It seems to occur when airflow flows over the crossbars. Just had my knees done arthroscopically and I have weak ankles. Totally bummed, as I really liked the concept. They feel very premium and durable. 7V battery arrived 90% charged, topped off quickly and appears to honor the 30 hour play-time expectation. I dont much like the sliding hooks meant to hold your hangers. I have callouses on the bottom and sides of my feet and the manicurist said it was from not wearing shoes. Die Ohrstöpsel besitzen je einen dicken Knopf an der Außenseite, mit denen man je nach Sonnenwind mal Musik und mal Podcasts starten oder stoppen kann. Lovely and sturdy material for the containers I use it in default configuration with my ifi nano black (24bit/96/192Khz, DSD256) and I think it need a very little enhanced in low frequency.