"Jesus Christ!" was my reaction, of course I forgot my volume was turned up so loud. Under 25.
The 25 is just a generalization, different frequencies will vary for different people. I seem to be particularly tuned to the frequency from a television, I can tell when one is turned on or off with my back turned or from a different room. I remember back in elementary school, when returning to the classroom, we'd be walking down the hall and as soon as I passed the point where the wall to my classroom would be, I could tell if we got to watch a video that day!