Every now and then, I have a client report that they can hear a continuous ‘hiss’ from their hearing aid. This usually occurs when they have a region of their hearing thresholds within normal tolerances, and they perhaps have a steeply sloping hearing loss and so the hearing aid is struggling to decide between keeping the noise floor low, and providing the amplification appropriate for the individual.
My most recent case involved an individual wearing Phonak Infinio Sphere 90 hearing aids and it required some careful fine tuning to alleviate this.
Phonak Target (fitting software) used to offer the ability to adjust gain for G20, which is the ability to adjust gain for very soft/quiet sounds. However, they have now removed this and hidden it within the ‘program options’ and made the description of the features a little more vague which can make it confusing so I figured I’d write a short blog to clarify what you can do to reduce internal circuitry noise.
Soft noise reduction
Soft noise reduction is Phonak’s term for ‘expansion’. The idea of expansion is to reduce gain for broadband inputs of a low level e.g. a background fan, internal circuitry hiss, or ticking clocks). As a default, it is set to off on the program options, so the first step would be to increase the strength of this. By turning it on, we can reduce the noise floor level of the hearing aid which may help to reduce the ‘circuit hiss’ that the client is reporting.
Soft Speech Enhancement (SSE)
Soft Speech Enhancement is a feature in the premium models of the Phonak hearing aids and is designed to apply an automatic, dynamic gain boost to low-level speech sounds. However, if hearing is near normal in the speech frequencies it may result in the increased perception of ‘circuit hiss’ in a quiet room. Reducing the strength or turning off soft speech enhancement may help to reduce the internal noise of the hearing aid.
Reduce gain for soft sounds (G50)
As a final measure, you can attempt to reduce gain for soft sounds (G50) on the hearing aid in the frequencies that are normal / near normal which will also help to lower the noise floor level of the hearing aid, but this may result in a small compromise to speech intelligibility for soft / disadvantaged speech.
Try our Simulator
To help you visualise how this may work, we have created a simple visualiser to demonstrate the impact of each adjustment. Try it out below.