tonal.fm
PRO

All tools offline & ad-free — $9 once

→

Dual Tone Generator

Two independent sine oscillators at once. Set each frequency, hear beats when they are close, phantom difference tones when they are loud and far apart - and every interval in between. For more oscillators, the multi-tone generator scales up.

440 + 443 Hz

≈ 3 beats per second

Two tones, three phenomena

Beats: set the tones a few hertz apart (440 + 443) and hear the volume pulse at exactly the difference rate - the effect every by-ear tuner relies on, taught in the tuning guide. Difference tones: with two loud high tones (2000 + 2500 Hz) many ears perceive a phantom low tone at 500 Hz - your cochlea doing nonlinear math. DTMF: telephone dialing is precisely two simultaneous tones - hear the real pairs on the DTMF page, or go past two oscillators with the multi-tone generator.

Dual Tone FAQ

What is a dual tone generator for?

Demonstrating beat frequencies (two close tones pulsing at their difference), producing difference tones, testing intermodulation distortion in equipment (feed two tones, listen for products that should not exist), and DTMF-style two-tone signaling experiments.

Why do two close frequencies pulse?

Their waveforms drift in and out of phase: aligned they add (loud), opposed they cancel (quiet), repeating at exactly the difference frequency. 440 Hz plus 443 Hz beats three times per second. Tuners exploit this - beats slow as pitches converge and stop at unison.

What is a difference tone?

A third tone your ear invents at the mathematical difference of two real ones - play 2000 and 2500 Hz loudly and a phantom 500 Hz appears. It is generated by nonlinearity in the cochlea itself: a genuinely psychoacoustic sound that is not present in the air.

How is this different from binaural beats?

Here both tones play in both ears and the beating physically exists in the air - speakers work fine. Binaural beats send one tone to each ear and the brain constructs the beat internally, requiring headphones. Our binaural beats generator covers that case.

Related Tools

Tone Generator

Single tones, 20 Hz - 20 kHz

Signal Generator

Test signals for engineers

Multi-Tone Generator

Several frequencies at once

Sweep Generator

Linear & exponential sweeps

Noise Generator

White, pink & brown noise

White Noise

Full-spectrum masking

Browse all tools →