Influence of stimulus parameters on amplitude-modulated stimulus frequency otoacoustic emissions

Abstract

The present study evaluated the influence of suppressor frequency (fs) and level (Ls) on stimulus-frequency otoacoustic emissions (SFOAEs) recorded using the amplitude-modulated (AM) suppressor technique described by Neely et al. [J. Acoust. Soc. Am. 118, 2124-2127 (2005a)]. Data were collected in normal-hearing subjects, with data collection occurring in two phases. In phase 1, SFOAEs were recorded with probe frequency (fp) = 1, 2, and 4 kHz and probe levels (Lp) ranging from 0 to 60 dB sound pressure level (SPL). At each fp, Ls ranged from Ls = Lp to Ls = Lp + 30 dB. Additionally, nine relationships between fs and fp were evaluated, ranging from fs/fp = 0.80 to fs/fp = 1.16. Results indicated that for low suppressor levels, suppressors higher in frequency than fp (fs > fp) resulted in higher AM-SFOAE levels than suppressors lower in frequency than fp (fs < fp). At higher suppressor levels, suppressors both higher and lower in frequency than fp produced similar AM-SFOAE levels, and, in many cases, low-frequency suppressors produced the largest response. Recommendations for stimulus parameters that maximize AM-SFOAE level were derived from these data. In phase 2, AM-SFOAEs were recorded using these parameters for fp = 0.7-8 kHz and Lp = 20-60 dB SPL. Robust AM-SFOAE responses were recorded in this group of subjects using the parameters developed in phase 1.

Cochlear Mechanisms and Otoacoustic Emission Test Performance

“…The frequency and level relationships between the suppressor and probe tones were f s / f p =0.88 and L s =42+0.58L p . These stimulus parameters previously have been shown to result in robust AM-SFOAEs in NH subjects (Johnson & Beshaler, 2013). For all conditions, the suppressor was amplitude modulated at a rate of 8 Hz, producing sidebands ±8 Hz relative to the f p , as shown in Fig.…”

“…3. As we have done previously (Johnson & Beshaler, 2013), the upper and lower sidebands were summed, using vector addition, to yield a single estimate for the SFOAE level, while the noise levels for the two side bands were averaged to obtain a single estimate of noise level. These single values representing the AM-SFOAE response and noise levels were used in all analyses where AM-SFOAE level was used to predict the presence or absence of hearing loss.…”

“…If test performance is improved when the reflection-source contribution is reduced, future studies could be undertaken to develop a clinically feasible approach such as the frequency-sweep technique (Long et al, 2008) that would reduce test time. Test performance of reflection-source OAEs was evaluated by recording SFOAEs using a recording technique and stimulus parameters identified previously (Neely et al, 2005;Johnson & Beshaler, 2013).…”

“…One limitation of our study is that the AM-SFOAE technique has not been thoroughly tested. The AM-SFOAE stimulus parameters used in this study were based on those recommended by Johnson and Beshaler (2013) as indicated by their AM-SFOAE data from 40 NH subjects. It is possible that alternate stimulus parameters may have produced different results.…”

Exploration of stimulus-frequency otoacoustic emission suppression tuning in hearing-impaired listeners

“…Hence, there is no stimulus energy at the frequencies of the side bands used to estimate SFOAE and thus, as observed for DPOAEs, there should be no on-band noise. Indeed, the noise levels of AM-SFOAE input-output functions fluctuated around −25 dB SPL across a 0–60 dB SPL range of probe level (Neely et al, 2005; Johnson & Beshaler, 2013). It is possible that adapting the AM-SFOAE method for tuning measurements may produce better data at the higher probe levels that must be used in cases of abnormal hearing thresholds, compared with the suppression method used in this study.…”