Interacoustics Eclipse Additional Information page 231

Eclipse Additional Information Page 221
Rejection Algorithm: Mathematical calculation formula used to obtain advanced evaluation of which
Epochs are to be rejected.
Smoothing: In the absence of good quality digital filters, smoothing has in the past been used to remove
unwanted detail from waveforms. With the quality of the digital filters of this unit, smoothing and its unwanted
data reduction can be substituted with the digital low pass filter for better results.
SNR: Signal-to-noise ratio
Stimulus: Auditory stimuli used in AEP tests include a click, tone burst and en element of speech, delivered
to the patient using a headphone, insert phone or bone conductor.
Stimulus Onset: The time at which the stimulus starts. For all stimuli, including long Tone Bursts, "0" on the
time scale equals Stimulus onset.
TEOAE: Transient Evoked Otoacoustic Emission.
Tone Burst: A stimulus made by a certain number of sine waves of a given frequency. Unlike a click which
has a broad spectrum and is therefore not frequency specific, tone bursts provide a useful degree of fre-
quency specificity because of their limited bandwidth. The selected window, which shapes the rise and fall
characteristics of the overall stimulus is very important in assuring good frequency specificity. The duration
and specification of tone bursts vary, depending on their application. Because of the short latencies of the
ABR a very brief tone busts is necessary if temporal smearing is to be avoided. These brief tone busts are
sometimes called tone pips or logons. Conventionally 5 cycles of the stimuli are presented, their amplitude
shaped by an envelope with specific rise, plateau and fall times. This envelope may have a simple (linear) or
more complex shape, which affects the frequency specificity of the stimulus. The most popular complex en-
velope is the Blackman envelope. A linear envelope is obtained in the Eclipse by selecting the manual func-
tion. Longer latency AEPs such as responses of cortical origin allow longer duration tone busts to be used,
which offer near-ideal frequency specificity. Note that the duration of a stimulus affects its subjective loud-
ness and therefore the normal threshold of the stimulus. See also Calibration.
Tone Pip: See Tone Burst.
Vertex: (Cz) The very top of the head, defined as being midline (left to right) and midway between the nasion
(bridge of the nose) and the inion (indentation at the back of the skull).
Wave: Often referred to as a "peak". One of several maximum points on a waveform indicating the presence
of electrical activity related to the sound stimulus. Such a Wave is often marked with a Waveform Mark. An
ABR curve is usually considered to have 5 Waves, each of which can be assigned an appropriate marker.
Wave I through Wave V are used for ABR testing.
Waveform: (Also Curve). The total result of the averaging process as displayed in a time window. Certain
points of interest on the waveform are called Waves – e.g. Wave V.
Waveform Markers: Wave Marks are used to indicate certain points on an AEP waveform, where electrical
activity can be detected – often at points of obvious strong deflection on the waveform. Wave I, Wave III and
Wave V are generally marked if visible. See also "ABR".
Wave Reproducibility: The degree to which a recorded waveform can be reproduced in another similar re-
cording event.
The wave repro works by evaluating the similarities on the waveform of the A buffer and the waveform of the
B buffer. High similarity gives a high wave repro score. As the area of interest is usually around wave V,
most users prefer to set the wave repro window to hold primarily the wave V area. This should include the
deep trough after the wave V peak, as this is significant in the evaluation, and contributes considerably to the
wave repro score, when pronounced.