Hearing Aids tested in the wind tunnel
While the majority of people hardly perceive a slight breeze or a breath of wind, it presents a real nuisance to hearing aid users. The air draft reaches the microphone inside the hearing aid, where it creates a pseudo noise. This “false” sound can be even much louder than the real noise. In short, it impairs the perception of those sounds the hearing aid user wishes to listen to, like for example music or a conversation of colleagues.
This affects a significant number of people: Approximately 48 million people in Germany live with a more or less serious hearing impairment. 60 percent of all persons aged over 65 years are hard of hearing. Moreover, 4 percent of all persons aged between 15 and 35 years already have an incurable hearing impairment. Even though suitable hearing aids - i.e. a combination of microphone, signal processing and loudspeaker- are not used by all persons affected, they are of considerable importance. From the users’ viewpoint, the quality of hearing aids depends on a number of factors, including their sensitivity to wind noise.
Researchers of the Fraunhofer Institute of Building Physics IBP deal with this topic: They perform tests by using an artificial head in the wind tunnel to optimize the post-processing of such background noises. How do wind speed and incidence angle of the wind interfere the ear and hearing aid? The researchers carried out a number of such investigations in the aeroacoustic wind tunnel of the Fraunhofer IBP on hearing aids worn both inside and outside the ear, installed on an artificial head that is rotated for a full 360 degrees in steps of 45 degrees. The measurements were made at five, eight and ten meters per second wind speed.
Based on the data measured at both ears, i.e. binaural, the differences in hearing and in the noise disturbance occurring with various wind conditions can be evaluated. The data can, of course, be used individually for each ear, if only one hearing aid is used. Comparative data gained with a calibrated microphone assist in analyzing and adapting the signal processing. The investigations provide important information for the manufacturers on how to adapt the signal processing of hearing aids to minimize the influence of wind noise at the microphone, thus creating an almost natural listening experience for the user.