The sound-field requirements in the hearing protector standard ISO 4869-1 are under discussion at present and are likely to be changed in a coming revision of the standard. The Nordic HAKK group comprises representatives from the hearing protector industry, labor protection institutes, audiological clinics, and universities. The test facilities at the laboratories of the members of the Nordic HAKK group cover various ways to fulfill the sound-field requirements of the ISO standard. Therefore, a round robin test was initiated with the aim of determining—and comparing between laboratories—the attenuation of two hearing protectors of the muff type and one of the plug type. The measurements were performed during the meetings of the group and with the group members (min. ten) as test subjects, thus permitting one group of subjects to be used by all laboratories. A statistical analysis of the results is in progress at the time of submission of this abstract. All factors (laboratory, protector-type, test-frequency, test-subject) are significant.