In a city, the noise levels represented by the equivalent sound pressure level over an 8-hour period were reported as 80 dB(A). What does 'A' refer to?

In 80 dB(A) the A stands for a type of frequency weighting applied so that the meter responds like the human ear.

It does not refer to any amplifier used inside the instrument.

It is not the name of a microphone type used for the reading.

It does not indicate that the measurement was taken during the day time.

A weighting reduces the contribution of very low and very high frequencies, which people hear poorly.

This makes A weighted decibel readings a good match for how loud noise actually seems to us.