The ear mold is a model of the ear shell and the external auditory meatus made of chemical materials according to a certain process.It will Hearing aid The amplified sound is transmitted to the external auditory canal, with a fixed Hearing aid , Change the acoustic effect, prevent acoustic feedback and wear comfortable, beautiful and other functions.
The ear mold transmits the amplified sound of the hearing aid from the receiver of the hearing aid to the external auditory canal or tympanic membrane.For custom hearing aids such as in-ear ear canal type, the shell of the hearing aid can be regarded as an ear mold.With the development of the history of hearing aids, the shape, material, and manufacturing process of ear molds have undergone great changes. People’s understanding of the acoustic properties of ear molds has gradually deepened. Ear molds are not only a sound transmission component, but also to a certain extent. Improve the sound quality after hearing aids.
The shape of the ear mold and its scope of application
Since the shell of in-ear and canal hearing aids is the ear mold, the shape of the ear mold has not changed much, so the shape of the ear mold discussed in this article is mainly based on the back-of-the-ear hearing aid.
①Standard type: suitable for high-power box type Hearing aid , The diameter of the sound hole is 2mm, and there is no vent hole. Because of the good sealing of the outer ear, it is suitable for severe and extremely deaf.
②Skeleton type: In order to increase the comfort level of the patient, the center part of the shell type ear mold can be hollowed out, leaving only the edge bone ring, and embedded in the ear concha cavity.Suitable for mild to moderate patients.There are many variations of the skeleton type, such as the 3/4-bone ring type and the half-bone ring type, which have a wider range of applications and are currently widely used ear mold styles.In some people, the concha cavity is shallow and the antihelix cannot fit in the bone ring.For aesthetic considerations, this part of the bone ring is removed, and it becomes a 3/4 bone ring type or a half bone ring type, which also reduces the weight of the tragus and makes the ear mold stronger.
③Shell type: The shell type is equivalent to the “standard type” in the ear mold of the BTE hearing aid.The ear mold occupies the entire concha cavity, and the sound holes and ventilation holes can be selected in different sizes. The external auditory canal is well sealed. It is mainly suitable for high-power hearing aids worn by patients with sagging deafness, which can prevent the occurrence of howling.The ear mold can be carved into a thin shell to reduce weight and increase aesthetic effect.
④Half-shell type: The ear mold only occupies the lower part of the concha cavity, covering the external auditory meatus and the tragus-to-tragus area, mainly from the aesthetic point of view, suitable for mild to moderate deafness.Large vents should not be used.
⑤Ear canal hook type: The ear canal hook type is based on the ear canal type. In order to increase the firmness, a short arm inserted into the ear canal socket is reserved, and it is also convenient to remove and wear the ear mold.
⑥Ear canal type: The ear mold only occupies the external auditory canal and can only be seen from the tragus notch, which is very concealed.It is suitable for patients with mild to moderate deafness, but it should be noted that the external auditory canal of the patient should be bent to a certain degree to ensure the durability of the ear mold.
①Ipsilateral signal diffraction type: In fact, since CROS hearing aids are no longer common, CROS ear molds are currently used as IROS methods.But since the hearing aid is on the same side as the IROS ear mold, acoustic feedback becomes a major problem.Therefore, IROS is only suitable for mild and high frequency in both earsHearing loss.
②Signal-to-transmission type: Signal-to-transmission hearing aids can avoid acoustic feedback well, and can use non-plugging ear molds without clogging; this type of hearing aid is not commonly used, but this type of ear mold is still in Europe and the United States. National extension.It requires the patient’s external auditory canal to be relatively thick, and the part where the CROS ear mold is inserted into the external auditory canal is very short. The external auditory canal is only partially blocked, and a certain amount of high-frequency resonance characteristics of the external auditory canal can still be preserved, and the sound sounds natural and true.
③Janssen type: The Janssen type ear mold is named after the inventor, and the shape is similar to the sound tube type, except that the tip of the ear mold is still polished into a thin cylinder for the sound tube to pass through.In the simple sound tube type, the position of the sound tube in the external auditory canal does not change due to the movement of the head.
④ Free field or sound tube: The difference between free field and IROS is that the free field does not block the ear canal at all, and there is only a bone ring to ensure the position of the sound tube in the external auditory canal.