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REM Procedure for CROS Users: Questions on Probe Tube and Poor Ear Testing

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Background and REM Experience

Thank you everyone for reminding me to ask the audiologist to perform Real-Ear Measurement () before purchasing my hearing aids. They finally performed the test yesterday during the adjustment session.

However, my audiologist seemed unsure about the procedure for users and had to consult with other colleagues. The initial decision was to insert the probe tube into the better ear first.

Questions Regarding the REM Procedure

I have two main concerns about the process:

  1. Probe Tube Depth: Why did the audiologist already mark the ‘insertion depth into the ear canal’ on the probe tube? Is the length of everyone’s ear canal the same? Furthermore, the hearing aid in that ear was not inserted as deep as possible, unlike how I usually wear mine.

  2. CROS Ear Testing: The audiologist then stated that because my right ear (the poorer hearing ear) wears the CROS side, they did not need to insert the probe tube or wear the hearing aid during the test. This meant my poorer ear was not wearing the CROS device throughout the entire REM. Is this test procedure correct?

My original understanding of REM was that it not only optimizes the gain in the better ear but also checks if the CROS side is receiving the correct volume and transmitting it effectively to the better ear.

Post-Adjustment Results

I really don’t want to spend money on the Signia Pure 7iX and not get the desired effect. In summary, after the REM and the subsequent adjustment, I feel the sound is a bit too loud and not very clear.

Can someone please clarify these procedures for me? Thank you everyone.

Ear canal lengths are close, yes. It’s good practice to set the marker to the male or female spot prior to insertion to help guide you.

If they are doing on the audioscan, the process to verify the cros is:

  1. Complete verification on the hearing aid with the muted. You could still place the CROS or do that later, and yes no probe tube in the CROS ear as it doesn’t produce any sound on that side, but the reference mic still needs to be hung on the ear.

  2. turn head 45 degrees with hearing aid towards speaker, run speech (or pink noise) at 65 (or whatever, as long as it’s the same in the next step).

  3. turn head 45 degrees with CROS towards speaker, adjust verifit so it knows you’re measuring the CROS (to change which reference mic is used), run the speech noise again (with a different line) to make sure it’s the same. If not, adjust CROS in software and try again.

On a different system it’s sometimes a bit different, I’d have to look it up.

Yes, hearing aid should be fully inserted for REM. If it’s an open dome having it sitting out a bit won’t be a huge deal but may sound a bit sharp when in all the way. can get weird if there’s extra venting and the clinician is cranking the lows to try to compensate.

thank you Neville, you help me alot!

As a user, my understanding of the Real-Ear Measurement () procedure is as follows:

1. Preparation and First Measurement (Better Ear Verification)

  • Both the CROS transmitter (poorer ear) and the hearing aid receiver (better ear) must be worn throughout the entire process.

  • The first REM measurement focuses on the better ear’s gain.

    • Procedure: I face forward, and the sound speaker is positioned at 45 degrees to my better ear. The sound from the CROS side (poorer ear) should be muted or switched off during this initial test.

    • Goal: The resulting curve () is adjusted to match the prescribed target curve (e.g., ) to achieve the optimal amplification for the better ear.

2. Second Measurement (CROS Transmission Verification)

  • The second measurement verifies the signal transmission from the CROS side.

    • Procedure: I turn my body to the opposite side, so the CROS transmitter (poorer ear) is facing the speaker at a 45-degree angle. The CROS signal is turned on for this test.

    • Goal: The resulting curve (REXR) is adjusted to match the Real-Ear Unaided Gain (REUG) curve of the better ear. This ensures the CROS signal volume is natural and sufficiently overcomes the head shadow effect.

3. Conclusion on Adjustment

My conclusion is that the gain for the better ear receiver and the CROS transmission level must be adjusted separately based on these two distinct REM verification results.

:memo: Note on Physical Fit (Open Dome)

I wear an open dome, but I usually insert the hearing aid very deeply, meaning I push it in until it passes the cartilaginous part of the outer ear canal (past the first bend/bone).

So, minor adjustment: the hearing aid is adjusted first in normal position (facing the speaker) with the turned off. It doesn’t matter if the CROS is on or off the ear for this but it should be muted.

Once the hearing aid is set, then you move to 45 with hearing aid towards the speaker, CROS is still muted (on or off the ear). You’re gathering this curve on order to then match with the CROS.

Then turn head to the other 45 so the CROS is towards the speaker, and this is when the CROS has to be turned on and in place. The most important step here for a clinician who isn’t familiar with this is to tell the audioscan that you are now measuring a CROS. It will still be measuring from the other ear but needs to know it’s through the CROS now so it will adjust the reference mic. Then yes, you run the speech curve to make sure it matches (overcomes head shadow). If it’s too low or to high you adjust the CROS balance in the software.

Again, this is for the verifit machine. As long as another machine has an option to set it to CROS and so swap the reference mics the procedure would be the same, but if it doesn’t you need to modify things a bit. There’s a way, but I’d have to look it up.

In reply to @tjp3wk4iu

Ideally verification should take place with the dome in the position the patient wears it. If the dome is further out, then once it is pushed in it will be a bit over target it some places (mostly high end for open dome). It’s not going to be so over-target that it’s damaging, so if you like the sound then that’s fine, you’re actually getting better audibility. If it’s too sharp, verification could be repeated with the dome in the correct place. New clinicians do sometimes need practice reaching full insertion, especially if they are nice and nervous about causing the patient discomfort.

Perhaps more commonly what happens is that is completed with full dome insertion (not your case) and then the patient wears the hearing aids with the dome much further out. This situation is worse to me, because they are just walking around underfit and can be quite dramatically underfit if this is happening with closed or power domes. For patients who can’t get their domes all the way in a custom tip offers more stable gain.

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