In this paper, we compare the performance of spectrogram and a new variation of multi-window (MW) spectrogram for various digital modulated signals. The windows used in the MW spectrogram are combination of Slepian sequences instead of using all the sequences. The comparison in the time-frequency representation is made in terms of main-lobe width (MLW) and peak to side-lobe ratio (PSLR) of the signals used. In the presence of noise, performance is compared in terms of variance in the estimated bit duration frequency. Bit duration and frequency are estimated from the instantaneous frequency (IF), which is derived from the time-frequency representation. The bias in the estimated bit duration is also calculated to compare the performance between spectrogram and MW spectrogram. In general, the time-frequency representation of the spectrogram is better than MW spectrogram. However, MW spectrogram is superior to spectrogram in terms of bit duration estimation.