A tone generator plays a pure tone at any frequency on the spot (sine, square, sawtooth or triangle). It looks simple, but it's useful for checking audio gear, hearing reference pitches and tracking down hum.
1. Check your speakers and headphones
Use sweep mode to see how far your speakers or headphones reach. Set the start to 20 Hz, the end to 20,000 Hz and the time to 20–30 seconds, then play. If the sound suddenly drops or disappears, that's the practical limit of the device. Budget speakers often get weak below about 100 Hz or above about 15 kHz.
2. Find room resonances
Rooms and speaker placement can make certain frequencies boom. Play a slow sweep (30–60 seconds) and walk around the room. You'll hear where some frequencies get noticeably louder. Handy when setting up a home studio or placing speakers.
3. Track down mains hum
A low "hmm" in audio gear or recordings is often mains hum. The power grid frequency depends on where you are: the US, Canada and South Korea use 60 Hz, while Europe, China and most of the world use 50 Hz. Play the 50 Hz and 60 Hz hum test tones and compare which sounds closer to the noise. Hum also often shows up at the second harmonic (100 or 120 Hz).
4. Hear a reference pitch
Play 440 Hz (A4), the international reference pitch, and compare your piano or other instrument by ear. For precise tuning, the Online Tuner listens through your mic and is easier: use the tone generator to hear a reference, and the tuner to match it.
5. Set levels with 1 kHz
The audio industry widely uses a 1 kHz sine wave as a reference signal. Play it while watching the meters on a mixer or recorder to set input levels consistently.
Protect your hearing first
High frequencies can feel unpleasantly loud even at low levels. Especially with headphones, always start quiet and stop if it's uncomfortable. Long exposure to sounds of 85 dB or more can damage hearing.
Waveforms at a glance
- Sine: the cleanest pure tone with no harmonics. Use it to test a specific frequency or hear a reference.
- Square: contains odd harmonics, so it sounds thicker and harder. Good for checking a speaker's broad response.
- Sawtooth: contains all harmonics for a rich sound, common in synthesizer sound design.
- Triangle: fewer harmonics than square, somewhere between sine and square.
Why it's not for music or sound effects
A tone generator makes pure tones. Real instruments mix many harmonics, so these tones sound plain. That's exactly what makes them useful for testing a single frequency band.
Common mistake
Pressing Play with the volume all the way up. Square and sawtooth waves sound harsher and louder than sine waves, so always start low and raise the volume gradually.
Frequently asked questions
What frequency is mains hum in the US?
60 Hz in the US and Canada (also South Korea). Europe, China and most of the world use 50 Hz. Hum often also appears at 100 or 120 Hz.
How do I test my speakers’ range?
Use sweep mode from 20 Hz to 20,000 Hz over 20–30 seconds and note where the sound drops off.
Can I tune an instrument with it?
You can hear A4 = 440 Hz as a reference, but for precise tuning the Online Tuner, which listens through your mic, is easier.
Is it safe to use with headphones?
Start at a low volume and stop if it’s uncomfortable. High frequencies can feel loud even at low levels.
Sources and date checked
Checked: October 4, 2026
- Wikipedia, Mains hum — https://en.wikipedia.org/wiki/Mains_hum
- Wikipedia, A440 (pitch standard) — https://en.wikipedia.org/wiki/A440_(pitch_standard)
This article is general information. Results can vary by equipment and environment.