Study On Ear Protection Technology Applied To Flight

Rapid changes from cabin pressure will lead to a large pressure difference on both sides of eardrum,and cause middle ear barotrauma.High-intensity noise in cabin will lead a higherintensity noise to Inner Ear,and cause noise-induced hearing loss.To reduce the damage from cabin pressure and noise to ear during flight,an Ear Protection Technique is put forward.Based on the technique,an Ear Protection Device is established.Analyses on decompression performance and denoising performance of Ear Protection Device are carried out.Decompression performance is the ability to reduce pressure difference on both sides of eardrum.Denoising performance is the ability to reduce in-ear noise intensity.Through mechanism analysis of Ear Protection Technique,it is found that increase of height difference,velocity difference and pressure loss of lateral eardrum channel can reduce pressure difference on both sides of eardrum.In this way,Ear Protection Device has better decompression performance.Besides,addition of perforated panel absorber and porous absorber in lateral eardrum channel can reduce in-ear noise intensity.In this way,Ear Protection Device has better denoising performance.Based on the decompression mechanism and denoising mechanism,Ear Protection Device has experienced four structural changes.The four structures are normal straight tube type,imitated-eustachian tube type,open-ball valve type,and decompression-acoustic type respectively.Numerical and experimental study on decompression performance of the devices are carried out.Reduction of pressure difference on both sides of eardrum is realized by the regulation of pressure outside the eardrum.Changes of air pressure and velocity outside the eardrum affected by each device during take-off and landing are simulated in FLUENT,and observed in an airflow experimental platform.Simulations and experiments show that decompression performance in decompression-acoustic device is better than other devices because of its imitation of Eustachian tube’s self-opening and closing function.Besides,the importance of the ball valve in decompression-acoustic device in regulating air pressure and reducing velocity,and the correctness of its imitation of Eustachian tube’s function are verified.Numerical and experimental study on denoising performance of the devices are carried out.Noise reduction is realized by the reduction of in-ear sound pressure level.Effects of each device on sound pressure level in ear under specific noise frequency are simulated in COMSOL,and observed in a noise reduction experimental platform.Simulations and experiments show that denoising performance in decompression-acoustic device is better than other devices in different frequency band,because its inner wall is adhered by a layer of melamine foam.Moreover,noise reduction under decompression-acoustic device will not affect normal information reception and communication.Besides,the importance of the porous absorber in decompression-acoustic device in reducing in-ear sound pressure level is verified.In conclusion,decompression-acoustic device has better decompression performance and denoising performance.It can reduce ear discomfort and bring better flight experience to passengers and flight attendants during flight.Therefore,Ear Protection Device applied to flight is Decompression-acoustic device.