Unaided Real Ear Measurements

Jack Bennett, International Clinical Trainer at the Interacoustics Academy, describes how to perform Unaided Real Ear Measurements. This includes how to check for contra indications during otoscopy, how to insert the probe tube microphone, how to measure Real Ear Unaided Response (REUR), how to perform Real Ear Occluded Response (REOG), and how to perform a calibrate for open fit.

If you prefer reading, find the transcript below.

Preparing for an REUG measurement

So I'm now joined by my colleague, Dennis, who has volunteered to be our patient for the day. So thank you very much, Dennis.

At this stage, we're now ready to do an REUG. Now we have selected a real ear aided response protocol. So the REUG is not actually necessary. But I would recommend it as it's a really good quality control step to help us understand if the probe is in the correct position. And a quality real ear measurement relies on a probe in a in the correct position.

1. Otoscopy

So the first thing to do now is to perform otoscopy and make sure that Dennis has got clear ears, and that he's got ears as we would expect them to be average ear canals. So I'll use the Viot™ video otoscope for this process. So just select that in the Affinity Suite. And Dennis if you could just turn so your left ear is facing towards me, please. Thank you very much.

So while I'm performing otoscopy, I'm looking for, for any obstructions. And just to understand if the ear canal is as I would expect it to be that we're normal, healthy, and that there are no contra-indications. Contra-indications to be aware of at this stage are:

• Pain or discharge potentially caused by an infection.
• A perforation that might make it dangerous to insert the probe tube as you don't want to enter into the middle ear space. Or a perforation so large that any measurements you take would be significantly impacted by the middle ear space.
• The presence of wax. If there is so much wax that you cannot safely observe the eardrum, or it was likely to occlude the end of the probe tube, then this is too much wax. In terms of the frequency response of the middle ear, however, the low frequencies would only be affected by so much wax that it filled a significant portion of the residual volume of the ear canal. Or for the high frequencies, these would be affected by ear wax that was affecting more than 1/3 of the cross-sectional area of any part of the ear canal.

And I actually take an image at this stage as well, just for good record keeping. So that's perfect.

2. Preparing the REM headset

So now I'm ready to actually prepare the REM headset. Now that I've seen that Dennis' ear canals are average and clear. So to do this, I need to set the probe depth and actually use a ruler at this stage. And on each probe, there's a small black marker, which can slide and that can help me then just mark the correct depth so that as I'm inserting the probe, I have a reference on the outside for me to mark up against.

So for an average male, we'd use a probe depth insertion probe insertion depth of 30 millimeters. So if I mark that on the ruler on both sides. Okay, so now my probe markers are in the correct position, I'm now ready to actually insert the probes into my patient's ear. So I'll place the headset over Dennis' ears here. So red for the right ear blue the left. And I'll just come round and I'm using that probe marker just at the tragal notch. So I know how deep the probe is actually going inside.

Now Dennis, you might feel some tickling and if it's uncomfortable at any point, please just let me know. Okay. So I've set the reference microphones just below the level of the ear so that the probe will sit in a secure position along the ear canal. Okay. And I'll review this with the otoscope as well being careful not to move the probe too much. And we can see that sitting in a good position. The angle is correct, and it's a nice deep insertion. So I'm happy with that side.

Dennis, if you could just turn around for me again. Thank you very much. And we'll do exactly the same on the left-hand side. So again, a bit of a tickle and let me know if it's uncomfortable. Just using that marker to guide the probe depth pointing down towards the ear canal down towards the eardrum as close to the eardrum as we can get. The closer we are to the ear drum the more effectively, it will measure the high frequency response, which is really important, especially with new modern hearing aids that have got a much higher frequency response – a much higher gain – in the high frequency regions.

An alternative method is to use the Probe Placement Indicator, where an auditory stimulus will enable the software to tell you when the probe is in the correct position and give you an indication as to when you can stop.

Performing an REUG measurement

So now we're ready to perform an REUG in the ear canal. On the screen, I've still got the REUG up from earlier from my probe tube calibration, because the system will only hold one REUG, I'll just delete those now.

So for this portion, all I need to do is ask my patient Dennis to keep nice and quiet and nice and still during the measurements. I'll select the REUG in the protocol and then press start.

So having performed the REUG measurement, we can review the results on screen just to check that the probes are in the correct position and that everything is symmetrical. So we're looking for the characteristic frequency response of the ear canal.

That's zero dB of gain in the low and mid frequencies, rising to a peak around 2 to 2.5 kilohertz and then dropping smoothly back down to around zero dB in the high frequencies. Being slightly negative in the high frequencies is okay, the most important thing really is that we're looking for that characteristic response and that they're symmetrical on both sides, which is what we've got.

So we're now happy to move on to our other measurements.

REOG measurement

So now that we've measured our REUG, we can move into the real ear occluded gain (REOG) measurement. So this is the same measurement, but with the hearing aids in and switched off. Again, it's not strictly necessary in a real ear aided response, but it does help us understand if the acoustic coupling is as transparent or as occluded as we want it to be, and that the probes are still in the correct position.

So to do this, we just select the REOG in the protocol and then press start. You can actually review the REUG and the REOG on the same screen to see the difference. And as we can see, broadly the shape is the same.

And we've not had much of a change from inserting the hearing aids. We should expect a small change because of course, we have changed the acoustics of the ear canal by inserting the hearing aids. But we haven't got so much of a change that we've introduced any error into our measurements. So I'm happy with these REOG's.

Calibrate for open fit

Having recorded the REOG, we've reviewed the data, and you might find that if you have a vented mold that you still have a fairly transparent open fitting. If you do have that then you will need to do a calibration for open fit, which is our next step. I'll select it in the protocol.

And the reason we run this measurement is so that any sound that leaks out of the ear canal while doing the hearing aid verification doesn't influence the stimulus. So what we need to do is select the stimulus which will be what we use for our real ear aided response measurements and then press start.

This is a very quick measurement. And you don't need to actually interpret the graph. This is just the stored equalization the system is using to set the stimulus level. It's really important that now that we've set this stored equalization level that the patient doesn't move throughout the test. And if they do move, you need to return them back to the position that they were in when you measured this result.

And now we're ready to turn the hearing aids on and verify the frequency response in the ear canal.