IOScope's available frequency domain measurements include:
The frequency resolution can be adjusted from 10 Hz to 0.2 Hz, which corresponds to FFT lengths of 4800 to 240000 lines (2400 to 120000 visible spectral lines) at a sample rate of 48 kHz.
A data cursor may be placed within the spectrum display with a single tap. You can move the data cursor by sliding your finger to the right or left inside the spectrum display. When the cursor is visible, spectrum information associated with the cursor is displayed in a small info view above the spectrum display. It is possible to zoom in or out on the spectrum display with a two-finger pinching gesture, and to pan the display, while zoomed in, with two fingers. A double-tap resets the display zoom and a second double tap turns off the data cursor. Cursor peak tracking can be toggled on and off with a triple tap.
A double tap inside the vertical axis label area toggles auto vertical scaling on and off (independently for each measurement type).
Depending on the current auto-scaling state, the vertical scale of the spectrum display may also be altered by a single-finger slide, or with a two-finger pinching gesture inside the vertical axis region (the region containing the vertical axis title and labels).
When the device is in a portrait orientation, measurement selection controls appear near the bottom of the screen. The measurement selection cannot be changed while the app is in landscape orientation.