New Thinking on Hearing in Noise: A Generalized Articulation Index

ABSTRACT

The articulation index (AI) theory serves to predict word recognition scores when the number of speech cues have been reduced by noise or lack of audibility. It fails to predict how poorly some subjects do in noise, even when all speech cues have been made audible with amplification. Such subjects require an unusually large signal-to-noise ratio (SNR) for a given performance level, and are said to have a large SNR loss. We have found that the AI can be generalized to predict word recognition scores in the case of missing (speech cue) dots. Some speech cues appear to be lost on the way to the brain even though they were audible. Corliss[1] suggested the term channel capacity to describe this phenomenon, and we adopt that term for our use. In this article, the substantial psychoacoustic and physiological evidence in favor of this generalized AI is described. Perhaps the strongest evidence is (1) the SNR loss of subjects is poorly predicted by the degree of their audiometric loss, and (2) their wideband word-recognition performance in noise can be predicted from their channel capacity inferred from filtered speech experiments.

KEYWORD

Articulation Index - signal-to-noise ratio loss - channel capacity - missing dots - audibility

REFERENCES

• 1 Corliss E. Estimate of the inherent channel capacity of the ear.  J Acoust Soc Am . 1971;  50(2/2) 671-677
• 2 Mueller H, Killion M. An easy method for calculating the Articulation Index.  Hear J . 1990;  9 14-17
• 3 Humes L. Selecting hearing aids for patients effectively (SHAPE).  Hear J . 1988;  1 15-18
• 4 Pavlovic C. Articulation index predictions of speech intelligibility in hearing aid selection.  ASHA . 1988;  30(6/7) 63-65
• 5 Tillmann T, Carhart R, Olsen W. Hearing aid efficiency in a competing speech situation.  J Speech Hear Res . 1970;  12 789-811
• 6 Plomp R. Auditory handicap of hearing impairment and the limited benefit of hearing aids.  J Acoust Soc Amer . 1978;  63 533-549
• 7 Dirks D, Morgan D, Dubno J. A procedure for quantifying the effects of noise on speech recognition.  J Speech Hear Dis . 1982;  47 114-123
• 8 Lyregaard P. Frequency selectivity and speech intelligibility in noise. In: Pedersen O, Poulsen T, eds. Binaural Effects in Normal and Impaired Hearing. From the 10th Danavox Symposium 1982. Denmark: Scand Audiol Suppl 15 1982
• 9 QuickSIN Speech in Noise Test. Elk Grove Village, IL: Etymotic Research.  2001; 
• 10 Moore B CJ, Huss M, Vickers D A, Glasberg B R, Alcántara J I. A test for the diagnosis of dead regions in the cochlea.  Brit Soc Audiol . 2000;  34 205-224
• 11 Fletcher H, Galt R. Perception of speech and its relation to telephony.  J Acoust Soc Amer . 1950;  22 89-151
• 12 Coker C. Speech as an error-resistant digital code.  J Acoust Soc Am Abst . 1974;  55 476
• 13 Skinner M. Speech intelligibility in noise-induced hearing loss: Effects of high-frequency compensation.  J Acoust Soc Am . 1980;  67 306-317
• 14 Rankovic C. Prediction of articulation scores. Invited lecture in session honoring Harvey Fletcher.  J Acoust Soc Am Abst . 1995;  97 358
• 15 Turner C, Cummings K. Speech audibility for listeners with high-frequency hearing loss.  Am J Audiol . 1999;  2 6-35
• 16 Jardine D, Sun W, Ding D, Salvi D. How many inner hair cells do we need to hear?. Poster at Winter Meeting of the Association for Research in Otolaryngology, St. Petersburg, FL February 4-8, 2001
• 17 Killion M, Christensen L. The case of the missing dots: AI and SNR loss.  Hear J . 1998;  51(5) 32-47
• 18 Villchur E. A different approach to the noise problem of the hearing impaired. Am J Audiol .  1993;  7 47-51
• 19 Pascoe D. Clinical implications of nonverbal methods of hearing aid selection and fitting.  Seminars in Hearing . 1980;  1 217-229
• 20 Dallos P, Berlin C. Outer hair cells: the inside story. Presented at the 1997 American Academy of Audiology Conference, Ft. Lauderdale, FL, April 19, 1997
• 21 Corliss E, Burnett E, Stimson H. ``Polyacusis,'' a hearing anomaly.  J Acoust Soc Am . 1968;  43 1231
• 22 Moore B CJ, Huss M, Vickers D A, Glasberg B R, Alcántara J I. A test for the diagnosis of dead regions in the cochlea.  Brit Soc Audiol . 2000;  34 205-224
• 23 Studebaker G A, Killion M C. A-weighted equivalents of permissible ambient noise during audiometric testing.  J Acoust Soc Am. 65 1622-1635
• 24 Moore B, Alcántara J. The use of psychophysical tuning curves to explore dead regions in the cochlea.  Ear Hear . 2001;  8 268-278
• 25 Corliss E. Mechanistic aspects of hearing.  JASA 1967, 41:1500-1516, and Erratum: Mechanistic aspects of hearing. Lett 1967: 42:1097
• 26 Margolis R. SNR lost and found: laboratory and real-world SNR performance of circuits and directional microphones in hearing aids. Roundtable Presentation at American Academy of Audiology Meeting, Los Angeles, CA April 13, 1998
• 27 McKenna M, Adams J. The biology of cochlear supporting cells and their critical role in hearing. Proceedings from the Fifth Annual Research Symposium at the 13th International SHHH Convention, Boston, MA, June 15, 1998
• 28 Killion M, Niquette P. What can the pure-tone audiogram tell us about a patient's SNR loss?.  Hear J . 2000;  53(3) 46-53
• 29 Schuknecht H. Pathology of the Ear.  2nd ed. Baltimore, MD: Lea Febiger 1993
• 30 Bredberg G. Cellular pattern and nerve supply of the human Organ of Corti.  Acta Oto-Laryngol . 1968;  Suppl 236 78-93
• 31 Bohne B, Clark W. Growth of hearing loss and cochlear lesion with increasing duration of noise exposure. In: Hamernik R., Henderson D, Salvi R, eds. New Perspectives on Noise-Induced Hearing Loss New York: Raven 1982
• 32 Mills J. The aging ear: results from animal and human studies. Presented at New Frontiers in the Amelioration of Hearing Loss Conference, St. Louis, MO March 24, 2001
• 33 Dreschler W. Noise reduction in hearing aids. Presented at the International Hearing Aid Research Conference, Lake Tahoe, CA August 23-27, 2000
• 34 Bentler R A, Duve M. Progression of hearing aid benefit over the 20^th century. Poster presentation, American Academy of Audiology convention, Fort Lauderdale, FL April 19, 1997