Mean input/output (I/O) functions measured as global response levels of TBOAEs for 4 different stimulus frequencies (center frequency given above each plot).

<p>Results are shown for ears with SSOAEs (solid line) and ears without SSOAEs (dashed line). Error bars indicate standard errors; asterisks at top of each panel indicate statistically significant differences (*–<i>p</i><0.05; **–<i>p</i><0.01).</p

Mean I/O functions for CEOAEs measured globally (top plot) and in half-octave bands (four bottom plots).

<p>Asterisks at top of each panel indicate statistically significant differences (*–p<0.05; **–<i>p</i><0.01; ***–<i>p</i><0.001). Other details as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192930#pone.0192930.g003" target="_blank">Fig 3</a>.</p

Example of the latency determination procedure.

<p>Envelopes of a 1 kHz TBOAE from a single subject are shown on a linear scale for stimulus levels from 40 to 80 dB. The white circles connected with solid lines mark the same maxima across different stimulus levels. Black circles (slightly offset for clearer presentation) connected with a dashed line mark the highest response for each stimulus level (the WS latency).</p

Otoacoustic emissions from ears with spontaneous activity behave differently to those without: Stronger responses to tone bursts as well as to clicks

<div><p>It has been reported that both click-evoked otoacoustic emissions (CEOAEs) and distortion product otoacoustic emissions (DPOAEs) have higher amplitudes in ears that possess spontaneous otoacoustic emissions (SOAEs). The general aim of the present study was to investigate whether the presence of spontaneous activity in the cochlea affected tone-burst evoked otoacoustic emissions (TBOAEs). As a benchmark, the study also measured growth functions of CEOAEs. Spontaneous activity in the cochlea was measured by the level of synchronized spontaneous otoacoustic emissions (SSOAEs), an emission evoked by a click but closely related to spontaneous otoacoustic emissions (SOAEs, which are detectable without any stimulus). Measurements were made on a group of 15 adults whose ears were categorized as either having recordable SSOAEs or no SSOAEs. In each ear, CEOAEs and TBOAEs were registered at frequencies of 0.5, 1, 2, and 4 kHz, and input/output functions were measured at 40, 50, 60, 70, and 80 dB SPL. Global and half-octave-band values of response level and latency were estimated. Our main finding was that in ears with spontaneous activity, TBOAEs had higher levels than in ears without. The difference was more apparent for global values, but were also seen with half-octave-band analysis. Input/output functions had similar growth rates for ears with and without SSOAEs. There were no significant differences in latencies between TBOAEs from ears with and without SSOAEs, although latencies tended to be longer for lower stimulus levels and lower stimulus frequencies. When TBOAE levels were compared to CEOAE levels, the latter showed greater differences between recordings from ears with and without SSOAEs. Although TBOAEs reflect activity from a more restricted cochlear region than CEOAEs, at all stimulus frequencies their behavior still depends on whether SSOAEs are present or not.</p></div

Comparison of mean TBOAE thresholds (left) and CEOAE thresholds (right) for cases with SSOAEs (solid line) and without SSOAEs (dashed line).

<p>Measurements were made in half-octave bands for both, and for TBOAEs the stimulus frequency matched the centre frequency of the analysis band. Error bars indicate standard errors; asterisks mark statistically significant differences (*–<i>p</i><0.05).</p

Mean I/O functions of TBOAEs measured in 4 half-octave bands (centre frequencies at top).

<p>Other details as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192930#pone.0192930.g003" target="_blank">Fig 3</a>.</p

Mean latencies of SL and LL components of TBOAEs (left) and corresponding I/O functions (right).

<p>Each row corresponds to a different TBOAE frequency.</p

Mean latencies of TBOAEs measured in half-octave bands as a function of stimulus level.

<p>The latencies were taken to be the location of the maximum of the whole signal (WS, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192930#pone.0192930.g002" target="_blank">Fig 2</a>). Results for 4 different stimulus frequencies are plotted for ears with SSOAEs (solid lines) and without SSOAEs (dashed lines). Error bars indicate standard errors. There were no statistically significant differences between ears with SSOAEs and without SSOAEs for any frequency and stimulus level.</p

TBOAE level plotted against CEOAE level, both measured in half-octave bands, for 60, 70, and 80 dB stimuli.

<p>The data are plotted for ears with SSOAEs (dots) and without SSOAEs (circles). Linear fits for each group are also shown (solid: with SSOAEs; dashed: without SSOAE). Dotted line shows y = x line as reference. Percent correlations and R2 values for fits shown (‘+’, with SSOAEs; ‘–′, without SSOAEs).</p

Probability of inconsistent selection [%] for competing GE and IG distributions by the <i>K</i> or <i>QK</i> discrimination procedures.

<p>Probability of inconsistent selection [%] for competing GE and IG distributions by the <i>K</i> or <i>QK</i> discrimination procedures.</p