How to use it
- Turn the system volume to a low setting and keep the Volume slider at 10 %.
- Choose a sweep length of 10, 20 or 40 seconds and press Start sweep.
- Raise the volume gradually until you can hear the 50–100 Hz part comfortably.
- Note the frequency shown when the bass first appears, when it is strongest and when anything rattles. Tick Repeat the sweep to loop.
How it works
One sine oscillator ramps its frequency exponentially from 10 Hz to 200 Hz. At time t of a sweep lasting D seconds, the frequency is 10 × 20^(t/D) Hz. The number on screen is calculated from the audio clock with that formula.
Worked example
In a 20 s sweep, halfway (t = 10 s) the frequency is 10 × 20^0.5 = about 44.7 Hz. At t = 15 s it is 10 × 20^0.75 = about 94.6 Hz. The sweep passes 40 Hz at 20 × ln(4) / ln(20) = about 9.3 s.
Tips
- Listen from where you normally sit, then walk around: bass is uneven across a room.
- Rattling at one frequency is usually a loose object, not the speaker.
- The sweep stops when you leave the tab.