A ready -made hearing protection device (HPD) is effective on preventing noise induced hearing loss (NIHS), but workers in noisy environment often resist to wear it. Because the ready -made products are uncomfortable and are hard to understand the others. To prevent hearing loss effectively it is important that workers keep wearing a HPD. So we proposed a made -to -order HPD in which a small acoustic filter is inserted. And we researched about the actual efficiency of a new developed custom-made HPD using a small size acoustic filter. Also, we found out that workers are more satisfied with new development than a former protection device from a workers' response.