1.正弦信号
A single sinusoid of amplitude A and frequency
The STFT of is given by
For the case , , and
2.啁啾信号
Consider the chirp signal
From a filter bank perspective, the chirp moves across the subbands as time progresses.
The progression of the chirp across the subbands is illustrated in Fig.12.6, which depicts the (non-subsampled) STFT filter bank subband signals for several subbands.
3.正弦合成信号
Consider a sum of weighted sinusoids
4.语音
It is clear that the STFT magnitude changes from frame to frame, but some of the spectral peaks persist; there can be interpreted as persistent sinusoids in the speech signal.