Aural Acoustic Stapedius-Muscle Reflex Threshold Procedures to Test Human Infants and Adults

Abstract

Power-based procedures are described to measure acoustic stapedius-muscle reflex threshold and supra-threshold responses in human adult and infant ears at frequencies from 0.2 to 8 kHz. The stimulus set included five clicks in which four pulsed activators were placed between each pair of clicks, with each stimulus set separated from the next by 0.79 s to allow for reflex decay. Each click response was used to detect the presence of reflex effects across frequency that were elicited by a pulsed broadband-noise or tonal activator in the ipsilateral or contralateral test ear. Acoustic reflex shifts were quantified in terms of the difference in absorbed sound power between the initial baseline click and the later four clicks in each set. Acoustic reflex shifts were measured over a 40-dB range of pulsed activators, and the acoustic reflex threshold was objectively calculated using a maximum 10 likelihood procedure. To illustrate the principles underlying these new reflex tests, reflex shifts in absorbed sound power and absorbance are presented for data acquired in an adult ear with normal hearing and in two infant ears in the initial and follow-up newborn hearing screening exams, one with normal hearing and the other with a conductive hearing loss. The use of absorbed sound power was helpful in classifying an acoustic reflex shift as present or absent. The resulting reflex tests are in use in a large study of wideband clinical diagnosis and monitoring of middle-ear and cochlear function in infant and adult ears.

Normative Wideband Reflectance, Equivalent Admittance at the Tympanic Membrane, and Acoustic Stapedius Reflex Threshold in Adults

“…The wideband ASRT test as described in Keefe et al (in press) was used for this study. This section contains a summary description of these test procedures.…”

“…The ASR was detected based on the method of Keefe et al (in press) by assessing the difference in absorbed sound power between the initial click and any of the other four clicks that followed each BBN activator pulse in each pulse-stimulus set. In contrast, Keefe et al (2010) detected the ASR in terms of the response difference in acoustic pressure between the initial and later clicks.…”

“…Otherwise, the ASR shift was classified as absent at the given activator level. After discarding the initial results measured at the lowest activator level, the ASRT was estimated using the ASR shifts classified in the remaining nine activator levels (Keefe et al in press). …”

“…Wideband ASR threshold (ASRT) tests have been performed in adult ears with normal hearing at ambient pressure (Feeney & Keefe 1999; 2001; Feeney et al 2003a; Feeney et al 2004; Schairer et al 2007; Keefe et al 2010) and at tympanometric peak pressure (TPP) (Keefe et al 2010). Keefe et al (in press) described a new wideband ASRT test, which is based on detecting ASR shifts in the sound power absorbed by the test ear from a reference sound. Using this power-based ASRT test in an ipsilateral mode, the present study describes the first reports on the mean ASRTs at TPP in a group of normal adult ears, and the test-retest reliability of the ASRT.…”

“…Using this power-based ASRT test in an ipsilateral mode, the present study describes the first reports on the mean ASRTs at TPP in a group of normal adult ears, and the test-retest reliability of the ASRT. Hunter et al (in press) presented group data for the ASRT in infants with normal, conductive and sensorineural hearing loss using procedures described in Keefe et al (in press).…”