Top 3 Most Important HIT Measurements and When to Do Them


Top 3 Most Important HIT Measurements and When to Do Them

Best Practices for hearing care professionals dictate that Hearing Instrument Test (HIT) Boxes are a key part of the hearing aid fitting and verification process.

Performing HIT measurements on your patient’s hearing aids will ensure they go home with a quality instrument free of technical issues. These measurements are also essential for conducting non-traditional fittings, such as with a child or difficult to fit patient.

Before starting with a new HIT box, it’s vital to understand the most important measurements you can capture and which situations they may arise in. MedRx’s Hearing Instrument Test Chamber (HIT+) performs the 3 most important HIT measurements, including the 10 standard ANSI and IEC tests for hearing aids, 2cc measurements, and RECD measurements.


1 - 10 Automated ANSI & IEC Tests

The American National Standards Institute (ANSI) and the International Electrotechnical Commission (IEC) define the standard tests that all hearing aids should be tested against. The results of these tests should match the hearing aid manufacturer’s claims for the instrument’s technical performance.

The 10 standard tests are:

  • OSPL-90
  • Full-On Gain
  • Reference Test Gain
  • Frequency Response
  • Equivalent Input Noise
  • Harmonic Distortion
  • Battery Current
  • Input/Output (AGC)
  • Attack/Release
  • Induction Coil (SPLITS)

With the MedRx HIT+, you can conduct these tests individually or run through each one automatically. Our simplified software provides an AutoTest mode that allows clinicians to set up the hearing aid and run through all 10 tests automatically, expediting the measurements.

To run the hearing aid through the HIT+ AutoTest, select the Right or Left ear icon in the main HIT tab and optionally input the hearing aid’s serial number. Select the tests you want to include in the AutoTest. While it can run all 10 tests, you may set your default settings to any combination of the tests.

To start, the hearing aid will need to be programed to Full on Gain (FOG) in the hearing aid manufacture’s software. Once properly coupled and positioned in the box, simply click Start Auto and the test will begin. Once the OSPL90 and Full-On Gain tests are completed, a prompt will instruct the clinician to adjust the hearing aids settings to Reference Test Gain (RTG). A HIT quick guide can be found here. Results from the HIT measurements should be reviewed alongside the manufacture’s technical datasheet then compared to the ANSI or IEC tolerances. Each test completed in the HIT measurements have a tolerance that the hearing aid should fall within to pass the test. In the HIT Studio Module, you can click help and then scroll down to see References and Tolerances. Once complete, save your session and print the reports for your records.

These 10 standard ANSI and IEC standard tests should be completed for every patient’s hearing instruments regularly. Testing hearing aids for faults and failings ensures the best patient experience and is more likely to improve customer satisfaction.


Watch the video to see where to find the References and Tolerances in the HIT Studio Module

2 - 2cc Coupler Measurements

The 2cc coupler used to connect the hearing aid in the 10 standard ANSI and IEC tests can also be used to pre-program a hearing aid for a patient’s prescriptive loss without them present by using a predicted RECD value. You will need your HIT+ device for this measurement, but not a REM (Real Ear Measurement) device.

The coupler acts as the patient’s ear, where you will perform the measurements to pre-program the device to the target levels. For this fitting, the program uses targets defined by NAL or DSL.

From the HIT module, go to the Fitting tab and select the target tab in the bottom right corner. Here, you will input the patient’s information, transducer type, and the hearing aid’s specifications. The targets will then be calculated using a predicted RECD value based on the information that was input. Select the wrench tab and run verification at desired presentation levels.

When performing 2CC measurements, it is important to note that all the measurements are in gain. This means the lower input levels will have higher gain and the higher input levels will have lower gain. This will reverse the graphing compared to Live Speech Mapping and place the 80 curve at the bottom and 50 curve at the top.

3 - RECD measurements

RECD, or Real Ear to Coupler Difference measurements, are best used in an instance where a child or a difficult to fit patient cannot sit for a Real Ear Measurement fitting. The probe tubes and delicate nature of the fitting can make it difficult for clinicians to get a younger child or a restless adult to remain quiet and still for the duration of the fitting.

While a live fitting is preferred, a RECD fitting in a hearing instrument test box allows the clinician to simulate the real ear fitting in a coupler with MedRx’s Studio software.

This measurement requires a REM system, HIT box, and RECD coupler kit to run successfully.

Similar to the HIT fitting described above, a 2cc coupler represents that patient’s ear. However, rather than using a predicted RECD value, you will use the patient’s recorded RECD values.

To measure the patient’s RECD, go to the REM module on your MedRx software and select RECD. Follow the instructions in our RECD Guide for details on capturing these measurement in the REM Module.

Next you couple the hearing aid to the HIT+ 2cc coupler. Return to the HIT module Fitting screen and select Client in the RECD selection box. This will use the difference between the coupler response and the patient’s ear canal response.

You are now ready to perform measurements and adjust the hearing aid gain to the desired prescriptive target.



MedRx HIT+

The MedRx HIT box was designed for streamlined hearing aid diagnostic testing. Its sturdy and discreet design makes it a great choice for any clinician or office looking to improve their Best Practice posture.

For more information on pricing or how to integrate the MedRx HIT+ system into your office’s hearing aid fittings, give us a call at (888)392-1234. You can also schedule a free online demo to see HIT performed in real time by one of our expert training representatives. 

In a demo, we’ll help you determine the best way to incorporate the MedRx HIT+ into your daily fittings and show you how to improve patient satisfaction in your office.