Electrophysiologic correlates of attention versus stimulus competition in young male and female listeners.

The effects of attention and stimulus competition on the late auditory-evoked potential (LAEP) were compared in 10 young males and 10 young females. Listeners attended to discriminably different oddball tonal sequences presented binaurally or monaurally. Peak amplitudes in response to the frequent tones were measured for N1, P2, and early and late N2 (N2e and N21) components of the LAEP Whereas N1 amplitudes increased, the amplitudes of P2 decreased when listeners attended to, rather than ignored, the tones. Competition effects for both N1 and P2 resulted in reduced amplitudes in the presence of contralateral competition. Although findings with N2e and N21 suggested possible attention and competition effects, as well as gender differences, the data were inconsistent and will need further experimental verification. The present findings with the N1 and P2 components provide evidence that different neural processes underlie the attention and competition effects in the human brain.

Developmental changes in aural acoustic admittance measurements.

Tympanometry is a clinical measurement routinely included in the assessment of middle ear function. Despite its widespread use, however, fundamental questions remain regarding the need for age-dependent normative data. This study examines normal developmental changes associated with four tympanometric measurements: (1) ear canal volume, (2) peak compensated acoustic admittance, (3) tympanometric width, and (4) tympanometric peak pressure. Of 221 infants and children, aged 6 months to 5 years, enrolled in this study, 99 met the criteria for normal middle ear function as determined via pneumatic tympanoscopy by an experienced pediatric otolaryngologist, and data analysis was confined to those 99 volunteers. Analysis of variance revealed statistically significant main effects showing increases in ear canal volume and peak compensated acoustic admittance and decreases in tympanometric width as age increased. Statistically significant differences were not achieved for tympanometric peak pressure. Although statistically significant differences were found, the differences were small and of questionable clinical significance.

Comparison of acoustic immittance measures obtained with different commercial instruments.

Three acoustic admittance measurements (tympanometric peak pressure, peak compensated static acoustic admittance, and tympanometric width) were compared across seven commercially available acoustic immittance systems. Forty-nine adult subjects (45 females and 4 males), 16 to 50 years of age (mean = 27.7 years), with normal middle ear function participated in this investigation. Small but statistically significant differences were observed for each of the tympanometric variables for several of the instruments evaluated. In most instances, the differences were small enough that the same normative data could be applied across the instrumentation employed in this study; however, there were two measurement conditions, peak compensated static acoustic admittance and tympanometric width, where, for selected instruments, the range in values differed by an amount great enough to warrant consideration in clinical decision making.

Reference threshold sound-pressure levels for the TDH-50 and ER-3A earphones.

Reference threshold sound-pressure levels were established for a new insert earphone, the ER-3A tubephone, and for the TDH-50 earphone. In test-retest comparisons, the tubephone produced estimates of auditory threshold as reliable as the thresholds produced by the supraaural earphone. Reference thresholds were developed for the two earphones from data contributed by three laboratories. While the TDH-50 data are in good agreement with the provisional ANSI 6-cc coupler reference levels (ASHA, 1982), the ER-3A data are at variance with the manufacturer's provisional recommendation for 2-cc coupler reference thresholds for frequencies below 1 kHz. The differences are attributed to physiologic noise that masked the lower frequency thresholds.

Spectral characteristics of air and bone conduction transducers used to record the auditory brain stem response.

This study sought to determine differences in the acoustic spectra of five different transducers commonly used for stimulus presentation to record the auditory brain stem response (ABR). The outputs of three commercially available bone conduction vibrators (Radioear B-70A, B-71 and B-72), a TDH-49 earphone, and an insert receiver were measured by applying a 0.1 msec rectangular electrical pulse to each transducer. The resultant output for each transducer was converted to one-third octave band data and plotted against reference threshold levels. Results demonstrated relatively flat acoustic spectra and high output levels for the two air conduction receivers. In contrast, each of the bone oscillators had its greatest concentration of energy in the 2000 Hz region with the spectrum characterized by a precipitous decrease in output at frequencies above and below this resonance peak. Maximum output never exceeded 35 dB HL for any of the three bone conduction devices. Of the three oscillators, however, the B-70A appeared to provide the highest output before reaching saturation. Results are discussed relative to the limitations for recording the auditory brain stem response to bone conducted transient signals.