In terms of audio perception, a sound wave does not become a flat line at any specific frequency. A flat line in audio representation typically refers to silence or the absence of sound.
However, when referring to the frequency response of audio equipment or systems, a flat line is used to describe a frequency range where the output remains relatively constant. In this context, a flat frequency response means that the system reproduces all frequencies equally without any significant boost or attenuation.
The specific range for a flat frequency response depends on the equipment or system being considered. For example, high-quality audio systems strive for a flat frequency response from around 20 Hz (the lower limit of human hearing) to 20,000 Hz (the upper limit of human hearing). This range is commonly referred to as the audible frequency range.
It's important to note that while the frequency range of human hearing is generally considered to be from 20 Hz to 20,000 Hz, individual hearing capabilities may vary. Some people may have reduced sensitivity to certain frequencies, especially at the extreme ends of the range.
To summarize, a sound wave does not become a flat line in terms of audio perception. However, a flat frequency response is a term used to describe a system that reproduces frequencies equally without significant boost or attenuation, typically in the audible frequency range of 20 Hz to 20,000 Hz.