Using microphones and receivers, FM and DM systems help you hear and reduce background noise.
Both systems improve the signal-to-noise ratio, explains clinical audiologist Sarah Sparks, Au.D, founder of Audiology Outside the Box PLLC in Washington, DC.
“They take sound that is farther away and bring it closer to the listener,” Sparks says.
Find out more about how these systems work, along with who might consider taking advantage of them, when FM/DM systems are ideal for use, and more.
What exactly are FM/DM systems?
Here’s how it works: The speaker uses a microphone, while the listener wears a receiver. The receiver can be a simple pair of headphones, ear-level receivers that deliver the sound into the ears, or a hearing device, such as cochlear implants or hearing aids, Sparks explains.
“An FM system is not a substitute for a hearing aid,” says Rhee Nesson, AuD, founder of Hearing Doctors of New Jersey—but these devices are often added to hearing aids, she says.
FM vs. DM
If you see “FM” and think “radio” you’re on the right track—this type of system uses FM radio signals designated by the FCC to transmit sound, Nesson says.
DM systems, in contrast, use digital signals, and tend to have better sound quality while avoiding potential for interference (think: the staticky sound of another FM station coming through), Sparks says.
“My own experience of using DM systems is that their sound quality is significantly clearer than that of FM systems, which reduces the challenges of the listening situation,” Sparks, who is deaf, notes.
Note: While they use different signals, perhaps since they operate fairly similarly, and FM has been around for a while, both systems are often referred to as FM. Audiologists and hearing instrument specialists prefer the term "remote microphone hearing assistive technology" (RM-HAT), since it’s inclusive of both types of systems.
Who benefits from using one? / Who should consider using FM/DM systems?
There’s a wide range of people who might benefit from using an FM/DM system:
Students: FM/DM systems are often used with children who are deaf or hard of hearing.
“Children that don't have hearing loss sometimes would benefit from an FM system as well,” Nesson says—that includes both children with an auditory processing disorder or students with difficulty hearing when there is background noise.
“For children in schools, these systems are often included in IEPs and 504 plans,” Sparks says. These plans put in place legally binding required accommodations to help kids with hearing loss.
Hearing aid candidates: At panel conversations, church, concerts, and other situations where hearing may be a challenge, adults who are hearing aid candidates might take advantage of these devices.
“Sometimes, asking for accessibility devices like FM and DM can be the beginning of a person's journey toward having their hearing tested and being fit with appropriate hearing devices,” Sparks says.
Adults with hearing aids: If you are fitted with hearing aids, using an FM/DM system can help reduce background noise. So in tricky hearing environments—such as a loud restaurant—having your dining companion wear a microphone can help.
Anyone, really: Even people with no difficulty hearing can benefit when FM/DM microphones are connected to loudspeakers and used in auditoriums, Sparks points out—that includes people with ADHD or auditory processing disorders, and non-native speakers. “Having a clearer and more accessible sound signal can help with understanding of the message,” she says. This also reduces listening fatigue.
It’s more common for kids to use FM/DM systems. “But that's not because adults don't benefit!” Sparks says—she notes that adults might have to put in some legwork, asking for them to be provided.
“Because of the stigma that is attached to reduced hearing sensitivity, many adults are hesitant to request these types of accommodations for work and university-level education,” she notes.
How do they work?
The simple version is as stated above: A microphone and receiver are paired up. But of course, there’s a bit more to it than that.
There are several types of microphones that can be used with these systems:
“For some DM systems, multiple types of microphones can be linked to each other within a single system so that listeners can hear from different speakers at different times,” Sparks says.
Then, there’s the receiver end:
Plus, some systems can be paired with other technology—for instance, Sparks pairs her DM system with her laptop and uses it during video chats.
Where you can use FM/DM systems
These can easily be used in many locations, including:
These systems are useful whenever there’s background noise and you want to listen to one other person, Sparks says. In some cases, ADA accessibilty laws may stipulate that FM/DM systems are provided.
How much do they cost?
FM systems can be purchased online, in electronics stores and through your local hearing healthcare professional. If you don't know how to get started or what device might work best for you, talk to your hearing care practitioner, and ask for a demonstration.
“An audiologist would be able to tell a person which receiver is most appropriate for their needs,” Sparks says. You’ll also need the microphone (which often can pair with several different receivers).
Be prepared for a wide price range with these devices, which can cost as low as $150 or be several thousand dollars.