Conductive hearing loss occurs when the sound is not conducted efficiently through the outer earcanal to the eardrum and the tiny bones (ossicles) of the middle ear. Conductive hearing loss usually involves a reduction in sound level or the ability to hear faint sounds. Some possible causes of conductive hearing loss is fluid in the middle ear from colds, ear infection(otitis media),allergies (serous otitis media), poor eustachian tube function, perforated eardrum,benign tumors, impacted earwax (cerumen), infection in the ear canal (external otitis), swimmer’s Ear(otitis ecxterna), presence of a foreign body and absence or malformation of the outer ear, ear canal, or middle ear. This type of hearing loss can often be corrected medically or surgically or/and by wearing hearing aids.
Sensorineural hearing loss (SNHL) occurs when there is damage to the inner ear (cochlea), or to the nerve pathways from the inner ear to the brain. SNHL reduces the ability to hear faint sounds. Even when speech is loud enough to hear, it may still be unclear or sound muffled. Some possible causes of SNHL are Illnesses, drugs that are toxic to hearing, hearing loss that runs in the family (genetic or hereditary), aging, head traum, malformation in the inner ear and exposure to loud noise. Most of the time, SNHL cannot be medically or surgically corrected. This is the most common type of permanent hearing loss. The only solution is wearing hearing aids. Today, many severe cases of SNHL are treated by cochlear implants, with great success!
Sometimes conductive hearing loss occurs in combination with sensorineural hearing loss(SNHL). In other words, there may be damage inthe outer or middle ear and in the inner ear(cochlea) or auditory nerve. When this occurs, hearing loss is referred to as a mixed hearing loss.
Some possible causes of conductive hearing loss:
- fluid in the middle ear from colds,
- ear infection(otitis media),
- allergies (serous otitis media),
- poor eustachian tube function,
- perforated eardrum,
- benign tumors,
- impacted earwax (cerumen),
- infection in the ear canal (external otitis),
- swimmer’s Ear(otitis externa),
- presence of a foreign body
- absence or malformation of the outer ear, ear canal, or middle ear.
Some possible causes of SNHL:
Illnesses, drugs that are toxic to hearing, hearing loss that runs in the family (genetic or hereditary), aging, head trauma, malformation of the inner ear exposure to loud noise
It is very important to keep in mind that SNHL hearing loss is progressing backwards only to get worse and that it cannot be medically or surgically corrected. The only solution is wearing hearing aids ideally as early as the diagnosis is made!
Degree of Hearing loss Audiometric Thresholds
- Normal hearing (0 to 20 dB HL)
- Mild hearing loss (21 to 40 dB HL)
- Moderate hearing loss (41 to 70 dB HL)
- Severe hearing loss (71 to 95 dB HL)
- Profound hearing loss (greater than 95 dB HL)
- Mild hearing loss: If one-to-one conversations are fine but you are having difficulty understanding some words when there is a lot of background noise, you may have mild hearing loss. Technically speaking, it’s defined as having hearing loss between 21 and 40 dB in the speech frequencies.
- Moderate hearing loss: At this level, you are asking people to repeat themselves a lot during conversations – in person and on the telephone. Individuals with this degree of hearing loss cannot hear sounds lower than 41-70 dB.
- Severe hearing loss: If you can’t hear what people are saying without the use of a hearing aid or other amplification, or you tend to rely on reading lips to understand the conversation, you may have severe hearing loss. Individuals with this degree of hearing loss cannot hear sound lower than 71-95 dB.
- Profound hearing loss: If you have profound hearing loss, you can only hear extremely loud conversation or sound – and even then it is difficult to understand without a hearing aid or cochlear implant. You may prefer using sign language to communicate. Individuals with this degree of hearing loss cannot hear sound lower than 95 dB.
There are various types of Hearing Aids available:
Behind the ear aids
Behind the ear aids (BTE) consist of a case, an ear mould or dome and a connection between them. The case contains the electronics, controls, battery, microphone(s) and often the loudspeaker. Generally, the case sits behind the pinna with the connection from the case coming down the front into the ear. The sound from the instrument can be routed acoustically or electrically to the ear. If the sound is routed electrically, the speaker (receiver) is located in the earmold or an open-fit dome, while acoustically coupled instruments use a plastic tube to deliver the sound from the loudspeaker to the earmold. BTEs can be used for mild to profound hearing loss. As the electrical components are located outside the ear, the chance of moisture and earwax damaging the components is reduced, which can increase the durability of the instrument. BTEs are also easily connected to assistive listening devices, such as FM systems, to directly integrate sound sources with the instrument. BTE aids are commonly worn by children who need a durable type of hearing aid.
”Mini” BTE (or “over-the-ear”) aids
A new type of BTE aid called the mini BTE (or “over-the-ear”) aid. It also fits behind/over the ear, but is smaller. A very thin, almost invisible tube is used to connect the aid to the ear canal. Mini BTEs may have a comfortable ear piece for insertion (“open fit”), but may also use a traditional earmold. Mini BTEs allow not only reduced occlusion or reduced “plugged up” sensations in the ear canal, but also increased comfort, reduced feedback and address cosmetic concerns for many users. Receiver in the canal/ear (CRT/RIC/RITE)
BTE hearing instruments that place the loudspeaker directly in the ear without a fitted earmold are often referred to as “Receiver in the Canal” instruments. These instruments use soft ear inserts, typically of silicone, to position the loudspeaker in the patient’s ear. Some of the advantages with this approach include improved sound quality, reduced case size, “open-fit” technology, and immediate patient fitting. BTE Cross System
Cross systems are used for people with hearing loss in one ear or significantly more in one ear, this system allows the user to wear technically a microphone in one ear and the speech is transferred into a speaker in the good ear, whilst the cone in the good ear allow normal hearing BTE Bi Cross System
BTE Bi Cross System is the same as the Cross system, however it can also enhance the hearing in the individuals better ear by enhancing the volume of the input, therefore channeling the sound into the good ear, whilst enhancing the clarity and volume. Ear moulds
An earmould is created from an impression taken of the individual’s outer ear. This usually ensures a comfortable fit and reduces the possibility offeedback. Earmoulds are made from a variety of hard (firm) and soft (pliable) materials. The colour of the case and earmould of a BTE aid can be modified and optional decorations can be added. In the ear aids
In the ear aid (ITE) devices fit in the outer ear bowl, and they are sometimes visible when standing face to face with someone. ITE hearing aids are custom made to fit the ear of the individual. They can be used in mild to severe hearing loss.?Feedback which is a squealing/whistling caused by sound (particularly high frequency sound) leaking and being amplified again, may be a problem in severe hearing loss. Some modern circuits are able to provide feedback regulation or cancellation to assist with this. Venting may also cause feedback. A vent is a tube primarily placed to offer pressure equalization. However, different vent styles and sizes can be used to prevent feedback.Traditionally, ITEs are not recommended for young children because their fitting cannot be as easily modified as with an earmould fitted with a BTE, and thus the aid itself would have to be replaced frequently as the child’s ear grows. However, there are new ITEs made from a silicone type material that mitigates the need for costly replacements. ITE hearing aids can be connected wirelessly to FM systems, for instance with a body-worn FM receiver with induction neck-loop which transmits the audio signal from the FM transmitter inductively to the telecoil inside the hearing instrument.
ITC aids are smaller, filling only the bottom half of the external ear. The aid cannot be seen when face to face with the wearer. MIC and CIC aids are generally not visible unless the viewer looks directly into the wearer’s ear. These aids are intended for mild to moderately severe loss. CICs are not usually recommended for people with good low-frequency hearing, as the occlusion effect is much more noticeable. In-the-ear hearing aids are typically more expensive than behind-the-ear counterparts of equal functionality, because they are custom fitted to the patient’s ear. During the fitting, an audiologist takes a physical impression of the ear. The mould is scanned by a specialized CAD system, resulting in a 3D model of the outer ear. During modelling, the venting tube is inserted. The digitally modeled shell is printed using a rapid prototyping technique such as stereolithography. Finally, the aid is assembled at the lab and returned to the audiologist after a quality check.
Invisible in canal hearing aid
Invisible in canal hearing aids (IIC) style hearing aids fit inside the ear canal completely, leaving little to no trace of an installed hearing aid visible. This is because they fit deeper in the canal than other types, so that they are out of view even when looking directly into the ear bowl (concha). A comfortable fit is achieved because the shell of the aid is custom-made to the individual ear canal after taking a mould. Invisible hearing aid types use venting and their deep placement in the ear canal to give a more natural experience of hearing. Unlike other hearing aid types, with the IIC aid the majority of the ear is not blocked (occluded) by a large plastic shell. This means that sound can be collected more naturally by the shape of the ear, and can travel down into the ear canal as it would with unassisted hearing. Depending on their size, some models allow the wearer to use a mobile phone as a remote control to alter memory and volume settings, instead of taking the IIC out to do this. IIC types are most suitable for users up to middle age, but are not suitable for more elderly people.