The Oster Curve was developed by Dr. Gerald Oster, a scientist who pioneered modern binaural beats research in the 1970s. His work focused on how binaural beats could act as a diagnostic tool in health and science, not as a method of brainwave entrainment for meditation or personal development. That idea came much later.
As we explain in our article here, Dr. Oster didn’t invent binaural beats, nor did he propose their use for altering brain states. What he did highlight was this:
The fact that sub-threshold sounds are effectively rendered audible by binaural beats suggests that there may be other stimuli processed by the brain of which we are not aware. Finally, it is possible that hormonally induced physiological or behavioral changes too subtle to detect by ordinary means may be made apparent by measuring the binaural beat spectrum.
In other words, Oster opened the door to the idea that binaural beats reveal hidden layers of perception, suggesting the brain may be influenced by subtle stimuli we don’t consciously register. That’s where later thinkers began connecting this phenomenon to ideas of energy, awareness, and expanded consciousness.
Oster published his findings in a landmark paper, “Auditory Beats in the Brain” (Scientific American, 1973).
A key part of that research included what became known as the Oster Curve – a graph showing which carrier (base) frequencies are most effective for perceiving binaural beats at different target frequencies. For example, the Curve suggests that Theta-frequency binaural beats are most audible when paired with carrier frequencies in the 160–210 Hz range.
However, we should clarify something important: The Oster Curve is not an exact guide to optimal carrier frequencies for brainwave entrainment.
Why? Because Oster was studying perception thresholds, not entrainment outcomes. His focus was on how clearly the brain detects binaural beats, not how effectively they shift brainwave states.
Even so, the Curve remains a valuable reference point. It gives audio engineers a helpful starting template for choosing appropriate carrier frequency ranges for different target frequencies.
Understanding Carrier Frequencies
With that in mind, let’s continue by defining a carrier frequency, also known as a base frequency.
Let’s go back to basics for a moment: to create a binaural beat we need two frequencies, one sent to the left ear and the other to the right.
If we are entraining the brain to 5 Hertz (Hz), both the left and right frequencies could technically be considered “carrier frequencies,” because both are carrying a tone that contributes to the beat.
However, things change when the target frequency ramps — for example, when a track starts at 5 Hz and gradually increases to 7 Hz after 10 or 15 minutes.
In this situation, only one of the two frequencies will change.
The frequency that stays constant becomes the true carrier frequency, because it acts as the stable reference point throughout the track.
By convention — and because it produces a more pleasant, stable listening experience — the carrier frequency is usually the lower of the two tones.
To illustrate this clearly, let’s return to our 5 Hz example:
Left ear: 200 Hz
Right ear: 205 Hz
Perceived binaural beat: 5 Hz (the difference)
The left frequency (200 Hz) would be considered the carrier frequency, because it remains constant as the foundation of the sound.
If we want to increase entrainment to 7 Hz, we simply increase the right-ear frequency to 207 Hz. The left ear stays at 200 Hz throughout.
The Oster Curve and Optimal Carrier Frequencies
According to the Oster Curve, the optimal carrier frequency for entrainment around 10 Hz (alpha) is roughly 230–240 Hz.
As noted earlier, the Oster Curve should not be treated as a strict rulebook. Dr. Gerald Oster’s research was not focused on brainwave entrainment or meditation audio — his goal was to understand the auditory perception of binaural beats.
However, later research shows that the Curve is reasonably accurate when applied to entrainment.
For example, one controlled study used theta-range entrainment at a carrier frequency of 250 Hz to produce a 6 Hz binaural beat.
Although the Oster Curve suggests that ~200 Hz is the “optimal” carrier frequency for a 6 Hz target, the study still produced strong results using 250 Hz.
This suggests that theta and alpha entrainment remains effective across a broad carrier frequency range, roughly 180–250 Hz.
That said, research is ongoing. Over time, both scientific studies and individual practitioners continue to report that certain carrier frequencies feel particularly effective for certain brainwave ranges.
However, this is not something we need to obsess over. Evidence shows that as long as we stay within a reasonable range for each brainwave category, the binaural beat will still be effective for most listeners.
Interestingly, what may influence a person’s sensitivity to binaural beats even more than carrier frequency are individual biological differences identified by Dr. Oster.
For example, he found that a woman’s ability to perceive binaural beats varies throughout the menstrual cycle, likely due to changes in oestrogen, which affects auditory processing.
The Oster Curve (Oster's Curve)
| Optimal Carrier Frequency (Hz) | Beat Frequency (Hz) |
|---|---|
| 10 | 0.235 |
| 20 | 0.444 |
| 30 | 0.615 |
| 40 | 0.768 |
| 50 | 0.964 |
| 60 | 1.21 |
| 70 | 1.451 |
| 80 | 1.659 |
| 90 | 1.856 |
| 100 | 2.054 |
| 110 | 2.265 |
| 120 | 2.581 |
| 130 | 2.903 |
| 140 | 3.266 |
| 150 | 3.669 |
| 160 | 4.073 |
| 170 | 4.596 |
| 180 | 5.104 |
| 190 | 5.835 |
| 200 | 6.821 |
| 210 | 7.66 |
| 220 | 8.599 |
| 230 | 9.551 |
| 240 | 10.604 |
| 250 | 12.037 |
| 260 | 13.935 |
| 270 | 15.396 |
| 280 | 17.023 |
| 290 | 18.571 |
| 300 | 19.453 |
| 310 | 20.815 |
| 320 | 21.767 |
| 330 | 22.41 |
| 340 | 23.248 |
| 350 | 23.843 |
| 360 | 24.459 |
| 370 | 24.813 |
| 380 | 25.14 |
| 390 | 25.604 |
| 400 | 25.771 |
| 410 | 26.026 |
| 420 | 26.103 |
| 430 | 26.185 |
| 440 | 26.232 |
| 450 | 26.249 |
| 460 | 26.25 |
| 470 | 26.108 |
| 480 | 25.775 |
| 490 | 25.566 |
| 500 | 25.41 |
| 510 | 25.083 |
| 520 | 24.688 |
| 530 | 24.257 |
| 540 | 23.836 |
| 550 | 23.393 |
| 560 | 22.993 |
| 570 | 22.387 |
| 580 | 21.466 |
| 590 | 20.535 |
| 600 | 19.513 |
| 610 | 18.116 |
| 620 | 17.206 |
| 630 | 16.295 |
| 640 | 15.479 |
| 650 | 14.836 |
| 660 | 14.087 |
| 670 | 13.155 |
| 680 | 12.58 |
| 690 | 11.896 |
| 700 | 11.21 |
| 710 | 10.61 |
| 720 | 10.029 |
| 730 | 9.492 |
| 740 | 8.722 |
| 750 | 8.364 |
| 760 | 8.059 |
| 770 | 7.703 |
| 780 | 7.318 |
| 790 | 7.002 |
| 800 | 6.661 |
| 810 | 6.356 |
| 820 | 6.116 |
| 830 | 5.881 |
| 840 | 5.642 |
| 850 | 5.44 |
| 860 | 5.28 |
| 870 | 5.138 |
| 880 | 4.846 |
| 890 | 4.703 |
| 900 | 4.565 |
| 910 | 4.396 |
| 920 | 4.203 |
| 930 | 4.053 |
| 940 | 3.894 |
| 950 | 3.744 |
| 960 | 3.623 |
| 970 | 3.514 |
| 980 | 3.391 |
| 990 | 3.274 |
| 1000 | 3.161 |
| 1010 | 3.015 |
| 1020 | 2.855 |
| 1030 | 2.697 |
| 1040 | 2.576 |
| 1050 | 2.46 |
| 1060 | 2.347 |
| 1070 | 2.236 |
| 1080 | 2.124 |
| 1090 | 2.011 |
| 1100 | 1.896 |
| 1110 | 1.775 |
| 1120 | 1.644 |
| 1130 | 1.523 |
| 1140 | 1.428 |
| 1150 | 1.354 |
| 1160 | 1.283 |
| 1170 | 1.199 |
| 1180 | 1.109 |
| 1190 | 1.021 |
| 1200 | 0.974 |
| 1210 | 0.968 |
| 1220 | 0.924 |
| 1230 | 0.85 |
| 1240 | 0.762 |
| 1250 | 0.666 |
| 1260 | 0.575 |
| 1270 | 0.555 |
| 1280 | 0.562 |
| 1290 | 0.536 |
| 1300 | 0.498 |
| 1310 | 0.453 |
| 1320 | 0.406 |
| 1330 | 0.372 |
| 1340 | 0.37 |
