Sine, square, sawtooth and triangle
Four shapes, one frequency, four completely different sounds. What is inside each and when to reach for it.
Why shape changes the sound
A 440 Hz sine and a 440 Hz square are the same pitch and sound nothing alike. The reason is harmonics: any repeating waveform can be described as a sum of sine waves at whole-number multiples of its fundamental, and the recipe of those multiples is what the ear hears as timbre.
A sine wave is the only one with no recipe at all. It is a single frequency, which is why it is the right tool whenever you care about the number rather than the character.
The four shapes
| Waveform | Contains | Sounds | Use it for |
|---|---|---|---|
| Sine | The fundamental only | Pure, smooth, slightly dull | Hearing tests, channel tests, speaker limits, tuning |
| Triangle | Odd harmonics, falling away quickly | Soft, flute-like | A gentler test tone; low-frequency work at higher volume |
| Square | Odd harmonics, falling away slowly | Hollow, loud, buzzy | Finding rattles and resonances; checking amplifier behaviour |
| Sawtooth | Every harmonic | Bright, harsh, full | Hearing distortion; the classic synthesiser sound |
Why a square wave sounds louder
At the same peak level, a square wave delivers substantially more energy than a sine, because it spends all its time at full amplitude rather than passing smoothly through zero. Add the harmonic content landing in the region where the ear is most sensitive and a square wave can sound dramatically louder than a sine at the same setting.
That is worth knowing before you switch waveform with the volume up. It is also the reason square waves are the best tool for finding a rattle: more energy spread across more frequencies excites more resonances.
Choosing the right one
Testing what a speaker can do. Sine, always. A square wave at 30 Hz contains energy at 90, 150 and 210 Hz, so a speaker that produces nothing at 30 Hz will still make a sound — and you will conclude it reaches lower than it does.
Testing your hearing. Sine, for the same reason. A 17 kHz square wave is inaudible to most adults but its behaviour near the sample rate can produce audible artefacts lower down, so you end up testing the wrong thing.
Finding a buzz. Square, swept slowly through 60 to 200 Hz. Press on panels and grilles until it stops.
Tuning an instrument. Sine or triangle. Beating between two pitches is much easier to hear when neither is cluttered with harmonics.
Aliasing, or why high square waves sound gritty
A square wave at 5 kHz asks for harmonics at 15, 25, 35 kHz and upwards. Digital audio cannot represent anything above half the sample rate, so those harmonics fold back down into the audible range at frequencies unrelated to the note. The result is a gritty, slightly detuned sound that gets worse as you go up.
Analogue synthesisers do not have this problem, and software ones avoid it with band-limited generators. The generator on this site produces simple shapes directly, so if a high square wave sounds rough, that is aliasing rather than your speakers. For anything above a few kilohertz, use a sine.
Hearing it for yourself
Open the tone generator, set 220 Hz, and cycle through the four waveforms while the tone plays. The pitch stays put and the character changes completely, which is the whole point of harmonics in one demonstration. Then take the same four up to 4 kHz and notice how much less difference there is: the harmonics that distinguish them have moved above your hearing.
Last reviewed 2026-09-22.