Insity and Frequency Discrimination Minitored by Evoked Response Audiometry: Clinical Application

Abstract

Δ_i and Δ_r repetitive stimuli superimposed on continuous 0.5-, 1- and 4-kHz carrier tones were administered to 20 normally hearing persons, 8 adults with sensorineural hearing loss, 10 adults with conductive hearing loss and 22 childrean subjected to evoked response audiometry (ERA) for assessment of hearing acuity. The intensity modulation depth ranged from +1 to 10 dB. In the subject with normal hearing and in the adult patients, three carrier tone levels were used whenever possible: 20, 40, and 60 dB SL. The frequency modulation depth ranged from –1 to –10% of the carrier tone frequency. The same leveles for the carrier tone were used: 20, 40, and 60 dB SL. With a carrier tone level of 20 dB SL, a clear-cut vertex responsewas noted in 80% of the teste carried out in the normal adults with 5-dB Δ_i stimuli and with Δ_r stimuli of –3 to –5% in magnitude; the same figure are valid for the patients with sensorineural and conductive hearing loss. The patients with sensorineural hearing loss showed a tendency to give vertex responses with lower Δ_i stimuli than subject with normal hearing. However, this difference was not statistically significant. According to our results, the children tested can be roughly divided into two groups, the first including subjects with responses to Δt stimuli of +5 and +10 dB and Δ_r stimuli of –5% and –10%; the second group including subjects with no clear-cut responses to these stimuli.

Key Words:

• Electric response audiometry
• Evoked response audiometry
• Vertex potentials
• Intensity discrimination
• Frequency discrimination
• Amplitude modulation
• Frequency modulation