The development of digital hearing aid technology in the mid 1990's allowed engineers to introduce some pretty amazing features inside of today's modern hearing aids. But perhaps one of the most important features is Compression.The easiest way to think of compression is for you to imagine someone who is speaking softly to you vs. someone who is yelling at you. If you have a hearing loss, you need to amplify the soft spoken person MORE than you need to amplify the sound of the person who is yelling. Before compression, hearing aids could only apply the same amount of amplification to every sound. Potentially making soft sounds too soft and loud sounds too loud. Someone with normal hearing has a wide range of sounds that they can hear.
All the way from very soft sounds, to very loud sounds. We call this the Dynamic Range. The reason compression is so important is that someone with a hearing loss has a more narrow range of sounds that are audible, and all of the same sounds that the normal hearing person can hear must be "compressed" into that narrow range. In order to make this happen, compression must be utilized when programming hearing aids. By adjusting the correct level of amplification for Loud, Average, and Soft level sounds, your hearing care professional can ensure that all of these sounds are audible and comfortable. By doing so, compression is also being adjusted. One of the best ways to ensure that compression is done correctly is to perform Real Ear Measurement (REM). If you don't know what REMs are, check out this video: https://youtu.be/cHR0Oa6I-wY
When using Real Ear Measurement to verify the correct amount of amplification & Compression for your hearing aids, Loud, Average, and Soft level Speech Sounds are presented from a loudspeaker in front of you. The amplification levels of your hearing aids are then measured inside of your ear canals with a Probe Microphone to determine if the correct amount of amplification is being given for each of these Input Levels. Your hearing care provider will make adjustments in the hearing aid programming software until they match the amplification to your prescriptive targets. What you are looking at here are amplification measurements taken inside of a patient’s ear canal.
The goal is to match the Solid lines which is the hearing aid amplification, with the Hash Mark Lines, which is the prescription for each of these sound inputs. If your hearing care professional matches these targets accurately, it will ensure that Loud, Average, and Soft sounds are correctly amplified with the right amount of compression. This should give you a basic level understanding of what compression is.
Hopefully it gives you an understanding of the complexity of what a hearing care professional is actually doing when programming your hearing aids. Programming hearing aids is more than adjusting overall volume. While compression isn't the most exciting hearing aid feature like Bluetooth and automatically adjusting programs, it could quite possibly be the most important hearing aid feature in today's modern hearing aids.