Spectrogram is a … spectrogram viewer which allows time frequency analysis.
-FFT resolution from 32 to 65536
-9 window algorithms to reduce spectrum leakage
-fast pause/resume button
-day or night mode

Note that amplitude value is not displayed because would cannot be accurate without calibration for your device.

Feel free to contribute to the development of the app:
https://bitbucket.org/galmiza/spectrogram-android