Designed with accuracy and easy of use in mind.
Can be used for monitoring or measuring environmental sound or noise; help tuning instruments; timing short sound events; and educational purpose.

Features:
* No Ads.
* With log or linear frequency axis.
* Can label frequency axis using music pitch note.
* Support all possible sampling rates and almost all recorder sources of your device.
* Graph with nice grid lines and labels easy to operate.
* FFT sample size range from 512 to 8192. Using half-overlapped (adjustable) time window to increase time resolution.
* Various window functions provided for different frequency resolution and dynamical range.
* Peak frequency detection (in unit of Hz and note+cent) with a moderate accuracy (FFT + interpolation).
* With dB or A-weighting dB (dBA).
* Can record the audio in wav (PCM) format.

* Pinch to zoom drag or swipe to move long-press to place cursor double touch to reset zoom.

Notes:
** May need some knowledge of discrete Fourier transform and spectrum analysis to use it well.
** The actual accuracy mainly depends on your device. No calibration interface provided.

Comments and suggestions are welcome.