Polarity flips the sign of a channel. Phase shifts it in time by a fraction of a cycle. Use headphones for channel and phase checks. On loudspeakers, out-of-phase bass cancels in the room while the cones still move fully, so do not turn it up to compensate.

Log spends equal time in every octave, which suits speakers and rooms. Linear spends most of its time in the treble. To find resonances below 100 Hz, sweep slowly: 15–200 Hz over 30 s or more. Press Hold here (or H) when you hear a rattle to park on that frequency.

AM keeps the peak constant, so raising depth never makes it louder. Rates from about 15 to 300 Hz sound rough and can be unpleasant at level. For binaural beats, unlink the channels and set the right channel a few hertz above the left, on headphones.

A 6.5-cycle Hann burst repeated every second is the CTA-2010 subwoofer test signal. Bursts let a driver cool between pulses, so keep the duty cycle low when testing at high level.

The file is rendered by the same engine that plays live, with a short fade at each end. The name records the settings, for example signal_1000Hz_sine_-24dBFS_48k.wav.

Levels are digital, in dBFS. How loud that is depends on your volume setting, amplifier and headphones, and a web page cannot read those. Bluetooth output resamples and compresses the signal, so phase, polarity and distortion checks are not reliable over Bluetooth. Turn off any “enhancements”, spatial audio or mono audio settings in your system before testing.