describing system per-formance(ex vivo)and,in particular,system output of animplantable middle ear hearing device(IMEHD)by measuringa physical quantity that is relevant to the insertion gain andoutput level of the IMEHD when implanted in the patient.1.2 This practice is similar to headphone calibration on anartificial ear in which the sound pressure level(in decibelsound pressure level(SPL)measured in the artificial ear canbe converted to patient hearing level(in decibel hearing level(HL)using a known transfer function,as defined byANSI 3.7.These measurements can then be used to predict systemparameters relevant for patient benefit such as functional gain,maximum output,and variability.Measurements defined in thispracticeshouldbeusefulforpatients,clinicians,manufacturers,investigators,and regulatory agencies in mak-ing comparative evaluations of IMEHDs.1.3 The values given in SI units are to be considered thestandard.1.4 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 and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ANSI Standards:2ANSI 3.6 Specification for AudiometersANSI 3.7 Method for Coupler Calibration of EarphonesANSI 3.22 Specification of Hearing Aid Characteristics3.Terminology3.1 Refer to the block diagram of Fig.1 for a clarification ofthe mathematical notations used in this section.3.2 In the following definitions,these symbols are used forphysical quantities:3.2.1 E=electrical drive signal(voltage or current)3.2.2 p=sound pressure3.2.3 v=vibration velocity3.3 All transfer functions are denoted by the symbol H,withthe following subscripts indicative of the type of transferfunction:3.3.1 A=IMEHD-aided3.3.2 E=electrical3.3.3 H=hearing level3.3.4 S=sound field sound pressure3.3.5 T=tympanic membrane(ear drum)sound pressure3.3.6 U=unimplanted3.3.7 V=vibration of stapes3.4 Definitions:3.4.1 coupling,npoints and methods of attachment.3.4.2 displacement,nintegral of velocity measured innanometres.3.4.3 ear-canal sound pressure,pT,nsound pressure pro-duced in the ear canal,at the tympanic membrane,by a soundfield stimulus,specified in units of pascals.3.4.4 equivalent hearing level,LH,nratio of an equivalentsound pressure,pQ,relative to the sound field pressure,pRETSPL,at 0 incidence that is just detectable monaurally by anormally hearing individual,as defined in ANSI S3.6,Table 9,expressed in decibels:LH=20log10(pQ/pRETSPL).3.4.5 equivalent sound pressure,pQ,nunimplanted inputsound field pressure needed to produce a stapes velocity equalto that produced by a specified IMEHD input in the IMEHD-aided condition:pQ=E HES.3.4.5.1 DiscussionThe equivalent sound pressure is theproduct of the equivalent sound pressure transfer function,HES,and the IMEHD output transducer electrical input E:pQ=E HES.The equivalent sound pressure can be expressed asequivalent sound pressure level in units of decibels,SPLeq,calculated as 20log10(pQ/210-5Pa).3.4.6 equivalent sound pressure level,LQ,nlogarithmicrepresentation of equivalent sound pressure,LQ=20log10(pQ).1This practice is under the jurisdiction ofASTM Committee F04 on Medical andSurgical Materials and Devices and is the direct responsibility of SubcommitteeF04.37 on Implantable Hearing Devices(IHDs).Current edition approved March 1,2014.Published April 2014.Originallyapproved in 2005.Last previous edition approved in 2005 as F2504 05.DOI:10.1520/F2504-05R14.2Available from American National Standards Institute(ANSI),25 W.43rd St.,4th Floor,New York,NY 10036,http:/www.ansi.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 3.4.7 hearing level(HL),L,nratio of the input sound fieldpressure,pS,relative to the sound field pressure pRETSPLat 0incidence that is just detectable monaurally by a normallyhearing individual,as defined inANSI S3.6,Table 9,expressedin decibels as:L=20log10(pS/pRETSPL).3.4.8 IMEHD electrical input at threshold Ethreshold,nelectrical input to the IMEHD output transducer at thresh-old of audibility.3.4.9 IMEHD harmonic distortion,nharmonic distortionof the stapes velocity IMEHD-aided analogous to ANSI S3.22,Section 6.11S,from sinusoidal inputs of the frequencies 500,800,and 1600 Hz;input levels shall be Emax 20 dB.3.4.10 IMEHD output transducer,nelectromechanicaloutput transduce