Assistive Listening Devices (ALDs) - radio aids and proprietary remote microphone systems - optimising listening opportunities

Using a Test box

Stuart Whyte has authored detailed content about test box measures in Audiology Refreshers Section 6.6.  “There are UK quality standards and practical guidance on electroacoustic measures for HAs, BCHDs, and auditory implant sound processors – most commonly CIs.

‘Quality Standards for the use of personal FM systems’ by the UK Children’s FM Working Group was published in July 2008 by the NDCS. This was updated in February 2017 as ‘Quality Standards for the use of personal radio aids: Promoting easier listening for deaf children’. The multi-agency group is now known as the UK Assistive Listening Technology Working Group (ALTWG).

The latest version of the guidance on QS8 Electroacoustic checks with auditory implants was published in March 2024

Of particular relevance is Section 5 of the Quality Standards on the Management and use of personal radio aids, which includes QS7 and QS8.

QS7: Subjective checks of radio aids must take place regularly.

Perform listening checks of the radio aid system daily, with and without the hearing instrument, using appropriate devices such as a stetoclip for hearing aids, monitor earphones for cochlear implants, listeners for bone conduction hearing implants, or a dedicated headphone set for the radio system.

QS8: Electroacoustic checks must be performed regularly and whenever a part of the system is changed.

Complete regular (test box) checks in order to compare the frequency response curves with baseline settings provided at the time of set-up.

A good practice minimum is every half term – this may need to be more often for young children and will depend on the user.”

A test box or hearing aid analyser is a means of analysing the output and performance of the hearing device, both with and without the radio aid.  This is done by putting the hearing device along with the radio aid through the test box; you can print off the graph as a visual record.  It is therefore a means of seeing the effect of the additional device and ensuring that the performance of the hearing device is not altered and that the child gets the maximum benefit from using the two together.  The test box will give you the ability to print off a visual record of what the two systems are doing together.

The performance of radio aids and hearing aids can be measured and recorded over time.  This is in accordance with MCHAS protocols.  

“There are three common test boxes in use today in the UK (others are also available): Frye FONIX FP35, Affinity systems, and Aurical Hearing Instrument Test (HIT).

The Affinity and Aurical systems meet modern requirements for testing hearing devices (BSI 2021; 2022) and have the ISTS (International Speech Test Signal). The FONIX FP35 Analyzer needs to have the latest software to be able to select ‘Aid Groups’ as ADAPTIVE and to select the test signal DIG SPCH (digital speech). DIG SPCH is an interrupted composite signal and is not equivalent to ISTS. In addition, measurement tolerance is higher with the FP35 (see tolerance section below). The latest FP35 software is also needed to test modern HA fittings with an Open Fit Coupler.

Telecoil (t-coil) responses are known to be reduced in the lower frequencies to avoid interference in this area (Putterman & Valente, 2012). Therefore, in all test boxes, induction-loop RM system curves will be reduced in the lower frequencies and the response curves are more likely to match above 1 kHz.” (Whyte. S  ‘Test box measures’ Audiology Refreshers Section 6.6)

The Ewing Foundation have produced some videos demonstrating the use of the FP35 test box.

It is important that the family, Qualified Teacher of Deaf Children and Young People, and the Cochlear/Auditory Implant Centre all work together on this at the point the CYP is ready.  The audiologists at the Implant Centre will need to enable the speech processor to work with an assistive listening device and make adjustments to the internal settings through the manufacturer’s software.