Free Online Tone Generator
Professional frequency generator for speaker testing, hearing tests, and audio calibration. Generate sine, square, triangle, and sawtooth waves from 20Hz to 20kHz. Free audio frequency generator with dual oscillator and sweep mode.
Tone Generator
Waveform Types Explained
Sine Wave
Pure energy. No harmonics. Smooth and clean. Best for precise testing.
Square Wave
Odd harmonics only. Hollow, retro game sound. Tests harmonic distortion.
Triangle Wave
Odd harmonics, but softer. Flute-like. Gentle on ears for extended tests.
Sawtooth Wave
All harmonics. Buzzy, rich, brassy. Full-spectrum stress test.
How to Test Speakers with a Tone Generator
- Start with 1kHz Reference
Play a 1kHz sine wave at low-medium volume (30-40%). This is your baseline. The speaker should reproduce it clearly with no buzz or distortion.
- Test Bass Response
Slowly sweep from 1kHz down to 40Hz. Note where bass starts to drop off. Small speakers stop reproducing below 80Hz. Subwoofers should remain strong down to 30Hz.
- Test Treble Response
Sweep from 1kHz up to 15kHz. Listen for harshness or missing frequencies. Tweeters should handle up to 20kHz smoothly without sibilance.
- Find Resonances
Play 80Hz, 100Hz, and 125Hz slowly. If the cabinet or port rattles or buzzes, you have found a mechanical resonance. Lower the volume or add damping material.
- Test at High Volume
Repeat the sweep at 70-80% volume. Listen for distortion that was not present at low volume. This indicates driver or amplifier clipping.
10 Professional Uses for a Tone Generator
1. Speaker Frequency Response Testing
Play a sine wave sweep from 20Hz to 20kHz at constant volume. Listen for frequencies that disappear or distort. Quality speakers reproduce all frequencies evenly; cheap speakers have gaps or peaks.
Pro tip: Set sweep mode, loop on, 20-second duration. Stand in your listening position. Note which frequencies sound quieter or louder.
2. Subwoofer Phase Alignment
When adding a subwoofer to existing speakers, phase alignment is critical. Play an 80Hz sine wave (typical crossover point). Flip the subwoofer's phase switch. The setting that sounds louder and fuller is the correct one.
Pro tip: Out-of-phase subs cancel bass instead of reinforcing it, making your system sound thin.
3. Finding Optimal Subwoofer Placement
The "subwoofer crawl" technique: Place the subwoofer in your listening position. Play a 40Hz sine wave on loop. Crawl around room edges. The spot where bass sounds deepest and smoothest is where your subwoofer should go.
Pro tip: Corners amplify bass but cause boom. Try 1/3 room positions for smoother response.
4. Headphone Burn-In
Many audiophiles "burn in" new headphones for 40-100 hours with pink noise or frequency sweeps. While the evidence is debated, the mechanical driver suspension does loosen over time, which can subtly change the sound.
Pro tip: Set sweep 20Hz-20kHz, loop on, volume at 50-60%, and let it run overnight for several days.
5. Tinnitus Frequency Identification
Tinnitus (ringing in the ears) has a specific pitch. Use this tool to narrow down your frequency (often 3-8kHz). Playing close to your tinnitus pitch can sometimes produce temporary relief through residual inhibition.
Pro tip: This is not medical treatment. See an audiologist for persistent tinnitus.
6. Room Mode Detection (Standing Waves)
Every room has resonant frequencies based on its dimensions. Formula: 1130 ÷ (2 × room length in feet) = primary mode. Sweep 30-200Hz to find where bass "booms" unnaturally.
Pro tip: Move your subwoofer, add bass traps, use DSP room correction, or avoid those frequencies in your EQ.
7. Testing Hearing Range by Age
Young adults hear 20Hz-20kHz. Most people over 50 can no longer hear above 12-15kHz. Use sine waves at 12kHz, 15kHz, and 17kHz to test your high-frequency hearing threshold.
Pro tip: Start at very low volume. High frequencies can damage ears even if they do not sound loud.
8. Car Audio Tuning
Car interiors have severe acoustic problems due to small size and reflective surfaces. Play 63Hz, 125Hz, and 250Hz test tones to find peaks. Adjust your EQ or damping material to flatten the response.
Pro tip: Door rattles usually appear at 80-120Hz. Sound deadening mat on door panels fixes most rattles.
9. Studio Monitor Calibration
Recording studios need flat frequency response. Play pink noise (or a frequency sweep) and measure with an SPL meter. Adjust monitor position and room treatment until 20Hz-20kHz measures ±3dB.
Pro tip: Mix position should measure 85dB SPL pink noise with peaks at 105dB.
10. Diagnosing Electrical Interference
If speakers hum at 60Hz (US) or 50Hz (EU), you have electrical interference from ground loops or EMI from power cables. Generate a 60Hz sine wave and compare it to the hum.
Pro tip: Fix by separating audio and power cables, using balanced connections, or adding a ground loop isolator.
Waveform Comparison Guide
| Waveform | Harmonics | Sound Character | Best Use |
|---|---|---|---|
| Sine | None (pure fundamental) | Smooth, flute-like, pure | Hearing tests, frequency isolation, speaker testing |
| Square | Odd harmonics (3rd, 5th, 7th...) | Hollow, retro video game, clarinet-like | Harmonic distortion testing, synthesizer sounds |
| Triangle | Odd harmonics (weaker than square) | Softer than square, mellow | Gentle test signals, less harsh on ears |
| Sawtooth | All harmonics (odd + even) | Bright, brassy, buzzy, rich | Full-spectrum speaker stress test, brass tones |
Free Online vs Hardware Tone Generators
| Feature | This Tool (Free) | Hardware ($200-$2000) |
|---|---|---|
| Frequency Range | 20Hz - 20kHz (audio) | DC to 20MHz+ (RF capable) |
| Accuracy | ±1Hz (browser dependent) | ±0.001Hz (crystal oscillator) |
| Output Level Control | Software volume | Calibrated dBm/Vrms output |
| Portability | Any device with browser | Benchtop or handheld unit |
| Cost | Free | $200-$2000+ |
| Best For | Home audio, hearing tests, speaker testing | Lab work, RF testing, precision calibration |
Bottom line: For audio applications (speakers, headphones, hearing), this free online hz generator is sufficient. Hardware generators are needed only for RF engineering, scientific research, or measurements requiring ±0.001Hz precision.
Audio Frequency Terminology
- Frequency (Hz)
- The number of sound wave cycles per second. 20Hz = very low bass (subwoofer territory). 20,000Hz (20kHz) = extreme high treble (cymbal shimmer). Human hearing spans 20Hz to 20kHz.
- Sine Wave
- The simplest waveform, consisting of a pure tone with no harmonics. It looks like a smooth "S" curve when graphed. Used for precise frequency testing because it isolates a single pitch.
- Harmonic
- A frequency that is a whole-number multiple of the fundamental. A 100Hz fundamental has harmonics at 200Hz (2nd), 300Hz (3rd), 400Hz (4th), and so on. Harmonics give sounds their character and timbre.
- Pink Noise
- Random noise with equal energy per octave. Sounds like soft rain or air flow. Used for speaker calibration because it tests all frequencies with perceptually equal loudness.
- Room Mode / Standing Wave
- Resonant frequencies where sound waves reflect between walls and reinforce each other, causing bass boom at certain spots in the room. Calculated: 1130 ÷ (2 × room dimension in feet).
- Crossover Frequency
- The frequency where speakers hand off to a subwoofer (typically 80Hz in home theater). Frequencies below the crossover go to the sub; frequencies above go to the main speakers.
- THD (Total Harmonic Distortion)
- Unwanted harmonics added by amplifiers or speakers. Good speakers have less than 1% THD. Test by playing a pure sine wave and listening for buzz or harshness.
- Fletcher-Munson Curve
- Human ears are less sensitive to bass and treble at low volumes. This is why your mix sounds different at bedroom volume versus concert volume. Louder playback makes bass and treble seem more present.
Binaural Beats Guide
Binaural beats are an auditory illusion created when two slightly different frequencies are played into each ear through headphones. The brain perceives a rhythmic pulse at the frequency difference. For example, 440Hz in one ear and 444Hz in the other produces a 4Hz perceived beat.
Delta (1-4 Hz)
Deep sleep and recovery
Theta (4-8 Hz)
Meditation and creativity
Alpha (8-14 Hz)
Relaxed focus and calm
Beta (14-30 Hz)
High alert and concentration
Requirement: Binaural beats only work with headphones. Each ear must receive a different frequency for the effect to occur.
Safety Warnings
High Frequency Hearing Damage
Frequencies above 10kHz can damage hearing even at "comfortable" volumes because you cannot perceive loudness accurately at those pitches. Always start at 10% volume when testing above 10kHz and increase slowly.
Subwoofer and Speaker Damage
Never play frequencies below the speaker's rated range at high volume. A 4-inch speaker fed 30Hz at high power will destroy its voice coil in seconds. Check your speaker specs before testing low bass.
Pets and Children
Dogs hear up to 45kHz, cats up to 64kHz. Even though this tool stops at 20kHz, nearby frequencies can cause distress to pets. Never play high frequencies around animals or young children.
Epilepsy Warning
Rapidly oscillating frequencies may trigger seizures in people with photosensitive epilepsy. Consult a doctor before use if you have epilepsy.
Frequently Asked Questions
What is a tone generator used for?+
A tone generator produces specific audio frequencies from 20Hz to 20kHz. Common uses include testing speaker frequency response, calibrating audio equipment, finding room acoustic problems, matching tinnitus pitch, testing hearing range, and burning in new headphones. Audio engineers use tone generators for phase alignment and crossover tuning.
What is the difference between a tone generator and frequency generator?+
The terms are used interchangeably for audio. A tone generator specifically produces audible frequencies (20Hz-20kHz), while frequency generator is a broader term that can include radio frequencies (RF) and other non-audio signals. For audio purposes, they are the same tool.
How do I test my speakers with a tone generator?+
Start with a 1kHz sine wave at low volume. Slowly increase volume while listening for distortion or rattling. Then sweep from 20Hz to 20kHz to check the full frequency range. If certain frequencies are missing or distorted, your speakers may have damaged drivers or crossover issues.
What frequency should I use to test my subwoofer?+
Test subwoofers with frequencies between 20Hz and 80Hz. Play 40Hz, 50Hz, and 60Hz sine waves to check deep bass response. If you hear rattling or port noise, lower the volume. Most subwoofers perform best between 30-60Hz.
Can I damage my speakers with a tone generator?+
Yes, if used incorrectly. Never play very low frequencies (below 30Hz) at high volume through small speakers. Always start at 10-20% volume and increase gradually. Square and sawtooth waves contain more energy than sine waves and can overheat voice coils if played too loud.
What is a sine wave and why use it?+
A sine wave is the purest form of sound, containing a single frequency with no harmonics. It is ideal for precise frequency testing, hearing tests, and finding exact tinnitus pitch. Audio engineers prefer sine waves for calibration because they isolate specific frequencies without harmonic interference.
How do I find room resonance frequencies?+
Play a sine wave sweep from 40Hz to 200Hz at moderate volume. Walk around the room. When certain frequencies suddenly sound much louder (boomy), you have found a room mode, which is a standing wave caused by room dimensions. Note these frequencies to adjust subwoofer placement or add bass traps.
What frequency is best for tinnitus relief?+
First, match your tinnitus frequency (usually 3kHz-8kHz for high-pitched ringing). Once found, some people get relief from playing that exact frequency at low volume, or from playing a frequency 1-2Hz different to create a masking effect. Results vary, so consult an audiologist for persistent tinnitus.
Can I use this instead of buying a frequency generator?+
Yes, for most audio applications. This free online tone generator works for speaker testing, hearing tests, room analysis, and basic calibration. Professional signal generators (like those from Fluke or Keysight) are needed only for RF engineering, precise lab measurements, or generating non-audio frequencies.
Do I need headphones or speakers?+
It depends on your use case. For hearing tests, use quality headphones to isolate each ear. For speaker/subwoofer testing, play through the speakers you are testing. For room acoustic analysis, use speakers to hear how frequencies interact with room dimensions.