Noise background when using a hearing aid. Microphone effect - acoustic feedback effect
WHAT ARE HEARING AIDS?
All hearing aids can be classified according to the following features:
- in appearance:
- behind the ear (located behind the ear) - miniature, designed for minimal to severe hearing loss,
- and regular size, suitable for any hearing loss,
- intra-ear (located partly in the external auditory canal, partly in the auricle), compensate for hearing loss from slight to severe (up to 80 dB);
- intracanal or so-called. deep immersion devices, almost invisible (located completely in the external auditory canal) are designed for mild to moderate hearing loss - (up to 60-70 dB);
- by setting method:
- TRIMMER - settings are adjusted with a screwdriver,
- PROGRAMMABLE - information about the settings is entered into the hearing aid using a special programmer via a computer;
- in terms of sound processing
- ANALOG (conventional),
- DIGITAL
Both analog hearing aids and those with digital sound processing can be trimmed and programmable, i.e. settings can be entered into the device manually or using a programmer via a computer.
- in terms of power - the hearing aid must exactly match the degree of hearing loss and never exceed the required amplification. All devices are divided into:
- LOW POWER - designed for hearing loss from slight to moderate, which corresponds to 1-2 degrees (up to 60-70 dB),
- MEDIUM POWER - designed for the degree of hearing loss from moderate to severe (2-3 degree - from 40 to 80 dB),
- POWERFUL - designed mainly for severe hearing loss (3-4 degree - from 60 to 95 dB),
- SUPER POWERFUL - HEARING AIDS, designed to compensate for severe and profound hearing loss (grade 4 - deafness with residual hearing - from 70 to 110 dB).
- sound processing capabilities
- so-called devices BASIC LEVEL OF PROSTHETICS. These include digital and analog hearing aids that have one or two independent tuning channels, LINEAR or NON-LINEAR GAIN, but with a limited number of adjustment options and manual volume control. If the patient has a satisfactory SPEECH INTELLIGIBILITY, these devices provide a fairly comfortable perception of surrounding sounds in silence.
- PROSTHETIC COMFORT LEVEL hearing aids are hearing aids with digital sound processing, non-linear amplification, independent bass and treble adjustment, and automatic volume control. Provides more comfortable listening to ambient sounds in silence due to a sufficient number of tuning options, the presence of a system for suppressing the microphone's own noise, extended dynamic range and very low non-linear distortion.
- HIGH-LEVEL PROSTHETIC devices - this group includes digital hearing aids with high tuning flexibility due to the presence of 3 or more independent channels, special digital algorithms for automatic adjustment in different acoustic situations, with suppression of ambient noise in order to improve speech intelligibility.
According to a number of researchers, background noise room ranges from 30 dB in a quiet room to 60 dB in public buildings (G. L. Navyazhsky, S. P. Alekseev, L. S. Godin, R. N. Gurvich, S. I. Murovannaya). Individual noise signals in rooms sometimes reach significantly higher values. Excessive amplification of these noises by the hearing aid causes discomfort to the patient.
There are a number of regularities between amplification external noise hearing aid and speech intelligibility when using it. As noted above, satisfactory speech intelligibility corresponds to an articulation of at least 75%. According to S. N. Rzhevkin, 70% articulation can be achieved when the speech intensity level exceeds the audibility threshold by 30 dB. If we take into account that the intensity of spoken speech is 50-60 dB, and the general noise background of residential and office premises is quite significant, reaching 30-60 dB, it becomes obvious that with the distance of the source of speech, the masking effect of external noise increases.
It reduces speech intelligibility, and a simple increase in the amplification of the hearing aid does not improve the conditions for using it (V. F. Shturbin).
Licklider and Miller established a relationship between speech masking and noise intensity as the ratio of average speech power to average noise power. According to them, for the majority of noise encountered in practical conditions, satisfactory speech intelligibility will be ensured if this ratio exceeds 6 dB.
Kuzniarz indicates that if the speech level exceeds the noise by 10 dB, a complete understanding of odisyllabic words is achieved, and complete masking of speech is observed when the noise level prevails over speech by 10 dB.
In addition to these reasons, hearing aid amplification limited by the possible occurrence of a microphone effect (acoustic feedback). So, R. F. Vaskov and A. I. Chebotarev note that even when using carefully made individual ear plugs, the gain is limited to the level of 70 dB, since acoustic feedback appears at a higher gain.
Special conditions hearing aid use are created with hearing loss with a pronounced loudness increase phenomenon. In such patients, when strong sounds are amplified by the hearing aid, their volume may increase excessively, which will cause discomfort in the ear. Under these conditions, it is advisable to limit the gain (compression), when weak sounds are amplified to a greater extent, and strong sounds - to a lesser extent, which will create an equalization of the output signal and protect the patient from the unpleasant influence of strong sounds.
This method allows use more powerful hearing aids for severe hearing loss (M. M. Ephrussi, Rebattu, Morgon).
At major hearing loss, accompanied by a significant decrease in the dynamic range of auditory perception (up to 15 dB on average), the dynamic range of speech, equal to 40-50 dB, in some cases significantly exceeds it. M. M. Ephrussi points out that only by compressing the range of sound levels transmitted by the hearing aid, it is possible to ensure the perception of speech without pain, if the output level of the hearing aid does not reach the threshold of unpleasant sensations.
Fletcher and Gemelli found that cutting off sections of speech frequencies with high peak amplitudes has little effect on speech intelligibility, only reducing its naturalness.
in hearing aids set automatic gain control (AGC), which maintains the required predetermined intensity of the output signal, regardless of fluctuations in the level of external sound (R. F. Vaskov, A. I. Chebotarev, A. S. Tokman, B. D. Tsireshkin, Dupon-Jersen ). However, the authors note that the use of AGC can also introduce additional distortions, masking the useful signal more than with simple amplification due to amplification of external noise, since weak signals, which include ambient noise, are amplified in this case to a greater extent.
The hearing aid amplifies ambient Sounds and transmits them to the internal structures of the ear.
Hearing aid whistles(a high-frequency whistle appears) when amplified Sound enters the Hearing Aid microphone, i.e. when the sounds begin forcibly pushed out. The main task is sealing ear canal and prevent the amplified Sound from escaping to the outside.
When the Hearing Aid is turned on (before it is installed in the ear), a whistle occurs, which indicates that the device is working. After you have put the device on your ear, whistling occurs only in cases when the earmould is incorrectly fitted or not firmly inserted into the ear canal.
There may be several reasons for this situation:
1. Excessive amount of wax in the ear canal.
Which leads to a violation of the normal passage of the amplified Sound.
Ears need to be cleaned periodically.
2. Turn on the Hearing Aid at full volume.
Turn down the volume of your Hearing Aid or contact your Hearing Aid Professional for advice on the need for a more powerful hearing aid for you.
3. Change in body position.
4. Wrong standard or custom earmould.
Contact the Hearing Care Center for a quality custom earmould.
Major Hearing Loss or Major Hearing Aid Gain requires an accurate fit of the earmold.
5. Worn out plastic straw that connects the behind-the-ear hearing aid to the earmold.
She pulls out the earmold of the Hearing Aid so that it no longer sits tightly in the ear.
The tubing needs to be replaced periodically.
In modern expensive models of hearing aids, the problem of feedback (whistling) has been successfully solved.
A special feedback suppression function allows you to perform any action without worrying about disturbing Sound.
The "whistle" or "beep" of hearing aids is a manifestation of the feedback effect. It appears due to the amplification of a sound that has already been amplified before. A fairly common phenomenon that can bring discomfort not only to the wearer of hearing aids, but also to others, attracting them, often, inappropriate attention. Sometimes the feedback effect can be so strong that it becomes impossible to use the device. Modern manufacturers have done a lot to "teach" hearing aids to suppress "whistling". And we have made significant progress in this. However, the problem still exists, especially in patients with severe degrees of hearing loss. There are several reasons for this.
The first and most common
Loose fitting to the ear canal and auricle. Most often, universal earbuds “sin” with this, which do not take into account the structural features of the ear. Properly made according to the mold, an individual insert is free from this drawback. Do you want to avoid "whistling"? Give preference to an individual insert.
In children, the appearance of a feedback effect may indicate that the child has "grown" out of the insert. This is especially noticeable in the first year of life, when the inserts have to be re-made every 2-3 months.
For intracanal devices, there is also such a problem if the body does not fit snugly against the walls of the external auditory canal.
The second reason
A crack in the tube connecting the earmold to the behind-the-ear hearing aid. It simply needs to be replaced or re-pasted in the otoplasty laboratory.
Third reason
Poor fitting of hearing aids. Many models have powerful feedback suppression algorithms that can be activated by a tuner.
The fourth reason is perhaps the most rare
Damage to the hearing aid, when the "leakage" of sound occurs in the case itself.
If you encounter a "feedback" problem, contact the medical center. Whatever the cause, our specialists will help you find and eliminate it.
Comfortable feeling when wearing a hearing aid is important both for you and for those around you.
However, almost all hearing aids can show signs of feedback. An ordinary person perceives the feedback phenomenon as a whistle.
There are several reasons for the occurrence of the feedback phenomenon:
First reason The whistle of the device is the presence of a large accumulation of sulfur in the ear canal, which prevents the penetration of sound, and the sound, reflected, again falls on the microphone of the device. If the device works all the time, then the feedback is a continuous process, which we hear in the form of a whistle.
It is necessary to get rid of sulfur, and you will feel that the sound has become clearer and the device will stop whistling.
The easiest way to get rid of earwax is to make an appointment with your local otolaryngologist.
The second reason If the device whistles, the earmold does not fit snugly against the walls of the external auditory canal, you may have chosen a smaller earmold.
It is very easy to check this by putting your finger on the earmold and holding it tighter in the ear canal if you feel that the whistling has stopped. then, it is better to contact your specialist and make a new individual insert.
Third reason whistling - the hearing aid is damaged.
This is a common cause if the sound guide tube has become rigid and micro-cracks appear on it. In the case of wearing intra-ear devices, such a reason may be cracks in the body of the device itself.
This can only be corrected by a specialist and a branded hearing aid repair center.
Fourth and the most rarely encountered feedback condition is a complex ear canal. Those. if the sound guide hits directly into the wall or down the passage, it can cause an amplified sound, and then, in order for the device to return to normal, a whistle begins. All these signs of feedback you can eliminate with your specialist.
It should be noted that the most modern hearing aids of the series Siemens Motion as an example, they are supplied with an automated feedback suppression system. When the device detects a hint of feedback, it automatically adjusts to suppress feedback, which unfortunately cannot be achieved in the simplest hearing aid that does not include these options.
Therefore, if you are tired of whistling (feedback), we are always happy to help you in the modern center of hearing and prosthetics of Dobry Rumor.
All work on the manufacture of earmoulds, replacement of tubes - sound guides, the manufacture of cases for in-ear hearing aids is carried out by engineers from Siemens and other manufacturers of hearing aids.