A decrease of 20 dB for current will result in what change to the original dB value?

A decrease of 20 dB indicates a reduction in the power level of the signal. In terms of power, a change of 10 dB represents a tenfold increase or decrease in the power level. Therefore, a decrease of 20 dB translates mathematically to a decrease in power by a factor of 100.

When we discuss the dB scale, particularly with voltage or current, we can use the relationship that a change of 20 dB corresponds to a change in the linear ratio of currents (or voltages) as follows:

For current (or voltage), every decrease of 20 dB implies a reduction by a factor of 10 (10 dB decrease) occurs twice. Thus, when you decrease by 20 dB, the current decreases to 1/10th of its original value, which effectively means a tenfold reduction.

Consequently, this is why the response indicates a decrease of 10 times the original voltage or current, accurately reflecting the relationship between decibels and real-world quantities like current and power.