The following files may be viewed or downloaded. More will be added in future.

Please read the notes on this page relating to the file in question.  Some of the files are quite large so unless you have a high speed internet connection be prepared to wait a while!

Brochure for the ERA & OAE Course (632KB) organised by the author in Harrogate, UK.  The one-week residential course is held every May but usually sells out several months in advance.  The brochure is in PDF format so you'll need to have Adobe Acrobat Reader.  This can be downloaded free by visiting www.Adobe.com

This web site can be downloaded, viewed & printed as a single PDF file (327KB) for personal or educational purposes.

Research
We recently completed a study on the performance of CERA in volunteer adults in order to assess the speed of our current system and to investigate the effects of certain stimulus presentation features. We presented some results at the IERASG symposium in Havana, Cuba, in June 2005 and the paper appeared in Ear & Hearing in 2006. You may download a pre-publication PDF version here (768KB).
An interesting paper by Van Maanen & Stapells comparing CERA and two rates of steady-state threshold estimation is available here (176KB).

Run an "optimised" Cortical ERA test yourself! Scroll down for the latest videos.
The following video clips are examples of patients being tested using the author's system in Liverpool, UK.  If you have a high speed (broadband) internet connection you will probably be able to view them on line (without having to download the files) and play them using Windows Media Player or similar software. Alternatively, right-click the link and download the file using "Save Target As". They are best viewed full screen.  They are a little jerky since they were recorded at 8 or 10 frames per second.

The first video (5.79MB) is a 3 kHz bone conduction Cortical ERA test, with masking, lasting 4.37 minutes.  Intensities used are 40, 20, 0 and 10 dBHL and yield a threshold of 5 dBHL. The lower panel is the incoming EEG (note how at the end of each sweep, the waveform becomes smoother - this is the 15 Hz low-pass digital filtering of individual sweeps).  The upper panel is the averaging area.  A repetition rate of 0.7Hz with 30% variability is used.  Three sub-averages are acquired in a cyclical fashion and at the end of 15 sweeps a grand average (in red - this is a right ear test) is automatically created.  Cursors are placed automatically, though the operator may reposition them, and a correlation coefficient calculated (lower left of the panel).  At 40 & 20 dBHL only 15 sweeps are needed but at the lower intensities, closer to threshold, further averaging is undertaken.  However, before this occurs, a 10 second stimulus-free period is provided to allow the response to recover and so minimise the effects of adaptation.  An intensity series is displayed, allowing the operator to assess the responses and so establish the hearing threshold or the need for further testing.

The second video (15MB) is a 1 kHz air conduction simultaneous right & left Cortical ERA test lasting 7.37 minutes.  The stimulus is presented in a random fashion to one or other ear (the colour of the incoming EEG waveform in the lower panel indicates right or left stimulation).  The video begins just after the first intensity (60 dBHL) has been completed.  Further averaging is undertaken at 40, 20, 0 and 10 dBHL.  The results suggest thresholds of 15 dBHL in both ears.

The third video (6.4MB) is a segment of tests at 1kHz by air conduction using the  simultaneous right & left Cortical ERA technique (3.22 minutes), this time shown on a computer running Windows XP. Again, the video starts just after completion of testing at 60dBHL and demonstrates the acquisition of tests at 40 and 20dBHL. The quality of this patient's responses are less than ideal, but this example is included here to demonstrate that even so, the technique is viable. Clearly, in such cases the precision of the threshold estimate will be modest.

Now here's something you wouldn't be able to do using ABR.
The forth video clip (19.1MB) shows a 250Hz air conduction test on both ears (5.23 minutes). Right & left ear intensities of 50/50, 30/30 and 20/40dBHL are employed, and suggest CERA thresholds that were within 5dB of the patient's behavioural thresholds. Using ABR, issues of neural synchrony make responses to low frequency stimuli at low sensation levels almost impossible to record. In contrast, CERA responses at low frequencies are just as well defined, accurate and frequency specific as those at higher frequencies.

Take home message?
The author designed and developed this system for his own clinical and medico-legal use with hardware and software from Cambridge Electronic Design (the assistance of their software engineer Dr Geoff Horseman is gratefully acknowledged).  Although this system is commercially available, it is a pity that such software has not been incorporated into existing ERA systems. 
This is because there in no demand. 
There is no demand because the possibilities and potential of this test have not been fully recognised.
That was a primary reason for the creation of this web site! 

If you are impressed with this technique then please give the manufacturer of your ERA system a hard time - point them at this site and tell them to make one available!