The ASHA Leader - August 11, 2009 - (Page 17)

Headphones), three supra-aural devices that rest on the pinna (two of which included active-noise reduction and were tested in the on- and off-modes), and four circumaural devices that seal around the pinna against the head (one of which was an active noise reduction device and tested in its two modes). We took measurements with two different halfinch and two different one-inch microphones held directly against the earphone diaphragms, with small dosimeter microphones in the ears under the devices in two different orientations (for the supra-aural and circumaural earphones) using Jolene; we also took measurements with a few devices (data not shown in Figure 3 on p. 16) with a standard earphone coupler used for audiometer calibration (NBS-9A). These values, without any TFOE corrections, were compared to what was considered “truth,” i.e., data measured using KEMAR with soft pinna and TFOE corrections. For the KEMAR measurements, the microphone output was monitored by the third author while he adjusted the earphones for best fit. The results are presented in Figure 3, grouped by earphone type. The vertical axis represents the error in the measurement of the overall A-weighted sound level of the IEC-shaped pink noise, compared to the “truth,” the TFOE-corrected KEMAR measurements (i.e., a positive result indicates that the casual method overestimated the actual sound field Selected References Holmes, A., Niskar, A. S., Kieszak, S., Rubin, C., & Brody, D. (2004). Mean and median hearing thresholds among children 6 to 19 years of age: The third National Health and Nutrition Examination Survey, 1988 to 1994, United States. Ear and Hearing, 25(4), 397–402. International Organization for Standardization (2004). Acoustics—Determination of sound immission from sound sources placed close to the ear—Part 2: Technique using a manikin (ISO 11904-2:2004). Geneva, Switzerland: Author. Keith, S. E., Michaud, D. S., & Chiu, V. (2008). Evaluating the maximum playback sound levels from portable digital audio players. Journal of the Acoustical Society of America, 123(6), 4227–4237. Martin, G. Y., & Martin, H. W. (2007). The Jolene Cookbook. Portland, OR: Oregon Health and Science University, www.dangerousdecibels.org. equivalent level). For the supra-aural and circumaural devices all methods agreed within ± 5 dB, except in one instance in which the one-inch microphone data were high by 10 dB. For the earbuds, the spread was greater with overestimates generally no more than 5 dB, but with one underestimate of almost 15 dB. The insert earphone data were the most variable with errors of + 20 to -15 dB. When viewing the Jolene data in this chart, note that the instructions for this device suggest a 5-dB TFOE correction (subtraction from measured level), which was not made for the data in this figure. In fact a 5-dB correction would closely align Jolene with the “truth” except for the insert earphones. This result was due to Jolene’s ear canal, which is short and does not allow for correct insertion of such devices. Thus, she is a fine teaching tool, but her use for determining risk of insert earphones is problematic. The hearing risks of excessive noise exposure have become increasingly publicized in the past decade. As PMP utilization pervades the culture, warnings about their hazard become more strident. In this report we endeavored to place the risk of PMP exposures in perspective compared to other noisy recreational activities, and to provide guidance on the accurate measurement of the sound levels they create. It is certainly laudable to educate our youth about the potential risks of PMPs, but exaggeration can diminish our credibility and divert attention from what are arguably more hazardous noisy activities. All efforts to quantify risk of hearing loss from various noise sources, including PMP use, must be based on accurate measurements of both the levels and durations of exposure. Based on our studies, we recommend the following: • Use accurate equipment (such as acoustic manikins) and standardized protocols (ISO 11904) for measuring output sound levels of all PMPs (and earphone types) when data are critical for research purposes or litigation. • Coupler/eardrum/manikin measurements must be TFOE-corrected; otherwise overestimates of 4–8 dB will occur when using resulting sound levels to predict hearing risk. • Hand-held mics can over- or underestimate levels by as much as 15 dB for insert and earbud devices, but are within about 5 dB for supra-aural and circumaural devices. • Jolene is a fine teaching tool and her suggested 5-dB TFOE correction is suitable for all types of earphones except insert earphones, for which she is not applicable. Elliott H. Berger, MS, is a senior scientist, auditory research, at 3M, E•A•RCALSM Laboratory, (Indianapolis, Ind.), where for more than 30 years he has studied noise and hearing conservation with an emphasis on hearing protection. He chairs the ANSI working group on hearing protectors and has been lead editor for two highly regarded texts on noise and hearing conservation. His recent research has focused on methods of measuring earphone levels and earphone systems. Contact him at Elliott.Berger@ mmm.com. Susan C. Megerson, MA, CCC-A, is an audiologist in the Hearing and Speech Department at the University of Kansas Medical Center, specializing in hearing conservation. She has served as ASHA’s liaison to and chair of the Council for Accreditation in Occupational Hearing Conservation. She is a past president of the National Hearing Conservation Association (NHCA) and serves on the NHCA Scholarship Foundation’s Board of Directors. Contact her at smegerson@kumc.edu. Michael E. Stergar, an acoustics technician at 3M, Electroacoustic Sound Laboratory, (Indianapolis, Ind.), evaluates a variety of electronic products and develops new test methods. Contact him at Mike. Stergar@mmm.com. Additional references for this article can be found at The Leader Online. Search on the title of the article. Speech Pathology Associates, LLC www.chewytubes.com 207-741-2443 17 August 11, 2009 http://www.chewytubes.com http://www.dangerousdecibels.org http://www.chewytubes.com

Table of Contents for the Digital Edition of The ASHA Leader - August 11, 2009

The ASHA Leader - August 11, 2009
Contents
Four Members Elected to Board of Directors
Readers Respond
Audiology
Congress Begins Health Care Reform Debate
Medicare Private Practice Poses Concerns for Some SLPs
Custom Fit Your Marketing
Personal Music Players
From the President
Convention Preview
2010 Dues Change
Ethics in Private Practice
Missouri SLPs Win on School Retirement Issue
Classifieds
A Deluge of Human Kindness
First Person on the Last Page

The ASHA Leader - August 11, 2009