(Originally published--Chial, M. (1998). Yet another audiogram. ASHA Hearing and Hearing Disorders: Research and Diagnostics Newsletter, 2 (1), pp. 2-3.)
This note describes an audiogram intended to help audiologists and their patients better understand the impact of hearing loss upon speech communication. It is based on earlier work (Chial and Kelly, 1987) and amplified by personal experience (my own) with hearing loss.
The accompanying figure presents a special-purpose audiogram that conforms to current requirements (American National Standards Institute, 1996) for aspect ratio (the distance assigned to 20 dB on the ordinate equals 1 octave on the abscissa). The shaded area represents the range of normal hearing as it is conventionally defined.
This audiogram also illustrates the spectrum of normal speech, that is, speech produced in quiet by a normal talker at a distance of 1 meter at an overall sound pressure level (SPL) of 65 dB. Translation of the speech spectrum to an audiogram format is based upon Olsen and Matkin's (1991) interpretation of the work of Pascoe (1980), Olsen (1984), and Olsen, Hawkins and Van Tasell (1987). Curve A represents the frequency-amplitude contour above which 90% of the energy of normal speech falls, while curve B depicts the contour above which 10% of the energy of normal speech falls. Thus, the hatched area between these two curves represents the amplitude-density function of 80% of the normal speech signal. To the extent that pure tone thresholds fall below this area, we would expect listeners to experience difficulty in understanding speech.
Beneath the audiogram are shown the frequency ranges of constituent portions of speech, specifically the frequency regions of vowel formants and the frequency ranges of selected consonants. These are based in part on the work of Tyler (1979) as cited by Olsen and Matkin (1991). To the extent that hearing threshold levels fall below contour B in these frequency ranges, we would expect difficulty in understanding particular groups of phonemes.
Finally, the bottom of the audiogram presents percentage contributions to word recognition by octave based upon Gerber's (1974) remapping of work by Dunn and White (1940) and by Fletcher (1995; originally, 1953). As indicated, about 70% of word recognition is determined by energy falling between 500 and 2000 Hz, and about 25% is determined by energy falling above 2000 Hz. To the extent that hearing threshold levels for pure tones fall below Curve B in these frequency regions, we would expect difficulty in understanding isolated words presented in quiet.
These four "chunks" of information together may be useful in exploring and explaining the impact of particular hearing losses upon speech communication. As noted by Olsen and Matkin (1991) an audiogram of this type may help patients understand the relation of pure tone thresholds to problems in perceiving and understanding speech. Because the supplemental data presented in the audiogram are based upon normal speech and normal hearing, it no doubt underestimates problems of speech understanding arising from distortion contributed by abnormal speech, from sensorineural damage, or from environmental factors such as reverberation and competing noise.
A persistent truism of clinical practice is that speech discrimination tests alone are imperfect indicators of receptive communication ability (Penrod, 1985, 1994). It is hoped that the audiogram described here will help audiologists engage patients in conversations that help both understand the effects of hearing loss upon communication.
REFERENCES
American National Standards Institute. S3.6-1996 American National Standard Specification for Audiometers. New York, NY: Author.Chial, M., and Kelly, L. (1987). Graphical computer tools for instruction and clinical practice. Journal for Computer Users in Speech and Hearing, 3 (1), pp. 86-33.
Dunn, H., and White, S. (1940). Statistical measurements of conversational speech. Journal of the Acoustical Society of America, 11, pp. 278-288.
Fletcher, H. (1995). The ASA Edition of Speech and Hearing in Communication (J. Allen, Editor). Woodbury, NY: Acoustical Society of America. [Reissue of Fletcher's (1953) Speech and Hearing in Communication.]
Gerber, S. (1974). The intelligibility of speech. Chapter 11 in Introduction to Hearing Science: Physical and Psychological Concepts. Philadelphia, PA: W. B. Saunders. Page 244.
Olsen, W. (1984). Speech spectrum, audiograms and functional gain. The Hearing Journal, 37, pp. 24-26.
Olsen, W., and Matkin, N. (1991). Speech audiometry. Chapter 2 in Hearing Assessment, 2nd Ed. (W. F. Rintelmann, Editor). Austin, TX: Pro-Ed.
Olsen, W., Hawkins, D., and Van Tasell, D. (1987). Representations of the long-term spectra of speech. Ear and Hearing, 8 (supplement), pp. 100S-108S.
Pascoe, D. (1980). Clinical implications of nonverbal methods of hearing aid selection and fitting. Seminars in Speech Language and Hearing, 1, pp. 217-229.
Penrod, J. (1985). Speech discrimination testing, Chapter 12 in Handbook of Clinical Audiology, 3rd Ed. (J. Katz, Editor). Baltimore, MD: Williams & Wilkins. Pages 249-250.
Penrod, J. (1994). Speech discrimination testing, Chapter 10 in Handbook of Clinical Audiology, 4th Ed. (J. Katz, Editor). Baltimore, MD: Williams & Wilkins. pp 159-160.
Tyler, R. (1979). Measuring hearing loss in the future. British Journal of Audiology Supplement, 2, pp. 29-40.