Microphone Sensitivity as a Source of Variation in Nasalance Scores A two-part study was conducted to determine the sources of variation in nasalance scores derived from the Nasometer. In Study #1, a function generator was used as a signal source to calibrate and input sine and square waves directly into the Nasometer. Ten stimuli ranging from 105 to 330 Hz ... Research Note
Research Note  |   December 01, 1996
Microphone Sensitivity as a Source of Variation in Nasalance Scores
 
Author Affiliations & Notes
  • David J. Zajac
    Department of Dental Ecology University of North Carolina at Chapel Hill
  • Richard Lutz
    Craniofacial Center University of North Carolina at Chapel Hill
  • Robert Mayo
    Department of Speech and Hearing Sciences University of North Carolina at Chapel Hill
  • Contact author: David J. Zajac, PhD, Craniofacial Center, CB# 7450, University of North Carolina, Chapel Hill, NC 27599. Email: dzajac.dentce@mhs.unc.edu
Article Information
Hearing & Speech Perception / Acoustics / Speech, Voice & Prosody / Speech / Research Notes
Research Note   |   December 01, 1996
Microphone Sensitivity as a Source of Variation in Nasalance Scores
Journal of Speech, Language, and Hearing Research, December 1996, Vol. 39, 1228-1231. doi:10.1044/jshr.3906.1228
History: Received March 11, 1996 , Accepted May 31, 1996
 
Journal of Speech, Language, and Hearing Research, December 1996, Vol. 39, 1228-1231. doi:10.1044/jshr.3906.1228
History: Received March 11, 1996; Accepted May 31, 1996

A two-part study was conducted to determine the sources of variation in nasalance scores derived from the Nasometer. In Study #1, a function generator was used as a signal source to calibrate and input sine and square waves directly into the Nasometer. Ten stimuli ranging from 105 to 330 Hz in 25 Hz increments were evaluated. In Study #2, the same signal source and an amplified loudspeaker were used to calibrate and present square waves to the Nasometer via five different sets of microphones. The sound pressure level of all stimuli was maintained at 88 dB. Each microphone set was calibrated using the 105 Hz signals. Results from Study #1 indicated consistent nasalance scores across all frequencies (i.e., all scores were within 2% of calibration). Results from Study #2 demonstrated deviations greater than 2% from calibration as a function of frequency for all five sets of microphones. The smallest deviation was 5%, whereas the largest deviation was 14%. We suggest that the variation in nasalance as a function of stimulus frequency may be due to a mismatch in the sensitivity of microphones (i.e., different frequency response characteristics). It is further suggested (a) that individual investigators determine the response characteristics of their microphones and (b) that relatively small variations in nasalance scores (i.e., 5–14%) either within or across speakers be interpreted with caution.

Acknowledgments
This study was supported in part by a grant from the National Institutes of Health, NIDR Grant DE10175. Portions of this study were presented at the Annual Meeting of the American Cleft Palate-Craniofacial Association, April 1996, San Diego, CA.
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