Comparison of real ear and simulated insertion gain in adults who use hearing aids

The real ear measurements are objectives and fast (about 10 minutes) measures of the sound pressure level in the ear canal. The equipment consists of a computer, a speaker, a reference microphone and a tiny tube that is linked with a measure microphone. The computer’s screen displays the patient’s data, the audiometric data and the graphics obtained with the real ear measurements. The audiologists control all parameters necessary on the computer. The speaker provides the acoustic signal for the measurements. The type of the signal depends on the hearing aid features (e.g. if they have feedback management or/and noise redactor) and the signal level depends on the hearing aid processing (e.g. if they have Automatic Gain Control or Wide Dynamic Range Compression) and the prescription rule, for example, National Acoustic Laboratories Non Linear number 1 (NAL-NL1), National Acoustic Laboratories Review (NAL-R), Prescription of Gain and Output (POGO). The data about the real ear measures are displayed in a graphic form where the information about the sound frequency is showed in the horizontal axis and the sound pressure level is showed in the vertical axis. The reference microphone controls the signal level around the patient’s ear and the tiny tube linked with a microphone measures the sound pressure level inside the ear canal. Firstly, we assess the Real Ear Unaided Response, which is the measure of the sound pressure level in a specific point of the ear canal while the patient is not using the hearing aid. This is the response about the amplification provided by the open ear. After this, we measure the Real Ear Occluded Response, which is the sound pressure level in a specific point of the ear canal while the patient is using the hearing aid off. This measure reflects the coupling of the hearing aid off and the earmold with the ear. This is the amount of amplification that is lost with the ear occlusion. Ultimately, is obtained the Real Ear Aided Response, which is the sound pressure level in a specific point of the ear canal while the patient is using the hearing aid on. This measure reflects the coupling of the hearing aid on and the earmold with the ear. This is the amount of amplification provided by the hearing aid. The insertion gain is the difference of the measurement obtained in real ear whilst the participant did not wear hearing aids (REUR) and whilst they did wear hearing aids (REAR). This measure is compared with individual amplification targets provided by fitting rules based on the audiometric data. This measurements are important at the verification step of amplification provided by hearing aids and at follow up sessions because is a objective and fast measure (about ten minutes) of the sound pressure level in the ear canal. Moreover, these measures are individual ones and reflect the sound pressure level when the hearing aids are in use. The real ear insertion gain can be obtained on several occasions. At the moment of verification these measures are used to compare the targets provided by a prescription rule with the amplification provided by the hearing aid. At follow up sessions that is defined according to each patient. In these occasions the measure helps us to fine tuning the amplification providing more or less amplification according to the targets. The real ear measurements can be obtained more than two times.