root mean square bandwith
RMS is just the average voltage of an AC signal which is 1/√2 × peak~peak voltage of the signal, the word bandwidth can often be found to describe the frequency response of an amplifier, it is usually measured from the 3dB roll off point of the highest frequency to the lowest frequency of an amplifier or vice versa. eg. if an amplifier has a 3db roll off point at 10Hz and 100hz, it has a frequency response of 10hz~100hz and bandwidth of 90hz.
The 3dB roll off point is the same for RMS or Peak~Peak voltage, the bandwidth is determined by the amplifier that amplifies the signal.