I'm a voice actor—commercials, corporate videos, etc.—and I own a voice booth, which is a small, completely-enclosed, essentially soundproof room within a room. Recently, I moved into a new home, and I converted one of the bedrooms into an office in which my voice booth is located. Although the room is located away from significant sources of noise in the house, the outside condenser fan for the AC is located less than six feet away from one of the room's windows, and I could hear the fan from inside the voice booth. I considered having the window completely replaced with a double-glazed fixture, but quickly realized the astronomical costs. Also, the downtime required to install a new window was unacceptable. I began looking for alternatives on the internet, and that's when I discovered Indow. Long story short, I decided on the acoustic insulation window material. I ordered and received the laser measurement device, quickly measured the opening, ordered the insert, and within a couple weeks, the Indow insert arrived. Installation was simple and fast, and the Indow perfectly matches the existing window frame. As my son said, "I wouldn't know there was anything there if you hadn't told me." The real test, however, was a recording session in my voice booth. I intentionally recorded while the AC was running and, true to the Indow claims, the sound level from the outside AC fan was negligible. I'd say that the apparent loudness level was diminished by 65 or 70 percent, enough that it would not register on my recording software's VU meters. I'm completely satisfied with the Indow window insert and very impressed by Indow's attentive and knowledgeable customer service and tech team. An all-around exceptional product and experience.