Hearing loss has affected humans for centuries, but assistive devices to aid hearing have dramatically evolved over time. From the earliest known hearing trumpets in the 17th century to the high-tech digital hearing aids of today, devices to help amplify sound have improved by leaps and bounds. This advancement has enabled people with hearing impairments to more fully engage with the world around them.
Early Hearing Devices
Some of the earliest hearing assistive devices on record are known as “ear trumpets.” These primitive funnels were first depicted in paintings from the 1600s. An ear trumpet was usually a large funnel shape that collected sound and directed it into the ear canal. They were entirely passive with no amplification, but the cone shape helped focus the sound waves for someone with hearing loss. Ear trumpets continued to develop through the 1700s and 1800s, with new designs and materials like tinned iron or brass. Some featured an earpiece that fits inside the ear for comfort. While bulky and cumbersome by today’s standards, ear trumpets represented the first attempts to engineer hearing solutions.
Acoustic Hearing Aids
The first major breakthrough came in the late 1800s with the invention of acoustic hearing aids. Instead of passively funneling sound, these devices used electronics to amplify noises. The earliest electric hearing aids converted audio signals into electronic signals, amplified them, and converted them back to audio. The first commercial models appeared in the early 1900s, like the Akouphone that used telephone technology. However, they were large tabletop devices that were only affordable to the wealthy.
Portable versions emerged in the 1920s and ‘30s. The Vacuum Tube Era produced small desk-top devices, while the transistor in the 1950s enabled wearable body aids and pocket amplifiers. While bulky, these offered the first practical hearing aids for everyday use. However, they still used primitive analog technology and lacked features like noise reduction or multiple settings. Still, acoustic amplifying hearing aids represented a major step forward in hearing technology.
Bone Conducting Hearing Aids
Bone conduction hearing aids work by transmitting sound vibrations through the bones of the skull to the inner ear, bypassing the outer ear and eardrum. The concept dates back to
the Renaissance, but the first electronic models were developed in the 1960s. While less common than air conduction aids, bone conduction can help people with outer or middle ear problems who aren’t helped by traditional hearing aids. Models worn on headbands or glasses frames place transducers in contact with the cheek or temple bone to amplify vibrations. Implantable models like the Bonebridge or BAHA system use titanium implants screwed into the skull. While invasive, they avoid external hardware. Bone conduction aids benefit specific types of hearing loss, helping restore functional hearing.
Cochlear Implants
Cochlear implants are small devices surgically. These devices are embedded into the inner ear to stimulate the auditory nerve directly, bypassing damaged hair cells that normally detect sound vibrations. The concept emerged in the 1950s, and the first commercial single-channel implant received FDA approval in 1984. Today’s models utilize multiple electrodes for more detailed sound information. The external processor captures and processes sound, which is wirelessly transmitted to the internal implant. While highly invasive, cochlear implants can provide a sense of sound to those with severe-to-profound hearing loss not helped by traditional hearing aids. The technology continues to improve speech comprehension and music perception.
Implantable Middle-Ear Devices
Newer implantable middle ear hearing devices represent less invasive alternatives to cochlear implants. Instead of going into the inner ear, they are attached to middle ear structures. Examples include direct acoustic cochlear stimulation (DACS), which uses a vibrating actuator on the outside of the cochlea, or implantable piezoelectric transducers, which stimulate the auditory nerve via the middle ear bones. These implants are geared toward people with moderate-to-severe hearing loss that is not sufficiently helped by conventional hearing aids. While still an emerging technology, early devices show promise in restoring useful hearing with lower costs and risks than cochlear implants.
Hearing Assistive Technologies
Beyond dedicated hearing aids, various assistive devices and technologies also help those with hearing impairment. Handheld amplifiers boost sound for conversations or TV listening. Smartphone apps provide transcriptions, alerts, sound enhancement, and more. Devices like Roger Pens transmit speech signals directly from the speaker’s mouth to the listener’s hearing aid. Alerting devices provide visual cues for sounds like doorbells and alarm clocks. From video relay services to hearing loops to captioning, various innovations supplement hearing aids to enable clearer communications.
Modern Digital Hearing Aids
The digital revolution transformed hearing aids. Digital signal processing (DSP) replaced simple amplification with sophisticated software algorithms that filter, process, and amplify sound tailored to an individual’s hearing loss profile. Digital hearing aids can filter out background noise, adjust volume automatically, and come programmed for specific frequencies of loss.
Modern hearing devices utilize several types of digital technology:
Digital signal processing (DSP) chips analyze and optimize sound.
Directional microphones differentiate front and back sound sources.
Wireless connectivity like Bluetooth allows control from smartphones and streaming of audio, music, or phone calls.
Rechargeable battery options offer convenience and cost savings.
Additionally, hearing aids now come in a variety of form factors like behind-the-ear, in-the-ear, receiver-in-canal, or completely-in-canal models. Some are virtually invisible.
AI Hearing Aids
The latest frontier is AI-powered hearing aids. Artificial intelligence allows hearing aids to automatically adapt to different listening environments in real-time, recognizing speech versus background noise. Machine learning algorithms train the device to learn a user’s preferences and optimize settings automatically. AI hearing aids also leverage big data to enhance sound processing by crowd-sourcing common settings preferred by those with similar hearing profiles. Leading manufacturers offer AI hearing devices and solutions that deliver the most personalized amplification ever achieved. AI promises more natural, effortless hearing tailored to each unique user.
Over the centuries, hearing devices have progressed immensely from primitive ear trumpets to today’s smart hearing aids. While early acoustic and analog models laid the groundwork, digital signal processing and artificial intelligence have revolutionized hearing aids in recent decades. With advanced computer technology and innovative engineering, modern hearing solutions allow people with hearing loss to hear the world around them with greater clarity, comfort, and convenience.