I don't know about Chaika... but I might be able to assist when it comes to audio books and radio commercials and why it might be difficult for you to determine where people are from. Casting agents look for people who have "Radio Quality" accents. As an example, my daughters have Radio Quality Spanish. It means when they speak Spanish, they have a neutral accent and you can't tell exactly where they are from. It doesn't mean that they pronounce anything incorrectly it just means you have trouble determining exactly where they come from so they sound good to almost anyone who listens to them. SO, when they hire British folks to read, they won't have a harsh British accent or an American, they won't have a Southern or New York accent. It should sound soothing and appealing.