You might have to implement it yourself using e.g. QwtPlotSpectrogram from Qwt - Qt Widgets for Technical Applications open source project whose license is LGPL with some exceptions. I haven't used the library myself so can't give any further assistance but the project seems to be active. By googling I noticed some implementations based on QwtPlotSpectrogram in GitHub, no idea of their quality level though.
You might have to implement it yourself using e.g. QwtPlotSpectrogram from Qwt - Qt Widgets for Technical Applications open source project whose license is LGPL with some exceptions. I haven't used the library myself so can't give any further assistance but the project seems to be active. By googling I noticed some implementations based on QwtPlotSpectrogram in GitHub, no idea of their quality level though.