HowLoudOnline tone generator
A4
Start with the volume low and turn it up slowly. On iPhone, switch off silent mode to hear the tone.
How to use the tone generator
- Pick a frequency with the slider, type it into the box, or tap a preset. The slider is logarithmic, like hearing itself: each step up the scale is the same musical distance, so low notes get as much room as high ones.
- Press Play. The tone fades in over a few milliseconds, so there is no click. Keep the volume low at first, especially with headphones.
- Fine-tune with the −1 / +1 buttons, or jump a whole octave with ÷2 and ×2. On a computer, the arrow keys move 1 Hz (10 Hz with Shift) and the space bar starts and stops the tone.
- Change the waveform or the channel while it plays. Left and Right send the tone to one speaker or one earbud only, which is a quick way to check stereo wiring.
The note name under the number tells you which musical note the frequency is closest to and how many cents it is off, handy when tuning an instrument by ear.
Common frequencies and what they are for
| Frequency | What it is |
|---|---|
| 20 Hz | The usual lower limit of human hearing; below it, sound is felt more than heard |
| 50 / 60 Hz | Mains hum: 50 Hz in Europe and most of the world, 60 Hz in North America |
| 100 Hz and below | Bass that most phone and laptop speakers cannot reproduce; use it to test a subwoofer or headphones |
| 440 Hz | A4, the standard tuning pitch for instruments |
| 1 kHz | The classic reference test tone; A-weighting is defined as 0 dB at 1 kHz |
| 2–5 kHz | Where human hearing is most sensitive |
| 10–15 kHz | Upper range that fades first with age |
| 17.4 kHz | The "mosquito" tone, used as a teen deterrent because many adults can no longer hear it |
| 20 kHz | The upper limit of hearing for young ears |
Sine, square, sawtooth or triangle?
- Sine is a pure tone with a single frequency and nothing else. Use it for hearing checks, tuning and speaker tests.
- Square adds every odd harmonic at strong levels and sounds hollow and buzzy, like an old video game.
- Sawtooth contains every harmonic and sounds bright and brassy; it is the starting point of many synthesizer sounds.
- Triangle has only odd harmonics, and they fade quickly, so it sounds soft, between a sine and a square.
Because square and sawtooth waves carry many higher harmonics, they sound louder than a sine at the same volume setting.
How high can you hear?
Young people usually hear up to about 17–20 kHz. The top end drops with age and with noise exposure: many people in their thirties stop hearing around 15–16 kHz, and many over fifty around 12 kHz. Play a high tone at low volume and raise the frequency until it disappears to get a rough idea of your own limit.
Treat it as a curiosity rather than a test: phone and laptop speakers, earbuds and browser audio all roll off at the top, so a tone you cannot hear may simply not be coming out. If you notice a change in your hearing, see an audiologist for a proper hearing test.
Practical uses
- Testing speakers and headphones: sweep from low to high and listen for rattles, buzzing or a channel that drops out. The Left and Right buttons check stereo wiring.
- Finding a room's bass problems: slow low tones between 30 and 120 Hz make standing waves easy to hear as you walk around the room.
- Tuning instruments: 440 Hz gives A4, and the note readout shows how far any frequency is from the nearest note.
- Describing tinnitus: some people match the pitch of their tinnitus to a tone so they can describe it to a doctor. It is not a treatment.
- Checking loudness: play a 1 kHz tone and measure it with the online decibel meter on a second device to compare speakers or settings.
Protect your ears. Pure tones can be uncomfortable or harmful at high volume, especially high frequencies through headphones. Start low, raise the volume slowly, and stop if a tone hurts or leaves your ears ringing. See safe decibel levels.
Frequently asked questions
Is this tone generator free?
Yes. It runs in your browser with no download, sign-up or ads, on iPhone, Android, Windows and Mac.
Why can't I hear low frequencies on my phone?
Small speakers cannot move enough air to reproduce deep bass, so most phones and laptops play little or nothing below 100–200 Hz. Use headphones or a speaker with a woofer for low tones.
Why is there no sound on my iPhone?
Check that silent mode is off: iOS mutes web audio while the ring/silent switch or Action button is set to silent. Then turn up the media volume.
What frequency is the A note?
A4, the A above middle C, is 440 Hz. Each octave doubles the frequency, so A5 is 880 Hz and A3 is 220 Hz.
Can a tone generator damage speakers?
Loud, very low or very high tones held for a long time can overheat or overstretch small drivers, especially tweeters. Keep the volume moderate and sweep instead of holding extreme frequencies.