On the megahit ‘Rock N Roll Ain’t Noise Pollution,’ ACDC’s Brian Johnson sings, “heavy decibels playing on my guitar / we got vibrations comin’ up from the floor.” For Johnson the lyrics might have been prescient—after decades of those heavy decibels and floor-shaking vibrations, he faced a rapid decline in his hearing ability, a symptom shared by many musicians who’ve spent their lives on stage. Progressive hearing loss has taken their inability to hear tone or pitch, and to recognize unique notes. For professional musicians it can mean not just a loss of livelihood, but loss of a vocation and passion.
Many musicians turn to standard hearing aids, which take in sound and amplify it further into the eardrum. But because it’s the eardrum itself that’s injured, this can only help for a little while, and then worsen the issue. It’s taken a fellow musician with a scientist’s bent and the help of some powerful tools to design the solution.
The Ambrose Diaphonic Ear Lens (ADEL) is a device created by Stephen Ambrose’s company, ASIUS Technologies, that not only restores the quality of sound, but can help the ear repair itself. Prototyped over 10,000 times with the Form 2, Form 3, and now Form 3+ stereolithography (SLA) printers from Formlabs, the ADEL has already helped musicians like Kelly Keagy, KT Tunstall, and ODESZA to hear better than they have in decades.
The First Iteration: Swimmer’s Cups, Putty, and a Transistor Radio
Ambrose grew up in a musical family—his father was a professor of classical and ecclesiastical music at Vanderbilt University, but only certain types of music were allowed in the house. The teenage Ambrose had to find creative ways to listen to Bob Dylan, Johnny Cash, and the other rock legends playing in houses everywhere but his. To dampen the sound of his guitar, Ambrose would only play behind closed doors, with an earphone attached to the transistor radio so he could play along to the songs. To improve the comfort of the earpiece, Ambrose got even more creative—he took two swimmers’ ear cups and drilled a hole into them, filling them with the transistor earpiece and silly putty to create improvised headphones.
That first DIY invention, spurred by his need to listen to the music he loved, started Ambrose on a long career in sound—making it into music, amplifying it, studying it, and eventually, protecting against it.
On The Road
The ADEL device has been prototyped over 10,000 times on the Form 3 generation printers by Ambrose and Hammer.
In Music City, you’re never too far away from a big break. Ambrose got the chance to record a demo at Sun Records, recording right down the hall from Johnny Cash. “From there, I got to sing with all my heroes. I did background vocals with Brian Wilson of the Beach Boys, Roger Mcguin, Stevie Wonder, 50 different artists, along with recording my own album,” says Ambrose. Onstage for these massive stadium concerts, Ambrose immediately noticed the poor sound quality bounced back to the artists, and the need for some type of solution. “In the 60’s and 70’s everyone on stage was hearing the echo of the PA (public address) system, and it sounded a million times worse on stage. Then in the ‘80s you had speakers pointed back at the stage, but those caused feedback with the mic,” says Ambrose.
Just like with the first swimmers’ cups, Ambrose was faced with a problem, but wasted no time in designing his own solution. “I introduced in-ear monitors and was the only person doing them for 20 years. It was basically to listen to the rest of the instruments in stereo—you didn’t have to turn up the volume over something else and mask it. It lowered stage sound so it wasn’t all coming through the mic. It changed the music industry. I toured with Simon and Garfunkel, Diana Ross, and Stevie Wonder for years working on this technology,” says Ambrose.
Bringing the Concert to the Consumer, For Better or Worse
After seeing monitors in the ears of performers at the Concert for Peace in Vietnam, Sony sound engineers developed the first version of the Walkman—a consumer electronic that would be the beginning of the billion dollar industry of speakers, headsets, and headphones we have today.
“I told them, ‘That’s wonderful, you’re going to sell millions of them. But you’re going to have to watch out for the hearing loss,” says Ambrose. “If earbuds or headphones were made by people that made internal combustion engines or shock absorbers, they’d see it in a second—this speaker is vibrating like a piston; the sound is making a pumping pressure.”
Ambrose had seen it for himself when designing a special microphone with a more dynamic range of sound. The microphone used a plastic membrane that vibrated when sound was pushed through and extended the range of notes that could be amplified. To increase the membrane’s elasticity, Ambrose would play a loud bass speaker directly into it. Just the force of the bass speaker would stretch and bend the membrane. “Then I thought, well if it’s doing that to plastic, what do you think it’s doing to our eardrums?”
Despite his warnings to several engineers in the industry, earbud and headphone technology proliferated. People weren’t aware of the percussive effect on the eardrum because the devices were modeled on hearing aids, which take only the high notes from the environment and turn them up. “They didn’t pick up the bass because it would beat the hell out of the eardrum,” says Ambrose. “But turns out, the high frequencies are doing it too, and over time, that can damage the eardrum fidelity.”
Ambrose started to notice that all the artists he worked with were turning up their ear monitor volumes up every concert, despite the stage noise being brought down. “These things were battering the ear and the musicians were getting hearing loss from my invention. In the ‘90s I decided I wouldn’t make them anymore.”
Pistons, Pumps, and Progress
Ambrose didn’t have a formal scientific education, but he had decades of practical experience seeing how sound traveled, its physical effect, and how modern sound equipment could manipulate that effect. He received grants from the National Institute of Health and National Scientific Foundation to work with doctors and PhDs to add in the formal aspects of education, then got to work discovering a way to help musicians and headphone-wearers everywhere repair their hearing.
“I was studying the coexistence of pneumatic and acoustic pressures, which hadn’t been much studied before. When you plug your ears and speak, your voice is much quieter because your fingers are holding your eardrums still. Singers will have in-ear monitors that plug the ear, but then have to turn the volume up four times louder than normal, and do enormous damage to their eardrums,” says Ambrose.
But slowly, through research efforts that involved countless tests, specialized equipment, and a team of scientists from many different institutions, Ambrose developed early prototypes of a new device, one that created a synthetic eardrum that could bear the brunt of the pumping force generated by sound. The synthetic eardrum is a gortex bubble, so that the energy that would beat up the eardrum, beats up the bubble instead and the sound is absorbed through bone conduction. The bubble is connected to a belt pack, which is where the sound input is from the mics and instruments on stage, and the user can adjust the inflation level with the fingers, using a small pump to inflate or deflate to adjust for volume.
“When you put it in your ear, it just takes about three pumps to inflate the bubble. Now you’re totally sealed and you have the most insulation ever achieved, two times quieter than with noise canceling headphones,” says Ambrose. “Then, if you want to hear the ambient noise, you can isolate variably.”
10,000 Iterations
The ADEL device had to be prototyped thousands of times, both with direct 3D printing and through silicone molding processes.
3D printing the silicone molding masters enables Ambrose and Hammer to create end-use components for functional testing, without investing into expensive tooling or outsourcing.