A monaural beat is the audible amplitude modulation that arises when two sine tones close in frequency are mixed into a single mono channel. The two tones add and subtract in the air at the difference frequency, producing a "wah-wah" envelope you can hear directly through speakers. Unlike binaural beats (which are constructed in the brain and require headphones) and unlike isochronic tones (which are a single carrier gated on/off), monaural beats rely on real-world acoustic interference between two pure tones — the simplest of the three entrainment audio types both physically and perceptually.
Why a tone-balance control?
The depth of the AM envelope depends on how close the two tones' amplitudes are. At 50/50 balance (equal amplitudes) you get the deepest possible AM — the waveform amplitude swings between zero and twice the single-tone level. As you push the balance away from 50/50, one tone starts to dominate; the AM envelope becomes shallower, and at full extremes (0 or 100) only one tone is present and there's no beating at all.
This control lets you tune beat depth from "obvious wah-wah-wah" to "subtle texture" without changing the beat rate or the frequencies themselves. Some practitioners find the deepest AM (50/50) most useful for focused entrainment work; others prefer subtler depths (e.g. 30/70 or 70/30) for ambient sessions where the beating sits more in the background.
The 20 Hz AM perception cutoff — important for high beat rates
The human ear perceives amplitude modulation as distinct "beating" up to about 20 Hz. Below that, the AM envelope is clearly audible as a slow-to-medium-fast pulsing texture. Above ~20 Hz the modulation rate becomes too fast for the ear to resolve as separate beats — instead, the two tones start to be heard as two close pitches with a slightly rough timbre. At beta and gamma rates (20+ Hz), monaural beats produce real physical AM in the audio, but you stop perceiving it as a beat. For those rates, the isochronic generator is a more honest choice if you want an audible entrainment cue.
The five brainwave bands
- Delta (0.5 – 4 Hz) — deep sleep, slow-wave restoration. Monaural's sweet spot — slow audible AM well within the perception window. Preset: 2 Hz.
- Theta (4 – 8 Hz) — meditation, creativity, hypnagogia. Still clearly audible as beats. Preset: 6 Hz. Schumann 7.83 Hz lives in this band.
- Alpha (8 – 12 Hz) — relaxation, calm focus. Faster beats but still distinct. Preset: 10 Hz.
- Beta (12 – 30 Hz) — active focus, alertness. Beats approach and cross the AM-perception cutoff (~20 Hz). Below 20 they're audible; above 20 they smear into timbre. Preset: 20 Hz (boundary case).
- Gamma (30 – 100 Hz) — peak cognition. At gamma rates monaural mode no longer produces audible beating — you just hear two close tones. Use isochronic or binaural for gamma if you want an audible cue. Preset: 40 Hz (included for completeness).
Why no headphones?
Monaural beats are physical acoustic AM — the modulation exists in the soundwave itself, not in your brain or in any single-channel signal that needs separation. Speakers reproduce this perfectly. Headphones work fine too, but they don't add anything you couldn't get from speakers. This makes monaural the most flexible entrainment mode for shared listening (multiple people, room ambient) and for sleep-onset use where you don't want to wear headphones to bed.
What's different about this tool vs the band-specific generators (Alpha, Beta, etc.)?
The band-specific tools (Alpha, Beta, Theta, Delta, Gamma) constrain the frequency to one band and offer three modes (binaural / isochronic / monaural). This tool is the opposite — full-range across all five bands, but monaural-only. Use the band tools for focused work in one band with mode flexibility; use this for cross-band exploration with the most expressive monaural controls (variable tone-balance / beat depth).
What's different from the Binaural Beats Generator?
The Binaural Beats Generator covers 0.5–40 Hz binaural-only — it needs headphones because the beat is constructed in the brain from two-ear separation. This tool covers the same range monaural-only — the beat exists physically as amplitude modulation in the air, so it works on speakers. Binaural produces the cleanest perceived beat in headphones; monaural produces a more "natural" tone-beating timbre that's speaker-friendly. Pick by listening setup.
What's different from the Isochronic Tone Generator?
Both work on speakers and cover 0.5–40 Hz. Isochronic uses a single carrier tone gated on/off at the beat rate — sharp distinct pulses. Monaural uses two close tones beating against each other — smoother "wah-wah" texture. Isochronic puts the rate explicitly into the audio envelope as a hard-edged pulse; monaural produces the rate as a smooth physical AM. Try both — they feel quite different even at the same beat rate.
What does the tone-balance / amplitude ratio control do?
It varies the relative amplitudes of the two tones. At 50/50 (equal), the AM beat is at full depth — the waveform amplitude swings between zero and twice the single-tone level. Moving the balance below or above 50 makes one tone louder than the other, reducing the AM depth (shallower beating). At full extremes (0 or 100), only one tone is audible and there's no beating. Useful for tuning beat depth from "obvious" to "subtle" without changing the beat rate or frequencies. Note: the extreme settings naturally sound about 3 dB quieter than 50/50 because only one tone is contributing acoustic energy — boost master volume slightly to compensate if you want to keep perceived loudness constant.
Why does the beating "stop" at high rates?
The human ear's amplitude-modulation perception cuts off around 20 Hz. Below 20 Hz the AM envelope is heard as distinct "wah-wah" beating. Above 20 Hz the modulation rate becomes too fast for the ear to resolve as separate beats, and instead the two tones blend into a single timbre that sounds like two close pitches with a slight roughness. At beta (20+ Hz) and gamma (30+ Hz) rates, monaural produces real physical AM in the audio, but perception turns it into a steady-timbre sound. For audible entrainment cues above 20 Hz, use the isochronic generator instead.
Why don't I need headphones?
Monaural beats are physical amplitude modulation in the audio signal itself — the modulation is created when the two tones add and subtract in the air at the difference frequency. That happens identically whether the audio plays through speakers, earbuds, or headphones. Binaural beats are different — they require channel separation so each ear gets its own tone, and the "beat" exists only as a perceptual construction. Monaural cuts out the constructed-in-brain step.
What does the live waveform show?
It shows the literal audio signal reaching your speakers — the sum of the two tones with their AM envelope. At low beat rates (e.g. 2 Hz) and 50/50 balance you'll see the carrier waveform amplitude smoothly swelling and shrinking at the beat rate — that's the AM envelope visually. At unequal balance (e.g. 20/80) the envelope is shallower. At high beat rates (e.g. 30 Hz) the analyser's 85 ms window only captures a couple of beat periods so the envelope is visible but compressed.
What's the beat-rate visual indicator?
A sine wave animated at the current beat frequency — a calm visual cue independent of the audio. At low beat rates (delta/theta/alpha) it looks like smooth breathing-paced motion. At beta rates (12–30 Hz) it gets faster and shimmery. At gamma rates (above 30 Hz) it strongly aliases on the typical 60 Hz display — see the high-band warning in the indicator label.
Why include all five brainwave bands in one tool?
Cross-band exploration is useful for finding what works for you. The live brainwave-band classification readout shows which conventional EEG band you're in (delta/theta/alpha/beta/gamma) with a one-line state description. Note that monaural's effective range is roughly delta through low beta (under ~20 Hz) where AM perception works — at higher rates the beating perceptually disappears and you're just listening to two close tones. Use isochronic for gamma if you want an audible cue.
Safety reminders?
Avoid brainwave-entrainment audio if you have epilepsy or a seizure disorder (consult your doctor first). Don't listen while driving or operating machinery, especially at delta/theta rates which promote drowsiness. Keep volume moderate. Not a medical treatment, not a cognitive supplement — see a clinician for managed conditions.