waves Online Tone Generator star

The Range Behind the Slider: 20Hz to 20,000Hz

The frequency slider spans 20Hz to 20,000Hz because that's the textbook range of human hearing — the audible span most young, healthy ears can detect. It isn't a fixed constant, though: the upper limit falls with age in a documented pattern called presbycusis, age-related hearing loss concentrated in high frequencies. A young adult can often still hear tones near 19-20kHz, while by middle age that ceiling commonly drops to around 15-16kHz and keeps receding. This is why the "mosquito tone" prank — audible to teenagers but not most adults in the room — actually works; it exploits a real, gradual decline, not an urban legend. Below roughly 20Hz, tones aren't so much heard as felt, registering as vibration or pressure rather than a musical pitch.

Because hearing sensitivity varies this much by person and age, this tool defaults its volume slider to a conservative 20% rather than 100%. A tone near the edges of the audible range, or run through headphones at high volume, can be uncomfortable or genuinely damaging well before it sounds obviously loud — extended exposure at high sound pressure is a well-established cause of permanent hearing damage. Starting low and raising the volume gradually is standard practice for any tool putting a pure, sustained tone directly into headphones.

Why the Same Volume Doesn't Sound Equally Loud at Every Frequency

Set this generator to a low bass frequency and a midrange frequency at what should be "the same" volume, and the midrange tone will almost always sound louder. That's not a flaw — it's how human hearing works, first mapped by Harvey Fletcher and Wilden Munson at Bell Labs in 1933. Their equal-loudness contours (the Fletcher-Munson curves, later refined into the modern ISO 226 standard) show the ear is far more sensitive to frequencies roughly between 1kHz and 5kHz — the range that overlaps most human speech — than to very low bass or very high treble at the identical sound pressure level. A 60Hz tone and a 1kHz tone at the exact same pressure are perceived as quite different in loudness, with the 1kHz tone sounding noticeably more prominent; audio engineers rely on this effect when mixing music and calibrating playback systems.

The waveform selector changes the tone's harmonic content, a property separate from loudness or frequency. A sine wave is the purest possible tone — a single frequency with no additional harmonics — which is why it's the standard waveform for calibration and hearing tests, including the 1kHz preset here. A square wave, by contrast, is built from the fundamental plus only its odd-numbered harmonics (3x, 5x, 7x…) at decreasing amplitude, giving it that hollow, "buzzy" character familiar from early video game sound chips. Sawtooth waves add both odd and even harmonics at full strength for a brighter, brassy tone, while triangle waves have odd harmonics like a square wave but with a much steeper rolloff, landing closer to a soft flute than a buzzy synth lead.