A§E Binaural Benefit

The Binaural Benefit test type is not really a separate module, but rather a script to guide you through 4 speech audiometric tests using the SoundC hardware to assess the benefit of a second (aided) ear in addition to a first (aided) ear.

It is required to have SoundC installed with at least 3 speakers!

See also A§E Localization test for a complementary test to assess binaural hearing.

Working principles

Head Shadow Benefit

With only one functional ear, speech coming from the contralateral side gets attenuated before arriving at the functional ear as a result of the head shadow.  When the contralateral ear becomes functional (typically by adding a hearing aid or hearing implant), the speech intelligibility improves.  This is called the head shadow benefit.  Head Shadow benefit can be expressed as improvement of SRT or of speech intelligibility score.  Audiqueen uses the latter.  

For this matter, Audiqueen executes a speech audiometry in noise test with both hearing aids and by means of an adaptive algorithm targeting 70% score (Figure 1 below).  Noise comes from the front, speech from the contralateral side ("second ear"). This yields an S/N ratio.  Then the same S/N ratio is used to execute a speech in noise test with  only one hearing aid ("first ear") and by means of manual scoring (Figure 2 below).  This score is typically lower than the 70% of the first test.  The difference between both scores is displayed as Head Shadow benefit.

In this example, the adaptive algorithm yields an S/N ratio of -12 dB (53 dB vs 65 dB) to obtain a score of 70%.  The subject was wearing 2 implants during the test.	Then, at the same S/N, a manual score of 50% was obtained with only one implant at the left ear.
This means that adding the second device in this test configuration improved the score with 20%.   This is the Head Shadow benefit.

Squelch Benefit

The squelch effect is defined as an improved speech understanding with two (aided) ears as compared to one, even if the monaural ear is favourably oriented relative to the speech in the noise background.  Squelch benefit can be expressed as improvement of SRT or of speech intelligibility score.  Audiqueen uses the latter.  

For this matter, Audiqueen executes a speech audiometry in noise test with both hearing aids and by means of an adaptive algorithm targeting 70% score (Figure 1 below).  Speech comes from the front, noise from the contralateral side ("second ear"). This yields an S/N ratio.  Then the same S/N ratio is used to execute a speech in noise test with only one hearing aid ("first ear") and by means of manual scoring (Figure 2 below).  This score is typically lower than the 70% of the first test.  The difference between both scores is displayed as Squelch benefit.

In this example, the adaptive algorithm yields an S/N ratio of -8 dB (57 dB vs 65 dB) to obtain a score of 70%.  The subject was wearing 2 implants during the test.	Then, at the same S/N, a manual score of 65% was obtained with only one implant at the left ear.
This means that adding the second device in this test configuration, even if this was in a less favourable S/N situation, improved the score with 5%.   This is the Squelch benefit.

Test execution

Select the test type Binaural Benefit in the ribbon.  After clicking on New Measurement, Audiqueen guides you through the 4 steps of the test.  

1. Select which ear is the 'first' ear
2. Select the speech test you want to use
3. Select the noise you want to use
4. make sure that 3 speakers are selected, one at the left (-90°), one in front (0°) and one at the right (+90°)
5. Click on Next

At the end of the test, you'll select the devices that the  patient has been wearing during the test.  After saving the result, Audiqueen shows the results in tabular form.  Double-click on one of the fields to see the details of the test.

Reference

Carhart RT, Young L.  Development of test procedures for evaluation of binaural hearing aids.  A final report.  Bulletin of Prothhetics Research.  1976; 9-45.

The test execution is not available in the webviewer.