Turn down the volume of the music!

New headphones to protect the hearing ability of users.

Millions of people are risking their hearing due to prolonged exposure to loud music on MP3 players and smartphones. A headset technology developed by dB Logic in Indianapolis, Indiana (USA), aims to prevent this type of damage by limiting the maximum volume of music, and is able to do so without distorting the loudest passages or making Soft sounds are inaudible.

People have been listening to portable music players through headphones since 1979, when Sony introduced the Walkman. However, the widespread adoption of digital music players in the last decade represents a new risk to public health, as the devices store so much digital music that users can listen to it without interruption for hours. In the era of portable CD players, users “listened for up to seven hours, in most cases,” a week, says Brian Fligor, director of diagnostic audiology at Children’s Hospital in Boston (USA). ) and hearing loss expert caused by portable media players. Fligor has recently studied a group of digital player users in New York and found that “on average, they listened to 18 hours [of music] a week. We had some people who were listening more than 70 hours each week.”

Users risk hearing loss when they combine long periods of listening with a high volume. An investigation sponsored by the European Commission concluded that digital music players produce maximum noise levels ranging from 88 to 113 decibels (dB), with levels up to 120 dB depending on the type and placement of the headphones. (The quietest audible sound is zero dB, a normal conversation produces about 60 dB, and 120 dB is equivalent to the noise of an airplane taking off near us.) It is estimated that between 2.5 million and 10 million users of music players in the European Union are at high risk of hearing loss.

The dB Logic system limits the volume of the headphones with a circuit powered by the audio signal, eliminating the need for batteries. At the heart of the circuit is a small transformer that intensifies the small audio output voltages of the music player to levels that can operate the transistors that regulate the volume. The system only attenuates the volume if the average volume is consistently above 85 dB. This means that soft sounds can pass at full volume and that short passages of more than 85 dB are not abruptly attenuated. Two other popular methods to limit the volume – using a resistor to attenuate the audio signal regardless of its volume, and using a pair of diodes to trim all sounds above a certain threshold – are not able to do the same.

Although the dB Logic system could have been established to begin limiting at any particular loudness level, the 85 dB was chosen since that is the threshold at which the US Occupational Safety and Health Administration. forces employers to start protecting workers’ hearing, says Med Dwyer, chief technology officer and co-founder of dB Logic. “Very few users will listen to music at that level and believe that ‘it is not strong enough for me’, especially in our demographic goal of young people,” says Dwyer.

The Fligor audiologist doubts that volume limitation technologies alone can really solve the problem. Eighty-five dB “is not a magic figure above which we suffer a risk, and we are safe below it,” he says, and also notes that the duration of exposure is a critical factor. (After confessing that he enjoys music at full volume, Fligor listens to it at 89 dB for a maximum of 90 minutes a day, a volume and duration that, according to his calculations, will not harm his hearing.) For Fligor, Ideally, digital players track volume over time so users can see if their accumulated exposure is putting them at risk. “It is not that the devices do not have the computing capacity to do so, but that there has been no real protest that forces them to do so,” he says. “And why would the manufacturer include something that could generate litigation?”

Dwyer agrees that the duration is important. dB Logic has considered the creation of a product that tracks exposure time, as well as a limitation of levels