Why Earphones, Sample Rates and Codecs Cut Off High Frequencies
When your high limit comes out low because of the device: the Nyquist limit, earphone frequency response, Bluetooth codecs, output latency and reaction time.
Published 2026-09-26
Your result is the narrower of ears and device
What this test measures is the narrower of two limits: what your ears can hear and what your device can produce. If the treble cuts off at 18 kHz, the result alone can't tell you whether that's your ears or your earphones. Testing again on a different device gives you a clue.
Sample rate and the Nyquist limit
Digital audio records and plays sound a fixed number of times per second. That number is the sample rate, and the highest frequency it can represent is half the sample rate (the Nyquist frequency).
| Sample rate | Nyquist limit | Typical use |
|---|---|---|
| 44.1 kHz | 22.05 kHz | CDs, many music files |
| 48 kHz | 24 kHz | Video, most computer and phone output |
| 96 kHz | 48 kHz | High-resolution recording |
In practice, anti-aliasing filters start trimming the sound just below Nyquist. So this site plays only up to 97.5% of half the sample rate, and on a 44.1 kHz device the high-limit sweep ends at about 21.4 kHz. Your browser's current sample rate is shown under 'Playback environment' on the results screen.
Frequency response of earphones and speakers
- Even when the spec sheet says '20 Hz–20 kHz', output often drops sharply at both ends. Spec sheets usually don't say by how many dB it falls within that range.
- Built-in laptop and phone speakers have small diaphragms and produce almost no bass below 100 Hz. Measure your low limit with headphones.
- If the ear tips don't seal well, bass leaks out and your low limit comes out higher than it really is.
Bluetooth and lossy codecs
Unlike a wired connection, Bluetooth earphones re-encode the sound with a lossy codec such as SBC or AAC before sending it. Lossy compression tends to reduce or cut the treble first, where people are less sensitive, so depending on the connection and codec your high limit may come out lower. Music files such as MP3 also have their treble cut by the encoder's low-pass filter at low bitrates.
This site synthesizes sine waves directly in the browser without any audio file, so file compression doesn't affect it — but compression on the Bluetooth link can't be avoided.
Output latency and reaction time
There is a delay between the moment you press the button and the sound that actually reached your ear. This site subtracts the output latency reported by the browser (Web Audio's outputLatency) when calculating the frequency, but Bluetooth devices sometimes don't report this value accurately.
Noticing a change in the sound and pressing the button also takes a few hundred milliseconds. The sweep keeps moving in the meantime, so the recorded value is pushed slightly past the true limit in the direction of the sweep. The fade-out and becomes-audible methods are skewed in opposite directions, so trying both shows how large the skew is.
Operating system and browser settings
- Sound effects such as equalizers, spatial audio and voice enhancement boost or cut certain bands. Turn them off while testing.
- Results are also steadier with noise cancelling and transparency modes turned off.
- If you hear sound in the other ear during a one-ear test, check whether 'Mono audio' is switched on in the accessibility settings.
Sources
- W3C, Web Audio API (AudioContext.outputLatency) — w3.org