Free Online Tone Generator
Play any frequency from 20 Hz to 20 kHz with sine, square, sawtooth, or triangle waveforms. Stereo, left ear, right ear, and 15-second sweep mode.
What is a tone generator and what is it used for?
A tone generator is a tool that produces a pure musical tone — a sine wave, square wave, or other basic waveform — at any frequency you specify. Unlike playing a recorded audio file, a generator synthesizes the sound in real time using mathematics. This gives you absolute precision: 440.00 Hz means exactly 440.00 Hz, not “somewhere around 440 depending on how the recording was made.”
Tone generators are used across dozens of fields. Musicians use them for reference pitch and tuning. Audio engineers use them to test speakers, headphones, and rooms. Doctors use them for hearing tests. Video editors use them to align audio and video. Even veterinarians use ultrasonic tones to test hearing in dogs and cats. Our tone generator gives you every waveform, every frequency, and per-ear output — all running as pure JavaScript in your browser.
How to use the tone generator
- Turn your device volume down first. Some frequencies (especially very low or very high) can be surprisingly loud or uncomfortable at moderate settings.
- Enter a frequency or use the slider. Or click one of the preset buttons (60, 100, 440, 1k, 4k, 8k, 15k, 17k Hz).
- Pick a waveform: sine (pure tone, no harmonics), square (buzzy, hollow), sawtooth (bright, cutting), or triangle (mellow, flute-like).
- Adjust volume.
- Choose output channel: both ears, left only, or right only. Left/right mode is essential for hearing tests and stereo imaging tests.
- Click Play tone to start, click again to stop.
- Click Sweep 20 Hz → 20 kHz to hear a 15-second logarithmic sweep across the entire audible spectrum — useful for finding resonances in your speakers or room.
What each waveform sounds like
| Waveform | Character | Best for |
|---|---|---|
| Sine | Pure, no harmonics — like a flute or tuning fork | Reference tones, hearing tests, tuning |
| Square | Buzzy, hollow — full of odd harmonics | Retro synth sounds, clarinet-like tones |
| Sawtooth | Bright, cutting — full harmonic content | String and brass simulation, aggressive synth leads |
| Triangle | Mellow, flute-like — softer than sine plus a slight edge | Softer synth tones, subtle bass |
Popular use cases
Hearing tests. Play tones from 20 Hz up to 20 kHz through headphones. Note where you can and cannot hear each frequency. Most adults can hear up to about 16-17 kHz; children up to 20 kHz; those with age-related hearing loss usually top out at 12-14 kHz. This is not a medical audiogram — see an audiologist for actual diagnosis — but it’s a useful self-check.
Speaker and headphone testing. Play a sweep. If certain frequencies sound significantly louder or quieter than others, your speakers or headphones have peaks and dips. This helps identify why some music “doesn’t sound right” on a particular playback system.
Room acoustics. Play the sweep in your room. Walk around while it plays. You’ll hear certain bass frequencies get much louder in specific spots — those are “room modes” or “standing waves” caused by parallel walls. This is professional audio-engineer methodology, simplified for anyone to hear.
Musical reference pitch. A4 is 440 Hz. Play it, then tune your instrument (or check your ear) against it.
Left/right ear testing. Compare each ear separately. If you can hear 12 kHz clearly in your right ear but not your left, you have asymmetric hearing — worth checking with an audiologist.
Testing subwoofer output. Play 30-60 Hz to see if your subwoofer actually reproduces bass properly. Many “bass-boosting” consumer speakers can’t produce anything below 60 Hz at all.
Audio troubleshooting. When mixing music, mixing engineers frequently sanity-check speakers with a 1 kHz reference tone.
The frequency spectrum you can hear
| Range | Frequency | What’s there |
|---|---|---|
| Sub-bass | 20-60 Hz | Feel more than hear — kick drum thump, sub |
| Bass | 60-250 Hz | Bass instruments, low male voice |
| Low midrange | 250-500 Hz | Voice fundamentals, guitar body |
| Midrange | 500-2000 Hz | Vocal clarity, most instruments |
| Upper midrange | 2-4 kHz | Presence, consonants in speech |
| Treble | 4-8 kHz | Cymbal sizzle, breath, sibilance |
| Air / brilliance | 8-20 kHz | Sparkle, upper harmonics, hi-hats |
Safety and hearing protection
Very loud tones can damage hearing quickly. Never blast a tone at maximum volume — even a moment above 100 dB can cause permanent damage. If a tone sounds uncomfortable, immediately lower the volume or stop. Some very low frequencies (below 30 Hz) can feel physical rather than audible; enjoy the sensation briefly but don’t linger. Some very high frequencies (above 17 kHz) can cause a fatiguing “ringing” sensation in the ears if played for extended periods — stop after a few seconds.
Common uses in audio engineering
Speaker calibration. Professional studios sweep tones to identify frequencies where speakers or rooms have problems. The sweep mode in this tool is a simplified version.
Level calibration. A 1 kHz reference tone at -18 dBFS is the industry standard for calibrating recording levels across equipment.
Phase check. Play the same tone in both channels while listening in mono. If it gets softer instead of louder, your speakers or channels are wired out of phase.
Frequently Asked Questions (FAQs)
Up to your device’s sample rate divided by 2. On most modern devices that’s 22.05 kHz (44.1 kHz sample rate) or 24 kHz (48 kHz). Anything above ~20 kHz is inaudible to most adults regardless.
Because laptop speakers physically cannot reproduce frequencies below about 100-150 Hz. To hear real sub-bass tones, use headphones with good bass response or a proper speaker system with a subwoofer.
Yes if played at high volume for extended time. Never play tones at maximum volume; if a tone feels uncomfortable, lower the volume immediately. Sustained exposure above 85 dB can cause hearing damage.
It’s a useful self-check but not a medical audiogram. It tells you the highest frequency you can currently hear at a comfortable volume, which is a rough indicator of hearing health. For actual diagnosis, see an audiologist.
A sine wave is a “pure” tone with no harmonics — it’s the mathematical foundation of all sound. A square wave contains many harmonics on top of the fundamental, making it sound buzzy and full. Sawtooth and triangle waves fall between these two extremes.
Dogs hear frequencies up to about 45 kHz — well above the human 20 kHz limit. Frequencies between 18-24 kHz are audible to dogs but inaudible to most humans, which is why dog whistles work. Play very high frequencies at low volume if you want to test this — but don’t play them loud, it’s uncomfortable for pets.
Not in a single instance. Open two browser tabs, set each to a different frequency, and play both simultaneously. This is useful for ear-training musical intervals (fifths, thirds, etc.).