Hearing Aid Fitting Selection Procedure and 11 Steps

In the selection of hearing aids, in addition to considering the details of the patient’s hearing loss, hearing aid performance and other details, the routine steps need to be followed to complete the selection.

Step 1. Medical history collection

Medical history collection includes the following:
① Understand the biggest confusion and obstacles brought by the patient’s current hearing status, that is, what problem to solve or the purpose of coming to the center, such as being able to hear but not clear, articulate, and not speaking. Many children are seen because they have not passed a newborn hearing screening.
② Understand medical history and judge the possibility of other medical rehabilitation (medicine, surgery, etc.).
③ Understand the history of ear surgery, and determine whether it requires special treatment and special precautions, such as precautions when taking ear samples after mastoid surgery.
④ Understand the patient’s expectations and special needs.

Medical contraindications for optional hearing aids include:
① Congenital atresia of external ear or malformation of external ear canal, foreign body in external ear canal.
② Deafness is unstable and the degree of hearing loss fluctuates.
③ It mainly describes patients with severe symptoms such as headache, dizziness, ear pain, tinnitus, or patients with sudden tinnitus and dizziness.
④In the past three months, those who have sudden deafness and progressive rapid deafness are obviously unilaterally deaf or suffer from other acute ear diseases.
⑤ inflammation of the external ear canal, middle ear effusion or frequent pus discharge.
⑥ Central deafness and non-organic deafness.

Step 2. Detection

1. Otoscopy

Learn about the contraindications for hearing aid fitting in the external and middle ears of patients. Every time a hearing worker checks a patient, they should routinely check the external auditory meatus and eardrum. If there are contraindications to hearing aids or other indications that require expert confirmation, the patient should first be referred to an otologist.

2. Check original hearing aid

If the patient has already used a hearing aid, he should first check his hearing aid for electro-acoustic function to see if it works normally; if it is a behind-the-ear hearing aid, check the functional status of the ear mold.

3. Description

According to the patient’s medical history and clinical manifestations, select the appropriate audiological examination method, and briefly introduce the patient, his family, and the content, steps, and time required for the hearing test.

4.Hearing test

Understand the patient’s hearing loss, including the detection of air conduction hearing threshold, bone conduction hearing threshold and discomfort threshold.
① Adults. The tone, bone conduction hearing threshold and discomfort threshold were measured with pure tone audiometer. When necessary (high expectations, severe tinnitus, severe revitalization, etc.), conduct loud-ness scaling (loudness mapping) tests.
② Children. Detailed child audiometry refers to basic or clinical audiology. Generally, children aged 3 to 7 years are advised to perform 1000Hz.4000Hz.500Hz listening threshold tests in turn, and then perform 2000Hz.2500Hz and 6000Hz listening threshold tests. The purpose of this test sequence is to first understand the hearing loss profile of deaf children as soon as possible, and then gradually complete the hearing threshold test. Children from 6 months to 3 years of age use visual intensive audiometry, that is, the use of conditioned reflex to perform the hearing threshold test, the test sequence is the same as above. Children under 6 months use behavioral observation audiometry, such as observation of shock reflex, blink reflex, sudden stop or change of an activity, etc. Deaf children who can not cooperate should be introduced to the hospital for otoacoustic emission, electrical response audiometry with frequency characteristics, etc. Keep in mind that when there is no response or no waveform elicitation in the electrical response audiometry, you can only judge that the hearing loss is serious, and it may not be completely deaf. Don’t let deaf children miss the opportunity for hearing rehabilitation.
According to the test results, explain to the patient several major factors that affect the effectiveness of the hearing aid with vivid and easy to understand metaphors: the length, nature, and degree of the history of hearing loss; whether there are central and systemic lesions related to hearing, and their extent; choose a hearing aid. Suitability, etc.
For patients with the above-mentioned severe conditions, it is recommended to go to the corresponding medical institution for treatment or wait for the condition to be relieved before selecting a hearing aid. Hearing aids are not suitable for all hearing impaired people.

Step 3. Pre-matching

We should reach the following consensus with the patients: ① my hearing is decreasing; ② my hearing is already affecting my life; ③ I hope to hear better; ④ my hearing problems can be helped by professionals; ⑤ Hear better with hearing aids. Then, we selected several different grades of hearing aids that are suitable or more suitable for patients from many brands of hearing aids, and briefly introduced the main functions, technical indicators and mutual comparison of selected hearing aids to patients.

1. Hearing aid selection method

Hearing aid selection methods include:
① Select the required technology according to the hearing loss of the patient, such as electronic cochlea, frequency-shift hearing aid or traditional hearing aid.
② When choosing a traditional hearing aid, choose the required gain according to the hearing loss of the patient. The general gain data is the average hearing loss in the speech band divided by 2 plus 10dB.
③ Select the compression circuit according to the patient’s hearing dynamic range.
④ Selection of maximum output. If the discomfort threshold has been measured, it can be calculated by the optional formula; if the discomfort threshold is not measured, it should be as large as possible without the patient feeling discomfort, but try not to exceed 132dB.
⑤ If the residual hearing of the child cannot be determined, and the hearing loss is estimated to be very serious, a super high-power hearing aid can be selected, and the gain is maximized, but the maximum output should not exceed 132dB.
⑥ The true ear coupling cavity difference (RECD) must be considered. The difference can reach more than 20dB for children within 6 months.
According to the above conditions, one hearing aid is selected from each of the high, middle and low price ranges for debugging.

2. Unless contraindicated, hearing aids are routinely recommended for both ears

(1) Advantages of binaural matching

Binaural hearing aids have many advantages over single-ear hearing aids. The advantages reflected here are based on the premise that speech signals can be received by both ears.
1) Improve positioning capabilities
The binaural option can better improve the ability to locate the sound source, because when the sound waves travel from different directions to both ears, different phase differences, time differences, and intensity differences will occur. Time difference is good for low frequency sound wave localization, and intensity difference is good for high frequency sound source localization.
The brain uses the small difference in the signals received by the ears to determine which direction the sound is coming from. If the information is received by one ear, no such positioning mechanism will be generated, and the function of judging the direction of the sound source will be lost. The positioning advantage of bilateral hearing aids is significantly better than that of unilateral hearing aids. The advantages of bilateral hearing aids are more obvious in people with moderate or severe hearing loss. Because of their poor perception of sound and strong dependence on hearing aids, the positioning effect of binaural hearing aids is better than that of single ear hearing aids. They are more visible in people with mild hearing loss. For any degree of hearing loss, the advantages of bilateral positioning increase as the intensity of the stimulus decreases.
2) Prevent head shadow effect
In the case of single-ear wearing, if the sound comes from the direction of the other ear, the sound will pass through the head block and then be received by the ear wearing the hearing aid. In this process, the intensity of the sound will be attenuated, especially at high frequencies. For high-frequency sounds greater than 1500Hz, the attenuation can reach 10-16dB, which is very light to high-frequency hearing loss and those high-frequency hearing loss are so high that The frequency component has a small effect on patients who do not help speech intelligibility, but if the high-frequency hearing-impaired listener is poor, the sound reception will be more difficult, and speech intelligibility and speech comprehension will be greatly affected. Large impact, Li binaural wear will not have the problem of head blocking.
3) Better suppression of noise
Our hearing system is a good noise reduction system. If the signal-to-noise ratio of the binaural receiving signal is large, the center will bias the ear with a higher signal-to-noise ratio, which can reduce the impact of noise on speech understanding. At the same time, the auditory system will generate an internal Signal, which has a higher signal-to-noise ratio than the unilateral ear. In other words, the two ears can reduce noise more effectively than the single ear, and hear more clearly in the noise: when both ears receive the same signal, there will be a slight time difference and phase difference. The brain can use these differences to distinguish Make the sound you want to hear and ignore the noise, so you can hear more clearly in the noise. Only with
One ear does not have this advantage. Binaural matching is particularly suitable for patients with poor speech intelligibility, because binaural matching helps to detect and distinguish speech signals. Binaural suppression can help when the low-frequency components of speech and noise in the unhearing ear do not sound clear. The advantages of bilateral selection resulting from suppression are not very helpful for patients with low frequency hearing loss. If speech and noise are above the binaural threshold in a unilateral situation, binaural suppression cannot produce significant bilateral advantages.
4) Avoid delayed hearing deprivation
If a patient with symmetrical hearing loss wears a hearing aid in only one ear, the ability of the side ear without hearing aid to recognize speech will gradually decrease in the next few years. This phenomenon is called delayed hearing deprivation. There are reports that ears without hearing aids degrade faster than ears that are stimulated by hearing aid sounds. This is what we call “use and disuse.” It affects most patients with unilateral investigations, and it often occurs in children, middle-aged people, and elderly people. The positive effects of children’s maturity partially offset the negative effects of hearing deprivation caused by unhearing ears. As a result, the speech score of unhearing ears will increase, but
The degree of improvement is less than the hearing aid. Hearing deprivation may occur because hearing ears send enough information to the brain so that the brain no longer pays attention to the unhearing ears, and continuous sound stimulation prevents the hearing ears from degenerating. So basically as long as you have hearing problems in both ears, you should try wearing hearing aids on both sides. The exact time when hearing deprivation occurs is not very clear, but some studies have found that it can occur from 7 months to 5 years after wearing one ear, and most people have hearing deprivation without ears about one year after mating.
5) Suppress tinnitus
Hearing aids can be used to mask or even suppress tinnitus. Tinnitus is usually bilateral, so bilateral hearing aids are more effective at masking tinnitus than unilateral hearing aids. One study showed that 66% of tinnitus patients reported that bilateral hearing aids weakened tinnitus, and 13% said
Unilateral hearing aids work. However, there are also reports of worse hearing aid users who have increased tinnitus.
6) binaural integration effect
To put it simply, the two ears show better listening ability than one. This integration effect can improve the hearing threshold 127 by at least 3dB. This is especially important for patients with severe or severe hearing loss: the volume of the hearing aid does not have to If it is too large, the same effect is achieved, and the scope of adaptation is expanded accordingly. In addition, if one hearing aid fails, there is another hearing aid to help you hear. In addition, the bilateral hearing aid requires slightly less gain than the single-sided hearing aid, and its gain is less likely to saturate than the single-sided hearing aid, and it can better ensure good sound quality at high input strength. Similarly, high intensity has a negative impact on speech intelligibility.
Lower gains will produce better results than unilateral hearing aids. Also, if the hearing aid gain is reduced, the feedback problem will be reduced.
Finally, patients with two hearing aids also have the freedom to choose-they can choose to wear both ears or one ear for either ear. Patients with unilateral hearing aids have much less choice.
7) other
The sound produced by binaural listening is better than that of single ear. These advantages include clarity, fullness, a sense of space, and overall sound quality. Binaural listening makes it easier to distinguish between sounds.
Disadvantages of binaural matching
1) High cost
Binaural options are relatively more expensive than single-ear options, unless hearing aids are free. During the use of two hearing aids, the cost of the battery also increases accordingly. For most hearing impaired people, the increase in financial burden is a negative factor. In well-off countries, hearing aids are free, and their costs are paid by the government or insurance providers. For binaural matching, the fund provider pays more for the extra cost, so they will ask the doctor to correct their ear matching behavior to reach what they think is reasonable.
2) Wind noise
In the single-ear option, a very light wind noise will also produce the equivalent of 100dB SPL input hearing aid in the hearing aid, while the two hearing aids in the binaural option will have more amplified noise, in a windy environment Patients may think that bilateral hearing aids are not necessarily better than unilateral hearing aids. Compared with other hearing aids, complete ear canal hearing aids can better avoid similar problems, but they still cannot be completely solved.
3) More inconvenient
For some elderly people or people with physical disabilities, binaural hearing aids will cause more inconvenience than single ears. It is much more tedious than single ear hearing aids in terms of wearing, changing batteries, turning on switches, adjusting volume, and maintaining . Especially in terms of adjusting the volume balance of the optional hearing aid on both sides, it is much more complicated than adjusting a hearing aid, and further increases the ear plugging effect. This is also difficult in some patients with good physical and mental conditions.
4) psychological factors
Some hearing-impaired people often associate hearing aids with old age or deafness. When choosing a bilateral hearing aid, they think they are deaf or older. From the perspective of aesthetics, the hearing impaired person thinks that wearing two hearing aids will be more easily found or noticed by others, especially some young people. They have aesthetic considerations when they choose deep ear canal hearing aids. Therefore, binaural matching will make it more psychologically burdensome in terms of aesthetics.
In addition, some hearing-impaired patients already believe that hearing aids are more satisfactory after wearing monoaural hearing aids. Therefore, they will recognize that a single hearing aid has solved their hearing problems and are overly optimistic about a single hearing aid.
Patients with mild hearing loss are hesitant about the choice of the second hearing aid because the effect of the hearing aid on themselves is not obvious. They believe that the second hearing aid will not be significant in the short term. improve.
It should be said that the advantages of binaural wearing are very clear, but some patients are not as effective as single ear wearing in both ears, and the detailed reasons are still being studied. Before matching, we can use various relevant tests to evaluate whether binaural wear is more helpful to individual patients than single-ear wear.

3． Single ear option

Of course, there are some patients who cannot or can’t perform binaural matching due to age, economic conditions and other factors.
Matching can be performed according to the following principles.
(1) Judging by the nature of deafness
Clinically, the nature of deafness is divided into three categories: conductive deafness, sensorineural deafness, and mixed deafness according to the location of deafness.
Conductive deafness is mainly caused by the outer and middle ears, which are obstacles to the transmission of sound pressure transformers and affect the transmission of sound waves. Conductive deaf air-guided hearing loss generally does not exceed 60dB HL. The characteristics of air-conductivity on pure-tone audiograms are mostly uphill curves, with low-frequency energy loss as the main factor, while bone-guided hearing is basically in the normal range.

Figure 7-4 Pure tone hearing performance of conductive hearing loss

Figure 7-5 Pure tone hearing performance of sensorineural hearing loss

The main clinical manifestation of conductive deafness is “inaudible”, because the impairment of sound transmission attenuates the sound, and the speech intelligibility of early patients does not decrease significantly. The design purpose of the hearing aid itself is to amplify the sound, so the effect of matching hearing aids for conductive deaf patients is relatively easy to see, and it is sure to benefit from hearing aids.

Sensorineural deafness is a collective term for sound sensations and nerve impulse conduction disorders that occur during the auditory conduction pathway. Among them, if the lesion is located in the hearing hair cells of the cochlea, it is also called sensorineural deafness or cochlear deafness, which is often accompanied by a revitalization phenomenon; if the lesion is located in the auditory nerve, it is referred to as deafness or post-cochlear hearing loss; The auditory center of the brain is called central deafness. Sensorineural hearing loss is often manifested on pure audiograms as follows: air-bone conductance decreases in the hearing curve; high-frequency hearing loss often occurs, and the hearing curve is mostly downhill or steeply down. The clinical manifestation of the patient is that the sound is audible and the sentence cannot understand pure tone hearing, as shown in Figure 7-5.

This part of the patient’s description is usually: the sound can be heard, but it is inaudible. After selecting hearing aids for patients with sensorineural hearing loss, it often takes a relatively long rehabilitation process to feel an increase in speech intelligibility.
In general, the diagnostic properties of patients’ ears are still much the same, and only a few of them will be the exception. Therefore, other considerations must be combined to determine the matching ear.

(2) Judging according to the characteristics of the audiogram
Hearing aids are selected according to the characteristics of the audiogram. Although it is not the most perfect method, it is the most direct means of judging whether patients can benefit from hearing aids. The characteristics of pure tone audiograms not only reflect the deafness of the patient, but also preliminary predict the compensation effect of hearing aid use. Experienced audiology professionals can infer the benefits of hearing aids based on the characteristics of the hearing curve.
When the hearing aid is selected, the ear with pure tone average hearing close to 60dB is generally selected. One side is a flat curve, and one side is a steeply descending curve. Then select the flat side first.
Of course, there are still many controversies in the above viewpoints. Different theories of individual differences or inconsistent evaluation standards and lack of seriousness of experimental investigation have formed different theories. Choosing a hearing aid based on the hearing curve requires a lot of clinical practice and rich experience. The selection methods provided here are only general and general methods for the reference of audiology professionals.
(3) Subjective feelings and objective limitations of patients
Some patients will stubbornly designate the optional ears subjectively, and some patients designate the optional ears due to some objective constraints, such as those with physical difficulties, special occupations, and so on.
The selection of matching ears is the interaction process between doctors and patients. Audiologists should help patients choose the deaf ears that will have the highest benefits, and guide patients not to affect the best results of hearing assistance due to some one-sided misunderstandings. .

Step 4. Audition

After selecting the appropriate hearing aid model and determining the single or double ear matching, the patient should be auditioned. The purpose is to check the required gain, slope, and maximum output of the patient, so that the patient can experience the listening effect after wearing the hearing aid.

Step 5. Optional

Instruct patients to choose the most suitable hearing aid style and ear type from several pre-selected hearing aids based on the evaluation results and their hearing loss and hearing requirements, as well as specific conditions and needs such as economic status, age, hobbies, cultural level, and working environment. Mold style.

Step 6. Ear samples

According to the patient’s final selection, ear samples are prepared for making ear molds for custom-made or back-ear machines.

Step 7. Confirm

Ask the patient to confirm the order for the hearing aid or ear mold of choice. In the case of a customized machine order, the model of the hearing aid, the optional ear side, the price of the hearing aid, the amount of the deposit paid, etc. should be written clearly. ; If it is a custom ear mold, it should clearly write the customized ear side, the type of ear mold, the degree of hearing loss of the patient, and the selected hearing aid model.

Step 8. Fitting

When the patient takes the machine, the hearing aid is fine-tuned according to the patient’s hearing status and feelings. It must first meet the needs of comfort and then the needs of hearing.

Step 9. Evaluation

For the evaluation of hearing aid effects, it is best to perform sound field hearing aid and true ear tests for those with conditions, especially for deaf children. We can further clarify whether the gain, frequency response, etc. are appropriate and whether the speech discrimination rate is improved. The time allower should evaluate the effect before and after the matching, and can also tell the patient that the hearing aid really helps him.

1. Heard assessment

In the sound field, the naked ear hearing threshold, hearing aid threshold A, hearing aid threshold B, and hearing aid threshold C were tested to determine the improvement of the patient’s “hear” at various frequencies before and after wearing different hearing aids.

2. Hearing assessment

Test the patients’ improvement of hearing vowels, voiced consonants and unvoiced consonants before and after wearing different hearing aids.

3. Intelligible assessment

Test patients’ improvement in language understanding before and after wearing different hearing aids. Adults with hearing loss within 70dB can be tested on site. Adults with hearing loss above 70dB and all deaf children should be tested after a period of speech training. You can use the correct response rate of daily conversation (10 sentences) or the correct rate of audiograms as indicators. Patients were compared before and after themselves without hearing aids and hearing aids. Through comparison, the comprehensive wearing effect of hearing aids was obtained.

Step 10. Instructions for use

Guidance on the use of hearing aids includes the following:
①Teach patients how to use and maintain hearing aids normally, including the installation and use time of batteries, moisture-proof methods, waterproof methods, and correct wearing methods.
② Work out a continuous service and maintenance plan with the patient.
② Introduce the four stages of hearing aid adaptation (1-2 months).
③ Remind patients to keep the dry box, payment voucher and warranty card.
④ Regular maintenance and preventive maintenance of hearing aids.

Step 11. Follow-up

Contact the patient regularly. Generally, once a week for the first month, every two weeks for the second and third months, and once a month thereafter. Understand the use of “How do you hear?” “What’s the problem?” (If you have any questions, please contact the hearing aid selection center at any time to re-evaluate the use of hearing aids and adjust technical parameters).