No abstract

Several recent studies have demonstrated that the ER-3A insert earphone may sometimes be directly substituted, without recalibrating, for a TDH-39/MX-41AR earphone. However, most available data have not been reduced to a form suitable for establishing a revised estimate of the reference threshold levels. This article reports such a data analysis performed on the results of five recent studies. The mean data from the five studies are typically within 1 dB of the provisional reference threshold SPLs given by the ER-3A manufacturer for calibration in a (HA-1) 2-cc coupler. After converting the mean data to equivalent Zwislocki-coupler-type ear simulator SPLs at each of the reported audiometric frequencies (125, 250, 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz), agreement within 1.5 dB was seen with the revised estimate of minimum audible pressures given by Killion [J. Acoust. Soc. Am. 63, 1501–1508 (1978)]. Either the manufacturer’s provisional SPLs or the average results from this study may be used with little noticeable difference for most purposes.

The advantages and disadvantages of three types of earphones for audiometric testing are discussed. Supraaural earphones continue to be recommended for this purpose, in preference to circumaural and insert types.

This study investigated the selective auditory attention skills of learning disabled children as compared with the performance of normal achievers aged 7 through 9 years. The task consisted of pointing to the appropriate picture of a monosyllabicword presented diotically. The task was always presented first in quiet and then under three noise (distractor) conditions: white noise (nonlinguistic), speech backwards (linguistic nonsemantic), and speech forward (semantic). The performance of the LD children was affected more than the performance of normal achievers under all distractor conditions, with the greatest difference found when the distractor was semantic. The performance of 8-year-olds was significantly better than 7-year-olds on these listening tasks. These findings suggest that LD children may be differentiated from normal achievers using a selective auditory attention task with a semantic distractor.

A small perforation (2 mm2) was placed in the posterosuperior quadrant of the feline tympanic membrane (TM). Sound pressures (amplitudes and phases) required for a 10-μV round window cochlear microphonic (CM) output were measured at third-octave intervals from 200 to 4000 Hz (a) in front and behind the TM, (b) in open and closed sound systems, and (c) before and after perforation, as were the corresponding voltages across the transducer. Sound pressure (SP) changes in front of the TM after perforation revealed low-frequency losses, identical in shape and magnitude for both open and closed sound systems, that vary inversely with frequency at a rate of 12 dB/octave below 1600 Hz. The transducer voltage changes, concomitant with SP’s in front of the TM necessary to produce the criterion CM, paralleled the SP changes only in the open system. However, considerably larger voltage changes were found in the closed system, especially between 630 and 2000 Hz. Furthermore, from the SP’s measured on both sides of the TM, the mean effective sound pressure (SPeff) acting on the TM was calculated. The changes in SPeff, taken in reference to a constant CM output, demonstrate that a small TM perforation produces a 10-dB frequency-independent loss in transmission.