Which audio signal level is considered to have a nominal level of 1 volt?

The choice indicating professional line level is correct because this standard typically defines a nominal operating level of 1 volt (specifically +4 dBu). Professional audio gear is designed to handle this line level, which ensures a sufficient signal-to-noise ratio and is compatible with various pro audio equipment like mixing consoles, microphones, and amplifiers.

Understanding the standards in audio levels is crucial for ensuring that equipment can interface properly. Consumer line level, on the other hand, generally operates around -10 dBV (approximately 0.316 volts), making it lower than professional line levels. Microphone levels are significantly lower than line levels, often in the range of millivolts, and require pre-amplification to reach line level. Speaker levels are also much higher, typically reflecting the range of voltage necessary to drive speaker drivers, and are not compatible with direct input to line level equipment without appropriate attenuation or sensitivity adjustments.