What is a 20 Hz to 20 kHz frequency sweep?
It is a continuous tone whose frequency rises (or falls) across the entire range of human hearing. 20 Hz is the lowest pitch a healthy young adult can perceive — felt more as vibration than sound — and 20 kHz is the theoretical upper limit, though most adults lose everything above 16 kHz by their thirties. Playing a sweep lets you hear exactly where your speakers, headphones, or ears stop responding. It is the fastest single test for diagnosing frequency response problems.
What should I listen for during the sweep?
Three things. First, dropouts: any frequency band where the tone briefly disappears reveals a resonance null in the room or a notch in your driver's response. Second, the low-end floor: cheap laptop speakers cut off around 200 Hz, decent bookshelves reach 60 Hz, and only subwoofers or large headphones produce true 20–40 Hz output. Third, the high-end ceiling: as the sweep climbs above 12 kHz, note where it fades — that point is your personal hearing limit. Confirm it with https://devicecheckonline.com/audio/hearing.
Why is the sweep logarithmic instead of linear?
Human hearing is logarithmic — we perceive the jump from 100 Hz to 200 Hz as the same musical interval as 1000 Hz to 2000 Hz (both are an octave). A linear sweep would spend 99 percent of its time in frequencies we hear as 'high', flying through the bass in a split second. A log sweep spends equal time on every octave, so 20–40 Hz takes as long as 10–20 kHz, giving each region a fair audition. This is also the standard for measurement microphones and room correction software.
My speakers buzz or rattle at certain frequencies — what does that mean?
Mechanical resonance. Something near the speaker — a loose grille, a desk panel, a window pane, a coin on the shelf — has a natural frequency that matches the tone, and it sympathetically vibrates. It is harmless but reveals your room. Persistent buzz from inside the speaker itself, especially in the bass, indicates a damaged voice coil or torn surround and is a hardware fault. Driver damage is permanent; stop the sweep immediately if you smell burning.
Is the sweep safe at full volume?
Output is held at -16 dBFS, lower than the stereo and tone tools, because sustained high-frequency tones can stress tweeters. Still, start with your OS volume around 30 percent. Tweeter coils can overheat from prolonged 5–15 kHz tones at high SPL, and your ears fatigue fast above 8 kHz. Never run a sweep through a guitar amp, PA, or vintage speaker without a limiter — old tweeters die in seconds. Test channels first with https://devicecheckonline.com/audio/stereo.
Why does my tone seem to fade above 16 kHz even on great headphones?
Probably your ears, not the gear. Presbycusis — age-related hearing loss — starts narrowing the upper range from your twenties onward. By 40, most people cannot hear above 15 kHz; by 60, the ceiling drops to 10–12 kHz. Noise exposure, ototoxic medication, and genetics accelerate the slope. To separate gear from ears, try the sweep on a second device and check the audible upper limit with the dedicated hearing test.