Consensus Statement: Eriksholm Workshop on Wideband Absorbance Measures of the Middle Ear

Feeney, M. Patrick1,2; Hunter, Lisa L.3; Kei, Joseph4; Lilly, David J.1; Margolis, Robert H.6; Nakajima, Hideko Heidi7,8; Neely, Stephen T.9; Prieve, Beth A.10; Rosowski, John J.7; Sanford, Chris A.11; Schairer, Kim S.12; Shahnaz, Navid13; Stenfelt, Stefan14; Voss, Susan E.15

doi: 10.1097/AUD.0b013e31829c726b

The participants in the Eriksholm Workshop on Wideband Absorbance Measures of the Middle Ear developed statements for this consensus article on the final morning of the Workshop. The presentations of the first 2 days of the Workshop motivated the discussion on that day. The article is divided into three general areas: terminology; research needs; and clinical application. The varied terminology in the area was seen as potentially confusing, and there was consensus on adopting an organizational structure that grouped the family of measures into the term wideband acoustic immittance (WAI), and dropped the term transmittance in favor of absorbance. There is clearly still a need to conduct research on WAI measurements. Several areas of research were emphasized, including the establishment of a greater WAI normative database, especially developmental norms, and more data on a variety of disorders; increased research on the temporal aspects of WAI; and methods to ensure the validity of test data. The area of clinical application will require training of clinicians in WAI technology. The clinical implementation of WAI would be facilitated by developing feature detectors for various pathologies that, for example, might combine data across ear-canal pressures or probe frequencies.

1National Center for Rehabilitative Auditory Research, Portland Veterans Affairs Medical Center, Portland, Oregon, USA. 2Department of Otolaryngology, Head and Neck Surgery, Oregon Health and Science University, Portland, Oregon, USA. 3Cincinnati Children’s Hospital Medical Center, Cincinnati, Ohio, USA; 4Hearing Research Unit for Children, School of Health and Rehabilitation Sciences, University of Queensland, Queensland, Australia; 5Department of Otolaryngology, University of Minnesota, Minneapolis, Minnesota, USA; 6Audiology Incorporated, Arden Hills, Minnesota, USA; 7Department of Otology & Laryngology, Harvard Medical School, Boston, Massachusetts, USA; 8Eaton-Peabody Laboratory, Massachusetts Eye & Ear Infirmary, Boston, Massachusetts, USA; 9Boys Town National Research Hospital, Omaha, Nebraska, USA; 10Department of Communication Sciences and Disorders, Syracuse University, Syracuse, New York, New York, USA; 11Department of Communication Sciences and Disorders, Idaho State University, Pocatello, Idaho, USA; 12Audiology and Speech-Language Pathology Service, James H. Quillen Veterans Affairs Medical Center, Mountain Home, Tennessee, USA; 13School of Audiology & Speech Sciences, University of British Columbia, Vancouver, British Columbia, Canada; 14Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden; and 15Picker Engineering Program, Smith College, Northampton, Massachusetts, USA.

ACKNOWLEDGMENTS: This article was based on discussions held at the Eriksholm Workshop on Wideband Absorbance Measures of the Middle Ear, for which support was provided by the Oticon Foundation. The content of this article does not represent the views of the Department of Veterans Affairs or of the U.S. Government.

All authors for this article have submitted individual disclosures, appearing in the respective Acknowledgments section in each article in this supplement.

Address for correspondence: M. Patrick Feeney, National Center for Rehabilitative Auditory Research, Portland Veterans Affairs Medical Center, 3710 SW US Veterans Hospital Road, NCRAR, Portland, OR 97239, USA. E-mail:

Received February 14, 2013

Accepted May 13, 2013

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On the final morning of the Workshop the participants discussed areas of consensus for the topic of the Workshop: Wideband Absorbance Measures of the Middle Ear. The discussion ranged across a number of topics and the following statements contain areas on which there was general agreement.

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There was consensus for a common terminology in this area. The authors of the introductory document by Rosowski et al. in this volume were tasked with addressing terminology in this area of middle ear measurement and the relationships between new measures and established measures. The group felt that it should be emphasized that the new wideband tests are based on a measurement of pressure in the ear canal, using a microphone from which all other measurements are derived. For example, ear canal impedance may be calculated from a pressure measurement (e.g., microphone voltage), and when this is combined with properties of the transducer (e.g., Thevenin equivalent), the ear canal area, density of air, and speed of sound, the pressure reflectance may be calculated.

Several different terms exist in the literature to describe wideband power–based measurements (such as power or energy reflectance and absorbance). It was the consensus of the group to use the term wideband acoustic immittance (WAI) to refer to the family of wideband measures including power-based and impedance-based measures. It should be noted that the term aural acoustic immittance was chosen to describe measures of impedance and admittance in the current American National Standards Institute standard for devices to measure aural acoustic immittance (American National Standards Institute S3.39–1987–R2012; see also International Electrotechnical Commission 60645-5, 2004).

It was recommended that the term transmittance that has been defined as (1 minus power reflectance) should be dropped from usage in favor of absorbance, which is also defined as (1 minus power reflectance). Absorbance would be represented on a linear scale as ranging from 0.0 to 1.0, or on a log scale (10 × Log10 Absorbance) as absorbance level.

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There was consensus that the preliminary results in WAI were promising and that there was a great need for additional research to increase the database. Data collection in this area should include population means, population variance, effect size, and sensitivity and specificity for detecting pathologies. The frequency resolution of measurements should be specified in all research reports. Current commercial systems use measurement resolutions defined either in terms of suboctaves or frequency bins of fixed width.

There was a strong recommendation from the group for future research to investigate the temporal aspects of WAI. Although the pressure reflectance phase has been reported in a number of early articles, there was consensus that the value of the temporal characteristics of WAI measurements has largely been ignored. A majority of publications in this area only refer to energy or power reflectance or absorbance, for which the phase information has been removed (see Rosowski et al. this volume, and Neely et al. this volume for a discussion).

Guidelines for determining the validity of a WAI test measurement are needed. For example, it is important to be able to detect a poor probe fit, especially for systems that do not permit or require a hermetic seal to obtain measurements. A valid absorbance measurement falls between 1.0 and 0.0 (see Rosowski et al. this volume), and acceptable limits for clinical test–retest variability should be established. Moreover, consistency of WAI measurement across different commercial systems should be documented for adults and children, as well as for various pathologies.

It is recognized that normative data collection is still in its infancy, and that there is a clear need for developmental norms for WAI, as well as more data on various pathologies. There is also a consensus that normative data should be provided in the literature or by the manufacturer rather than requiring clinicians to establish their own norms. To facilitate this effort, it was suggested that a shared data repository for norms and clinical cases should be developed. It was recognized that the establishment of such a database would require guidance from various institutional review boards and government entities. Parameters for data inclusion would need to be established, such as the system used for data collection, age, ear, gender, and ethnicity, among others. Several of the Workshop members are investigating the establishment of such a repository for WAI data.

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Given the novelty of data acquisition and interpretation in the area of WAI, it is recognized that training in the use and interpretation of these measurements will be required for audiologists and otolaryngologists. As with any test, WAI measurements must be interpreted in light of the patient history, the physical examination, and other auditory tests as part of a test battery. Finally, the development of automated feature detection in clinical equipment should be investigated to help identify various pathologies using the large data set obtained across pressure and frequency with WAI.

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The Eriksholm Workshop participants are very optimistic about WAI as a tool for studying the middle ear across the life span and improving the diagnosis of middle ear disorders. Human WAI measurements have been reported in the literature for 20 years; the database is impressive, but additional research is needed to achieve the potential for clinical use of this technology.

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American National Standards Institute (ANSI). . Specifications for instruments to measure aural acoustic impedance and admittance (aural acoustic immittance) (ANSI S3.39–1987–R2012). (2012) New York, NY American National Standards Institute
International Electrotechnical Commission (IEC). . Electroacoustics—Audiometric equipment—Part 5: Instruments for the measurement of aural acoustic impedance/admittance. (IEC 60645-5, 2004). (2004) Geneva, Switzerland International Electrotechnical Commission
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