Structured Abstract Objectives To develop normative data for wideband middle-ear reflectance in a newborn hearing-screening population, and to compare test performance with 1-kHz tympanometry for prediction of OAE screening outcome. Design Wideband middle-ear reflectance (using both tone and chirp stimuli over 0.2 to 6 kHz), 1-kHz tympanometry, and distortion-product otoacoustic emissions (DPs) were measured in 324 infants at two test sites. Ears were categorized into DP-pass and DP-refer groups. Results Normative reflectance values were defined over various frequency regions for both tone and chirp stimuli in ambient pressure conditions, and for reflectance area indices (RAIs) integrated over various frequency ranges. Receiver-operating-characteristic (ROC) analyses showed that reflectance provides the best discriminability of DP status in frequency ranges involving 2 kHz, and greater discriminability of DP status than 1-kHz tympanometry. Repeated-measures analyses of variance (ANOVA) established that (a) there were significant differences in reflectance as a function of DP status and frequency, but not sex or ear; (b) tone and chirp stimulus reflectance values are essentially indistinguishable, and (c) newborns from two geographic sites had similar reflectance patterns above 1-kHz. Birth type and weight did not contribute to differences in reflectance. Conclusions Referrals in OAE-based infant hearing screening were strongly associated with increased wideband reflectance, suggesting middle-ear dysfunction at birth. Reflectance improved significantly over the first 4 days after birth with normalization of middle-ear function. Reflectance scores can be achieved within seconds using the same equipment used for OAE screening. Newborns with high reflectance scores at Stage I screening should be rescreened within a few hours to a few days, as most middle-ear problems are transient and resolve spontaneously. If reflectance and OAE are not passed upon Stage II screening, referral to an otologist for ear examination is suggested along with diagnostic testing. Newborns with normal reflectance and a refer result for the OAE screen should be referred immediately to an audiologist for diagnostic testing with threshold auditory brainstem response (ABR) due to higher risk for permanent hearing loss.

Measurements of middle ear (ME) acoustic power flow (power reflectance, power absorption, and transmittance) and normalized impedance (acoustic resistance, acoustic reactance, and impedance magnitude) were compared for their utility in clinical applications. Transmittance, a measure of the acoustic power absorbed by the ME, was found to have several important advantages over other measures of acoustic power flow. In addition to its simple and audiologically relevant physical interpretation (absorbed power), the normal transmittance curve has a simple shape that is visually similar to the ME transfer function. The acoustic impedance measures (resistance and reactance) provided important additional information about ME status and supplemented transmittance measurements. Together these measurements can help identify unusual conditions such as eardrum perforations. While this article is largely a review of the development of a commercial power reflectance measurement system, previously unpublished experimental results are presented.

In this paper, a method that has been developed for the assessment and quantification of loudness perception in normal-hearing and hearing-impaired persons is described. The method has been named LGOB, which stands for loudness growth in 1/2-octave bands. The method uses 1/2-octave bands of noise, centered at 0.25, 0.5, 1.0, 2.0, and 4.0 kHz, with subjective levels between a subject's threshold of hearing and the "too loud" level. The noise bands are presented to the subject, randomized over frequency and level, and the subject is asked to respond with a loudness rating (one of: VERY SOFT, SOFT, OK, LOUD, VERY LOUD, TOO LOUD). Subject responses (normal and hearing-impaired) are then compared to the average responses of a group of normal-hearing subjects. This procedure allows one to estimate the subject's loudness growth relative to normals, as a function of frequency and level. The results may be displayed either as isoloudness contours or as recruitment curves. In its present form, the measurements take less than 30 min. The signal presentation and analysis is done using a PC and a PC plug-in board having a digital to analog converter.

Quantifying how the sound delivered to the ear canal relates to hearing threshold has historically relied on acoustic calibration in physical assemblies with an input impedance intended to match the human ear (e.g., a Zwislocki coupler). The variation in the input impedance of the human ear makes such a method of calibration questionable. It is preferable to calibrate the acoustic signal in each ear individually. By using a calibrated sound source and microphone, the acoustic input impedance of the ear can be determined, and the sound delivered to the ear calibrated in terms of either (i) the incident sound pressure wave or (ii) that portion of the incident sound pressure wave transmitted to the middle ear and cochlea. Hearing thresholds expressed in terms of these quantities are reported, these in situ calibrations not being confounded by ear canal standing waves. Either would serve as a suitable replacement for the current practice of hearing thresholds expressed in terms of sound pressure level calibrated in a 6cc or 2cc coupler.

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The validity of transient-evoked otoacoustic emissions (TEOAEs), as implemented on the Mimosa Acoustics T2K Measurement System (v. 3.1.3), was assessed for a variety of transient stimuli. Stimuli evaluated included clicks, Dau chirps, and Shera chirps, all with bandwidth 1 to 5 kHz and stimulus levels from 38 to 53 dB SPL, and clicks with bandwidth 1 to 2.5 kHz. A new form of in-the-ear calibration was used that corrected the stimulus to give the desired spectrum and group delay. Both linear and nonlinear modes were evaluated. Validity testing was done using moderate-to-profoundly hearing-impaired ears, which should not produce TEOAEs. Any measurable response is an indication of artifact. Validity was established for all TEOAE stimuli up to 50 dB SPL(rms) when testing was done in nonlinear mode. Validity could not be established for any stimulus when testing was done in linear mode, where linear artifact was not subtracted out. Spectral calibration showed more artifacts at lower frequencies and fewer artifacts at higher frequencies, when compared with wideband calibration for clicks measured in linear mode. Chirp stimuli produced fewer artifacts than clicks, presumably due to their lower crest factors and longer durations. Minor enhancements to the spectral calibration should improve validity further. Stimulus Bandwidth (kHz) RMS Stimulus Level (dB SPL) Peak Stimulus Level 2 (dB pSPL) Description Click 1 to 5

Hearing screening programs using otoacoustic emissions can have high false positive rates, due to temporary middle-ear and outer-ear disorders. This is especially the case for newborns, infants, and young children. Standard tympanometry is limited, uncomfortable, and unreliable in young ears. By incorporating wideband acoustic power flow measurements into hearing screening (using the same equipment), middle-ear and outer-ear disorders can be detected, thus allowing for rescreening rather than more expensive audiological referrals. Wideband acoustic power flow is described in detail and four case examples are provided for adults and children.

To make measurements a person sometimes has the need for many different test instruments on ones bench. The philosophy behind SYSid (SYStem identification) is to integrate many commonly used test instruments into a single yet accurate and easy to use system. The SYSid software package runs on a DOS platform with the Ariel DSP-16+installed. The theory of operation in SYSid is simple. SYSid excites the system being measured with a stimulus and synchronously averages the measured response of the system. The stimulus can be a chirp, single tone, or multiple tones, MLS, or it can be user-defined (i.e., speech, pink noise, octave-band noise, etc.). It is important to synchronously average a system response in order to obtain accurate phase information. Synchronous averaging also allows one to measure a signal that is below the system noise floor. SYSid then uses FFT techniques to deconvolve the stimulus from the measured response and to further analyze the data. From this basic mode of operation SYSid can perform many types of analyses including phase responses, group delay, impulse response, Hilbert envelope, reverse energy time curve, RT60, waterfall displays, electrical impedance, etc. In addition to these linear measurements, SYSid also provides the capabilities to make distortion measurements due to nonlinearities in the system. These include harmonic distortion, intermodulation distortion, THD+N, input–output functions, and spectral contamination.