Time–frequency analysis of linear and nonlinear otoacoustic emissions and removal of a short-latency stimulus artifact

Abstract

Click-evoked otoacoustic emissions (CEOAEs) are commonly recorded as average responses to a repetitive click stimulus. If the click train has constant polarity, a linear average results; if it contains a sequence of clicks of differing polarity and amplitude, a nonlinear average can be calculated. The purpose of this study was to record both protocols from the same set of ears and characterize the differences between them. The major features of CEOAEs were similar under both protocols with the exception of a region spanning 0-5 ms in time and 0-2.2 kHz in frequency. It was assumed that the signal derived from the linear protocol was contaminated by stimulus artifact, and so a simple procedure was used--involving high-pass filtering and time-windowing--to remove components of this artifact. This procedure preserved the short-latency, high-frequency responses; it also produced a marked similarity in the time-frequency plots of recordings made under the two protocols. This result means it is possible to take advantage of the better signal-to-noise ratio of the linear data compared to its nonlinear counterpart. Additionally, it was shown that CEOAEs recorded under the linear protocol appear to be less dependent on the presence of spontaneous otoacoustic emissions (SOAEs).

Time-Frequency Properties of Neonatal Transiently Evoked Otoacoustic Emissions Measured in Three Different Acquisition Modes

“…Additionally, it was shown that when the method of artifact reduction was applied to the linear mode TEOAE recordings, the time-frequency properties of the data were similar to the responses elicited by the non-linear protocol. The TEOAE latency-frequency dependence for newborn ears studied here was found to have similar characteristics to those of adults [7] . In terms of latency-frequency properties, there seemed to be no maturational effects [21] , which are found with response level [22] .…”

“…Only the range 0-5 ms in time and 0-2200 Hz in frequency was windowed and filtered, while for frequencies above 2200 Hz, only the initial 2.5 ms were windowed. The effect of this change was preservation of the high frequency response when using the linear protocol [7] .…”

“…In line with the procedure proposed by Jedrzejczak et al [7] , the signal in the range of 0-5 ms and 0-2200 Hz was filtered out. This was done using the MP method, which makes it possible to algebraically subtract unwanted components from the original signal.…”

“…Recently, a new procedure for cancelling linear artifacts was introduced [7] . This work showed that the linear artifacts were contained mainly in a time window of 0-5 ms and in a frequency range of 0-2200 Hz.…”

Time–frequency decomposition of click evoked otoacoustic emissions in children

“…Additionally, participants with an excessive number of SOAEs, greater than five, were excluded since it may impact the CEOAE levels. This criterion was set based on the mean incidence of SOAEs consolidated from several studies (Jedrzejczak et al, 2008;Penner and Zhang, 1997;Strickland et al, 1985;Talmadge et al, 1993). This condition was strict because CEOAEs recorded by the linear recording technique are less influenced by synchronous SOAEs (Jedrzejczak et al, 2012).…”