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Effective masking levels for bone conduction auditory steady state responses in infants and adults with normal hearing.
Ear Hear. 2012 Mar-Apr; 33(2):257-66.EH

Abstract

OBJECTIVE

To obtain ear-specific bone conduction thresholds, masking of the nontest ear is often required. Bone conduction masking has not been formally investigated for infants assessed physiologically. The objective of this study was to determine effective masking levels (EMLs) for auditory steady state responses (ASSRs) elicited by bone-conducted stimuli in a group of normal-hearing infants and adults.

DESIGN

Participants were 15 infants younger than 6 mo and 15 adults, all with normal hearing. EML was defined as the lowest level of a binaural air-conducted masker that resulted in absent bone conduction ASSRs. Stimuli were single bone-conducted tones that were 100% amplitude modulated and 25% frequency modulated at 85 and 101 for 1000 and 4000 Hz, respectively. The stimuli were calibrated in dB HL (ANSI S3.6-1996) and expressed in dB HL or dB SL (dB relative to mean bone conduction ASSR thresholds reported in a previous study). The maskers were 1 and 4 kHz narrowband noise generated by a clinical audiometer. Unmasked and masked ASSRs were obtained for each participant. Real ear-to-coupler differences (RECDs) were also obtained for each participant and were used to convert masker dB SPL measured in the coupler to dB SPL in the individual ear canal.

RESULTS

Infant EMLs for ASSRs elicited to bone-conducted stimuli in dB HL were 6 to 7 dB higher and 8 to 10 dB lower for 1000 and 4000 Hz, respectively, compared with adults. When masker was adjusted for RECDs, infant EMLs were 12 dB higher at 1000 Hz and similar at 4000 Hz compared with adults. When the stimulus levels were corrected for the mean differences in ASSR bone conduction thresholds between infants and adults and the masker levels adjusted for RECDs, infants had lower EMLs at 1000 Hz and equal EMLs at 4000 Hz, in comparison to adults. Frequency- and level-dependent effects on ASSR amplitude due to masking were found and differed between infants and adults.

CONCLUSIONS

Our findings indicate that there are frequency- and level-dependent infant-adult differences in EMLs for bone conduction ASSRs and confirm that a 1000 Hz stimulus is 12 dB more effective for infants compared with adults. The following infant preliminary masking levels for bone conduction stimuli are recommended: (i) 1000 Hz: 48 and 58 dB SPL at 15 and 25 dB HL, respectively, and (ii) 4000 Hz: 40 and 45 dB SPL at 25 and 35 dB HL, respectively.

Authors+Show Affiliations

School of Audiology and Speech Sciences, The University of British Columbia, Vancouver, British Columbia, Canada.No affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

21926629

Citation

Hansen, Erin E., and Susan A. Small. "Effective Masking Levels for Bone Conduction Auditory Steady State Responses in Infants and Adults With Normal Hearing." Ear and Hearing, vol. 33, no. 2, 2012, pp. 257-66.
Hansen EE, Small SA. Effective masking levels for bone conduction auditory steady state responses in infants and adults with normal hearing. Ear Hear. 2012;33(2):257-66.
Hansen, E. E., & Small, S. A. (2012). Effective masking levels for bone conduction auditory steady state responses in infants and adults with normal hearing. Ear and Hearing, 33(2), 257-66. https://doi.org/10.1097/AUD.0b013e31822f67f6
Hansen EE, Small SA. Effective Masking Levels for Bone Conduction Auditory Steady State Responses in Infants and Adults With Normal Hearing. Ear Hear. 2012 Mar-Apr;33(2):257-66. PubMed PMID: 21926629.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effective masking levels for bone conduction auditory steady state responses in infants and adults with normal hearing. AU - Hansen,Erin E, AU - Small,Susan A, PY - 2011/9/20/entrez PY - 2011/9/20/pubmed PY - 2012/6/27/medline SP - 257 EP - 66 JF - Ear and hearing JO - Ear Hear VL - 33 IS - 2 N2 - OBJECTIVE: To obtain ear-specific bone conduction thresholds, masking of the nontest ear is often required. Bone conduction masking has not been formally investigated for infants assessed physiologically. The objective of this study was to determine effective masking levels (EMLs) for auditory steady state responses (ASSRs) elicited by bone-conducted stimuli in a group of normal-hearing infants and adults. DESIGN: Participants were 15 infants younger than 6 mo and 15 adults, all with normal hearing. EML was defined as the lowest level of a binaural air-conducted masker that resulted in absent bone conduction ASSRs. Stimuli were single bone-conducted tones that were 100% amplitude modulated and 25% frequency modulated at 85 and 101 for 1000 and 4000 Hz, respectively. The stimuli were calibrated in dB HL (ANSI S3.6-1996) and expressed in dB HL or dB SL (dB relative to mean bone conduction ASSR thresholds reported in a previous study). The maskers were 1 and 4 kHz narrowband noise generated by a clinical audiometer. Unmasked and masked ASSRs were obtained for each participant. Real ear-to-coupler differences (RECDs) were also obtained for each participant and were used to convert masker dB SPL measured in the coupler to dB SPL in the individual ear canal. RESULTS: Infant EMLs for ASSRs elicited to bone-conducted stimuli in dB HL were 6 to 7 dB higher and 8 to 10 dB lower for 1000 and 4000 Hz, respectively, compared with adults. When masker was adjusted for RECDs, infant EMLs were 12 dB higher at 1000 Hz and similar at 4000 Hz compared with adults. When the stimulus levels were corrected for the mean differences in ASSR bone conduction thresholds between infants and adults and the masker levels adjusted for RECDs, infants had lower EMLs at 1000 Hz and equal EMLs at 4000 Hz, in comparison to adults. Frequency- and level-dependent effects on ASSR amplitude due to masking were found and differed between infants and adults. CONCLUSIONS: Our findings indicate that there are frequency- and level-dependent infant-adult differences in EMLs for bone conduction ASSRs and confirm that a 1000 Hz stimulus is 12 dB more effective for infants compared with adults. The following infant preliminary masking levels for bone conduction stimuli are recommended: (i) 1000 Hz: 48 and 58 dB SPL at 15 and 25 dB HL, respectively, and (ii) 4000 Hz: 40 and 45 dB SPL at 25 and 35 dB HL, respectively. SN - 1538-4667 UR - https://www.unboundmedicine.com/medline/citation/21926629/Effective_masking_levels_for_bone_conduction_auditory_steady_state_responses_in_infants_and_adults_with_normal_hearing_ L2 - https://doi.org/10.1097/AUD.0b013e31822f67f6 DB - PRIME DP - Unbound Medicine ER -