Check out this Blog from Adam Walker (Audiological Scientist) about conventional air conduction hearing aids!

What is a hearing aid?

A hearing aid is a device that amplifies sound according to the patient’s hearing levels, to provide access to the frequencies at which the patient does not hear as well as they should.  Hearing aids should be programmed using ‘Real Ear Measurements’ to ensure accuracy of fitting and optimal sound quality.  A correctly programmed hearing aid will usually apply more gain (volume) to quiet sounds than to loud sounds (called ‘compression’), with the aim to ‘normalise’ loudness growth whilst avoiding discomfort caused by loud sounds being ‘too loud’.  Hearing aids come in a wide range of sizes, styles, colours and technology levels, based on the patients needs and hearing levels.

Hearing aids are battery operated and one battery will last somewhere between 7 and 10 days, depending on the size and power of the hearing aid.  Whilst hearing aids can be set to have ‘volume control’ this is usually turned-off for children, therefore meaning that fluctuations in hearing (e.g. due to glue ear) cannot be managed via the hearing aid controls without them being retuned by an audiologist.  Hearing aids are an effective intervention to manage mildto severe hearing loss, but may struggle to provide enough amplification to allow access to speech sounds in the case of profound hearing loss.

Hearing aid success may be limited by the ‘site’ of the hearing loss.  Hearing losses that are conductive (e.g. glue ear) or at the level of the outer hair cells (responsible for ‘detection’ of sound) in the cochlea will generally be well managed with hearing aids, as the reduced ability to detect sound is overcome by the amplification. However, in types of hearing loss that include neural transmission problems (e.g. auditory neuropathy), or loss of inner hair cell function (responsible for ‘fine tuning’ of the sound we hear), despite making sounds louder, a hearing aid is unable to overcome the loss of the ‘fine-structure’ of the hearing signal generated and carried along the hearing nerve to the brain. Ultimately, resulting in poorer clarity for the patient than may be expected from looking at the pattern and severity of the hearing loss recorded on the audiogram alone.