The National Catholic Reporter has published a story featuring the concerns of individuals who find it hard to hear, and how this affects their participation at Mass. Although 
mild to moderate hearing loss is a common phenomenon, especially among older parishioners, there is not always an awareness of it and accommodations may not be made for their needs at church.
“Hearing loss is the invisible disability,” Ely told NCR. “People don’t make allowances for it.”
People using wheelchairs often will have doors opened for them. Even people who have had lifelong hearing impairment can find sign language Masses. All of these are good, emphasized Ely, but he would like to extend that kind of sensitivity towards those like himself.
The article discussed practical “fixes” using technology, but also noted that the human dimension of this challenge — removing barriers such as anger and pride that can stand in the way of getting help — is also formidable.
You can read the whole story here.
Installing loop systems where the inputs to the microphone are broadcast on a radio signal and then played back in the inner ear without the buzz of the surrounding crowd can be very helpful. Such systems should be heavily encouraged by the USCCB.
Communication Access Real-time Translation (CART) aka real time captioning with text appearing on a screen is another viable low-cost option. I only know of one parish that has a captioned mass. There might be more out there. There’s definitely a need.
A friend of mine works in a protestant church that has jacks discretely installed around the church to plug in headphones. Not as convenient as wireless but it is easy to use and has been working trouble free for years.
“How are they do believe if they don’t hear?” Investing in a quality sound system is the best capital investment a church can make. A few years ago my church replaced a functional yet inadequate system with a new custom-engineered system and the results have been amazing. The volume is actually lower than before, but we have greater clarity than many people thought possible in such a large room. We do offer wireless headphones, but even people with moderate hearing loss say than can hear well with the new speaker system in place. It’s like upgrading from and old tube television to a new HD flatscreen: once you see the difference you would never choose to go back.