In this blog post, we’ll explore the principles and potential of “alarm glasses,” which convert sound into visual signals and vibrations to help people with hearing impairments—who have difficulty hearing—reduce the inconveniences and dangers they may face in daily life.
For humans, “hearing” is one of the five senses and serves as a vital means of conveying a great deal of information. In particular, we rely on sound to perceive our surroundings when we cannot see. For example, if a fire breaks out on another floor of a building, it may be difficult for us to immediately recognize it through other senses, such as sight or smell. Therefore, fire alarms are installed to emit a loud warning sound when a fire breaks out, allowing people who hear the alarm to recognize the danger and evacuate. In this way, when it is difficult to detect dangerous situations using other senses, we rely heavily on “hearing,” which has a relatively wide range of perception. We use hearing rather than sight not only in such dangerous situations but also in everyday life, such as when someone rings the doorbell outside our home. However, people with hearing impairments, who cannot rely on their sense of hearing, find it difficult to recognize these situations and consequently face significant inconvenience and danger.
“Alarm glasses” were designed to reduce the inconvenience and danger experienced by people with hearing impairments. Since these glasses cannot alert the wearer audibly, they convert auditory signals into visual signals or vibrations to warn of danger. When a sound above a certain volume—such as a car horn or a doorbell—is detected, the glasses recognize the sound level and, depending on that level, display a visual signal on the lenses or emit a vibration, allowing the wearer to perceive the auditory signal. The component responsible for detecting sound levels is a high-performance, ultra-compact microphone mounted on the glasses.
A microphone is a device that converts sound into electrical signals. It generally consists of a diaphragm that receives sound vibrations, a transducer that converts those vibrations into electrical signals, and a section that processes or outputs the converted signals. The components used in these glasses are the microphone’s diaphragm and transducer—that is, the parts that convert sound vibrations into electrical signals. The diaphragm consists of a vibrating plate connected to a coil, with a magnet arranged around it. Sound is a wave that propagates through the medium of air. When sound reaches the microphone’s vibrating plate, the plate vibrates, causing the connected coil to move back and forth as well.
As the coil moves within the magnet’s magnetic field, an electric current is generated; this is called an induced current. An induced current is a current generated by the phenomenon of electromagnetic induction. Electromagnetic induction, a phenomenon discovered by Faraday and Henry, refers to the phenomenon where a current flows through a wire when a magnet is moved inside a coil formed by winding a conductor into a loop. The motion of inserting and removing the magnet causes a change in the magnetic field passing through the coil. In other words, electromagnetic induction is the phenomenon in which a current flows when the magnetic field changes around a conductor capable of carrying current, and the current generated at this time is called an induced current.
In this way, when a microphone uses the phenomenon of electromagnetic induction to convert sound into an electrical signal, the amplitude of the electrical signal corresponding to the sound level can be quantified through measurement. Based on the quantified electrical signal, if a sound loud enough to be identified as a warning tone is detected, the electrical signal is transmitted to the glasses’ vibration mechanism or a device that displays visual signals. When the glasses receive this electrical signal, a visual animation appears on the lenses and a vibration is emitted, allowing people with hearing impairments to see or feel loud sounds, such as warning tones. This is the basic function by which “alarm glasses” convey sound.
The technology behind “alarm glasses” utilizes a relatively simple and widely available microphone. Nevertheless, at the time, these glasses were closer to a concept in the design phase than an actual commercial product. If this design were to be commercialized as a real product, it could be of great help to people with hearing impairments. While there are many designs aimed at reducing the risks and inconveniences that people with disabilities may face, some remain mere ideas and are not fully utilized in everyday life. If more people take an interest in these designs in the future and efforts are made to turn them into actual products and services, we can look forward to a world where people with disabilities face fewer inconveniences and dangers in their daily lives and can live more safely.
