The Atlas · Chapter 5

The Normal Reflex

Before a pattern can be called abnormal, the normal picture must be clear: a present reflex in all four conditions, at expected levels, well sustained over time.

The normal grid

In an ear with normal middle-ear mechanics, a normal cochlea and an intact reflex arc, all four conditions of the grid show a present reflex. Thresholds for tonal stimuli typically fall in the region of 70–100 dB HL[10].

Stim. Right
Stim. Left
Probe Right
Present
85 dB HL
Present
90 dB HL
Probe Left
Present
90 dB HL
Present
85 dB HL
The normal four-cell grid: a present reflex in every probe/stimulus combination.

Normative thresholds

Reflex thresholds vary with frequency and stimulus type. The table below gives representative tonal values; broadband noise typically elicits the reflex some 20 dB lower.

StimulusTypical normal ART
500 Hz tone85–100 dB HL
1000 Hz tone85–100 dB HL
2000 Hz tone80–100 dB HL
4000 Hz tone80–105 dB HL
Broadband noise~20 dB lower than tones

Normal decay

Tested at 500 or 1000 Hz, a normal reflex holds its amplitude across the full 10-second presentation. Some gradual reduction is acceptable; what matters is that the amplitude does not fall to half its initial value.

0s2s4s6s8s10s0%50%100%50% criterion
Negative (normal) decay — amplitude is well maintained across the 10-second hold. A normal, well-sustained reflex — the curve stays well above the 50% line.
The reference picture.Four present reflexes, thresholds around 70–100 dB HL for tones, and amplitudes that hold across a 10-second hold. Every condition page is a departure from this baseline in a specific, interpretable direction.