Limiting Noise In The Test Environment; Grounding; The Best Test Site & Setup For Abr Recordings - Interacoustics Eclipse Additional Information

Eclipse Additional Information
2.2

Limiting noise in the test environment

The smallest ABR signals are in the size of 100-150nV close to threshold, so it can be difficult to obtain a
good SNR.
Proper grounding is essential in order to obtain a response with a minimum of electrical noise.
Try to ensure:
1. A dedicated ground for the Eclipse will reduce noise, please consult with the chapter Grounding.
2. Electrical interference must be minimize in order to get the best ABR waves for threshold estimation;
please turn off other equipment's not used or move them further away from patient.
3. Always connect the patient bed/chair to the Eclipse ground outlet; this will reduce electrical noise fur-
ther.
4. An electrical shielded room can be used to avoid electrical noisy from the environment.

2.2.1 Grounding

Grounding is crucial for cleaner ABR waves and safe operation. The ABR system cabinet is connected to the
ground lead. If the ground lead is not connected or poor, the ABR system will pick up electrical noise/interfer-
ence. This is on the screen as very large harmonic distortion curves completely overlaying the ABR curves.
An electrician can often easily wire a separate ground to the power outlet and swap the ground in this
socket. The time/money the electrician spends is much worth when it comes to the saved time for less noisy
ABR measurements.
Due to High Voltage, only experienced technicians/ properly trained staff must change and check the ground. Typically
an electrician has a dedicated ground tester where they can measure the quality of the ground.
Do not connect the Eclipse to a safety transformer, as a safety transformer is built in to the Eclipse already.
When ensuring grounding be aware of the following:
1. We must instruct the electrician that we are trying to record ABR signals as tiny as 100nV, as most of
them will determine that their ground is good enough for the house. Yes is might be good enough for
laptops, PC's or televisions – BUT NOT for ABR!
2. It is highly recommended to use a separate ground, as other equipment in the building can easily pol-
lute the ground (discharging current, spikes and noise to the ground).
3. There should be maximum 8 ohm between the earth rods to the place where ground is used with the
Eclipse.
2.2.2 The best Test Site & Setup for ABR recordings
1. If Laptop/PC is connected to power outlet – an optical USB cable must be used in order to maintain
patient safety (optical cable available).
2. An electric magnetic shielded room – typically soundproof.
3. Dedicated separated ground for only the ABR recording site.
4. The bed framing may act as an antenna. Ground it to the backside of the Eclipse and turn of the
power when connecting the cable . In worst case replace the bed with a wooden/plastic chair bed
and check whether the metal bed was the reason for noise.
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