What effects does noise have on a child’s hearing and how can children be protected from damage to their health?? Experts from -medicine, research and practice provide answers.
Two to three from 1.000 children acquire hearing loss by the age of two. Among school children, up to 24 percent fail the hearing screening test. More than 500.000 children are affected by hearing loss. Since the 1980s, the number of children and adolescents exposed to noise has tripled. These results were presented by Professor Dr. Martin Walger at the "Children in Noise" event, to which the Federal Guild of Hearing Aid Acousticians and the German Tinnitus League had invited to the Chamber of Crafts in Cologne. Walger is Head of Audiology and Pediatric Audiology at the Department of Otolaryngology at Cologne University Hospital.
Internationally, the situation is even bleaker. More than 32 million children worldwide have hearing impairments that require treatment. Over 60 percent of these could have been prevented, with noise playing a major role, explained Professor Dr. Katrin Neumann, head of the Hearing Competence and CI Center Ruhr Area and working as an audiology consultant for the WHO.
Hearing influences speech
Since hearing affects the entire speech development of children, impairment is dramatic, especially since the damage is irreversible. Impairment should be diagnosed by the third month of life, warned Dr. Ruth Lang-Roth, Head of Phoniatrics and Pedaudiology at the ENT Clinic of the University Hospital of Cologne, Germany. By the age of six months, it should be taken care of, and no child is too young for a hearing aid or a radio frequency (FM) system. Newborn hearing screening, in which the outer hair cells in the inner ear are tested, has been in place since 2009. In 2016, a second mandatory screening for children up to eight years of age was added to the early detection program in order to also cover children with progressive hearing impairment.
Even with these preventive measures, not all cases can be detected, which is why Lang-Roth recommended that parents remain vigilant at all times, because unexpected dangers lurk even in the children’s room. Hearing is endangered at a noise level of 85 dB(A), the pain threshold is 125 dB(A), as Siegrid Meier, lecturer at the Academy for Hearing Acoustics in Lubeck, pointed out. Hearing protection is mandatory at work above 80 dB(A). Even harmless-looking toys reach this limit. According to Meier, the noise level of a music box is 65 to 90 dB(A), a squeaky toy reaches 130 dB(A), comparable to the noise of an airplane, and a toy gun reaches 150 dB(A).
Toy safety standard
DIN EN 71-1 is a standard for the safety of toys that also lists acoustic requirements. A warning must be affixed to play equipment above a volume of 110 dB. But Neumann criticized that this only applies to playground equipment that is designed to emit sound, while other equipment also generates noise. Walger argued that physiologically based models should be used as a basis for setting limits for the loudness of toys.
The experts advised keeping loud toys away from children’s ears. For comparison: a child’s trumpet sounding 2.5 centimeters away from the ear reaches 109 to 125 dB(A), while 25 centimeters away it reaches 92 to 110 dB(A). Room acoustics also play a role. Meier emphasized that even inexpensive measures such as carpets or walls and ceilings with absorbers could dampen reverberation and noise in schools and daycare centers.
Solutions from the hearing care professional
Technical solutions for prevention presented by master hearing care professional Dirk Kottgen. There is a choice of standard hearing protection such as capsules, plugs or lamellas, as well as individual solutions that are made after measuring the auditory canal. For children, there would be capsules with a "very potent" antidote attenuation value (expressed in SNR: Signal to Noise Ratio) of 27 dB, for babies with 23 dB. The high level of attenuation is an advantage, as is the ease of use and low risk of loss. Disadvantages: It gets warm under the capsules, they can pinch and limit directional hearing. Lamellae are inexpensive and easy to use, but do not last long, have only low sound attenuation and can also be depressing. Individual hearing protection fits precisely, achieves a high attenuation value across all frequencies equally, lasts a long time and is easy to clean, but it cannot be used quickly, loses its accuracy of fit over time and is unsuitable if the ear canal is too narrow. Kottgen’s other recommendations: educate people about the dangers, avoid noise, give your ears a break, listen to music at a reasonable volume and use headphones with individual earpieces.
Sound: Sounds are produced by vibrations that propagate as sound waves. Loudness can be measured. The measure of the physical sound pressure produced by a sound source at the ear is called sound pressure level. It is expressed in decibels (dB). This is a -logarithmic measure. A level change of 10 dB corresponds to a doubling or halving of the perceived loudness. The human hearing threshold is 0 dB, and the pain threshold is reached at 125 to 130 dB, whereby the human ear perceives high and low tones more quietly than those in the middle range around 1.000 Hertz lying around. In order to take this into account, the sound pressure level is adjusted to a rating curve, which corrects quieter perceived frequencies accordingly. As a rule, it is the so-called "A rating", which is why the resulting sound pressure levels are given in dB(A). Since sound propagates spherically, the most effective protection against noise is to move away from the source of the sound. For comparison: a child’s trumpet sounding only 2.5 cm away from the child’s ear reaches 109 to 125 dB(A), while 25 cm away the level is between 92 and 110 dB(A).