# Tone Generator

> How does this frequency sound? Play a test tone from 1 Hz to 20 kHz and see its note, period and wavelength.

Free online tone generator: play sine, square, triangle or sawtooth waves from 1 Hz to 20 kHz, sweep frequencies and find the nearest note.

- Page: https://how.box/physics/tone/
- Runs entirely in the browser.

## Inputs

Answer link: https://how.box/physics/tone/?f={f}&w={w}&a4={a4}&m={m}&e={e}&s={s}&c={c}

- `f` (number 1 to 20000): Frequency in Hz, 1 to 20000 (the sweep start in sweep mode). Example: `440`.
- `w` (sine, square, triangle or sawtooth): Wave shape: sine, square, triangle or sawtooth. Example: `sine`.
- `a4` (number 400 to 480): Reference pitch A4 in Hz, 400 to 480 (standard 440), for the note name. Example: `440`.
- `m` (tone or sweep): tone (steady) or sweep. Example: `tone`.
- `e` (number 1 to 20000): Sweep end frequency in Hz, 1 to 20000. Example: `2000`.
- `s` (number 0.1 to 300): Sweep duration in seconds, 0.1 to 300. Example: `5`.
- `c` (linear or logarithmic): linear (equal Hz per second) or logarithmic (equal octaves per second). Example: `logarithmic`.

Example answer: https://how.box/physics/tone/?f=440&w=sine&a4=440&m=tone&e=2000&s=5&c=logarithmic

The page computes the answer in the browser: read results from the agent tools below, not from the page HTML.

## Agent tools

- `tone_describe_frequency`: Describes a sound frequency: its period, its wavelength in air, and the nearest musical note with the offset in cents.
  - Page only: runs on this page (WebMCP), not over MCP.
- `tone_note_to_frequency`: Gives the frequency of a musical note in twelve-tone equal temperament.
  - Page only: runs on this page (WebMCP), not over MCP.

## How it works

Sound is air vibrating. A tone is a vibration that repeats at a steady rate, its frequency f, measured in hertz (Hz): 440 Hz means 440 vibrations every second, and the higher the frequency, the higher the tone. One vibration lasts T = 1 / f, and the wave it makes in the air is λ = c / f long, where c is the speed of sound (343 m/s at 20 °C): at 440 Hz, 2.27 ms and 78 cm.

A speaker makes a tone by moving back and forth at that rate. The shape of the movement is the waveform: a sine wave is one pure frequency, while square, triangle and sawtooth waves add quieter tones at whole multiples of it (harmonics), which makes them sound brighter or buzzier.

Musical notes are frequencies too. Each octave doubles the frequency and is divided into 12 equal steps: f = 440 · 2^(n / 12), where n is how many steps the note is above A4 (440 Hz). Middle C is 9 steps below A4, so it is 440 · 2^(−9 / 12) ≈ 261.63 Hz.

Young ears hear about 20 Hz to 20 000 Hz, and the top end drops with age. Small speakers can't play deep bass. Loud tones can damage hearing permanently, so start quiet. Sources: ISO 16 (A4 = 440 Hz), ISO 9613-1 (speed of sound), WHO-ITU H.870 (safe listening).

## FAQ

**Why is 440 Hz the standard tuning note?**
It was agreed internationally so that instruments everywhere tune to the same pitch; ISO 16 sets A4 at 440 Hz.

**I can't hear the high or low tones. Is something wrong?**
Probably not. Hearing above about 15 000 Hz fades with age for most adults, and small speakers simply can't play very low tones.

**Why does the square wave sound louder than the sine wave?**
It carries more energy at the same volume setting, spread over its harmonics, so it sounds louder and harsher.

**Is using a tone generator safe?**
Yes, at sensible volumes. Pure tones can be piercing, especially in headphones: keep the volume low and sessions short.

**How do I test a subwoofer?**
Play a sine tone, start quiet and step down from 100 Hz towards 20 Hz. Most subwoofers reach 30–40 Hz; a rattle at one frequency usually comes from the room or the furniture, not the speaker.

**What is the mosquito tone?**
A tone around 17,000 Hz that many teenagers hear and most adults no longer do. Whether you hear it also depends on your speakers or headphones.

**Is this a hearing test?**
Only a rough one: it shows which tones you hear on your own speakers at an unknown level. A real hearing test uses calibrated equipment, so see a professional if you notice changes in your hearing.

**What is 528 Hz?**
A tone a little above C5 (523.25 Hz). Claims that it heals or repairs DNA have no scientific support.

**What does the waveform show?**
Before Play, it shows a still preview at the selected frequency and volume. While playing, it shows the sound signal; during a sweep, the waves move closer together as pitch rises. With reduced motion, the preview stays still.

More: [HowToolbox index](https://how.box/llms.txt) · [agent guide](https://how.box/agents.md) · [agent terms](https://how.box/about/agents/)