Monday, April 10, 2006
Open Fitting Moulds
we are now currently trying out these open fitting moulds (by siemens). we are using these for people with normal hearing to about mild hearing loss from low to mid freq. then slopes down at higher frequencies. but our boss said they have tried fitting a be55d (that's for profound loss) with this mould and there was no feedback!
advantages of an open fitting mould:
1. ensures that the ear is well ventilated, avoid overheating thus reduces collection of moisture in the tube.
2. avoids distortion in the wearer's own voice and unnatural amplification of swallowing and chewing noises (similar to the effect of talking or chewing with a finger in the ear).
3. The wearer experiences a more natural sound because the sound propagation to the ear drum and the directional function of the outer ear and the ear channel are maintained.
4. there is optimal amplification in particular in the high frequency range.
it will, however, only work with selected hearing aids. The hearing aid must have an excellent quality of sound reproduction, with imperceptible noise levels and an effective suppression of feedback. On the other hand the open set could lead to unwanted amplification of signals picked up by the microphone and amplified again (feedback) causing an unpleasant high-pitched whistling sound.
An open system is not suitable for all kinds of hearing loss. It is most appropriate for cases of slight to medium loss of hearing, or for loss in the high-frequency range (precipitous hearing loss). The greater the hearing impairment, the more closed the ear mould needs to be, thus reducing the occurrence of feedback and achieving the necessary amplification.
info taken from: siemens' website.
anyways, its advantage to our department is that, it cuts down patient journey time. with people being fitted with the aids on the same day as their first assessments, that's like taking 4 months (only in our department - other places have diff. waiting times) off the waiting times (as you know, before you get medical help here, you have to wait for months before you get seen). if fitted properly, it matches rem targets very well and patient happier with the sound being close to 'natural' - none of the occlusion effect.
disadvantage though is, it's not for people with dexterity problems (e that's mostly our patients). insertion could be fiddly. you will need to insert the thin silicon strip into the the flap of the of the ear and get the aid over the top of the ear. with the mould not really securely in place, patients would have difficulty keeping the mould in while getting the aid in place.
anyhoo, we're still in the trial stage. and so far, so good. i've only fitted one and it worked really well. it definitely makes a difference. too bad it's not for everybody.
read more about the studies made for these open fitting moulds here
