When I am in bed I have the sensation of hearing a beeping sound, I think it happens after using my Chinese trademark headphones. I have never used them with high volume, because of that I wonder if it could be due to ultrasounds produced by the device.
The frequency response of a headphone is one of the biggest selling points with a wider and flatter response being "better". Ultrasound is typically defined as sounds above 20 kHz. The high end Sennheiser HD 800 S headphones have a flat frequency response out to 51 kHz. Even more reasonably priced headphones can still produce ultra sound (e.g., the Sennheiser HD 25 can produce frequencies up to 22 kHz).