On this page we outline the CERA studies we are currently undertaking or have recently completed.

Accuracy of the CERA threshold estimate in adults

Previous studies have used conventional stimulus presentation and data acquisition / manipulation methods. We know that our method is a good deal faster than conventional methods, mainly because we automate most of the predictable manual tasks. What we needed to demonstrate was the accuracy of the threshold estimate. Of course, this has been done before but not using our random pseudo-binaural stimulus and not at high frequencies. We employed 24 volunteers (mostly hospital staff) whose pure tone audiogram (PTA) was recorded by experimenter 1. Their CERA was then conducted by experimenter 2, blind to the PTA results. Test frequencies of 1, 3 & 8 kHz (balanced order) were been chosen because most hearing disability schemes use the frequencies of 1, 2 & 3 kHz. Conventional wisdom suggests that the CERA amplitude is lower at high frequencies so we included 8 kHz to test this. Though not used in disability calculations, high frequencies are often helpful in matters of causation - demonstrating an audiometric notch associated with noise trauma.
Results: The mean error in the N1-P2 threshold estimate was 6.5 dB, with no significant effect of frequency. After correcting for this bias, 94% of individual threshold estimates were within 15 dB of the behavioural threshold and 80% were within 10 dB. Establishing the 6 threshold estimates (3 frequencies, 2 ears) took on average 20.6 minutes.

Effectiveness of certain stimulus presentation features in increasing the N1-P2 amplitude

We developed our "Optimised" CERA test paradigm from the findings of the available literature (for details, see the page on this). However, we have taken much of this on trust and we certainly did not know whether there is any interaction between the effects of the parameters we have chosen. This study therefore addressed this issue by looking at them in isolation and in combination. Again, 24 volunteer staff are being used but only one ear is under scrutiny, at one frequency (3 kHz), at an intensity close to threshold (25 dB sensation level). In this study we hoped to identify any effect on CERA amplitude of:

Results: There appeared to be no effect of any of the above on N1-P2 response amplitude.

These findings were somewhat of a surprise and disappointing - apparently suggesting that these novel stimulus presentation features that we have developed and used for many years actually bring no advantage. Still, that's the point of undertaking the research!
In fact, the results must be viewed with an important fact in mind: the nature of the experimental design was such that subjects were exposed to ever-changing stimuli over a period of about 20 minutes. Thus, there appears to be no significant short-term effect of these features. What we have not addressed in our study is whether these features offer any advantage over conventional stimulation - i.e. monotonous monaural stimulation lasting up to an hour. We suspect we would see an advantage but that's another study!

We have produced a paper on this study, Lightfoot & Kennedy (2006). See the Downloads page for a pdf version.