Comparing bone- and air-conduction thresholds distinguishes conductive from sensorineural hearing loss

Evidence

The bone-conduction phenomenon is utilized in bone-conduction audiometry. In contrast to air-conduction pure-tone audiometry (discussed above), the test stimuli are fed as vibration to the skull at the back of the ear in bone-conduction pure-tone audiometry. The bone-conduction hearing thresholds are then measured in a similar manner to air-conduction pure-tone audiometry. If the bone-conduction threshold is normal but the air-conduction threshold is elevated, the hearing impairment is likely to be conductive. If the bone-conduction threshold has increased by the same amount as the air-conduction threshold, the impairment is likely to be sensorineural or due to a problem at some higher level of the auditory system. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 2712

The lower part of Figure 7.36 shows example audiograms for two hearing-loss conditions. The audiogram in the lower-left position shows a conductive hearing loss in the left ear because the bone-conduction plot is normal, but the air-conduction plot shows a significant hearing loss that would be termed a “moderate hearing loss” (see Table 7.1). This indicates a problem between the outside world and the inner ear, and a hearing aid, tailored to the audiogram, could be used to correct for the air-conduction loss. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2362

The upper part of Figure 7.36 shows audiograms for a young adult with normal healthy hearing within both ears based on airand bone-conduction tests in the left and right ears (a key to the symbols used on audiograms is given in the figure). … Pure-tone audiometry is the technique that enables the normal deterioration of hearing with age, or presbycusis (see Section 2.3 and Figure 2.11) to be monitored. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2361

Categorization

• DEFINE: Explains how bone-conduction audiometry works and how its diagnostic logic discriminates conductive from sensorineural impairment.
• corroborated: 3 independent passages support this claim — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 2712; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2362; David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2361