Selecting Your Hearing Aid
A test needs to be carried out before any hearing aid or hearing equipment recommendations can be made. After reviewing the test results and determining the type and degree of loss to each ear, a decision must be made whether to suggest one hearing aid ( monaural amplification ) or two hearing aids ( binaural amplification ). For most binaural hearing losses, two hearing aids are advocated. Besides determining the dimensions of the hearing aid and whether to fit monaurally or binaurally, the backbone of frequency reply, gain, and overall output of the hearing aid must be decided.
In numerous settings, Real Ear measurements are made to help choose the correct traits of the hearing aid.
These measurements are made in a 2-cm3 coupler. This coupler is used to simulate the condition of the aid in an ear, but many differences exist between a metal 2-cm3 coupler and the volume and texture of an ear canal and eardrum, and many individual differences exist between ears. Due to these differences, a genuine Ear probe-tube measurement is used to make clear the actual frequency response, gain, and maximum output of the hearing aid in the ear at the location of the eardrum. Using the genuine Ear apparatus, the audiologist places a probe microphone into the ear canal and presents a known auditory signal to the patient. The info from the microphone when the impulse is present yields a genuine Ear unaided response ( REUR ).
This reply unearths the resonating traits of the ear canal without the hearing equipment in place and can aid in formulating the best 2-cm3 coupler reply for a patient at the time a hearing aid is ordered. A selection of prescriptive strategies for fitting hearing aids use information from Real Ear measures.
These systems include the half-gain rule and the prescription of gain and output ( POGO ). One of the hottest prescriptive systems is the process developed by the nation’s Acoustics Lab ( NAL ) in Australia for picking gain and frequency reply of a hearing aid. The NAL algorithm is used to figure out the most acceptable Real Ear gain.
This can be procured by measuring the real-ear aided reply. The REAR is taken with the hearing aid and the probe microphone in the ear, and the aid’s gain is turned to match the figured out Real Ear gain. The REAR is the gain in decibels relative to the impulse level presented to the patient. The real-ear insertion gain ( REIG ) is the difference between the REAR and the REUR and is used to confirm the destined target insertion gain has been achieved.
In the past ten years, hearing aids using digital signal processing ( DSP ) have been introduced into the market. These aids, when compared to standard analog hearing aids, make allowance for a more exact control over a wider range of parameters.
In 2005, more than ninety percent of all hearing aids dispensed in the US were digital. Some analog hearing aids can be digitally programmed ; the digital programmer can adjust the gain, frequency reply, and output of the analog circuit.
Some analog hearing aids also could have multiple channels ( frequency bands ) that may be digitally programmed.
The difference between a DSP hearing instrument and an analog aid is that the analog signals from the microphone are converted into a digital form by an analog-to-digital converter. Once in the digital form, the signals are manipulated by complicated processing algorithms and then converted back to analog form by digital-to-analog conversion. The digitally controlled hearing aids often use an external programming unit the dispenser uses to adjust the gain, output, and frequency reply of the unit.
Plenty of these aids have multiple channels that permit the dispenser to program individual gain, output, and compression for each frequency channel.
Almost all of the digital hearing aids and some of the digitally programmed analog hearing aids employ a common PC platform database called NOAH. This database can carry the audiometric info and office-based info on each patient. Software from each manufacturer can be installed on the platform. The aids are hooked up to a typical interface called HI-PRO that permits the software from the maker to interface with the hearing aid.
The fitting paradigms vary with each manufacturer. For behind-the-ear fittings, ear mold impressions of the patient are taken, and these impressions are sent to a manufacturer who makes the ear mold that will be fit to the selected behind-the-ear instrument. The maker is instructed on the kind of material to be used, the kind of mold to be made, and any alterations, venting, and tubing that is to be included with the mold. For in-the-ear instruments, ear mold impressions are sent to the hearing aid manufacturer, who makes the surrounding of the in-the-ear hearing aid from the impression. This process allows for a more correct ear mold and loses the shipping of ear mold impressions and order forms and decreases turnaround time by a couple of days.